An 
OUTLINE OF 
Practical Anatomy 
BY 
JOHN WARREN I 
• * * 
Harvard Medical School 
AND 
ALEXANDER S. BEGG 
Boston University School of Medicine 
BOSTON 
1924 Copyrighted 1924 
by 
J. W. and A. S. B. 
All rights reserved INTRODUCTION 
Care of the subject. Students must realize that it is a great 
privilege to have the opportunity of dissecting a human body, 
and that they cannot show too much care and respect for the 
remains. The Anatomical Act of the State of Massachusetts 
requires that the remains of any subject after dissection be 
decently buried; that all parts of a subject must be kept together 
and must not be mixed with those of another; that no part of 
the subject be removed from the laboratories except by proper 
authority. The subjects should be placed on the wooden blocks 
so that no part of the subject is in contact with the table top. 
This allows free drainage of fluids and prevents the collection 
of dirt and debris under the subject. Any portions of the subject 
removed in the course of dissection must not be left on the 
blocks, table, or dropped on the floor. They should be placed on 
a piece of paper and at the end of the day's work the paper should 
be rolled up and placed in the pail that belongs to that particular 
table and subject. Students will be held responsible for the care 
and neatness of their subject, of the table, and of the floor about 
the table, and this will be considered in their practical mark for 
the course. By paying proper attention to these details the 
dissecting rooms can be kept in appearance as neat and clean as 
an operating room, and conditions will be much more favorable 
for the comfort of all. Students are requested to take special 
pains to observe the above requirements of the Anatomical Act 
and also the rules governing the use of the dissecting rooms, 
copies of which will be posted in each laboratory. 
Methods of study and technique. In the study of the human 
body an unusual opportunity is offered for the training of the 
student's sense of observation and touch. Such training, if 
properly exercised, will be of great value to him in other labor- 
atory and clinical work. The student should make a point of 
palpating not only the cadaver but himself and living subjects 
at every opportunity, sinc'effhe 'surface markings vary consider- 
ably with the development and condition of the individual. In 
performing the' actual dissection the student must bear in mind 
3 that he is not merely working to learn anatomical facts, but is 
really training his eye and hand in the manipulation of instru- 
ments, which will be of great value to him in other laboratory 
work and especially in surgery. From the very start it is essen- 
tial that a neat and careful technique in dissection and in the 
use of instruments should be cultivated. In all other laboratory 
work, and especially where any operative procedures are to be 
carried on, cleanliness and neatness are absolutely essential to 
insure proper results. This applies not only to the instruments 
but to the student's hand, the cadaver, and the dissecting room 
tables and floor. 
Before beginning any dissection, the student should study 
the skeleton of the part, using the specimens in his bone box. 
He should then palpate carefully and identify all the superficial 
landmarks, and read over the account of the superficial dissection 
of the region before making any incisions. This method should 
be followed at all stages of the dissection, as it is necessary that 
the student have some idea of the general position of the parts at 
any given level or plane so as to avoid injuring them in his dis- 
section. First year students in Anatomy .have an unfortunate 
tendency to disregard their dissections, and to try to learn as 
many details as possible from their text books. Such a method 
only increases the difficulty of their task. The student should 
regard his own dissection as the chief source of his anatomical 
knowledge, and should make a point of obtaining a mental pic- 
ture of his dissection. This must, of course, be carefully checked 
up with the statements in the book, as there are many variations 
in the positions and relation of the parts. The student should 
examine any dissections and special specimens which will be 
shown before any given dissection is undertaken. This will give 
him some idea of the relations of the structures in such regions, 
so that he will know where to look for them when he begins 
his own work dissection. When any given region is fully dis- 
sected he should carefully study all necessary relations and de- 
tails and then check them carefully with the account in the books. 
.His final knowledge of the region should be the picture given in 
the actual dissection rather than that in the text or illustrations 
4 of his book. Text books are really books of reference and the 
beginner should not be required or expected to learn all the de- 
tails, the relative valne of which he is unable to determine. 
Methods of dissection. Incisions and removal of skin. Be- 
fore beginning the dissection of any region all hair on the sur- 
face should be removed by the razor, care being taken not to 
strip off the epidermis at the same time. The skin should be 
removed only over the actual area that is to be dissected. It is 
the tendency of beginners to raise an unnecessarily large amount 
of skin, with consequent exposure and possible injury to the 
parts beneath it. The skin is the best protection for the under- 
lying structures, and should be kept in situ as long as possible. 
The epidermis can very easily be injured or stripped off by rough 
or careless handling, and such areas promptly dry up. The stu- 
dent must therefore handle the subject with great care to avoid 
injuring the epidermis, especially in manipulating the limbs or 
turning the subject over. In making the incision through the 
skin the integument should be put on the stretch with the thumb 
and forefinger of the left hand. The incision should then be 
made with the belly of the knife, using a slow, steady stroke and 
not a short, choppy stroke. As the knife pierces the skin, the 
edges of the cut do not at first readily separate, but when the 
subcutaneous tissue has been reached, the edges of the incision 
will readily open. When this level has been reached, the greyish 
yellow fat of the subcutaneous tissue will be seen at the bottom 
of the cut, and the student will then know that the incision is 
deep enough. An incision according to the above directions 
should be made over the whole region to be exposed, leaving the 
skin flap, however, attached at one side. A corner of the cut 
skin can then be seized with the toothed forceps and raised. 
The edge of the knife should be directed against the under sur- 
face of the skin, so as to separate as far as possible all fatty tis- 
sue from the under surface of the skin flap. The knife should be 
grasped firmly between the thumb and all four fingers, the belly 
of the blade directed downwards, and the cutting largely done 
with the rounded belly of the blade. At the same time the flap 
should be kept tense with the forceps, or, as it is gradually 
5 raised, with the fingers of the left hand. If the dissection has 
been properly performed, the skin flap can be lifted with a mini- 
mum amount of fatty tissue on its deep surface. 
Subcutaneous Tissues. Superficial Fascia. The subcuta- 
neous tissue or superficial fascia is characterized by the fat which 
is contained within it. The amount of fat varies with the nutri- 
tion of the individual. Besides the fat the superficial fascia con- 
tains the branches of the cutaneous vessels and nerves. After 
the main trunks of these vessels and nerves have been isolated 
and secured, what is left of the superficial fascia can then be 
removed. In some regions where the cutaneous vessels and 
nerves are too small to be readily dissected, this fatty superficial 
fascia can be removed in one layer. Special directions as to the 
dissection of the cutaneous structures will be given from time to 
time. 
Deep Fascia. Beneath the superficial fascia is found another 
layer known as the deep fascia. The deep fascia is distinguished 
from the superficial fascia by its firm cobweb-like appearance and 
by the absence of fat. In removing the fatty superficial fascia, the 
incision should be carried through the fatty layer until the grey- 
ish non-fatty membrane appears beneath. With a little care 
the fatty superficial fascia can be readily separated from the non- 
fatty membraneous deep fascia. This deep fascia varies con- 
siderably in thickness in different parts of the body. In some 
cases it is so thin as to be almost transparent; in other cases it 
is thick and contains tendinous fibers. It forms an investment 
for the underlying musculature, and also forms fascial compart- 
ments, in which are found different groups of muscles with the 
corresponding vessels and nerves. It is important that the 
student should note the character and the arrangement of these 
tascial planes and compartments in the different regions of the 
body, as their relations to the musculature and vessels and nerves 
are often of great topographical significance. 
Dissection of muscles. The superficial musculature of the 
body lies immediately beneath the deep fascia. This fascia blends 
with the connective tissue sheaths of the muscles beneath it. 
In order to expose the actual muscle fibers in a given muscle, the 
6 deep fascia and the connective tissue sheath of the muscle must 
be removed. This is known as cleaning a muscle. The muscle 
should always be put on the stretch and made as tense as pos- 
sible before removing the connective tissue covering. This can 
almost always be done by manipulating the part or limb, as the 
student can readily discover for himself. The deep fascia or the 
connective tissue sheath of a muscle should be cut through at 
the most firmly fixed end or side of a given muscle. The point 
or blade of the knife should always be carried parallel to the 
muscle fibers. If the knife is carried across the fibers they will 
be cut, their edges will turn up, and the muscle will have a 
ragged and untidy appearance. The student should raise the 
fascial covering of the muscle in much the same way as he has 
been told to raise the skin. The fascia should be removed as far 
as possible in an even, continuous layer over the whole extent 
of a given muscle, leaving no isolated patches of fascia behind. 
By slightly moistening the muscle one can always tell whether 
the fascia has been completely removed. The large bellied 
knife will usually be found the most convenient in the dissec- 
tion of fascia and muscles. 
Dissection of vessels and nerves. The arteries of the body 
have been injected with a starch mass. The student should be 
careful to avoid cutting arterial branches as far as possible, as 
the starch mass is not absolutely solid and considerable oozing 
takes place, especially from the larger vessels. The veins are 
not injected, and it will not be necessary to, preserve the small 
branches of the veins, as they get in the way and cover up other 
parts of the dissection. Particular care should be taken in fol- 
lowing out the various branches of the nerves. In the dissection 
of the vessels and nerves, the student had better use the smaller 
thinner bellied knife, and always dissect parallel with the main 
trunks of the vessels and nerves, which are usually found more 
or less together. 
General instructions. The student should endeavor to dis- 
sect as far as possible in definite layers or planes, so as to ex- 
pose in an orderly manner the various groups of structures from 
the skin down to the deepest parts. Care should be taken to 
7 avoid cutting any structure which has been dissected, unless it 
is absolutely necessary in order to expose some deeper part. 
The student should never make a cut with the knife or scissors 
until he is reasonably sure of what lies beneath the blade of his 
instrument, as many a nice dissection has been ruined by a care- 
less cut of this character. It is often necessary to cut some of 
the superficial muscles in order to expose a deeper set. In such 
a case a given muscle can be severed near its center so as to leave 
the ends intact. Vessels and nerves, however, can usually be 
drawn to one side and preserved. Any variations or abnormali- 
ties should also be noted. Rough freehand sketches of any dis- 
section, if time permits, will prove to be of great value to the 
student. When the day's work is completed, the skin flaps 
should be sewn together with the autopsy needle, the parts 
wrapped and moistened according to directions, and the whole 
subject covered with the blanket which is found on each table. 
8 Skeleton. The axial skeleton forms the framework of the 
trunk and consists of the Vertebral column or spine, the ribs and 
sternum, and thV skull. The bony framework of the dorsal re- 
gion of the trunk is made up of the spine and the ribs as far as 
their angles. The rest of the ribs and the sternum form the 
framework of the laterowentral aspect of the trunk and will be 
studied with "that region. The skull will be studied with the 
head and neck. ' !i■•••' 
Vertebrae. The spine is made up of thirty-three yertebrae 
and is divided into four regions-cervical, thoracic, lumbar, and 
sacro-coccygeal. Each region has a type of vertebra peculiar to 
it, and at the lower end of each region occur atypical vertebrae 
a\ hich represent a transition to the type characteristic of the 
region below. At the upper end of the cervical region are two 
peculiar vertebrae whose characteristics are determined by the 
movements of the head on the spine. In the sacral region the 
vertebrae are fused into one, and this is also true with the in- 
significant coccygeal vertebrae. The sacrum and coccyx com- 
plete the wall of the bony pelvis. 
A vertebra consists of a Solid part, the body or centrum, and 
an arch made up of two parts,' the pedicles and the laminae. The 
arch supports the articular, transverse, and spinous processes. 
The cavity in the center forms part of the neural or spinal canal 
for the spinal cord. The student should study the features of 
the vertebrae peculiar to the cervical, thoracic, and lumbar re- 
gions, and compare the different features in each. He can then 
take up the atypical vertebrae of each of these regions, paying 
special attention to the first two cervical and to the sacrum and 
coccyx. After studying the individual vertebrae he should study 
the spine as a whole. 
Spine. The spinal column consists of the row of vertebral 
bodies and of the row of neural arches and their processes. The 
bodies are connected by the intervertebral disks of fibro-carti- 
lage, which represent about one-quarter of the total length of 
the spine, and by various ligaments. The bodies give origin to 
DISSECTION OF THE BACK 
9 certain muscles which act on the ventral aspect of the spine. 
The row of bodies supports the weight of the head and trunk, 
and the movements of which the spine is capable occur in the 
disks between the bodies. The column of bodies and disks is 
mechanically the most important part of the spine. The arches 
are also connected by various ligaments, give attachment to the 
axial muscles which act on the dorsal aspect of the spine, and 
complete the boundaries of the spinal or vertebral canal which 
contains the spinal cord, the membranes surrounding the cord, 
and the origins of the spinal nerves. 
The intervertebral forminae are found between each pair of 
pedicles and permit the passage of the spinal nerves and the 
spinal arteries and veins. In each foramen lies a spinal ganglion, 
which is associated with the sensory root of the corresponding- 
spinal nerve. In the thoracic region the laminae overlap, while 
in the cervical and lumbar regions, especially in the latter, there 
is a space between them. This arrangement allows a needle 
to be passed into the spinal canal in the lumbar region and is 
of practical importance in lumbar puncture and spinal anaes- 
thesia. 
Curves of the spine. The spine is not straight, but is made 
up of four curves. The thoracic and sacral curves are concave 
forward; they appear during embryonic life, give greater room 
for the organs in the thorax, abdomen and pelvis, and are known 
as primary curves. The cervical and lumbar curves are convex 
forward and are shorter and sharper than the other two. They 
appear after birth and are known as the secondary curves. The 
cervical curve appears when the child begins to hold up its head; 
the lumbar curve appears when the child begins to assume the 
erect position. They are due to the need of supporting weight. 
The cervical and lumbar curves are deeply seated in the trunk 
and are covered in behind by the deep muscles of the loins and 
neck. The thoracic and sacral curves are very near the surface. 
The cervical curve extends from the top of the spine to the top 
of the second thoracic vertebra; the thoracic curve from the 
second to the eleventh thoracic; the lumbar curve from the 
eleventh thoracic to the promotory of the sacrum. The line of 
10 gravity of the head and neck passes through the points where the 
curves join each other. ..The. curves are comparable to a series 
of superimposed springs and the elasticity they give is of great 
importance in enabling .the spine to carry weight with a mini- 
mum of muscular effort. 
Movements of the spine. , The spine is freely movable, the 
various movements depending on the compression or stretching 
of any given disk. While there is only very slight movement 
between any two vertebrae, is a considerable range of 
movement when the spine is considered as a whole. The move- 
ments are most free in those regions where the disks are thick- 
est ; consequently movements ,are more marked in the neck and 
loins and much more limited in the thoracic region, where the 
ribs also tend to restrict motion. There is of course none in the 
sacral region, with the exception of a little play between the sac- 
rum and coccyx. Flexion and extension of the spine, bending 
forward and backward, are most marked in the neck and loins 
but are limited in the thoracic region. Lateral movement, bend- 
ing from side to side, is free in the neck and lumbar region, but 
limited by the ribs in the thoracic region. Rotation is freest 
in the neck, fairly free in the upper thoracic region, but very 
slight in the lumbar region due to the peculiar shape of the 
lumbar articular processes, Lateral motion is always associated 
with some rotation, a fact of practical importance in the condi- 
tion known as lateral curvature of the spine. 
Shoulder and pelvic girdles. The appendicular skeleton 
forms the framework of the limbs. In the upper limb it consists 
of the clavicle, and scapula; the humerus; the radius and ulna; 
the bones of the hand. Jn the lower limb it consists of the in- 
nominate bone, made up of the ilium, ischium, and pubis; the 
femur; the tibia and fibula; the bones of the foot. The appen- 
dicular skeleton will be studied during the dissection of the ex- 
tremities, but parts of the scapula and ilium will be met in the 
dissection of the dorsal surface of the trunk. The student should 
note the general position of the scapula in this region, its verte- 
bral border and its spinous and acromion processes. These parts 
of the bone will give attachment to some of the more superficial 
11 appendicular muscles of the back and can be felt through the 
skin. Lower down the crest and posterior spines of the ilium 
should be noted. 
Superficial anatomy. The student should palpate and iden- 
tify the following: the external occipital protuberance of the oc- 
cipital bone; the spinous processes of the vertebrae, noting vari- 
ations in depth from the surface owing to the curves of the spine; 
the dorsal surface of the sacrum and coccyx; the posterior spines 
and crest of the ilium; the ribs, especially their curves and in- 
clinations, the position of their angles, the length of the last rib 
and the distance between it and the iliac crest; the scapula, es- 
pecially the spine and acromion processes and the position of 
the bone in relation to the spinous processes and the ribs; the 
outline of the trapezius; the upper border of the latissimus dorsi; 
and the longitudinal mass of the axial musculature along the 
spine. 
Incisions. In this dissection the student will only expose 
the parts from the level of the last cervical vertebra above, to 
the crests of the ilia and lower end of sacrum below. The skin 
and tissues of the back of the neck will be left intact for a later 
dissection. 1. From the level of last cervical vertebra in the 
midline to the lower end of the sacrum. 2. From the upper end 
of the first incision horizontally outward to the acromion process. 
3. From the level of the 11th or 12th thoracic spine horizontally 
outward for about six inches. 4. From the lower end of the 
first incision following the course of the iliac crests to a point 
about six inches from the median line. Raise the flaps along the 
median line and reflect them outward. The thickness of the 
skin over the back of the neck and shoulders should be noted. 
Superficial fascia. Observe its thickness and firm connec- 
tion to the skin over the back. Reflect this layer by the same 
cuts and same methods as those used for the skin. 
Cutaneous nerves. The cutaneous nerves are the termina- 
tions of the dorsal divisions of the spinal nerves. These nerves 
divide usually into internal and external branches which supply 
both the skin and the axial musculature of the back. The in- 
ternal branches pierce the subcutaneous layers close to the 
12 spinous processes of the vertebrae, while the external branches 
are found several inches from this midline. Subject to some 
variation the following is the usual arrangement. In the neck 
and upper part of the thoracic regions the internal branches sup- 
ply muscles and also the skin, while the external branches sup- 
ply muscles only. In the lower thoracic, lumbar, and sacral re- 
gions the internal branches supply muscles only, while the ex- 
ternal branches supply muscles and also the skin. The superficial 
arteries and veins are the dorsal branches of the intercostal ves- 
sels. They are small and usually are poorly injected. They 
follow the course of the cutaneous nerves, and, if they are in- 
jected, serve as a convenient guide to the nerves. 
Deep fascia. The deep fascia forms a fairly thick and dense 
layer which is closely connected to the superficial fascia and also 
closely invests the underlying muscles, trapezius and latissimus 
dorsi. At the anterior borders of these muscles it is continuous 
with the deep fascia of the neck and that of the ventral thoracic 
and abdominal regions. 
Dorsal Musculature. The muscles of the back consist of 
two main groups: a superficial appendicular group connecting 
the shoulder girdle and the arm to the trunk; and a deeper axial 
group, which is attached to the ilium spine, ribs, and cranium. 
The appendicular muscles form the two most superficial layers 
and are the trapezius and latissimus dorsi; the levator scapulae 
and the rhomboids. For purposes of dissection the various 
muscles can be conveniently arranged in the following layers. 
Appendicular muscles. 1. Trapezius and latissimus dorsi. 
Make an incision through the deep fascia along the line of the 
first skin incision, raise the deep fascia over the whole extent of 
the trapezius muscle and turn this fascia as far as possible from 
within outward. Manipulate the arms so as to make the trape- 
zius muscle tense. As the fascia is raised, it may be necessary 
to alter the position of the limbs, depending on the direction of 
the fibers in the trapezius muscle. Observe its origin from the 
cranium and vertebral column, its relation to the latissimus dorsi 
and vertebral aponeurosis, its insertion into the clavicle and 
scapula, and its relation to the muscles on the dorsum of the 
13 scapula. Nerve supply from the spinal accessory (11th cranial) 
and third and fourth cervical nerves. 
Latissimus dorsi muscle. Note particularly the origin of 
this muscle from the vertebral column and the pelvis through 
the lumbo-dorsal fascia (vertebral aponeurosis), the direction of 
its fibers, its relation to the scapula and the lower border of the 
trapezius muscle, and its insertion into the humerus. The inser- 
tion of this muscle will be seen at a later dissection. Nerve sup- 
ply from the brachial plexus. 
2. Levator scapulae and rhomboideus minor and major. 
Make a vertical incision through the trapezius muscle about 
midway between the midline of the back and the vertebral bor- 
der of the scapula. The lower border of the trapezius muscle 
should be freed with the fingers from the parts beneath before 
making the incision, as the muscles are often so thin that the 
knife can easily cut two or more layers at once. Turn the two 
halves of the trapezius inward and outward to disclose the two 
rhomboid muscles and the lower end of the levator scapulae. 
The greater part of the latter muscle is in the neck and will ap- 
pear in a later dissection. Note the origin of the rhomboids from 
the spine and their insertion iruto the greater part of the vertebral 
border of the scapula. The levator scapula arises from the 
transverse processes of the upper cervical vertebrae and is in- 
serted into the vertebral border of the scapula above the rhom- 
boids. Nerve supply from the cervical and brachial plexuses. 
Axial muscles. Lumbo-dorsal fascia. This layer of fascia 
is especially well marked in the lower part of the back and con- 
sists of two layers in this region. The superficial layer is thick 
and tendinous, and is sometimes called the vertebral aponeurosis. 
It is attached below to the crest of the ilium and along the mid- 
line to the spinous processes of the vertebrae. Laterally it is 
attached along the angles of the ribs. It covers the dorsal axial 
muscles and gives origin in part to the latissimus dorsi and ser- 
ratus posticus inferior muscles. Traced towards the head the 
layer becomes thinner, being reduced to the thickness of ordinary 
deep fascia. It passes under the origin of the serratus posticus 
superior, over the splenitis, and is lost in the fascial coverings 
14 of the deep muscles of the neck. The deep layer extends from 
the crest of the ilium to the last rib and is attached medially to 
the tips of the lumbar transverse processes. These two layers 
enclose the dorsal axial muscles and are fused together along the 
outer border of the sacrospinalis muscle. Laterally from this 
line the lumbo-dorsal fascia gives origin to part of the ventral 
axial muscles. This important connection can be verified with 
the dissection of the abdominal muscles. 
3. Serratus posticus inferior; serratus posticus superior. 
To expose the serratus posticus inferior, make a vertical incision 
through the latissimus dorsi muscle approximately in line with 
the middle of the scapula. The incision should pass through the 
muscular fibers of this muscle and not through its aponeurotic 
origin. The serratus posticus inferior is attached to the last four 
ribs. Be careful not to include it in the incision through the latis- 
simus. The serratus posticus superior is concealed beneath the 
rhomboid muscles. Cut through the rhomboid muscles about 
three inches from their insertion into the vertebral border of the 
scapula. Do not cut the levator scapulae. Clear the under sur- 
face of the rhomboids with the fingers before making the cut. 
The serratus posticus superior is a very thin muscle attached to 
the lipper ribs, and tends to adhere to the deep side of the rhom- 
boids. The serrati muscles arise from the vertebral column and 
act on the upper and lower ribs. They are supplied by the ven- 
tral divisions of the thoracic nerves and belong to the group of 
muscles of respiration. 
4. Splenius and sacrospinalis muscles. The splenitis 
muscle lies beneath the lumbo-dorsal fascia in the upper thoracic 
and in the cervical region. It is partly covered by the serratus 
posticus superior and only the lower end of the muscle will ap- 
pear in this dissection. The splenius arises from the spinous 
processes of the upper thoracic vertebrae and here lies superficial 
to the upper part of the sacro-spinalis muscle. The upper part 
will be exposed in the dissection of the back of the neck. 
The sacrospinalis muscle (erector spinae) lies immediately 
beneath the superficial layer of the lumbo-dorsal fascia. The 
muscle arises from the ilium, sacrum, and lumbar spine and soon 
15 divides into three parallel columns which are in turn partly sub- 
divided. The muscle covers the spine from the spinous processes 
to the angles of the ribs, and forms a continuous muscular col- 
umn up to the skull. It is attached to all parts of the dorsal 
aspect of the spine and to the ribs as far as their angles, and ends 
at the temporal bone. 
1. Outer column 
Iliocostalis lumborum 
dorsi 
cervicis 
2. Middle column 
longissimus dorsi 
cervicis 
capitis 
3. Internal column 
spinalis dorsi 
cervicis 
The spinalis cervicis is usually very small or absent. What 
would correspond to a spinalis capitis portiop is included in the 
semispinalis (complexus) which belongs in the next layer. 
The main longitudinal columns can be differentiated without 
much trouble but the various subdivisions are more difficult to 
demonstrate, especially as the cervical part of the muscle mass 
cannot be dissected until the dissection of the lateral part of the 
neck has been finished. The dissector will have to be content 
to study the divisions of the muscle in the back and loins only. 
He should observe the passage of the dorsal vessels and nerves 
through the muscles, and these structures are often a good guide 
to the subdivisions. 
5. Transverso-spinalis. The muscles which lie beneath 
the sacrospinalis form a narrow muscular column which fills 
the groove between the spinous and transverse processes of the 
vertebrae. It is usually divided into three layers, the fibers of 
each arising from a transverse process below and ending in a 
spinous process above. The division into three layers is largely 
artificial, as the muscle really forms a continuous mass extend- 
ing from the sacrum to the occipital bone. The most superficial 
layer is the semispinalis and is divided into three parts similar 
to the longissimus. The semispinalis capitis (complexus) is the 
most striking part of the muscle. It begins in the upper thoracic 
region and forms a broad mass on either side of the spinous 
processes. As the splenitis turns laterally as it ascends, the 
complexus appears between the right and left splenius in the 
upper part of the neck. The second layer is the multifidus, and 
16 the deepest is that of the rotatores. The only distinction be- 
tween these three layers lies in the length of their fibers. Those 
of the semispinalis being the longest, those of the multifidus of 
medium length, and those of the rotatores being very short, pass- 
ing only from one vertebra to the next. 
In addition to the above, there are small muscles between 
each pair of transverse and spinous processes, called respectively 
the intertransversales and interspinales. Finally the levatores 
costarum are small respiratory muscles passing from a trans- 
verse process to the rib just below. The student will not be 
required to dissect any of the muscles beneath the sacrospinalis 
but should have a general idea of their arrangement as outlined 
above. 
Action of Muscles. The sacrospinalis and the deeper axial 
muscles maintain the erect position of the spine and bend the 
trunk backward or from side to side. The upward extention to 
the head and neck steady and support this part of the body and 
fix them in the upright position. If the muscles of both sides act 
together the head and spine are bent backward; if those of one 
side only act we get lateral bending or twisting of the spine to 
that side. The arrangement of many fiber bundles attached to 
all parts of the spine ensures an even and widely distributed 
action over all parts of the vertebral column. The dorsal axial 
muscles oppose and counterbalance the action of the ventral 
axial muscles, a point of some practical importance in paralysis 
of the trunk muscles. 
Spinal canal. The next stage in the dissection of the back 
will be the exposure of the contents of the spinal canal. The 
student should study carefully the dorsal view of the vertebrae 
throughout the entire back, paying particular attention to the 
position and relations of the spinous processes, the laminae, the 
transverse processes, and the ribs as far as their angles. The 
dorsal surface of the sacrum should be carefully studied and com- 
pared with the dorsal aspect of the vertebrae higher up. Note 
the curves of the spine and their varying depth from the surface 
in the midline. The sacrospinalis and the deeper muscles should 
be dissected roughly with the cartilage knife from the dorsal 
17 side of the spinous processes, laminae, and transverse processes. 
The laminae should be cut through with the saw close to the 
junction of the laminae and the transverse processes. This cut 
should extend from about the middle of the dorsal surface of 
the sacrum below to the upper part of the thoracic portion of 
the vertebral column above. When the two cuts have been made 
on either side, the spinous processes with a portion of the laminae 
can be lifted up like the lid from a long narrow box. 
Membranes of the spinal cord. Dura mater. The dura 
mater is the most external of the three coverings of the cord. 
It is a dense white membrane attached above to the edge of the 
foramen magnum, where it is continuous with the cranial dura. 
It forms a long tubular sac, which surrounds the cord, and is 
prolonged over the roots of each of the spinal nerves to become 
continuous with the sheath of that nerve. It supports the cord 
in the canal. The lower end of the dural sac lies at the level of 
the second or third sacral vertebra. The end of the sac is car- 
ried down in the form of a fibrous strand, the filum terminale 
externum, to the back of the coccyx. The dura can now be 
opened up, and the difference in the appearance of its outer and 
inner surfaces, the relations of the membrane to the nerve roots, 
and the lower end of the tube should be noted. 
Arachnoid and pia mater. These are the second and third 
coverings respectively. They are so thin that they appear to 
the naked eye as a very delicate membrane. The arachnoid lies 
next to the dura, being separated from it by the subdural space, 
a linear cleft containing a modified lymph. The arachnoid is 
made up of a very delicate spongy network in the meshes of 
which is the cerebro-spinal fluid which forms a sort of water 
jacket about the cord. The pia lies next to the cord and is a 
very vascular membrane. The vessels which supply the cord 
ramify in the pia before they enter the central nervous system 
and portions of the pia are prolonged into the cord on the vessels. 
The nerve roots are invested by these two membranes as far as 
the spinal ganglia. Beyond that point the nerve is covered by 
dura only. 
Spinal cord. The pia-archnoid should be carefully removed 
18 in order to expose clearly the dorsal surface of the cord and the 
dorsal or sensory nerve roots. The cord begins at the level of 
foramen magnum where it is continuous with the brain stem. It 
ends below by a narrow pointed end at the bottom of the first 
or the top of the second lumbar vertebra. Here there is a deli- 
cate fibrous prolongation, white and glistening, known as the 
filum terminale internum, which extends to the bottom of the 
spinal canal. There is a groove along the midline of the cord. 
This marks the posterior median septum, which partly subdivides 
the cord. More laterally is the postero-lateral groove into which 
the posterior or sensory nerve roots enter. By raising the cord 
or by cutting it transversely and lifting up the ends, the student 
can see the anterior median furrow and the antero-lateral groove 
from which the anterior or motor nerve roots emerge. The cord 
has two marked enlargements. The cervical enlargement is the 
more developed of the two and extends from the top of the cord 
to the second thoracic vertebra. The lumbar enlargement is 
not so well developed. It begins at the tenth thoracic vertebra 
and tapers off to the lower end of the cord. These enlargements 
give origin to the nerves which supply the limbs. The student 
should note particularly the position obliquity of the nerves 
as they pass from the cord to the intervertebral foramina. While 
the upper nerves are nearly horizontal, the lower become more 
and more oblique, until the lumbar and sacral nerves run straight 
down, forming a mass of nerve trunks known as the cauda 
equina. This obliquity is due to the difference in length between 
the cord and the spinal canal. As a result the level at which 
a given nerve leaves the cord does not correspond to the level 
at which it leaves the spinal canal. This is a matter of practical 
importance in lesions of the cord and of the peripheral nerves. 
The student will obtain a very interesting view of the contents 
of the spinal canal if directions are followed and all of the above 
details carefully studied. 
19 DISSECTION OF THE PECTORAL AND ABDOMINAL 
REGIONS 
Skeleton. The axial skeleton of the anterior aspect of the 
trunk is formed by the sternum, the anterior ends of the ribs, 
and the costal cartilages. In addition to the axial skeleton, parts 
of the shoulder and pelvic girdles are found on the anterior as- 
pect of the trunk. Above, the clavicle extends from the top of 
the sternum to the acromion process of the scapula at the apex of 
the shoulder, and just below the outer third of the clavicle is 
found the coracoid process of the scapula. Below, the two pubic 
portions of the innominate bones are joined together in the 
midline (just above the penis) by the pubic symphysis, and the 
pubic crest and spine lie lateral to this joint. Above the level of 
the pubis and still more lateral, will be found the anterior su- 
perior spine of the ilium and part of the iliac crests. 
Sternum. The sternum, or breast bone, occupies a very su- 
perficial position in the center of the anterior thoracic wall. It 
supports the clavicles above and the first seven ribs on either 
side. It has three parts. The manubrium forms the upper por- 
tion of the sternum and is its broadest part. On its upper border 
are the two articular surfaces for the sternoclavicular joints. 
This is the only joint between the axial skeleton and the shoul- 
der girdle. Between the joints is the interclavicular notch. On 
either side, just below the joint, is the point of attachment of 
the cartilage of the first rib. The lower border of the manu- 
brium is joined to the top of the body of the sternum by fibro- 
cartilage. This joint makes a rather prominent ridge beneath 
the skin and is a landmark of some importance, as the cartilage 
of the second rib articulates with the sternum at this point. 
The body forms roughly about two-thirds of the sternum 
and consists of four pieces, which develop as separate bones but 
are fused into one piece by the twentieth year. The anterior 
surface has three transverse ridges, which mark the original sep- 
arate pieces. At the end of these ridges are small oval facets 
for the cartilages of the third, fourth, and fifth ribs. The carti- 
20 lage of the seventh rib articulates with the side of the last piece 
of the body and base of the xiphoid cartilage. 
The third piece of the sternum is the xiphoid cartilage, a 
small spatula-shaped piece of cartilage, which is thinner than 
the sternum and lies on a level with the posterior surface 
of the bone. In this way there is formed the infrasternal depres- 
sion at the lower end of the body of the sternum. The xiphoid 
becomes more or less ossified with advancing years. The 
sternum gives origin anteriorly on either side to the pectoralis 
major muscles. At the upper part of the manubrium are the 
insertions of the sternomastoid. sternohyoid, and sternothyroid 
muscles. On the xyphoid is part of the insertion of the rectus 
abdominus muscle. (The transversus thoracis is attached to the 
deep surface of the sternum and costal cartilages.) The sternum 
is subcutaneous and is readily palpated. Its superficial surface 
is rough, its deep surface is smooth. The whole bone is some- 
what convex anteriorly and slopes downwards and forwards to 
give greater room in the thoracic cavity. 
Ribs. The ribs, twelve in number on each side, constitute 
a series of curved elastic bones which form the greater part of 
the wall of the thorax. They articulate posteriorly with the 
thoracic vertebrae and terminate anteriorly in the costal carti- 
lages. The first seven pair articulate with the sternum. The 
eighth, ninth, and tenth pair of cartilages are articulated with 
each other and do not reach the sternum. The eleventh and 
twelfth pair are the smallest and least developed of the ribs, and 
end in free cartilage tips. These are known as the floating ribs. 
Each rib consists of a head, neck, tubercle and shaft. The 
head carries two articular facets divided by a ridge on its pos- 
terior aspect. These articulate with two vertebrae and the in- 
tervening disk. The neck is somewhat constricted and rough- 
ened posteriorly, where it is attached by ligaments to the trans- 
verse process of the lower of the two vertebrae with which it 
is associated. At the end of the neck is the tubercle, a small 
elevation, which carries the articular surface for articulation 
with the facet on the transverse process. By means of these two 
joints, the costocentral and the costotransverse, the ribs are 
21 firmly supported on the vertebral column and are elevated or 
depressed in respiration. Beyond the tubercle, the shaft of the 
rib runs outward and backward to the angle, which is flush with 
the tips of the spinous processes. This not only gives the neces- 
sary flatness to the back, but also increases the space in the 
posterior part of the thoracic cavity needed for the lungs. At the 
angle the shaft makes a sudden change in direction. It now runs 
forward and downward and is somewhat bent on itself, so that 
its lower border is slightly tilted outwards and its outer surface 
looks outward and upward. This eversion of the lower border 
of the shaft is important as it increases the transverse diameter 
of the thorax between each pair of ribs, and gives additional 
room for the lungs, especially during respiration. At the ex- 
treme anterior end, the shaft is turned a little upwards. The 
vertebral end of the rib is always higher than the sternal end. 
The curves and twist of the ribs are complicated, but are of great 
practical importance in their movements during respiration. 
The first rib differs in some respects from the typical rib 
just described. It is short, more horizontal, and the tubercle 
and angle correspond in position. On its superior surface there 
are two grooves divided by a small facet, which marks the inser- 
tion of the scalenus anticus muscle. This muscle arises from the 
transverse processes of the cervical vertebrae and helps to ele- 
vate the ribs. The groove in front of the muscle is for the sub- 
clavian vein; that behind for the subclavian artery. These two 
vessels arch over the first rib as they leave the thorax on their 
way to the axilla. The second rib is a little longer, the tubercle 
and the angle are now separated, and the shaft begins to be a 
bit curved and twisted. The third rib shows all the typical rib 
characteristics. These increase with the length of the rib to the 
eighth. From that point on, the ribs become shorter, their char- 
acteristics less and less marked, and their articulation with the 
transverse process less complete. The twelfth rib is the shortest 
and most rudimentary of the whole series. The greatest bulk 
of the lung is found in relation to the third to eighth pair of 
ribs. Here we need the greatest space in the thorax and the 
greatest extent of motion in the ribs during respiration. The 
22 apex and the lower borders of the lung recpiire less room as 
expansion is less extensive here. Hence the upper and lower 
ribs, which are in relation to these portions of the lungs, are 
short and do not move much in respiration. 
Superficial anatomy. Identify and palpate the following 
bony landmarks. Clavicle: the sternal and acromial ends, the 
position and curves of the shaft. Scapula: the coracoid and ac- 
romial processes and their relation to the outer end of the clav- 
icle. Sternum: the suprasternal notch and sternoclavicular artic- 
ulation, the ridge between the manubrium and body and its re- 
lation to the second pair of costal cartilages, the body of the 
sternum and the xiphoid cartilage and their relation to the ster- 
nal ribs. Ribs and costal cartilages: count the ribs from above 
downward noting the direction of the shafts and the size of the 
intercostal spaces. Innominate bone. Pubes: the pubic symphy- 
sis, crest and spine. Ilium: the anterior superior spine and the 
iliac crest. 
Note the supra and infra clavicular fossae; the anterior fold 
of the armpit of axilla and its relation to the pectoralis major 
muscle. Study the position of the nipple, areola, and mammary 
gland, especially as regards the intercostal spaces. Observe the 
linea alba, the linea semilunaris and their relation to the recti 
muscles; also the position of the umbilicus in the linea alba be- 
tween the sternum and pubes. Identify Poupart's (inguinal) 
ligament between the anterior superior spine of the ilium and 
the spine of the pubis; the position of the external abdominal 
ring and its relation to the pubic spine; the fold formed by the 
spermatic cord passing from the external abdominal ring to the 
scrotum. 
Preparation for incisions. Before making any incision in 
the skin it will be necessary to distend the abdominal wall with 
air to make the muscle layers tense. Make a circular incision 
through the skin around the periphery of the umbilicus. Make 
a tiny puncture in the center of the umbilicus into the abdominal 
cavity large enough to admit the tip of the blow pipe. Care 
should be taken to keep this puncture as small as possible. Tie 
a piece of string around the umbilicus and then distend the ab- 
23 dominal wall as much as possible. The blow pipe can then be 
withdrawn and the ligature around the umbilicus tied securely. 
Take particular pains to distend fully the abdominal wall, as it 
will greatly facilitate dissection of the muscles. Avoid leaning 
or pressing on the wall after it is distended. 
Incisions. 1. From the suprasternal notch above to the 
symphysis pubis below, passing just to the left of the umbilicus. 
2. From the suprasternal notch outward along the clavicle 
to the acromion process and then downwards for about three 
inches over the front of the shoulder. 
3. From the tip of the ensiform horizontally outward for 
about six inches. 
4. From the lower end of incision number 1 obliquely 
upward and outward to the anterior superior spine and along 
the iliac crest for three or four inches. A circular cut can be 
made in the upper flap around the areola and nipple as the flap 
is being reflected. 
Superficial fascia. In the thoracic region note the thickness 
and amount of fat in the superficial fascia and especially the re- 
lations of this fascia to the mammary gland. The mammary 
gland in both sexes is actually imbedded in the superficial fascia. 
The cutaneous or superficial vessels and nerves are found in 
the deeper stratum of the superficial fascia. In the abdominal 
wall the thickness and amount of fat in the superficial fascia is 
usually greater than in the pectoral region, especially in stout 
subjects. The fascia is thicker in the region of the groin and 
along Poupart's ligament where it can usually be subdivided into 
two fairly distinct layers. In the midline it forms a thick mass, 
the so-called suspensory ligament of the penis. 
Cutaneous vessels and nerves. The chief cutaneous vein in 
the pectoral region is the cephalic vein passing upward from 
the arm. It is relatively deeply placed in the furrow between 
the pectoralis major and the deltoid muscles. The other super- 
ficial veins of the pectoral region drain toward the armpit but 
can be disregarded in this dissection. The cutaneous arteries 
are small and are branches of the intercostal and internal mam- 
mary arteries. They are found chiefly in the intercostal spaces 
24 near the margin of the sternum. In the abdomen the superficial 
veins are best marked towards the groin where they pass across 
Poupart's ligament to enter the femoral vein in the thigh. With 
them are usually found several small cutaneous arteries, the su- 
perficial epigastric, pudic, and circumflex iliac arteries. These 
are derived from the femoral artery of the thigh and supply the 
lower portion of the abdominal wall. 
The cutaneous nerves of the upper part of the pectoral re- 
gion are derived from branches of the cervical plexus which pass 
down from the neck and supply the skin just below the clavicle. 
These nerves will be found again later in the dissection of the 
neck. Over the anterior and lateral aspect of the thoracic and 
abdominal walls the terminal branches of the ventral divisions of 
the intercostal or thoracic nerves supply the skin. The lateral 
branches of the ventral divisions emerge along the side of the 
trunk. The terminal branches of the ventral divisions appear in 
the fascia near the midline. In the thoracic region the branches 
emerge from the intercostal spaces near the sternum and repre- 
sent the terminations of the first six thoracic nerves. In the 
abdominal wall are found the terminal branches of the lower six 
intercostal nerves, which come through the musculature in ir- 
regular branches a short distance from either side of the mid- 
line. Just above the pubis the terminal branches of the first 
lumbar nerve complete the cutaneous supply to the belly wall. 
The cutaneous vessels accompany all these nerves. Before re- 
moving the superficial fascia the student should endeavor to se- 
cure the above mentioned nerves. Having secured them, the su- 
perficial fascia can then be removed more or less in one layer 
by means of the same incisions as were used for the skin. 
Deep fascia. The deep fascia over the pectoral region is a 
typical, thin, cobwebby layer of fascia investing the pectoralis 
major muscle. In the abdominal wall it is a little thicker and 
here invests the external oblique muscle and its aponeurosis. 
The fascia over the abdominal wall is more adherent to the apo- 
neurotic fibers than to the muscle fibers. In the pectoral region, 
cut through the deep fascia along the line of the clavicle and 
turn the fascia downward and outward following the fibers of 
25 the pectoralis major muscle. The fascia should be reflected only 
as far as the outer border of this muscle. Over the abdominal 
wall the incision should be made through the deep fascia along 
the upper border of the external oblique muscle and the layer 
can then be turned downwards and outwards, following the line 
of the fibers of the muscle. The fascia should be cleaned from 
the aponeurosis as well as from the muscle fibers. 
Muscles. The anterior thoracic wall or pectoral region is 
covered, as was the case of the back, by two layers of appendicu- 
lar muscles which act on the shoulder girdle and the humerus. 
These muscles arise from the superficial surface of the ribs and 
sternum and from the anterior surface of the clavicle. The 
first layer is composed of the pectoralis major and the del- 
toid ; the second layer of the pectoralis minor, the subclavius, 
and the serratus anterior. The latter muscle lies chiefly on the 
lateral aspect of the thorax and will be seen in the dissection of 
the axilla. The axial muscles of this region are; the two in- 
tercostal muscles, the external and the internal, which occupy 
the intercostal spaces and lie between the ribs, and the trans- 
versus thoracis and the diaphragm, which lie on the deep surface 
of the ribs and sternum. 
The abdominal wall is formed laterally by the muscular 
portions of three broad flat muscles, the external and internal 
oblique and the transversalis. Anteriorly the wall is formed 
by the aponeuroses of these muscles and by the rectus muscles, 
which lie on either side of the midline. On the deep aspect of 
these muscles is found a layer of fascia, the transversalis fascia 
which separates the muscles from the parietal peritoneum of 
the abdominal cavity. The fibers of the two obliques and of the 
transversalis muscles run in different directions to give greater 
strength to the abdominal wall. Those of the external oblique 
are directed downwards and inwards, those of the internal 
oblique upwards and inwards, and those of the transversalis 
horizontally. The aponeuroses represent the tendons of inser- 
tion of the greater part of these muscles. They begin laterally 
at the linea semilunaris along the outer border of the rectus 
muscle, form a sheath surrounding the rectus, and meet again 
26 in the midline along the linea alba. Above the aponeuroses are 
attached to the ribs and sternum, and below partly to the pubes. 
Here their attachments are more complicated and will be con- 
sidered in detail as the dissection progresses. The dissection of 
the thoracic and abdominal walls will be done at the same time. 
Pectoral region. Pectoralis major and deltoid muscles. 
Study and identify the origin of the pectoralis major from the 
sternum, ribs, and clavicle, its insertion into the humerus, and 
the direction of the fibers especially at the outer border. Clean 
the deep fascia from this muscle, keeping the knife as nearly 
as possible parallel to the muscle fibers. Note the relation of 
the deltoid to the pectoralis major, and secure the cephalic vein 
in the groove between the two muscles before cleaning off the 
deep fascia. The anterior border of the deltoid should be cleaned 
at this time over an area about one and one-half inches wide. 
This muscle will be fully dissected later with the back of the 
shoulder, but its origin from the clavicle and the scapula and its 
insertion into the humerus should be noted at this time. To ex- 
pose the parts beneath the pectoralis major, divide that muscle 
by a vertical incision from the middle of the clavicle to the lower 
border of the muscle. Make the incision with caution until the 
layer of fascia on the deep side of the muscle comes into view. 
The two parts of this muscle may now be turned outward and 
inward to expose the fascia and pectoralis minor lying beneath. 
In reflecting the two parts of the pectoralis major, note the ves- 
sels and the .nerves entering its deep surface and avoid cutting 
them if possible. These are branches from the axillary artery 
and brachial plexus of nerves. 
Pectoralis minor and subclavius. The pectoralis minor 
arises from the second to the fifth ribs, and is inserted into the 
coracoid process of the scapula. Its upper border lies a little 
below the clavicle, the interval between the two being filled by 
the costocoracoid membrane. T he two pectoral muscles are 
supplied by the external and internal anterior thoracic nerves 
from the brachial plexus. The subclavius muscle is a narrow 
rounded muscle which passes from the first rib to the under 
surface of the clavicle. It is surrounded by the costocoracoid 
27 membrane and is supplied by a small nerve from the brachial 
plexus. 
Costocoracoid membrane. The costocoracoid membrane is 
a well marked layer of fascia which is attached above along the 
under side of the clavicle. Here it splits to inclose the subclavius 
muscle. The membrane passes downward to the upper border of 
the pectoralis minor muscle and splits to inclose this muscle. 
At the lower border of the pectoralis minor the fascia again 
unites. The deep fascia over the pectoralis major muscle turns 
around the outer border of that muscle and then passes over the 
armpit as the axillary fascia. The prolongation of the costo- 
coracoid membrane, which incloses the pectoralis minor muscle, 
fuses with this axillary fascia just below the lower border of that 
muscle. This arrangement will be seen later when the axilla is 
opened. At the present time the axilla must not be disturbed 
and the dissector should on no account cut into the costocora- 
coid membrane above the pectoralis minor muscle, but merely 
clean the fascia from the anterior aspect of that muscle. 
Vessels and nerves. The cephalic vein from the arm, the 
acromiothoracic artery from the axillary artery, and the external 
anterior thoracic nerve pierce the costocoracoid membrane just 
above the upper border of the pectoralis minor. The internal 
anterior thoracic nerve pierces the pectoralis minor and supplies 
that muscle. Both nerves supply the pectoralis major and must 
not be confused with the intercostal (thoracic) nerves. The ac- 
romiothoracic artery is distributed chiefly to the pectoral muscles 
and to the deltoid. The long thoracic artery, a branch of the axil- 
lary, runs along the lower border of the pectoralis minor muscle, 
but will be exposed later when the axilla is opened. 
Intercostal muscles. The fibers of the external intercostal 
muscle run downward from the lower border of a rib to the upper 
border of the rib below. The muscle begins posteriorly at the 
tubercle of the rib. Anteriorly it does not extend beyond the 
costochondral junction, but is prolonged by the anterior inter- 
costal membrane to the sternum. The fibers of the internal in- 
tercostal muscle run downwards and backwards from the deep 
surface of a rib above the subcostal groove to the upper border of 
28 the rib below. This muscle begins at the sternum and ends 
near the angles of the ribs; from here it is prolonged by the 
posterior intercostal membrane to the end of the space. The 
subcostal muscles are found over the internal surface of the 
lower ribs near their angles. They are slight muscular slips 
which pass over two or more ribs and lie in series with the in- 
ternal intercostal muscles. The intercostal muscles act on the 
ribs, are muscles of respiration, and are supplied by the ventral 
divisions of the thoracic (intercostal) nerves. The student should 
clean the external intercostal muscles in the second to the fifth 
spaces as far lateral as is convenient. He should then remove 
the anterior intercostal membranes in these spaces to expose the 
interchondral part of the internal intercostal muscles. The ex- 
ternal muscles can then be removed and the internal muscles and 
the vessels and nerves dissected. 
Intercostal vessels and nerves. The intercostal vessels and 
nerves lie in the intercostal spaces between the two intercostal 
muscles and follow the general direction of the ribs. The upper 
six, therefore, are directed towards the anterior aspect of the 
thorax where they end in the skin. The lower six, owing to 
the increased obliquity of the ribs, are directed downwards and 
forwards towards the anterior abdominal wall. These nerves 
leave the anterior end of their intercostal spaces and must run 
between the internal oblique and the transversalis muscles. 
They can be traced to the outer edge of the rectus muscle where 
they enter the rectus sheath. 
The intercostal vessels and nerves lie under cover of the 
lower border of the rib above and are difficult to reach. In ad- 
dition to the inte: stal arteries, which are branches of the aorta, 
there is the inter; mammary artery, a branch of the subclavian, 
which sends vess to the anterior part of each intercostal space, 
and to the skin ith the terminal branches of the intercostal 
nerves. This vc el lies parallel to and on either side of the 
sternum under cc r of the costal cartilages. After the dissector 
has finished the tercostal spaces, he should cut through the 
third, fourth and fth costal cartilages with the cartilage knife 
close to the stern n and then remove about one inch from their 
29 anterior ends. The cut must be made with great care in order to 
avoid injury to the pleura which lies just beneath the cartilages. 
It is advisable to clean out the remains of the internal intercostal 
muscles near the sternum, expose the internal mammary artery 
in the space, and then endeavor to free the deep surface of the 
cartilage from the underlying artery and pleura before making 
the cuts. The origin and relations of the various vessels and 
nerves in the intercostal spaces should be carefully studied. 
Abdominal region. External oblique muscle. The pecto- 
ralis major should not be cut until the external oblique has been 
cleaned so that the students can get an idea of the superficial 
musculature of the whole anterior aspect of the trunk. The fibers 
of the external oblique muscle arise from the outer surface of 
the eight lower ribs in the same plane with the pectoralis and ser- 
ratus anterior muscles. The fibers interdigitate with those of 
the serratus and lower down to a more limited extent with the 
fibers of the latissimus dorsi, but the larger portion is attached 
to its own aponeurosis. The aponeurosis of this muscle is con- 
nected above with the origin of the pectoralis major. Below it 
has a distinct border which extends from the anterior superior 
spine of the ilium to the spine of the pubis. This lower border is 
known as Poupart's (inguinal) ligament. To it are attached por- 
tions of the internal oblique and transversalis muscles and the 
transversalis fascia of the abdominal wall and portions of the 
fasciae of the thigh. From the inner end of this ligament at its 
point of insertion into the pubic spine, fibers arise which are at- 
tached for about three-quarters of an inch along the iliopectineal 
line of the pubic bone. These form a small flat triangular layer 
which is known as Gimbernat's ligament (lacunar). This liga- 
ment will appear later in the dissection of the inguinal canal. 
External abdominal ring. (Subcutaneous inguinal ring). 
There is a triangular-shaped split in the fibers of the aponeurosis 
of the external oblique, which begins at the spine of the pubis 
and extends outward above Poupart's ligament for about three- 
quarters of an inch. This is known as the external abdominal 
ring or subcutaneous inguinal ring. It is a region of much prac- 
tical importance in the anatomy and surgery of inguinal hernia. 
30 A special set of fibers in the aponeurosis, the intercolumnar or 
intercrural fibers, arch over the outer order of the ring. In the 
male a rounded cord-like mass of tissue, the spermatic cord, 
emerges from the opening and runs down into the scrotum. The 
margins of the ring and the cord are obscured by a delicate layer 
of fascia, external spermatic or intercrural fascia. This fascia 
arises from the margins of the ring and forms the most super- 
ficial covering to the cord and testes. It must not be touched 
at present and will be removed later in the dissection of the in- 
guinal canal. If the superficial and deep fasciae are reflected 
carefully, the cord and the ring with this tissue covering them 
will be left intact for a later dissection. The position and mar- 
gins of the ring can, however, be palpated with the finger-tip. 
In the female a small indistinct ligament with some fat is found 
at the external ring. This is the round ligament of the uterus 
and will be considered later in the dissection of the inguinal 
canal. 
Internal oblique muscle. To reflect the external oblique, 
a vertical incision should be made through the muscle fibers 
downward to the iliac crest passing just anterior to the tip of 
the eleventh rib. A second incision should then be made from 
the anterior superior spine horizontally inward to the linea semi- 
lunaris to a point about three inches above the pubic symphysis. 
A third incision may be made at the upper end of the first inci- 
sion horizontally inward to the linea semilunaris and the muscle 
raised and turned inward along this line. The aponeurosis can 
be separated from that of the internal oblique for a short distance 
medial to the linea semilunaris. At that point, however, its fibers 
fuse with those of the internal oblique and cannot be separated 
further. The origin of the internal oblique from the crest of 
the ilium can be seen, but its origin from Poupart's ligament 
will be concealed by the lower part of the external oblique that 
is still in situ. The fibers of the internal oblique pass to its 
aponeurosis and to the lower borders of the last four ribs. It 
should be noted that this muscle lies in the same plane with 
the intercostal muscles. After this muscle has been cleaned, 
it can be reflected by the same incisions and in the same direc- 
31 tion as the external oblique. The deep surface of the internal 
oblique should be cleaned with care to avoid injury to the lower 
intercostal and first lumbar nerves which lie between the in- 
ternal oblique and the transversalis muscles. The second inci- 
sion which passes vertically through the internal oblique will be 
practically at right angles with the trunks of these nerves and 
should be made with great caution, as the nerves tend to adhere 
rather to the deep side of the internal oblique than to the super- 
ficial side of the transversalis muscle. 
Transversalis muscle. This muscle arises from Poupart's 
ligament and the iliac crest and is inserted into its aponeurosis 
and also into the deep aspect of the last six ribs. This muscle, 
therefore, lies in the same plane with the diaphragm and trans- 
versus thoracis. The intercostal nerves must be carefully dis- 
sected out of the fascia over the muscle. In searching for 
them, carry the knife horizontally through the tissues. After 
each nerve has been secured and dissected as far as the outer 
border of the rectus sheath, the muscle itself should be cleaned. 
Branches of the intercostal and lumbar arteries may be observed 
with the nerves. A fairly constant branch from the deep cir- 
cumflex iliac artery will be seen running vertically upward over 
the lower part of the muscle. 
The rectus muscle and its sheath remain to be exposed. 
When the rectus sheath is opened, the tissues of the lower ab- 
dominal wall tend to collapse and therefore this dissection should 
be put off until the dissection of the inguinal canal and genitalia 
has been completed. 
Dissection of the inguinal canal and external genitalia. In 
making this dissection, the student should pay particular atten- 
tion to the position and relation of the inguinal canal, the in- 
guinal rings, and the spermatic cord to the layers of the ab- 
dominal wall and to Poupart's ligament. 
External oblique. Note carefully the following points: Re- 
lation of Poupart's ligament (inguinal ligament) to the lower 
border of the aponeurosis of the external oblique and the bony 
attachments of this ligament; the external abdominal (inguinal) 
ring, and its relation to Poupart's ligament and to the spine 
32 of the pubis. Observe how the spermatic cord emerges from 
the aponeurosis of this muscle through an opening which is 
obscured by a delicate layer of fascia prolonged downward along 
the cord. Clear this external spermatic fascia with the point of 
the knife from the cord and expose the edges of the opening. 
Note the position of the margins or pillars of the opening, its 
shape, and the position of the intercolumnar fibers in the apo- 
neurosis of the external oblique. In clearing the external sper- 
matic fascia from the cord and margins of the external ring, look 
out for the ilio-inguinal nerve. This nerve usually emerges from 
the ring lying along the posterolateral aspect of the cord and 
follows the cord to the scrotum, where it supplies the skin. Oc- 
casionally the nerve pierces the internal pillar of the ring. 
In the female the external ring is smaller and the superficial 
end of the round ligament is rather ill-defined and difficult to 
follow as it emerges from the opening. It spreads out in fine 
strands which are attached to the subcutaneous tissues in the 
pubic region. It is often obscured by a small mass of fat at the 
external ring. 
Reflection of the external oblique. To reflect the remains 
of this muscle and expose the deeper parts of the inguinal canal, 
make the following incisions. Continue the incision along the 
upper border of the external oblique downwards and inwards 
to about the middle line. The inner end of this cut should pass 
not less than one inch above the inner pillar of the external ring, 
and great care should be taken to avoid tearing this inner pillar, 
especially in fat subjects. Turn the external oblique downward 
and outward using Poupart's ligament as a hinge. The fibers 
near the anterior superior spine can be freed sufficiently to per- 
mit this. 
Internal oblique. Observe the origin of the lower fibers of 
this muscle from the outer half of Poupart's ligament and how 
the lowest fibers of all arch inward and downward to terminate 
the so-called conjoined tendon posterior to the spine of the pubis, 
The relation of the lower border of this muscle to Poupart's 
ligament and the spermatic cord should be carefully studied. 
Conjoined tendon (inguinal aponeurotic falx). Its formation, 
33 insertion into the pubis, and relation to the external ring and 
spermatic cord are of great importance. In this connection ob- 
serve if possible and study Gimbernat's (lacunar) ligament. The 
reflex inguinal ligament is a poorly developed band of fibers, 
which extends over the medial end of the conjoined tendon im- 
mediately beneath the medial margin of the external ring. They 
are rarely seen in a dissection. 
Cremasteric fascia and cremaster muscle. The delicate 
muscle bundles of this muscle may be seen in the thin layer of 
cremasteric fascia passing in the form of loops from Poupart's 
ligament and the lower border of the internal oblique to the 
spermatic cord. This layer is the second covering of the cord 
and lies immediately beneath the external spermatic fascia. 
Enough of the cremasteric fibers and fascia can be removed to 
expose the cord and lower border of the internal oblique. In 
cleaning the deep fascia off the internal oblique look out for 
the ilio-inguinal nerve, which pierces the muscular fibers of 
this muscle before reaching the external abdominal ring. 
Reflection of the internal oblique. Take hold of the cut up- 
per border of this muscle near the anterior superior spine and 
separate it carefully from the transversalis muscle. The internal 
oblique can then be cut from the crest of the ilium and from 
Poupart's ligament and turned up and in. It is important to 
establish definitely the plane of separation between this muscle 
and the transversalis to avoid injury to the lower border of the 
latter when the internal oblique is detached from Poupart's liga- 
ment. 
Transversalis muscle. Observe that the fibers of the trans- 
versalis muscle rise to a less extent from Poupart's ligament 
than was the case with the similar fibers of the internal oblique. 
Follow the lower fibers of this muscle and compare them with 
those of the internal oblique in relation to Poupart's ligament, 
the spermatic cord, and in the formation of the conjoined tendon. 
Observe that below the lowest fibers of the internal oblique, and 
to a still greater extent below those of the transversalis muscle, 
there is a gap in the abdominal wall extending down to Poupart's 
ligament. This gap or weak area is filled up by a layer of fascia, 
34 the transversalis fascia. Note the attachment of this fascia be- 
low to Poupart's ligament and the relation of the spermatic cord 
to it. 
Internal abdominal (inguinal) ring. By making slight trac- 
tion on the spermatic cord, the point where the cord emerges 
from the transversalis fascia will be emphasized. This is the 
position of the internal abdominal ring which is obscured by a 
prolongation from the transversalis fascia known as the infundi- 
buliform or internal spermatic fascia. This extends downward 
over the cord, and forms its third or deepest covering. Note 
carefully the position of the internal ring with reference to the 
transversalis fascia, the lower border of the transversalis muscle, 
Poupart's ligament, and the anterior superior spine of the ilium 
and the spine of the pubes. 
Deep epigastric artery. In a well injected subject this ves- 
sel can be felt through the transversalis fascia on the internal 
border of the internal abdominal ring. This artery lies along 
the medial border of the internal ring between the transversalis 
fascia and the peritoneum. It passes upward and inward to the 
rectus sheath. With careful dissection it can be exposed in this 
fascia. Note particularly its relation to the ring and to the sper- 
matic cord. In exposing this vessel be careful not to cut the 
peritoneum which is the last layer of the abdominal wall im- 
mediately beneath the transversalis fascia. A little fat occa- 
sionally intervenes between the two layers. 
Deep circumflex iliac artery. This vessel can probably be 
seen beneath the transversalis fascia following the course of 
Poupart's ligament towards the iliac crest. These two vessels 
are branches of the external iliac artery. 
The triangular space between the deep epigastric artery 
laterally, the outer border of the rectus muscle medially, and 
Poupart's ligament below is known as Hesselbach's Triangle. 
Hesselbach's (interfoveolar) ligament is the name given to a 
rather ill-defined layer of tissue which runs down from the lower 
border of the transversalis muscle in front of the deep epigastric 
artery to the pubic bone. It tends to reinforce the inner border 
of the internal ring. 
35 Inguinal canal. Replace the internal oblique and external 
oblique muscles and study carefully the boundaries of the in- 
guinal canal. The aponeurosis of the external oblique forms the 
entire anterior wall of the canal while the muscle fibers of the 
internal oblique appear in the outer third of the anterior wall 
only. The posterior wall of the canal is formed from within 
outward by the conjoined tendon and secondly by the trans- 
versalis fascia. The inferior limit of the canal is formed by the 
fusion of the layers in the anterior and posterior walls with Pou- 
part's ligament. The arched lower borders of the internal oblique 
and transversalis muscles may be regarded as the upper limit. 
The boundaries and relations of the various layers of the ab- 
dominal wall to the canal and spermatic cord are of practical 
importance in the anatomy and surgery of inguinal hernia and 
should be studied with reference to this condition. 
Coverings of the Spermatic Cord. There are three cover- 
ings of the spermatic cord. The most superficial is the external 
spermatic fascia derived from the aponeurosis of the external 
oblique. The second is the cremasteric fascia and muscle from 
the lower border of the internal oblique and transversalis 
muscles. The third or deepest is the infundibuliform or internal 
spermatic fascia, derived from the transversalis fascia. While 
these three layers can be regarded as separate layers develop- 
mentally. they form really one fascial investment to the cord 
and their separation is not as a rule practicable or necessary. 
These layers are carried down into the scrotum where they en- 
close the spermatic cord and the testicle. 
Inguinal Canal in the female. All structures mentioned in 
the male are to be found in the female inguinal region except the 
spermatic cord whose place is taken by the round ligament of 
the uterus. The layers of fascia and the cremasteric fibers are, 
however, poorly developed. The round ligament is larger inside 
the canal and should be followed to the internal ring. 
Rectus muscle. This muscle can now be exposed by a verti- 
cal incision along the middle of the sheath and the two flaps 
turned inward and outward. Note how the sheath separates 
readily from the muscle- fibers, but with difficulty from the 
36 tendinous interceptions in the muscle. The origin and inser- 
tions of this muscle and the number and position of the inter- 
ceptions should be carefully studied. Note that along its medial 
margin the rectus derives fibers of origin from the linea alba. 
The outer border of the muscle can then be raised and the nerves 
which were left at the outer border followed inward beneath 
it into the sheath. Observe the position and relations of the deep 
and superior epigastric arteries on the deep surface of the muscle. 
The muscle can then be divided transversely in the middle and 
turned up and down to expose the dorsal wall of the sheath. The 
difference in thickness between the upper and lower parts of the 
posterior wall should be noted and the formation of the sheath 
by the aponeuroses of the three abdominal muscles and by the 
transversalis fascia carefully studied. 
In the upper three-fourths of the rectus the aponeuroses of 
the abdominal muscles divide so that there is aponeurosis in both 
the anterior and posterior walls of the sheath. In the lower 
fourth, all three aponeuroses pass in front of the rectus, and the 
posterior wall is composed of the transversalis fascia and peri- 
toneum only. It is consequently very thin in this area, and the 
line of demarcation between the thick and thin parts of the pos- 
terior wall of the sheath is usually shown by a fold, the semilunar 
fold of Douglas. Before leaving the abdominal wall the impor- 
tant connections between the dorsal and ventral axial muscles 
by means of the lumbodorsal fascia should be studied. The 
posterior border of the external oblique is free and lies against 
or overlaps the anterior edge of the latissimus dorsi. It, there- 
fore, is not directly connected with the lumbodorsal fascia. The 
posterior border of the internal oblique and of the transversalis 
muscles are directly connected with and arise from this fascia 
between the crest of the ilium below and the last rib above. 
37 ACTION OF THE ABDOMINAL MUSCLES 
The abdominal muscles compress the abdominal walls and 
the viscera, especially when the diaphragm is fixed by the closure 
of the glottis (holding the breath and straining). They act thus 
in vomiting and in the expulsion of urine, faeces, or the foetus. 
They oppose the elevation of the ribs, and by contracting on the 
abdominal contents and forcing the diaphragm up into the thor- 
ax, act as muscles of expiration. They act as flexors of the 
spine and antagonize the dorsal spinal muscles. These act to 
prevent the trunk from falling forward; the abdominal muscles 
prevent it from falling backward. The abdominal muscles from 
below act on the thorax, and, through the scaleni above, on the 
upper part of the spine. They bend the body forward when the 
muscles of both sides act together, or laterally when those of 
one side act alone. Combined action of the muscles of the ab- 
domen and of the back on one side or the other produce various 
degrees of rotation and twisting of the trunk. The abdominal 
muscles may act on the pelvis, if the thorax is fixed by the ex- 
tensors of the spine, and raise it as in climbing or in raising the 
lower limbs. The iliopsoas, when the legs are fixed, acts as a 
flexor of the lower part of the spine. 
Spermatic cord. That portion of the spermatic cord occu- 
pying the inguinal canal should next be dissected. Before re- 
moving the fascial coverings of the cord, palpate and identify 
the vas deferens which can be distinguished by its hard cord- 
like feeling. Trace this with the fingers beneath the skin of the 
scrotum down to the testicle. The constituent parts of the sper- 
matic cord are : the vas deferens; the spermatic artery, cremas- 
teric artery, artery to vas deferens; the plexus of the spermatic 
veins concentrating to the single or double spermatic vein near 
the internal ring, and small branches of the genito-crural (lumbo- 
inguinal) nerve. All these structures are covered by the layers 
of fascia mentioned above. Having identified as far as possible 
the above parts between the internal and external abdominal 
rings, the dissector should next begin the dissection of the scro- 
tum and the testicle. 
38 Scrotum and testes. Make an incision from the external 
ring downward along the side of the scrotum. Note the peculiar 
character of the subcutaneous tissue, which appears reddish 
brown owing to the presence of smooth muscle fibers, the dartos 
muscle. Follow the constituent parts of the spermatic cord 
beneath this dartos layer down to the testicle. 'The scrotum con- 
sists of two separate halves divided by a median septum. In 
each half is found the spermatic cord and the testicle surrounded 
by the layers of fascia derived from the layers of the abdominal 
wall as above described. Beneath the three coverings derived 
from the muscles of the abdominal wall, is the tunica vaginalis, 
which forms the immediate covering of the testicle, and the wall 
of the sac in which the organ lies. The tunica vaginalis is a 
good example of a serous membrane, one part of which forms 
the wall of the cavity containing one or more organs. This 
part is called the parietal layer. The other part, which is re- 
flected over the organ or organs involved, is thinner and is 
called the visceral layer. A similar arrangement in a more 
complicated form will be found in the pleural, pericardial and 
peritoneal cavities. 
The testicle consists of the testicle proper and the epididy- 
mis. The testicle is an oval organ about one and one-half inches 
long and about an inch wide. The epididymis is a narrow elon- 
gated structure, which lies along the posterior border of the 
testis. Both organs are surrounded by a dense white fibrous 
under the visceral layer of the tunica vaginalis. The ducts of 
the testis pass directly into the epididymis where they join the 
duct of the epididymis. This duct is very tortuous and runs 
the whole length of the epididymis. At the lower end of the 
epididymis it becomes the vas deferens. The vas passes upward 
through the inguinal canal to the internal ring. Then it passes 
into the abdominal and pelvic cavities, runs through the prostate 
gland, and opens as the ejaculatory duct into the prostatic ureth- 
ra. Lay open the tunica vaginalis. Observe the smooth serous 
character of its inner surface and the relation of the tunica vagin- 
alis to the testicle and the epididymis. The position and rela- 
tion of the epididymis to the testicle should be noted and the 
/ elation and connection of the constituent parts of the spermatic 
39 cord to the epididymis. Make sections through the testicle to 
observe details of the internal structure of the organ. It is sug- 
gested that a transverse section be made through the testicle on 
one side and a vertical or sagittal section on the other to observe 
the internal arrangements, though this part of the dissection is 
not as a rule very satisfactory. The relations of the cord, the 
fascial coverings of the cord, tunica vaginalis, and testicle to the 
various forms of hernia are of great practical importance. 
Penis. Only the dorsal surface of the penis will be studied 
in this dissection. The whole organ will be studied later in 
the dissection of the pelvis and perineum. The penis is made 
up of three parts. The corpora cavernosa form dorso-lateral 
parts of the organ. They end just behind the head or glans 
penis. Posteriorly they diverge to form the crura of the penis, 
and are attached to the pelvic bones. The corpus spongiosum 
forms the ventral part of the organ and the head or glans penis. 
The urethra passes through the corpus spongiosum. The deep 
fascia of the abdominal wall is carried down over the penis to 
form the fascia penis. Beneath this fascia lie the dorsal vessels 
and nerves of the penis. These structures are derived from the 
vessels and nerves of the pelvic cavity and will be met with in 
the dissection of that region. They should be dissected at this 
time before the penis has dried up. Make an incision along the 
midline of the dorsum of the penis as far as the base of the glans 
penis. A superficial dorsal vein will often be found just below 
the skin. Cut through the fascis and the dorsal vein will be 
found in the midline. Lateral to the vein lie the two dorsal 
arteries, and lateral to the arteries are the dorsal nerves. Clean 
these vessels as far as the glans. Small branches of the vessels 
pass around the side of the penis. 
40 DISSECTION OF THE THORACIC CAVITY 
Skeleton of thorax. The bony wall of the thorax is formed 
by the thoracic part of the vertebral column, the twelve pairs of 
ribs and their cartilages, and the sternum. The bony thorax 
forms an irregular cone, the anterior wall of which is shorter 
than the posterior. The apex of the cone is formed by the first 
thoracic vertebra, the first pair of ribs, and the upper part of the 
sternum. The space included in these boundaries is the thor- 
acic inlet. It slants downward and forward and its outline is 
somewhat kidney-shaped. The spices of the pleural sacs and 
of the lungs occupy the lateral portions of this space, extending 
upwards to the level of the necks of the first ribs. Between 
them lie the terminations of the internal jugular and subclavian, 
and the .origins of the innominate veins; the innominate, left 
common carotid and left• subclavian arteries; the phrenic and 
vagus nerves; the thoracic duct; the trachea and the oesophagus. 
The subclavian vessels and the nerves of the brachial plexus, 
which come from the lower four cervical and first thoracic 
nerves, pass over the apex of the pleura and lung on their way 
to the axilla. The three scalene muscles, which arise from the 
transverse processes of the cervical veitebrae and insert in the 
first two ribs, surround these vessels and nerves and cover in 
the apex of pleura and lung. 
The base of the thorax, or thoracic outlet, is bounded by the 
last thoracic vertebra, the twelfth pair of ribs, the lower borders 
of the eleventh to the seventh pair of ribs, and the xiphoid car- 
tilage. This large opening is closed by the diaphragm. This 
muscle arises from the margins of the outlet and arches up into 
the thoracic cavity like a dome, the highest point of which reach- 
es to the upper border of the fifth rib or fourth space on the right, 
and to the lower border of the fifth rib on the left. The dia- 
phragm forms the lower boundary or floor of the thoracic cavity 
and separates the thoracic organs above from the abdominal 
organs below. The peculiar form of the diaphragm has as im- 
portant effect on the size and space of the thoracic and abdom- 
inal cavities, and on the relations of the thoracic and abdominal 
organs to each other. 
41 The posterior wall of the thorax is made up of the thoracic 
vertebrae and the ribs as far as their angles. The ribs are di- 
rected backward so that their angles are on a level with the tips 
of the spinous processes. This gives the necessary flatness to 
the back and also sufficient room for the massive posterior por- 
tion of the lung. 
The anterior wall consists of the sternum and ensiform 
cartilage and is shorter than the posterior to permit of free flex- 
ion of the trunk. The upper border of the manubrium is usually 
opposite the disk between the second and third thoracic verte- 
brae ; the lower border opposite the disk between the fourth and 
fifth vertebrae, and the lower end of the body opposite the body 
of the ninth vertebra. 
The lateral walls extend down to the lowest part of the 
eleventh or the tip of the twelfth ribs and are usually about three 
or four fingers breadth above the highest part of the iliac crests. 
The intercostal spaces are wider in front than behind but are 
narrower and more crowded together below and at the sides. 
The bony wall of the thorax is covered by the dorsal and ventral 
axial muscles and by the appendicfilar muscles of the upper ex- 
tremity, which pass to the shoulder girdle and humerus. The 
greater part of the wall can be easily palpated except that part 
of the dorsal wall covered by the dorsal axial muscles and that 
part of the lateral wall in relation to the upper part of the axilla. 
Endothoracic fascia. The thoracic wall is lined by a layer 
fascia, the endothoracic fascia, which covers the deep surface 
of the ribs, sternum, intercostal and transversus thoracic muscles 
and separates them from the pleura. Below the fascia is reflect- 
ed over the diaphragm. This fascia corresponds to the trans- 
versalis fascia of the abdominal wall. It is thin and so closely 
adherent to the pleura that it is impracticable to attempt their 
separation. 
General plan of thorax. The thoracic cavity is divided into 
three regions-the two pleural cavities, and the mediastinum 
or space between them. The pleural cavities are typical serous 
sacs, which contain the lungs. They have a parietal layer which 
forms the wall of the cavity, and a visceral layer which covers 
the surface of the lung. Between these two sacs in the median 
42 line is the space known as the mediastinum, which extends from 
the sternum in front to the vertebral column behind and from 
the plane of the first pair of ribs above to the diaphragm below. 
This region contains the following structures : the heart enclosed 
in the pericardium (a serous sac like the pleura) ; the great ves- 
sels, which enter and leave the heart;' the trachea; the oesopha- 
gus; the vagus, phrenic and sympathetic nerves; the azygos 
veins ; the thoracic duct. Since the diaphragm rises as high as 
the level of the fifth costal cartilages, the three regions just 
mentioned are relatively short in front, but at the sides and be- 
hind they fall away to the lower limit of the thoracic cavity 
conforming to the dome-like shape of the diaphragm. All the 
organs above and below the diaphragm must necessarily conform 
to its peculiar shape, and this accounts for the overlapping of 
the thoracic and abdominal viscera above and below this muscle, 
which is of the greatest practical importance in clinical examina- 
tions. !.:• 
Removal of thoracic wall. To open the thorax it is nec- 
essary to. remove the sternum and the costal cartilages, but 
before cutting the ribs; and the cartilages the pleura must be 
• separated from their deep surfaces. This is often difficult owing 
to pathological adhesions and thickenings in the lung and pleura. 
The student should first dissect the intercostal muscles from two 
or three neighboring intercostal spaces, beginning at the edge 
of the stetrnum and working outward to beyond the junction of 
the ribs and the cartilages. It is suggested that the student 
begin with the third, fourth and fifth spaces. Remove the in- 
ternal intercostal muscle with care. Immediately beneath it 
there is a thin layer of-fascia, the endothoracfc fascia, which lies 
in the same plane with the transversalis fascia of the abdominal 
wall and is closely adherent to the pleura. W hen the pleura has 
been exposed, pressure with the finge ' will probably be sufficient 
to separate it from the deep surface of the ribs. The finger then 
can be passed under the rib and the pleura stripped from it as 
far as the sternum on the one hand and just beyond the junction 
of the rib and its costal cartilage on the other. As soon as the 
membrane is cleared, cut through the junction of the rib and the 
cartilage. This process can be repeated until all of the carti- 
43 lages from the seventh or eighth below to the first above have 
been divided. Then cut through the costal cartilages along the 
lower costal border (leaving simply an edge to hold the origin 
of the diaphragm) to the ensiform and separate the ensiform 
from the lower end of the sternum. Saw through the manu- 
brium sterni just below the sterno-clavicular joints. Do not 
disarticulate this joint, as the clavicle must remain in place until 
the axilla and neck have been dissected. The sternum should 
be preserved for further use and study. It is important to be 
cautious in clearing the pleura and other structures from the 
deep surface of the sternum, as the great veins of the upper 
part of the thorax are just beneath it. After this has been done, 
trim off the ribs to get more room. They should be cut off along 
a line running from the sternoclavicular joint downward and out- 
ward through the nipple. The student is advised to cover over 
the rough edges of the ribs with a cloth or with the skin to avoid 
injury to the hands while working in the thorax. 
Pleura. The relations of the pleura and of the lung to the 
thoracic walls and to the heart and pericardium are of the great- 
est practical importance. The attachments of the pleurae to 
the anterior wall will of course have been disturbed with the 
removal of the sternum and ribs. The anterior edges of the two 
sacs meet or even slightly overlap in the midline from the lower 
border of the manubrium above to the level of the fifth or sixth 
costal cartilages below. Above, behind the manubrium, the 
margins of two sacs diverge, pass behind the sternoclavicular 
joints, and end in an apex one-half inch above the clavicle. The 
outer margin of the apex corresponds closely with the outer 
edge of the insertion of the sternomastoid muscle. Below the 
level of the fifth o sixth rib, the anterior edge of the right pleural 
sac passes down behind the sternum to the junction of it and 
the seventh cartilage, then turns outward and downward follow- 
ing the attachment of the diaphragm to the ribs, reaches the 
level of the tenth rib in the axillary line, and usually the level of 
the last rib behind. Here there is some variation, as the pleura 
may extend a little lower down, which is of some practical im- 
portance in its relation to the kidney. The left pleural sac 
turns out at the level of the fifth or sixth costal cartilage so as 
44 to clear the edge of the sternum. Thus a part of the anterior 
surface of the pericardium and of the heart is exposed between 
the pleural sacs at this point which is of great clinical import- 
ance in the examination of the heart and pericardium. At the 
level of the seventh left costal cartilage the lower border of the 
left pleura extends down and back to the same extent as on the 
right side. 
Having determined the relations of the anterior margins of 
the sacs behind the sternum, lay open the pleura along the mam- 
mary line and explore the sac with the fingers. Fluid often 
collects in the pleura and it will be necessary to sponge it out. 
It is rare to find a normal lung and pleura in the dissecting room, 
and more or less adhesions will be found between the parietal 
and visceral layers of the pleura with corresponding obliteration 
of the cavity. These adhesions can usually be broken up with 
the fingers, and the lung should be separated from the parietal 
pleura throughout the whole space if possible. Explore with 
the finger the apex of the pleural sac with special reference to 
the plane of the first rib, clavicle, and lower part of the neck. 
Then carry the hand downward over the heart and pericardium 
and sweep it finally backward so as to explore the whole lower 
limit of the space. On the right side the resistant mass of the 
liver will be felt below the diaphragm, while on the left there 
will be less resistance, as only the left lobe of the liver, the 
spleen, and the soft yielding stomach will be felt. It is con- 
venient to distinguish that part of the parietal pleura in contact 
with the thoracic wall as the costal pleura, that part over the 
diaphragm as the diaphragmatic pleura, and that part extending 
from the anterior border of the pleural sac just behind the ster- 
num back to the vertebral column and the neck of the ribs as 
the mediastinal pleura. 
Lung. The lung has the form of an irregular cone with an 
apex, a base, and two surfaces. The apex lies in the thoracic 
inlet extending about one-half inch above the clavicle. It co- 
incides closely with the apex of the pleura and has practically 
the same relations to the structures in the lower part of the 
neck. The subclavian vessels make a groove on the lung just 
below and in front of the apex. The base is concave and is 
45 moulded over the diaphragm and the abdominal organs below 
the diaphragm. The base of the right lung is indirectly in rela- 
tion with the right lobe of the liver; that of the left lung with 
the left lobe of the liver, the spleen, and stomach. 
The external or sterno-costal surface is convex and lies 
against the wall of the thorax. It is separated from the internal 
or mediastinal surface by a sharp anterior border and a rounded 
posterior border. The mediastinal surface is concave and is in 
relation to the structures in the mediastinum, the mediastinal 
pleural, of course, intervening. On this surface is the hilum of 
the lung, an oval slit, containing the bronchus, the pulmonary 
artery and vein, the bronchial arteries and veins, the pulmonary 
plexus of nerves, and lymph glands. As these structures enter 
the hilum they make up the root of the lung. The parietal 
pleura is reflected over the root and then passes as the visceral 
pleura over the surface of the lung. A fold of the pleura extends 
down from the hilum to the base of the lung and is known as 
the broad ligament of the lung. 
Certain of the structures in the mediastinum groove the 
mediastinal surfaces of the lungs. On the right lung is the 
relatively deep cardiac fossa in front and below the hilum. The 
groove for the subclavian vein is carried down in front of the 
hilum for the innominate vein and superior cava. The azygos 
vein makes a groove which is seen just above the hilum, and 
the oesophagus a shallow groove behind the broad ligament. On 
the left lung there is a very deep cardiac depression. The aortic 
arch and its carotid and subclavian branches make grooves above 
the hilum, and the descending aorta makes a deep depression 
behind the hilum down to the lower border. All of these struc- 
tures will be found in the dissection of the mediastinum. The 
lungs are divided into lobes by fissures. The left lung is di- 
vided into a superior and inferior lobe by the interlobar fissure, 
which runs through the lung from side to side both above and 
below the hilum. The superior lobe lies above and in front of 
the fissure and includes the apex and ventral border of the lung. 
The inferior lies below and behind the fissure and includes the 
thick dorsal part and most of the base of the lung. The right 
lung has two interlobar fissures which divide it into three lobes. 
46 The main fissure is essentially similar to the fissure of the left 
lung; the second fissure leaves the main fissure on the dorsal 
aspect of the organ and runs horizontally forward to the anterior 
border at the level of the fourth costal cartilage. The middle lobe 
lies between these two fissures, is wedge-shaped, and includes 
the lower part of the anterior border and the anterior part of 
the base of the lung. These fissures are often obscured by ad- 
hesions and are not easy to find in the dissecting room. 
The lung is usually so pathological that it cannot be studied 
satisfactorily in the dissecting room, and if it is normal it will 
be collapsed and its shape lost. If there are only few adhesions 
or if by chance the lung is normal, it should be handled very 
gently as the pleural cavity is being explored. Later when the 
trachea has been dissected, it may be possible to inflate the lung 
through the wind pipe and get some idea of its shape and the 
fissures that are found on the surface. If the thin surface is 
at all injured, there will be leaks and the organ cannot be in- 
flated. The student will have to depend chiefly on his text- 
book for the gross anatomy of the organ. The relation of the 
lung to the pleura and to the chest wall is most important. In 
the living, when the chest is in the position of expiration, which 
corresponds with the condition in the cadaver before the thorax 
is opened, the anterior borders of both lungs are in close con- 
tact with the parietal pleura from the apex to the level of 
the fourth costal cartilage. The anterior border of the right 
lung continues down in contact with its pleural sac as far as 
the junction of the sixth rib and the sternum. It then turns 
outward, leaves the lower border of the pleural sac, in the 
axillary line is at the level of the eighth rib, and ends behind 
at the level of the tenth rib. The anterior border of the left 
lung at the fourth left costal cartilage turns outward to a point 
midway between the mid sternal and mammary lines, and at the 
level of the sixth left cartilage passes downward and backward 
along the same levels as on the right side. This cut-out on the 
part of the left lung exposes a further amount of the pericardium 
and the heart at the left border of the sternum, which is of 
importance in the clinical examination of that organ. 
Pericardium. Turn the anterior edges of each pleural sac 
47 outward to expose the pericardium. The pleura usually can 
be stripped back from the pericardium, though adhesions may 
complicate this dissection. Care should be taken to avoid in- 
juring the phrenic nerve, which lies between these two mem- 
branes, attached usually more closely to the pericardium than 
to the pleura. This nerve is derived from the third, fourth, and 
fifth cervical nerves. Its course in the neck and upper part of 
the mediastinum can be followed in a later dissection, but it 
should be secured as it passes between the pleura and pericar- 
dium to the diaphragm, which it supplies. Note carefully the 
shape, character, and extent of the pericardium. The pericar- 
dium, like the pleura, consists of two layers, a parietal and a 
visceral. The parietal layer has a thicker fibrous outer layer and 
a thin smooth deeper layer. The parietal pericardium is at- 
tached below to the diaphragm and above blends with the outer 
coats of the vena cava, aorta, and pulmonary artery. The deep- 
er layer is reflected from these vessels and is continuous with 
the visceral layer. The attachments of the parietal pericardium 
and its extent can be clearly shown by blowing up the sac. 
Make a small puncture low down in the anterior wall and in- 
sert the blow pipe. A stitch can be taken at this point to hold 
the pipe in place. Then gently inflate the sac and note the 
peculiar line of attachment of the membrane to the great ves- 
sels above the heart and also the line of attachment to the 
diaphragm. The pericardium acts as a sort of support to the 
central part of the diaphragm. The pericardium can now be 
opened in the midline and the flaps turned back. Note carefully 
the line of reflection of the parietal pericardium and its continu- 
ity with the visceral layer. Preserve the pericardial flaps until 
the dissection of the root of the lung. 
Heart. The heart is a muscular organ containing four 
chambers, the right auricle and ventricle and the left auricle 
and ventricle. The right chambers are separated from the left 
by a septum, but the auricles open into the ventricles by the 
auriculo-ventricular openings. These openings are guarded by 
valves, the tricuspid valve on the right, and the mitral valve on 
the left. The superior and inferior vena cava and coronary sinus 
open into the right auricle. The pulmonary artery passes from 
47-a the right ventricle to the lung and its opening into the ventricle 
is provided with the pulmonary valve. The left auricle receives 
the four pulmonary veins and the left ventricle is continuous 
with the aorta. The opening of the aorta at the heart is pro- 
vided with the aortic valve. These valves are intended to pre- 
vent any regurgitation of the blood as it passes through the 
heart, and are of the greatest importance in the physiological 
action of the heart. Any interference with their proper mechan- 
ism causes serious pathological results. 
The muscular wall of the heart is made up of the special 
cardiac muscle tissue and is called the myocardium. The outer 
surface of the organ is covered by the pericardium, while the 
inner surface of the chambers is lined with the endocardium. 
This is continuous with the lining of the great vessels, which 
enter and leave the heart. The auricles are the receiving 
chambers of the heart, blood entering them from the venous 
system and from the lungs. Each auricle consists of two parts. 
The auricle proper (atrium) is that part of the chamber into 
which the veins open. Its walls are smooth and thin like the 
walls of the big veins. The auricular appendage (auricle) ex- 
tends forward, its walls are thicker and the musculature is 
thrown into elevations and ridges. The auricles do not have 
to contract as strongly as the ventricles, and their walls are 
quite thin. The ventricles are the transmitting chambers and 
force the blood either to the lung by the pulmonary artery or 
over all the body through the aorta. The ventricles therefore 
have to contract forcibly, and their walls are thick, especially 
that of the left ventricle. 
Venous blood from all parts of the body is brought to the 
right auricle by the two vena cavae. The stream then passes 
through the right auriculo-ventricular opening (tricuspid valve) 
into the right ventricle. It is then forced from the ventricle 
through the pulmonary artery (pulmonary valve) to the lung 
where its waste products are removed and a fresh supply of 
oxygen taken up. The blood then passes back to the heart by 
the pulmonary veins, enters the left auricle, and passes through 
the left auriculo-ventricular opening (mitral valve) to the left 
47-b ventricle. From this chamber it is sent out through the aorta 
(aortic valve) to all parts of the body. 
The heart has a sternocostal surface which is directed for- 
ward in relation to the pleura, lungs, and anterior thoracic wall; 
a diaphragmatic surface resting on the diaphragm and indirectly 
in relation to the abdominal organs below the diaphragm; a 
posterior surface directed backward in relation to the structures 
in the posterior mediastinum and to the vertebral column; a 
base looking upward, where the superior vena cava, the pul- 
monary artery, and the aorta enter or leave the heart; an apex 
directed downward and to the left. About one-third of the heart 
is to the right and about two-thirds to the left of the median 
line. 
Sternocostal surface. The anterior surface of the heart will 
now be exposed and the following details should be carefully 
noted: The right auricular appendage and part of the right 
auricle forming the right border of the organ; the greater part 
of the right ventricle separated from the left ventricle by the 
interventricular groove; the small part of the left ventricle vis- 
ible forms the left border and the apex; the tip of the left auric- 
ular appendage may be seen just above the left ventricle. Sep- 
arating the auricles from the ventricles is the auriculo-ventricu- 
lar groove. At the upper border of the organ are three great 
vessels; from right to left, the superior vena cava, the aorta, and 
the pulmonary artery. The latter lies at first in front and then 
to the left of the aorta. Draw the heart to the left, and the 
right pulmonary veins will be partially seen behind its right 
border. Raise the heart upward and to the right, and the left 
pulmonary veins will be seen behind the heart on the dorsal 
aspect of the pericardium. Note carefully the relation of the 
pericardium to the heart and vessels. This can best be done by 
exploring with the finger. The finger can be passed by way 
of the transverse sinus of the pericardium around both the 
aorta and the pulmonary artery together, which are in a common 
tube of pericardium. The finger cannot be passed around the 
veins which are only partly surrounded by pericardium and pro- 
ject into the cavity. 
47-c Subdivision of the mediastinum. This space is arbitrarily 
subdivided into a superior mediastinum, which is that portion 
above a line from the lower border of the manubrium to the disk 
between the fourth and fifth thoracic vertebrae. Below that 
level the space is divided into an anterior mediastinum, which 
is the shallow space between the sternum and the pericardium ; 
a middle mediastinum, which is the space occupied by the peri- 
cardium and its contents; and a posterior mediastinum, which 
is the space between the pericardium and the vertebral column. 
The last three subdivisions are bounded below by the dia- 
phragm and all four subdivisions are bounded laterally by the 
mediastinal pleura. 
Superior mediastinum. Boundaries. Above by the plane 
of the first pair of ribs and top of sternum; below by a line from 
the lower border of the manubrium to the disk between the 
fourth and fifth thoracic vertebrae. (This line corresponds 
fairly closely with the upper limits of the heart and pericar- 
dium) ; laterally by the pleura. Contents. The most important 
structures in this region are: 1. Viscera; trachea and bronchi, 
oesophagus, and remains of thymus gland. 2. Nerves; phrenic, 
vagi, left recurrent laryngeal, and sympathetic nerves. 3. Ar- 
teries ; aortic arch and its branches. 4. Veins; superior vena 
cava, innominate veins, and azygos veins. 
The anterior mediastinum has been exposed by the removal 
of the anterior thoracic wall. Its contents are a few lymph 
glands and the internal mammary vessels at the fifth and sixth 
intercostal spaces on the left. Its chief importance lies in the 
fact that here the pericardium is exposed between the edges of 
the pleural sacs. 
Middle mediastinum. This is represented by the space oc- 
cupied by the pericardium. Contents. The pericardium, the 
heart, and those portions of the vena cava, the pulmonary veins, 
the aorta, and pulmonary artery associated with the pericardium. 
The phrenic nerves. The structures passing to the roots of the 
lungs. 
The posterior mediastinum. This area lies between the peri- 
cardium in front and the vertebral column behind. It contains 
47-d the descending aorta and its branches, the azygos veins, the 
vagus and sympathetic nerves, the oesophagus, and the thoracic 
duct. 
Dissection of the middle mediastinum. The phrenic nerves 
should have been secured when the pleura was separated from 
the pericardium. The heart will be dissected at a later stage, and 
the vena cava superior, aorta, and pulmonary artery will be fol- 
lowed up into the superior mediastinum in the present dissec- 
tion. The relative position of these three vessels at the 
upper border of the heart and their relation to the pericardium 
should be carefully noted before beginning the dissection of the 
superior mediastinum. 
Dissection of the superior mediastinum. Thymus gland. 
The most superficial structure is the thymus gland which lies 
between the edges of the pleural sacs, behind the manubrium, 
and in front of the great vessels at this level. In young adult 
subjects there may be some traces of its two lobes, but usually 
it is represented by a shapeless mass of thick fascia, which can 
be removed. The student should study the anatomy of the 
gland at this stage of his dissection. Remove this tissue care- 
fully, as the thin-walled innominate veins lie directly behind it. 
It will be best to begin with the vena cava at the point where 
the pericardium passes over it and trace that vessel upward. Just 
above the point where the pericardium crosses the vein a large 
tributary, the azygos vein, enters its dorsal surface. Opposite the 
second intercostal space the vena cava is formed by the junction 
of the two innominate veins. 
Veins. The innominate veins are formed behind the sterno- 
clavicular joints by the union of the internal jugular and sub- 
clavian veins. The origin of the veins is concealed by the 
sternoclavicular joint. The right innominate vein is relatively 
short and passes straight down from the right sterno- 
clavicular articulation to the second intercostal space. The 
right phrenic nerve lies external to this vein and to the 
cava. The right vagus nerve lies posterior to the innominate 
vein and the cava. The left innominate vein extends from the 
left sternoclavicular articulation to the second right intercostal 
47-e space where it joins the right innominate vein. It is about three 
inches long and is obliquely placed. The stumps of the in- 
ternal mammary veins will be found at the lower border of the 
innominate veins, and the inferior thyroid vein should be found 
at the upper border of the left innominate vein near its junction 
with the right. The inferior thyroid vein passes down in the 
midline from the thyroid gland in the neck. Behind and below 
the left innominate vein lies the aortic arch. The left phrenic 
and vagus nerves pass between the aortic arch and the left in- 
nominate vein. Follow the innominate veins as far as the sterno- 
clavicular joint but do not attempt to work up beyond that 
point. 
Arteries. Turn next to the aorta just above the point where 
the pericardium invests it. Dissect along the anterior surface 
of the vessel up to the level of the left innominate vein. Draw 
the vein downward to expose the arch. Be careful to secure 
the left phrenic and vagus nerves as they cross the arch behind 
the vein. The first branch from the arch is the right innominate 
artery, which passes along the right side of the trachea, medial 
to the corresponding vein, to sternoclavicular joint, where it 
divides into the right subclavian and common carotid arteries. 
These will not be seen at this stage. The next branch from the 
aortic arch is the left common carotid, which passes along the 
left side of the trachea into the neck. The third branch is the 
left subclavian, which lies distinctly posterior to the left com- 
mon carotid and disappears behind the clavicle. Do not attempt 
to follow these arteries beyond the point where they disappear 
behind the sternoclavicular joint. Do not injure or disturb the 
line of reflection of the pericardium across the front of the great 
vessels. 
Nerves. The superficial cardiac plexus, formed by a branch 
from the left vagus and a branch from the left cervical sym- 
pathetic nerves, lies in front of the aortic arch. These small 
nerves should be sought for before the tissue is cleaned away 
from the arch. They are not particularly easy to demonstrate. 
The left phrenic and vagus nerves pass between and anterior 
to the left subclavian and left common carotid arteries and cross 
47-f the anterior aspect of the aortic arch. At the lower border of 
the arch the phrenic nerve passes anterior to the root of the 
lung (pulmonary vessels and bronchus). It continues down- 
ward between the parietal pleura and pericardium to the dia- 
phragm. The vagus nerve passes behind the root of the lung 
and leaves this stage of the dissection. It gives off branches to 
the lung behind the root, and will be followed in the dissection 
of the posterior mediastinum. At the under side of the arch of 
the aorta a soft fibrous cord (known as the ligamentum arterio- 
sum) will be found passing to the origin of the left pulmonary 
artery. This is the remains of the ductus arteriosus, which con- 
nects the aorta and pulmonary artery in the foetus and is ob- 
literated after birth. The left recurrent laryngeal nerve, a branch 
of the vagus, hooks around this cord and passes up behind the 
aortic arch to reach the neck. Be careful to secure the cord and 
the nerve at the lower border of the arch, as they can easily be 
cut at this point. The right phrenic and vagus nerves pass be- 
tween the right subclavian artery and vein in the lower part 
of the neck. The phrenic nerve runs on the lateral side of the 
right innominate vein and superior cava and passes in front of 
the root of the lung to the diaphragm. The vagus nerve runs 
behind the innominate vein and the cava, and then passes be- 
hind the pulmonary root. The right recurrent laryngeal nerve 
is given off at the level of the right subclavian artery and will 
not be seen in this dissection. The student should note care- 
fully the relations of the vagus and phrenic nerves to the root 
of the lung and the different position and origin of the recurrent 
laryngeal nerves. 
Pulmonary artery. Follow this vessel to the left of the 
aorta. It divides at that point into the right and left pulmonary 
branches. The left branch passes to the lung just below the 
aortic arch, and its connection to the arch by the obliterated 
ductus arteriosus has been noted. The right branch passes out 
of sight to the right behind the aorta and vena cava. The right 
and left pulmonary arteries will be followed in the dissection of 
the roots of the lungs. 
Trachea and oesophagus. The trachea lies in the midline 
47-g between the right innominate and left common carotid arteries. 
The inferior thyroid veins are anterior to it. It disappears be- 
hind the aortic arch and divides into the two bronchi just below 
the arch. The dissection of this structure can be completed 
with the dissection of the root of the lung. Just posterior to the 
trachea is the oesophagus, but only a glimpse of it can be ob- 
tained along the left border of the former. The oesophagus will 
be dissected in the posterior mediastinum. 
Dissection of the heart.. Coronary arteries. The right and 
left coronary arteries are the first branches of the aorta and 
supply the walls of the heart. They arise from the aortic sinuses 
just above the aortic valves and form an arterial circle about 
the heart in the auriculo-ventricular groove. They send branch- 
es in the interventricular furrows on the front and back of the 
heart, and are covered by the visceral pericardium and the fat 
which is usually found in the grooves on the surface of the organ. 
Those portions of the coronary arteries which are distributed to 
the anterior surface should now be exposed by dissecting off the 
visceral pericardium. The branches distributed to the posterior 
surface will be dissected when the heart is removed. 
The right coronary artery arises from the anterior aortic 
sinus, lies at first under cover of the right auricular appendage, 
and winds around the right side of the heart in the auriculo- 
ventricular groove to reach the posterior surface. It anastomoses 
here with the terminal branch of the left coronary artery and 
is prolonged downward in the interventricular furrow on the 
diaphragmatic surface to the apex, where it anastomoses with 
the corresponding- branch from the left coronary artery. 
The left coronary artery arises from the left posterior aortic 
sinus, passes between the pulmonary artery and the left auricu- 
lar appendage, and divides into (1) a circumflex branch which 
winds around the left side of the heart in the auriculo-ventricu- 
lar groove to anastomose with the right artery on the posterior 
surface, and (2) a descending branch which runs in the inter- 
ventricular furrow on the sternocostal surface to the apex. Both 
coronary arteries give off numerous branches to the wall of the 
heart. The coronary veins correspond in general to the arteries 
47-h but are collected finally into one large vessel, the coronary 
sinus,, which lies in the auriculo-ventricular groove on the pos- 
terior surface and empties into the right auricle. 
Right ventricle. Tricuspid and pulmonary valves. It is 
desirable that the student get a clear idea of the position of the 
valves of the heart while the organ is in situ. The right ventricle 
should be opened first to get a view of the internal architecture 
of the ventricle and of the tricuspid and pulmonary valves. 
Make an incision through the wall of the ventricle about one- 
fourth inch from the auriculo-ventricular groove near the right 
border of the heart, and carry the cut upward along the groove 
to a point opposite the tip of the right auricular appendage. 
Then cut transversely to the left across the conus arteriosus of 
the ventricle to the interventricular septum. Make another in- 
cision at the beginning of the first cut for about one and one-half 
inches along the right border of the ventricle, and turn the flap 
over to the left. The anterior papillary muscle springs from 
the deep surface of the anterior wall of the ventricle and the 
last cut must not be too extensive, as there is danger of injury 
to this muscle when the flap is turned up. The tricuspid valve 
will now be exposed and the student should observe carefully 
the papillary muscles, chordae tendinae and the position of the 
three flaps of the valve. To expose the pulmonary valve raise 
the lower border of the cut across the top of the ventricle, and 
note the position of the three cusps of the pulmonary valve. 
They will probably be folded back against the wall of the heart 
and obscured by blood clot. Cut upward between the two an- 
terior cusps and then transversely across the artery just above 
them. Cut the anterior wall of the artery only and leave its 
posterior wall intact. The arterial wall can then be turned to 
either side to display the three cusps. Note the difference in 
structure between them and the cusps of the tricuspid valve. 
Right auricle. The right auricle can now be opened. Seize 
the tip of the auricular appendage, cut into its anterior wall, and 
carry the incision to the right a short distance below the lower 
end of the superior cava. Start again at the apex and cut down- 
wards and to the right along the auriculo-ventricular groove to 
47-i the upper end of the inferior vena cava. The whole anterior 
wall can then be turned to the right. Some blood clot will prob- 
ably have to be washed out of the chamber. Note the difference 
in structure between the wall of the appendage and that of the 
auricle or atrium. Observe the fossa ovalis on the wall be- 
tween the two auricles. A trace of the foetal foramen ovale 
may be seen in some cases. The Eustachian fold, the remains 
of the Eustachian valve, varies somewhat in size but can al- 
ways be seen. Note also the position of the opening of the 
coronary sinus, guarded by a slight fold of endocardium, be- 
tween the Eustachian fold and the auriculo-ventricular opening. 
A good view of the three flaps of the tricuspid valve can now 
be obtained with both of the right chambers open. 
Left ventricle. Mitral and aortic valves. The left ventricle 
should next be opened to display the mitral and aortic valves. 
Complete the cut through the whole of the pulmonary artery, 
turn it down, and dissect it carefully away from the front of 
the aorta for about an inch. Then cut transversely through the 
the anterior wall of the aorta, leaving a portion of its posterior 
wall intact so as not to completely sever the vessel. The aorta 
will be full of starch mass which must be cleaned out with care 
to avoid injury to the aortic valve. Look down the aorta to 
determine the position of the cusps of the valve and then cut 
downward between the anterior and left posterior cusps. Care 
must be taken to cut between these cusps and to avoid injuring 
either. The finger can now be passed into1 the left ventricle 
close to the interventricular septum. Cut along the finger, 
keeping close to the septum to avoid injuring the mitral valve 
and the anterior papillary muscle, as far as the apex. This cut 
must be carefully made, especially if the ventricle is full of the 
starch mass. Any such mass must then be thoroughly washed 
out. In making this cut the left coronary artery will have to be 
divided. The whole ventricle will now open up and the student 
will get a most instructive view of the mitral and aortic valves. 
All parts off the valvular apparatus should be carefully studied 
and compared with those already seen in the right ventricle. 
These dissections have the advantage of giving a view of both 
47-j auriculo-ventricular valves and also a part of the pulmonary and 
aortic valves undisturbed with the heart still in position. 
Left auricle. The left auricle should be opened last of all, 
as its dissection necessitates considerable disturbance bf the 
heart. Cut through the superior vena cava just below the point 
where the pericardium crosses it. Dissect the posterior wall of 
the vessel carefully away from the right pulmonary artery as 
that vessel passes behind the cava. Turn the cava downward 
as far as the upper border of the right auricular appendage. Then 
cut through the posterior wall of the aorta, dissect that vessel 
away from the right pulmonary artery, and turn it down with 
the cava. The sternocostal surface of the left auricle will now 
be exposed with the right branch of the pulmonary artery lying 
just above it. This dissection gives an excellent view of the 
position of the left auricle and its relations to the great vessels 
at the upper border of the heart. Next open the anterior wall of 
the auricle along the lower border of the pulmonary artery, 
carry the cut on the right sight down as far as the back of the 
superior cava, and on the left to the apex of the auricular ap- 
pendage. The whole wall can then be turned down and for- 
ward and the cavity of the auricle displayed. Blood clot or 
starch mass will have to be cleaned out to expose the openings 
of the pulmonary veins, which enter the posterior wall of the 
chamber. Compare the interior with that of the right auricle. 
A very instructive demonstration can now be obtained of all the 
chambers of the heart, with their relations and connections. The 
chambers can now be stuffed with cotton, the flaps secured with 
stitches, and the contours of the heart restored. 
Root of the lung. It is advisable to begin the dissection of 
the root of the lung before the heart is removed, as the pul- 
monary arteries and veins will be held in place by the heart and 
the line of reflection of the pericardium across the front of the 
root will not be disturbed. The root of the lung consists of the 
following structures: The bronchi, the pulmonary artery and 
vein, the bronchial arteries and veins, the pulmonary plexuses 
of nerves and lymph glands. The parietal pleura is reflected 
around the root to become continuous with the visceral pleura, 
47-k and the deep layer of the parietal pericardium is also reflected 
over the front of the root onto the anterior surface of the pul- 
monary artery and veins. It is important to preserve carefully 
this line of reflection of the pericardium as it separates that part 
of the pulmonary vessels in relation to the pericardium from that 
part in relation to the lung. The heart should be drawn over 
to the left, the right lung to the right, and the dissection should 
be begun just external to the line of pericardial reflection on the 
root. The pulmonary veins are the most anterior of the struc- 
tures, the artery comes next, and the bronchus is most posterior. 
On the right side the pulmonary artery crosses the bronchus just 
below the highest (eparterial) branch of the bronchus. This 
part of the bronchus is the most superior element in the root. 
The veins and arteries cover up the bronchi to such an extent 
that very little of the branches of the bronchi can be seen at this 
stage of the dissection. Follow the vessels a very short distance 
into the lung, as the deeper dissection of the bronchial tree can 
be done better when the heart is removed. The left root can 
be dissected next in the same manner. On the left side the 
artery crosses the bronchus above its highest branch and here 
the artery is the highest element in the root. The bronchial 
vessels and the nerves will not be seen at this stage. Remove 
any enlarged glands that are in the way. 
Removal of the heart. Posterior wall of pericardium. The 
heart may now be removed to show the dorsal wall of the 
pericardium, and the base and inferior surface of the heart. Be- 
fore removing the organ, explore once again the attachment of 
the heart along the great veins. The heart has a vertical line 
of attachment along the line of the two cavae and a horizontal 
line of attachment at right angles to the former along the line 
of the pulmonary veins. Carry the finger upward along the 
left side of the inferior vena cava and it will enter and stop in 
the deep pocket behind the transverse line of attachment of the 
left pulmonary veins. Where the finger stops is the line of re- 
flection of the pericardium from the back wall of the left auricle. 
Withdraw the finger from the pocket, carry it over the front of 
the left pulmonary veins, and it will enter the transverse sinus 
47-l of the pericardium behind the pulmonary artery and aorta. 
Raise the apex of the heart, and cut the superior cava just above 
the diaphragm. Continue the cut through the line of attachment 
of the heart between the inferior cava and the right pulmonary 
veins. Cut these veins just inside the pericardium. The heart 
can now be drawn to' the left, the line of attachment along the 
back of the left auricle cut, and finally the left pulmonary veins. 
If this has been successfully done, the line of attachment of the 
heart to the dorsal wall of the pericardium and the relation of 
the pericardium to the great vessels and to the root of the lung 
will be clearly shown. 
Base and diaphragmatic surfaces of heart. The base of the 
heart is formed by a part of the right auricle and by nearly all 
of the left auricle. The inferior cava opens at the lower part 
of the right auricle, and the four pulmonary veins open into the 
posterior wall of the left auricle. This surface of the heart is 
separated from the diaphragmatic surface by the posterior au- 
riculo-ventricular groove, in which lie part of the coronary 
arteries and the coronary sinus. The diaphragmatic surface lies 
on the diaphragm, and is made up of a small part of the right 
ventricle and the greater part of the left ventricle. The pos- 
terior inter-ventricular furrow separates the ventricles on this 
surface. 
The student should now study the base and the inferior 
or diaphragmatic surface of the heart, and compare the vessels 
and line of pericardial reflection at the base with the corre- 
sponding structures on the dorsal wall of the pericardium. The 
coronary arteries and the coronary sinus on the dorsal aspect 
of the heart should be thorouhgly dissected. The heart can 
now be laid aside in preserving fluid for future study. During 
the dissection of the neck it can be replaced in the thorax, the 
cut ends of the superior cava and aorta sutured, in order to 
give support to the great vessels of the neck. 
Trachea and bronchi. To expose the bifurcation of the 
trachea and the bronchi, the innominate artery should be cut 
one-half above the arch and pulled with the superior cava over 
to the right. The aortic arch should be separated from the 
47-m pulmonary artery and turned over to the left. Secure the left 
recurrent laryngeal nerve as it hooks around under the arch. 
The pulmonary artery should be cut just to the right of its 
bifurcation; its two parts can then be turned to either side, 
and the bifurcation of the trachea exposed. The cardiac 
branches of the vagus, recurrent laryngeal and sympathetic 
nerves pass down on either side of the trachea to the pulmonary 
artery and the heart. They are small and usually not easy to 
secure. The pericardium can then be removed from the pul- 
monary veins, and the larger components of the root of the lung 
followed into the lung. It will be easier to sacrifice the veins and 
follow chiefly the bronchi and the arteries for a short distance to 
get an idea of the branching. If the lung is in bad shape, not 
much can be done. Finally dissect the remains of the pericar- 
dium downward as far as the inferior vena cava and remove it. 
The knife should be carried close to the deep aspect of the peri- 
cardium below the bifurcation of the trachea as it is being- 
turned down, to avoid injuring the branches of the vagus nerve 
on the oesophagus which lies just behind the pericardium. Note 
carefully the position and shape of the bronchi at the bifurca- 
tion and the relation of the bronchi to the great vessels and to 
the oesophagus. 
Posterior mediastinum. The trachea and bronchi must be 
removed to expose the structures in the posterior mediastinum. 
Cut each bronchus on either side of the bifurcation and turn 
their distal ends over towards the lungs. Be sure to secure 
the recurrent laryngeal nerve on the left. This nerve can now 
be followed up into the superior mediastinum. Both vagus 
nerves should be followed behind the roots of the lungs, and 
their pulmonary branches to the posterior aspect of the roots 
observed. The trachea can now be raised and turned up towards 
the neck. It should not be detached, as it will be needed later in 
the dissection of the neck, when the deep parts of the neck will 
be connected up with the superior and posterior mediastinum. 
The anterior aspect of the oesophagus will now be exposed, and 
it should be cleaned down to the diaphragm. The vagus nerves 
must be carefully dissected and secured first, as they form a 
47-n plexus all about the oesophagus. The descending aorta will 
then be followed along the left side of the oesophagus to the 
diaphrgam. 
Posterior mediastinum. Aorta. The aortic arch ends at 
the lower border of the fourth thoracic vertebra on the left of 
the median line. The descending or third part of the aorta 
passes downward from this point along the left side of the 
vertebral column, gradually inclining inward, but never quite 
reaching the midline. It passes through the aortic opening in 
the diaphragm with the thoracic duct and azygos vein at the 
level of the last thoracic vertrebra and becomes the abdominal 
aorta. To its right is the oesophagus, and on the left it lies 
against the mediastinal pleura and grooves of the left lung. It 
gives off numerous branches to the pericardium, oesophagus, 
bronchi, and eight or nine pairs of intercostal arteries to the last 
eight or nine intercostal spaces. The root of the left lung has 
already been seen crossing in front of the beginning of this 
part of the aorta. 
Oesophagus. Like the trachea, this structure begins in the 
neck at the level of the sixth cervical vertebra. It lies posterior 
to the trachea in the superior mediastinum, passes behind the 
origin of the left bronchus, and runs along the right side of the 
aorta in the posterior mediastinum. It inclines gradually to the 
left and crosses in front of the lower end of the aorta just be- 
fore passing through the oesophageal opening of the diaphragm 
at the level of the tenth thoracic vertebra. It grooves slightly 
the mediastinal surface of the right lung. Its walls are soft and 
collapsed and it resembles a long narrow muscle. 
Vagus nerves. These nerves pass posterior to the root 
of the lung, where they form the pulmonary plexuses behind the 
bronchi. Below the root of the lung the nerves form the 
oesophagus plexus, which surrounds the oesophagus and passes 
with that structure through the diaphragm to reach the stom- 
ach. Preserve the main trunks of these nerves in cleaning the 
oesophagus. Behind the oesophagus and the aorta lie the azygos 
veins and the thoracic duct. 
Azygos veins. These veins are formed in the upper part 
47-o of the abdomen on either side by the ascending lumbar veins. 
The vena azygos major lies usually on the right. It passes 
through the aortic opening of the diaphragm and along the 
vertebral column behind and to the right of the oesophagus. It 
runs behind the root of the right lung and arches over the root 
to empty into the superior vena cava. It receives the right in- 
tercostal veins.' The vena azygos minor inferior is usually on 
the left side, passes through a special opening in the diaphragm, 
and joins the great azygos vein at about the middle of the 
thorax. The vena azygos minor superior lies on the left of the 
vertebral column in the upper part of the thorax. It receives 
the upper left intercostal veins and usually empties into the 
great azygos vein close to the vena azygos minor inferior. Very 
often a branch, the left superior intercostal vein, drains the up- 
per three or four spaces on the left, and crosses the aortic arch 
to empty into the left innominate vein. The azygos system 
of veins drains the dorso-lateral body wall and forms an im- 
portant collateral connection between the inferior vena cava be- 
low the diaphragm through its connections with the renal veins, 
and the superior vena cava above the diaphragm. 
Thoracic duct. This is the largest lymphatic vessel in the 
body. It begins at the level of the second lumbar vertebra in 
a dilatation, the receptaculum chyli, enters the thorax by the 
aortic opening of the diaphragm, and lies close to the midline 
between the aorta and oesophagus. In the upper part of the 
thorax it inclines to the left behind the oesophagus and arch of 
the aorta and enters the neck where it empties into the junction 
of the left subclavian and internal jugular veins. It receives 
all the lymph except that from the right side of the head and 
right upper extremity, which is collected by the right lymphatic 
duct. This is a short vessel which empties into the corre- 
sponding veins on the right side and is not easy to demonstrate 
in an ordinary dissection. To find the thoracic duct and azygos 
vein,, cut the oesophagus in the middle and turn the ends up 
and down. There will be no difficulty in dissecting the azygos 
vein and its branches. Clean up at the same time several of the 
right intercostal arteries from the aorta and the corresponding 
47-p branches of the azygos vein to the point where they disappear 
under the internal intercostal muscle. The thoracic duct is like 
a small vein and should be sought for along the median line to 
the left of the azygos vein. Trace it up as far as possible. In 
the dissection of the neck it can be inflated from below and 
traced to its entrance into the left subclavian and internal jug- 
ular veins. 
Sympathetic nerves. The sympathetic nerves and their 
ganglia form two continuous cords that lie opposite the necks 
of the ribs throughout the thorax. They are placed behind the 
parietal pleura and communicate with the intercostal nerves. 
They give off the greater and lesser splancnic nerves, which 
pass through special openings in the diaphragm. The main 
trunks should be secured, but the lower ends and the splancnic 
branches can be more readily dissected after the diaphragm and 
the adominal cavity have been opened. 
Diaphragm. Having completed the dissection of the pos- 
terior mediastinum, the mediastinal pleura and the lung can 
be removed and the whole thoracic surface of the diaphragm ex- 
posed. Study the attachments of the muscle to the lower border 
of the thorax and note carefully the position of the central ten- 
don and its relation to the pericardium. Pay particular attention 
to the three main openings in the muscle and to the structures 
passing through each. That for the vena cava inferior is the 
highest of the three, lies opposite the level of the ninth thoracic 
vertebra, and is wholly in the central tendon to the right of the 
median line. The oesophageal opening is just to the left of the 
midline and is wholly in the muscular tissue. The aortic open- 
ing is the lowest and most posterior and really lies behind the 
tendinous fibers, which forms the crura of the diaphragm, and 
are attached to the upper lumbar vertebrae. 
Muscles of respiration; movements of the ribs. Each pair 
of ribs and the part of the sternum included between them may 
be regarded as a series of bony rings which slant downward and 
forward from the spine, with an increasing length and obliquity 
from the first to the eighth or ninth. The rings articulate with 
the spine by the costocentral and costotransverse joints. By 
47-q raising these rings the anterior-posterior diameter of the thorax 
is increased. The lower borders of the rings are everted, es- 
pecially in the longer ribs. The rings move on an axis which 
runs through the head anc| tubercle of the ribs obliquely back- 
ward and outward. This axis becomes more oblique from the 
upper ribs to the eighth or ninth and, consequently, when the 
ring is raised, it is also tilted laterally and the eversion of the 
lower borders increased. In this way the transverse diameter 
of the thorax is enlarged. The vertical dimension of the thorax 
is increased by the contraction of the diaphragm, by which its 
lateral parts are flattened and the abdominal contents forced 
downward. The lung follows the movements of the ribs and 
any elevation of them is accompanied by an expansion of the 
lung, air being forced in by outside pressure. 
Muscles which elevate the ribs and increase the capacity of 
the thoracic cavity are muscles of inspiration. Those which 
depress the ribs and diminish the capacity are muscles of expira- 
tion. The muscles of ordinary inspiration are the diaphragm, 
the external intercostal, and the interchondral part of the in- 
ternal intercostal muscles. In deeper and forced inspiration the 
following muscles come into play: the scaleni; the sternomas- 
toids and infrahyoids, with the head extended and fixed by the 
muscles of the back of the neck; the extensors of the spine, to 
extend the thoracic portion of the spine and raise the thorax; the 
shoulder girdle muscles to fix the shoulder girdles and to allow 
the subclavius and pectorals to take their fixed point from the 
shoulder and act on the ribs. The levatores costarum and the 
serratus posticus superior have only a slight action in raising the 
ribs. 
In expiration the relaxation of the inspiratory muscles and 
the weight and elasticity of the thorax tend to lower the ribs. 
The intercostal part of the internal intercostals, the transversus 
thoracis, the subcostals, and the transversalis are the muscles 
of ordinary expiration. In deeper and forced expiration all the 
abdominal muscles are forcibly contracted together with the 
quadratus lumborum and iliocostales muscles. The serratus 
posticus inferior may have some slight expiratory action. 
47-r DISSECTION OF THE UPPER EXTREMITY 
Shoulder girdle. Clavicle and scapula. The upper extrem- 
ity is attached to the trunk by the shoulder girdle, which is made 
up of two separate bones, the clavicle and scapula. The clavicle 
lies in the upper part of the pectoral region; its inner or sternal 
end articulates with the sternum, its outer or acromial end with 
the acromion process of the scapula. The sternal end is club- 
shaped and carries a triangular articular surface for articula- 
tion with the manubrium sterni. The shaft of the bone is 
curved in two directions and is weakest at the point where the 
two curves meet. In the middle two-thirds the curve is convex 
forward; here the shaft is roughly cylindrical with four rather 
poorly marked surfaces, superior and inferior, anterior and pos- 
terior. In the outer third the curve is concave forward, and the 
shaft is flattened from above downward so that the anterior and 
posterior surfaces are reduced to mere borders. 
On the inferior surface of medial portion of the shaft, close 
to the sternal end, is a rough area for the costoclavicular (rhom- 
boid) ligament, which connects the clavicle with the first rib. 
insertion of the subclavius muscle. On the inferior aspect of 
the outer third of the shaft is a tubercle and ridge for the coraco- 
clavicular (conoid and trapezoid) ligament, which connects the 
outer end of the clavicle with the coracoid process of the scapula. 
On the outer side of the acromial end of the clavicle is a small 
oval facet which articulates with the acromion process of the 
scapula. The acromion overlaps the outer end of the clavicle 
and forms the bony apex of the shoulder. The clavicle is sub- 
cutaneous and can be easily palpated. The acromion end of the 
clavicle is a little higher than the acromion process. This makes 
a ridge which can be felt through the skin and is a landmark for 
the outer end of the clavicle and the joint between it and the 
scapula. 
Muscle attachments. The clavicle gives insertion to two 
muscles: the trapezius (from the spines of the vertebrae) which 
inserts partly into the posterior border of the outer third of 
the shaft; and the subclavius (from the first rib) which inserts 
48 into the inferior aspect of the shaft. The clavicle provides 
origin for the following muscles. The clavicular head of the 
sterno-mastoid arises from the upper surface near the sternal 
end and passes to the temporal bone. The pectoralis major 
arises from the inner two-thirds of the anterior surface, the del- 
toid from the outer third, and both these muscles pass to the 
humerus. The sterno-hyoid may arise partly from the posterior 
aspect of the sternal end of the shaft. 
The clavicle is the only part of the shoulder girdle which is 
connected directly with the trunk. The clavicle gives the lateral 
expansion to the shoulders which is necessary to permit of free 
lateral movements at the shoulder joint. It steadies and sup- 
ports the scapula and acts as the radius of the circle on which 
the scapula moves in all movements of the shoulder girdle and 
shoulder joint. 
Scapula. The scapula is a flat triangular-shaped bone which 
lies on the dorso-lateral aspect of the trunk opposite the second 
to eighth pair of ribs. It articulates with the humerus and with 
the clavicle. The bone is expanded to give a broad origin for 
the muscles, which attach the shoulder girdle to the trunk and 
arm, and also to provide suitable leverage for their action on the 
upper extremity. 
The body of the scapula is thin and triangular in outline. Its 
ventral surface is smooth and slightly concave to adapt itself 
to the convexity of the posterior aspect of the ribs, over which 
the scapula moves freely. This surface is known as the sub- 
scapular fossa. The dorsal surface is rougher and slightly con- 
vex. It is divided unequally by the spine of the scapula into 
a supraspinous fossa and an infraspinous fossa. The former oc- 
cupies about one-fourth, and the latter about three-fourths of 
the dorsal surface. The anterior or axillary border is rather 
thick, while the medial or vertebral and the superior borders are 
thin. On the latter, close to the base of the coracoid process, 
is the scapular notch, covered by a small transverse ligament. 
The dorsal scapular artery and vein pass over the ligament, 
the dorsal scapular nerve under it, as they run from the neck to 
the muscles on the do; sum of the scapula. 
Glenoid fossa. The upper lateral angle of the scapula is 
49 enlarged and thickened, and carries the glenoid fossa for articu- 
lation with the head of the humerus. This is the thickest and 
strongest part of the scapula, as it has to carry the weight of the 
humerus and of the other bones of the arm and hand. The fossa 
is oval and shallow, it looks forward and outward, and is sur- 
rounded by a well marked rim. The supraglenoid tubercle just 
above the fossa gives origin to the long head of the biceps; the 
infraglenoid tubercle just below the fossa on the axillary border 
gives origin to the long head of the triceps. Below the rim the 
upper angle narrows as it joins the body of the bone, and this 
area is known as the neck of the scapula. 
The coracoid process is a strong process, bent on itself at 
almost a right angle. It springs from the upper border of the 
scapula close to the base of the glenoid cavity, extends forward 
and upward under the outer third of the clavicle, and overhangs 
the glenoid fossa and the shoulder joint. The coracoclavicular 
ligament is attached to its upper surface. 
The spine of the scapula is a strong triangular plate of bone 
attached to the dorsal surface of the body and having a horizon- 
tal position when the body is erect. It begins at the vertebral 
border near the lower limit of its upper fourth, and ends laterally 
in a free concave border a short distance from the glenoid fossa, 
from which it is separated by the great scapular notch. The 
outer angle of the spine is prolonged forward and outward and 
torms a flat expanded process, the acromion process. This pro- 
cess carries a small oval facet for articulation with the clavicle, 
overlaps the outer end of the bone, and forms the bony promi- 
nence at the tip of the shoulder. It overhangs the glenoid fossa 
and the shoulder joint. 
In the erect position with the arm at the side, the upper 
angle of the scapula is usually opposite the second rib and the 
lower angle opposite the seventh or eighth ribs. The vertebral 
border is parallel with and about one and one-half inches from 
the spines of the vertebrae. The dorsal aspect of the bone is 
well covered with muscles, but the free edge of the spine, the 
acromion process, and the lower part of the vertebral border 
are easily felt through the skin. The tip of the coracoid process 
can be felt by deep pressure at the inner side of the humerus 
50 below the outer end of the clavicle. 
Muscle attachments. The muscles attached to the scapula 
may be divided into two groups. The first group comprises 
those muscles which arise from the trunk and are inserted into 
the bone ; the second group those which arise from the scapula 
and insert lower down on the humerus or bones of the forearm. 
Muscles inserted into scapula; ventral surface. 
Vertebral border: serratus anterior (from 1st to 8th ribs) 
Coracoid process : pectoralis minor (from 2nd to 5th ribs) 
Muscles arising from scapula; ventral surface and glenoid fossa. 
Subscapular fossa: subscapularis (to lesser tuberosity of 
humerus) 
Coracoid process: biceps, short head (to bicipital tubercle 
of radius) coracobrachialis (to shaft of humerus) 
Upper border : omohyoid, posterior belly (to neck) 
Supraglenoid tubercle : biceps long head (to bicipital tuber- 
cle of radius) 
Infraglenoid tubercle: triceps long head (to olecranon proc- 
ess of ulna) 
Muscles inserted into scapula; dorsal surface. 
Vertebral border, above spine: levator scapulae (from 
vertebrae) 
below spine: rhomboids (from vertebrae) 
Spine, upper lip : trapezius (from vertebrae and skull) 
Muscles arising from scapula; dorsal surface. 
Spine, lower lip: deltoid (to shaft of 
humerus) 
Supraspinous fossa : supraspinatus 
Infraspinous fossa : infraspinatus 
Axillary border, upper part: teres minor 
to greater tuber- 
osity of 
humerus. 
Axillary border, lower end: teres major 
Axillary border, tip : latissimus dorsi 
to bicipital groove 
of humerus. 
51 Position and boundaries. The axilla lies between the upper 
lateral part of the thoracic wall and the upper part of the humer- 
us. It contains the axillary vessels, the nerves of the brachial 
plexus, and numerous lymphatic glands, imbedded in a mass of 
fatty connective tissue. The axilla is bounded laterally by the 
upper part of the humerus, and the coracobrachialis and biceps 
muscles; medially by the first four or five ribs, the corresponding 
intercostal muscles, and the serrations of the serratus anterior; 
anteriorly by the pectoralis major and minor muscles, and the 
costocoracoid membrane ; posteriorly by the ventral surface of 
the scapula and the subscapularis, latissimus dorsi and teres 
major muscles. The apex of the axilla is directed towards the 
neck and lies between the first rib, the clavicle, and the upper 
border of the scapula. Through the apex the vessels and nerves 
enter the axilla. The base is formed by the skin and axillary 
fascia stretching across the armpit from the pectoralis major to 
the latissimus dorsi muscles. These two muscles form the an- 
terior and posterior folds of the armpit. 
Dissection of anterior wall of axilla. This has been partly 
done in the dissection of the anterior thoracic wall, and can 
now be completed. The vessels and nerves which have been 
seen entering the deep surface of the pectoralis major can now 
be cut close to that muscle, and the two parts of the muscle re- 
flected. The costocoracoid membrane can then be split open 
just below the clavicle to demonstrate the subclavius muscle. 
The membrane should then be removed down to the upper bor- 
der of the pectoralis minor. This must be done carefully, as the 
axillary vessels, especially the vein, lie just behind it. Preserve 
the cephalic vein and trace it to the axillary vein. A portion 
of the axillary vessels with the large nerves of the brachial plex- 
us on their outer suiface will appea" in the gap between the cla- 
vicle and the pectoralis minor. They are embedded in fascia 
and before attempting to clean them the pectoralis minor muscle 
should be reflected. Cut the muscle near its origin and turn it 
outward, separating its deep surface with care from the underly- 
ing vessels and ne.ves. 
DISSECTION OF THE AXILLA. 
52 The axillary artery and vein. These vessels begin at the 
outer border of the first rib and are the direct continuations of 
the subclavian artery and vein. They pass downward through 
the axilla and end at the lower border of the pectoralis major 
muscle, where they become the brachial vessels. The vein is 
internal and a bit anterior to the artery. The pectoralis minor 
muscle divides the vessels arbitrarily into three parts, which are 
useful in studying their relations. The chief branches are (1) 
acromiothoracic (thoraco acromial), and (2) long thoracic (lat- 
eral thoracic) from the second part. The former supplies the 
pectoral muscles and region of the shoulder; the latter the inner 
wall of the axilla. It runs along the lower border of the pec- 
toralis minor. (3) Subscapular and two circumflex arteries from 
the third portion. The subscapular will be found along the 
outer border of the Subscapularis muscle. It supplies the dorsal 
wall of the space and sends a large branch to the dorsal aspect 
of the scapula to supply the muscles on its dorsal surface. This 
branch will be found in the dissection of the back of the limb. 
The posterior circumflex is the larger and more important of 
the two circumflex arteries. These vessels form an arterial 
circle around the surgical neck of the humerus, the posterior 
following the course of the circumflex nerve. Its dissection will 
be completed from behind. There are other small muscular 
branches of slight importance. 
The brachial plexus. The brachial plexus is formed by the 
ventral divisions of the last four cervical and first thoracic 
nerves. Consequently the upper or supraclavicular portion lies 
in the neck and will not be seen until a later dissection. The 
lower or infraclavicular part lies in the axilla and has fairly con- 
stant relations to each of the three parts of the axillary vessels. 
These relations should be carefully borne in mind to aid in iden- 
tifying the nerves in the dissection. The five nerves, more or 
less wrapped together in fascia, lie along the outer side of the 
first part of the axillary vessels, or that part above the pectoralis 
minor. The five nerves there unite to form an outer, an inner, 
and a posterior cord, so named because of their relations to the 
axillary artery in its second part, or the part behind the pector- 
alis minor muscle. The inner cord lies between the artery and 
53 vein at this point. The cords next give off numerous branches, 
which are grouped about the third part of the artery, the part 
below the pectoralis minor. The branches from the outer cord 
are external to the artery; those from the posterior cord are pos- 
terior to it, and the branches from the inner cord are internal and 
a little anterior, lying between the artery and vein. 
The best method of dissection is to begin at the clavicle and 
trace each structure in turn through the axilla. If this is prop- 
erly done a neat dissection of these most important structures 
can be made. The axilla is filled with fascia and contains lymph 
nodes which may be enlarged. All this tissue must be removed 
with the greatest care to avoid injury to the nerves and vessels. 
All veins except the main axillary vein and the cephalic vein 
can be sacrificed, but all arteries and nerves must be saved. The 
subclavius muscle and clavicle must not be cut. They will be 
removed in the dissection of the neck. The dissector should 
look out for the long or posterior thoracic nerve (respiratory 
nerve of Bell) which arises in the neck from the 5th, 6th, and 
Zth cervical nerves and enters the axilla just behind the first 
part ol the axillary vessels. It then lies in the fascia covering 
the serratus magnus (anterior) muscle on the inner wall of the 
axilla posterior to the lateral thoracic vessels. 
Branches of the brachial plexus. The branches of each cord 
will be found to a great extent in corresponding relation to the 
third part of the axillary artery. The musculocutaneous nerve 
lies along its outer side and soon leaves it to pass under the 
biceps and the coracobrachialis muscles. The anterior thoracic 
nerves form a sort of loop in front of the first and second parts 
of the artery and pass into the deep side of the pectoral muscles. 
The branches from the inner cord lie at first to the inner side of 
the artery between it and the vein. The inner head of the me- 
dian is a very short trunk, which crosses directly in front of the 
artery to join the outer head along the external side of the vessel. 
The musculospiral (radial) and the circumflex (axillary) nerves 
lie behind the third part of the artery. The former passes down 
the arm, while the latter turns outward and backward behind the 
surgical neck of the humerus with the posterior circumflex artery 
to supply the deltoid and te:es minor muscles. Only a short 
54 portion of this nerve will be seen in this stage of the dissection at 
the outer border of the subscapularis between it and the teres 
major muscles. The subscapular nerves lie in the fascia on the 
subscapularis muscle. The middle or long subscapular is found 
without trouble and runs down into the latissimus dorsi muscle. 
The other two are small, and usually enter the subscapularis 
high up. They are easily lost in removing the fascia over the dor- 
sal wall of the axilla, and should be sought for before the fascia is 
disturbed. The long thoracic nerve lies in the fascia over the 
serratus magnus, and should be secured before that muscle is 
cleaned. Having followed out all the nerves and arteries, the 
muscles on the walls of the space should be cleaned last of all. 
Note the presence of any enlarged lymph glands, and remember 
their importance in connection with the mammary gland in the 
female. 
55 DISSECTION OF THE ARM. 
Humerus. The humerus forms the skeleton of the upper 
arm and articulates above with the scapula, below with the ra- 
dius and ulna. The upper extremity carries the head, a smooth, 
rounded elevation, covered by hyaline cartilage, which articu- 
lates with the glenoid fossa and is directed upwards and inwards. 
The periphery of the head is marked by a groove, the anatomical 
neck, to which the capsule of the shoulder joint is attached. 
This neck separates the head from the greater and lesser tuber- 
osities. The lesser tuberosity is directed forward in line with 
the anterior aspect of the shaft; the greater is continued upward 
from the outer surface of the shaft. These tuberosities give in- 
sertion to the muscles which surround the capsule of the shoul- 
der joint. Below the tuberosities the bone narrows as it passes 
into the shaft, and this area is known as the surgical neck of the 
humerus. The bicipital or intertuburcular groove begins be- 
tween the two tuberosities and is prolonged down onto the an- 
terior aspect of the shaft. It is bounded by two prominent lips, 
which give attachment to certain of the muscles of the shoulder 
girdle. 
The shaft is thick and cylindrical in the upper two-thirds: 
in the lower third it becomes somewhat three-sided and expand- 
ed laterally, and is bounded by two well marked borders, the 
external and internal epicondyloid ridges, which end below in 
the corresponding epicondyles. The shaft is curved in two di- 
rections ; in the upper part it is slightly convex forward, while 
in the lower third it is slightly concave forward. On the upper 
part of the anterior surface is the bicipital groove; the lower part 
is covered by the origin of the brachialis muscle. Near the 
middle of the lateral aspect of the shaft is the deltoid tubercle 
for the insertion of that muscle. On the posterior surface of the 
shaft, in the middle third, is found a shallow groove, the mus- 
culospiral or radial g.oove for the superior profunda artery from 
the brachial, and the musculospiral or radial nerve from the 
brachial plexus. All the posterior surface above and below the 
groove is covered by the triceps muscle. 
The lower extremity is marked on either side by the two 
56 epicondyles. The outer is a mere knob; the inner is one-half 
to three-quarters of an inch in length and extends backward and 
inward. The outer epicondyle and the epicondyloid ridge give 
origin to the supinator and extensor group of muscles of the 
forearm and hand, and to the external lateral ligament of the 
elbow joint. The inner epicondyle gives origin to part of the 
pronator flexor group of muscles of the forearm and hand and 
to the internal lateral ligament of the elbow joint. 
The articular surfaces for the radius and ulna are found on 
the inferior aspect of the lower end of the bone. That for the 
radius is towards the outer side and consists of a small rounded 
elevation, the capitellum, which does not extend onto the back 
of the humerus. Just above it on the anterior surface of the shaft 
is the shallow radial fossa, which receives the head of the radius 
in full flexion of the elbow. The articular surface for the ulna is 
just medial to the capitellum. This is known as the trochlea 
and has the form of a spool or pulley with a central concavity 
and two lips, the inner one of which extends downward to a 
lower level than the outer. The whole articular surface winds 
somewhat obliquely from the front to the back of the shaft, and 
is a little broader behind than in front. Above the trochlea on 
the anterior surface is the coronoid fossa for the tip of the cor- 
onoid process of the ulna in full flexion ; on the posterior surface 
above the trochlea is the larger olecranon fossa for the tip of the 
olecranon process of the ulna in full extension of the elbow. 
The bone between these fossae is as thin as paper and may be 
perforated. 
The long axis of the lower end of the humerus slants down- 
ward and inward from the outer to the inner condyle, and forms 
an angle of about 80 degrees with the long axis of the shaft. 
The whole bone is inclined downward and slightly inward from 
the shoulder and is slightly turned, so that the anterior aspect 
looks forward and a little inward, and the inner condyle is direct- 
ed backward and inward. The bone is almost completely cov- 
ered by must?,les. The head may be felt by pressure high up in 
the axilla if the arm is rotated. Both condyles and a part of the 
supracondyloid ridges are subcutaneous and can be easily palpat- 
ed. 
57 Muscle attachments. The humerus provides insertion for 
muscles which arise from the trunk and shoulder girdle, and 
gives origin to others which arise from the humerus and insert in 
the forearm or hand. 
Muscles inserted into humerus, anterior aspect. 
Greater tuberosity: supraspinatus (from dorsum of scapula) 
Lesser tuberosity: subscapularis (from venter of scapula) 
Bicipital groove, outer lip: pectoralis major (from thorax 
and clavicle) 
Bicipital groove, inner lip: teres major (from dorsum of 
scapula) 
Bicipital groove, floor: latissimus dorsi (from spine) 
Shaft, deltoid eminence: deltoid (from shoulder girdle) 
Shaft, middle of medial surface: coracobrachialis (from cor- 
acoid process of scapula) 
Muscles arising from humerus, anterior aspect. 
Shaft, lower half: brachialis (to coronoid process of ulna) 
Shaft, lateral epicondyloid ridge : brachioradialis (to styloid 
process of radius) 
Shaft, lateral epicondyloid ridge: extensor carpi, radialis 
longior (to 2nd metacarpal) 
Shaft, lateral epicondyle: extensors of hand (to metacarpals 
and phalanges) 
Shaft, medial epicondyle: pronators and flexors of forearm 
and hand (to radius, metacarpals and phalanges) 
Muscles inserted into humerus, posterior aspect. 
Greater tuberosity: infraspinatus, teres minor (from dor- 
sum of scapula) 
Muscles arising from humerus, posterior aspect. 
Shaft, whole surface : triceps, lateral and medial heads (to 
olecranon p.ocess of ulna) 
Lateral epicondyle: anconeus (to olecranon and shaft of 
ulna) 
Superficial anatomy. Feel and identify the following bony 
landmarks : the greater tuberosity of the humerus, felt with great 
difficulty through the deltoid ; the epicondyloid ridges and epi- 
condyles of the lower end of the humerus; the olecranon process 
58 of the ulna, and its relations to the condyles; the head of the 
radius behind and below the outer condyle. Note the elevation 
made on the front of the arm by the biceps muscle and the posi- 
tion of the tendon of insertion of that muscle in the cubital space. 
Incisions. 1. Along the middle of the arm to a point about 
two inches below the line of the condyles; 2. a transverse in- 
cision across the limb at that level. 
Superficial and deep fasciae. The superficial fascia of the 
arm is a rather thin loose-meshed layer. The deep fascia is a 
thin firm membrane closely investing the muscles and becoming 
rather thicker at the elbow. The internal and external inter- 
muscular septa are prolonged from this layer to be attached to 
the inner and outer border of the humerus and divide the arm 
into an anterior (flexor) and a posterior (extensor) compart- 
ment. 
Superficial veins. The superficial veins of the lower arm 
form roughly a median, radial, and ulnar group. The median 
veins divide at the cubital space into a median basilic, which re- 
ceives the ulnar veins and forms the basilic vein of the upper 
arm, and into a median cephalic which receives the radial veins 
and becomes the cephalic vein of the upper arm. Great varia- 
tion in this arrangement is, however, to be expected. These 
superficial veins should be dissected out of the fascia and pre- 
served, as they will be needed in the dissection of the forearm. 
The cutaneous nerves should be dissected at the same time and 
preserved so that they can be followed in the dissection of the 
forearm. 
Superficial nerves. The skin over the outer side of the 
shoulder and arm is supplied by small branches from the circum- 
flex and musculospiral nerves. Along the inner side the inter- 
costohumeral (2d or 3d intercostal nerves) supplies the skin over 
the armpit; next come branches from the lesser internal cutan- 
eous (medial brachial cutaneous), and from the internal cutan- 
eous (medial antibrachial cutaneous). The latter continues on 
to the forearm. At the outer border of the tendon of insertion 
of the biceps muscle the cutaneous portion of the musculocutan- 
eous nerve (lateral antibrachial cutaneous) enters the skin and 
59 runs down the outside of the forearm. It is easily cut at this 
point. 
Muscles of arm. The biceps is the most superficial muscle 
of this region, and arises by two heads. The long head arises 
fiom the top of the glenoid fossa, passes through the shoulder 
joint over the head of the humerus, and runs down in the bicip- 
ital groove. The short head arises with the coracobrachialis 
from the coracoid process of the scapula, and unites with the 
long head in the upper part of the arm. The muscle is inserted 
into the bicipital tubercle on the neck of the radius and by the 
bicipital fascia (lacerta fibrosa) into the deep fascia at the upper, 
inner part of the forearm. The coracobrachialis lies just medial 
to the biceps and is inserted into the middle of the inner aspect 
of the shaft of the humerus. Beneath the biceps, in the lower 
half of the arm, is the brachialis muscle which arises from the 
anterior aspect of the humerus and inserts into the coronoid pro- 
cess of the ulna. The brachialis flexes the ulna and the biceps 
flexes the radius in movements at the elbow. The biceps is also 
a supinator of the forearm. These muscles lie in the anterior 
compartment of the arm and are supplied by the musculocutan- 
eous nerve. The inner border of the triceps will come into this 
dissection at the inner side of the arm. It belongs with the pos- 
terior compartment and will be dissected with that region. 
Vessels. The chief artery of the arm is the brachial, which 
is the continuation of the axillary, and begins at the lower border 
of the axilla. It passes down the inner side of the arm under 
cover of the biceps and rests on the triceps, the insertion of the 
coracobrachialis, and on the brachialis. At the elbow it lies in 
the median line and divides into the radial and ulnar arteries. 
In the arm it gives off the following branches: the superior pro- 
funda, which follows the radial nerve; the inferior profunda, 
which follows the ulnar nerve; and an anastomatic branch which 
anastomoses with recurrent branches from the arteries of the 
forearm. There are also muscular and cutaneous branches. 
The brachial artery is accompanied by venae comites, which 
end above in the axillary vein. These receive veins which ac- 
company branches of the artery, and also the basilic vein at 
about the middle of the arm. 
60 Nerves. Note especially their relation to the brachial artery. 
The musculocutaneous nerve lies along the outer side, then 
passes outward under the coracobrachialis and biceps, and runs 
down on the brachialis anticus muscle. It supplies these three 
muscles and the skin on the outer side of the forearm to the 
wrist. The internal cutaneous nerve lies along the inner side 
and in front of the artery until it enters the skin in the lower part 
of the arm, and supplies the skin along the inner side to the 
wrist. The median nerve lies at first to the outer side and then 
crosses usually in front of the artery about half-way down, and 
in the cubital space lies to its inner side. The ulnar nerve lies 
to the inner side of the artery as far as the lower part of the 
arm, where is passes backward and disappears behind the internal 
epicondyle. The musculospiral (radial) nerve passes behind the 
artery and disappears in the musculospiral groove behind the 
humerus. It lies behind the middle third of the bone and re- 
appears on the anterior side of the arm between the brachialis 
anticus and the extensor muscles above the outer condyle. It 
supplies the triceps muscle and the skin on the outer and poster- 
ior side of the limb and the extensor muscles of the forearm and 
hand. The circumflex (axillary) nerve passes behind the axil- 
lary artery between the subscapularis and teres major muscles 
around the surgical neck of the humerus. It supplies the deltoid 
and teres minor muscles and the skin over the deltoid. 
Cut though the deep fascia over the biceps muscle and clean 
that muscle. Leave the bicipital fascia intact for the present. 
Note both the long and short heads of the biceps and the rela- 
tion of the coracobrachialis to the short head. Follow the an- 
terior border of the deltoid to its insertion into the outer part 
of the humerus. The remainder of the muscle will be cleaned 
with the dissection of the back. Turn the inner edge of the bi- 
ceps outward to expose the brachial artery. Note its superior 
profunda branch following the musculospiral nerve to the 
groove on the dorsal side of the humerus. A smaller inferior 
profunda branch may be found with the ulnar nerve above the 
inner condyle. The basilic vein will usually enter one of the 
venae comites of the brachial artery in the middle part of the 
arm. These veins should be saved. 
61 Deep dissection of the shoulder. The fibers of the deltoid 
should be cut from the clavicle as far as the tip of the acromion, 
and the muscle turned out. The short head of the biceps and 
the coracobrachialis may now be cut. Do not cut the long head. 
The long head with the axillary vessels and nerves can be drawn 
outward and secured, if necessary, with a ligature, to expose the 
insertion of the subscapularis. This should be cleaned and at 
the same time the axillary nerve and the posterior circumflex 
artery can be traced into the quadrilateral space, a space between 
the teres muscles, which leads around to the back of the arm. 
This space will be dissected more profitably from behind, and the 
vessels and nerves should be followed only as far as the point 
where they disappear around the neck of the humerus. 
The cubital space. This is the region on the anterior aspect 
of the elbow. It is bounded above by the line of the epicondyles, 
externally by the brachioradialis muscle, and internally by the 
pronator radii teres muscle. The floor is formed chiefly by the 
insertion of the brachialis anticus. The basilic and cephalic 
veins and the internal cutaneous and musculocutaneous nerves 
lie in the fascia over this space. A layer of fascia passes from 
the tendon of the biceps to blend with the thick deep fascia of 
the inner side of the forearm below the internal condyle. This 
is known as the bicipital fascia and serves as an additional in- 
sertion for the muscle. Beneath the deep fascia are found from 
without inward the tendon of the biceps, the lower end of the 
brachial and the origin of the radial and ulnar arteries, and the 
median nerve. The musculospiral nerve divides deep in the 
space into the radial and posterior interosseous, the former going 
down the front, and the latter winding to the back of the limb. 
Note the origin of the two different groups of the muscles of the 
forearm as they arise from the epicondyles. They will be worked 
out in detail with the dissection of the forearm. It will not be 
necessary to cut the biceps, as it can easily be turned from side 
to side to reach the parts beneath. The bicipital fascia should 
be kept in place until the dissector is ready to work in the depths 
of the cubital space, when it can be cut at its insertion into the 
fascia of the forearm. 
62 DISSECTION OF THE FOREARM. 
Radius and ulna. These bones form the framework of the 
forearm, the radius lying to the outer and the ulna to the inner 
side of the limb. The two bones articulate above with the humer- 
us, below with the carpal bones of the wrist, and also with each 
other at their upper and lower extremities. The two bones are 
firmly united by the ligaments of the superior and inferior radio- 
ulnar joints, and by the interosseous membrane which stretches 
between their shafts. The radius and ulna form one piece of 
apparatus, which is so arranged that the radius, supporting the 
whole hand, can revolve on a vertical axis about the ulna. This 
action takes place in the radio-ulnar joints and provides the 
movements of pronation and supination, which are so essential 
in the function of the forearm and hand. 
The ulna is the most important bone at the elbow, and with 
the humerus plays the chief part in the elbow joint. The radius 
has only a secondary role in the joint. At the wrist these condi- 
tions are reversed. Here the radius articulates with the carpus 
and supports the whole hand. The ulna does not enter into the 
wrist joint. Roth bones have a shaft and two extremities, the 
smaller end being more or less rounded and known as the head. 
The head of the radius is in direct relation to the humerus; the 
head of the ulna is in indirect relation to the carpus. 
The upper extremity of the ulna is enlarged and has two 
processes, the coronoid and the olecranon. Between them is the 
great sigmoid cavity or semilunar notch, which is covered with 
hyaline cartilage and articulates with the trochlea of the humer- 
us. The coronoid process is the shorter of the two and is pro- 
longed upwards from the anterior surface of the shaft. It forms 
the anterior and lower boundary of the sigmoid fossa. A rough 
tuberosity at its base provides insertion for the brachialis muscle 
and origin for several of the pronator flexor muscles of the fore- 
arm and hand. 
The olecranon process is larger and more massive and ends 
in a beak. It is prolonged upward from the back of the shaft 
and forms the posterior boundary of the sigmoid fossa. The 
63 triceps and anconeous are inserted into it. The great sigmoid 
cavity articulates with the trochlea of the humerus. It is elevat- 
ed in the center to fit the concavity of the trochlea and depressed 
or Hat at the sides to receive the lips of the trochlea. The arti- 
cular surface is carried over the edge on the radial side, where it 
forms an oval cavity, the lesser sigmoid or radial notch, for 
articulation with the head of the radius. 
The head of the radius is covered with hyaline cartilage. It 
is rounded, with a depression on its summit surrounded by a con- 
vex rim which articulates with the capitellum of the humerus. 
The articular surface is carried over onto the lateral aspect of 
the head and forms a convex surface which rotates in the lesser 
sigmoid cavity during pronation and supination of the forearm 
and hand. The head is supported on a rounded neck which is 
limited below and to the ulnar side by the bicipital tubercle for 
the insertion of the biceps muscle. 
The shafts of both bones incline towards each other above, 
but lower down diverge. They draw close together again at the 
inferior radio-ulnar joint. The shafts are curved with a slight 
concavity forward. The shaft of the ulna is three-sided above; 
it tapers from above down and at the lower end is slender and 
cylindrical. The shaft of the radius is curved with the convex- 
ity directed laterally, and is much larger at its distal than at its 
proximal end. The shafts of both bones have three surfaces, 
anterior, posterior, and lateral, separated by three borders. The 
medial or intei osseous borders, which are directed towards each 
other and give attachment to the interosseous membrane, are the 
most sharply defined. The anterior surfaces of the shafts and 
the interosseous membrane are covered by the pronator flexor 
muscles of the forearm and hand; the posterior surfaces by 
the supinators and extensors. 
The lower extremity of the ulna carries the rounded head 
with a short styloid process on its inner and posterior surface. 
The articular surface on the inferior aspect of the head is flat 
and semilunar in outline, and is carried over onto the lateral 
side of the head where it forms a narrow convex surface. This 
lateral part articulates with the lesser sigmoid cavity of the radi- 
us. The inferior aspect of the head is separated from direct 
64 articulation with the carpus by a triangular disk of fibrocartilage. 
The apex of the disk is attached to the styloid process of the 
ulna; the base of the disk to the lower margin of the lesser sig- 
moid cavity of the radius. The head of the ulna is excluded by 
the disk from the wrist joint and is confined to the inferior radio- 
ulnar articulation. The styloid process is separated from the 
head by a groove behind and by a depression below. It gives 
attachment to the disk and to the ulnar collateral ligament of 
the wrist joint. 
The lower end of the radius is broad and thick with a large 
articular surface, which articulates with the first row of the 
carpal bones. 'The pyramidal styloid process is prolonged down- 
wards from the lateral surface, and gives attachment to the radial 
collateral ligament of the wrist joint. The inferior articular 
surface is concave and divided by a line into a triangular lateral 
and a quadrilateral medial portion. These areas articulate with 
the navicular and semilunar bones of the wrist. The articular 
surface is carried around the medial border onto the ulnar side 
of the lower end, and forms the lesser sigmoid or ulnar notch 
for articulation with the head of the ulna. The disk, which 
connects the lower end of the bones, is attached to the lower 
border of this notch and acts as a pivot on which the radius 
moves around the lower end of the ulna in pronation and supina- 
tion. The anterior and posterior borders of the lower end are 
prominent; the posterior border is grooved for the tendons of the 
extensor muscles as they pass into the hand. 
The olecranon process and the posterior border of the shaft 
of the ulna are subcutaneous in their length. The lower part 
of the medial surface and the styloid process can be felt at the 
wrist. In the supine position the styloid process projects on the 
medial and posterior part of the wrist, but in the position of 
pronation the head of the ulna becomes prominent. The upper 
part of the radius is deeply placed. The lower part of the lateral 
surface and the styloid process are superficial. It always pro- 
jects to a lower level than the ulnar styloid. The head can be 
felt below the lateral epicondyle when the arm is pronated and 
supinated. 
Muscle attachments. The bones of the forearm provide in- 
65 sertion for muscles which arise from the scapula or humerus and 
act on the radius and ulna. They give origin to muscles which 
are inserted in the bones of the wrist and fingers, and to two 
muscles which pass from ulna to radius. 
Muscles inserted into radius and ulna, anterior aspect. 
Ulna, coronoid process: brachialis (from shaft of humerus) 
Radius, bicipital tubercle: biceps (from scapula) 
Radius, neck and anterio-lateral surface of shaft: supinator 
(from ulna) 
Radius, shaft, middle of lateral surface; pronator radii 
teies (from medial epicondyle of humerus) 
Radius, shaft, anterior surface, lower quarter: pronator 
quadratus (from ulna) 
Radius, styloid process, base: brachioradialis (from lateral 
epicondyloid ridge of humerus) 
Muscles arising from radius and ulna, anterior aspect. 
Ulna, coronoid process: pronator radii teres, deep head (to 
radius) 
Ulna, coronoid process : flexor sublimis digitorum (to middle 
phalanges, fingers) 
Ulna, coronoid process: flexor longus pollicis (to terminal 
phalanx of thumb) 
Ulna, shaft, below radial notch : supinator (to neck of radi- 
us) 
Ulna, shaft, ante.ior and medial surfaces: flexor profundus 
digit am (to terminal phalanges, fingers) 
Ulna, shaft, anterior surface, lower quarter: pronator quad- 
ratus (to ulna) 
Radius, shaft, anterior aspect: flexor sublimis digitorum (to 
middle phalanges of fingers) 
Radius, shaft, anterior aspect: flexor longus pollicis (to ter- 
minal phalanx of thumb) 
Muscles inserted into radius and ulna, posterior aspect. 
Ulna, apex of olecranon: triceps (from scapula and humer- 
us) 
Ulna, olecranon and shaft below: anconeus (from lateral 
epicondyle of humerus) 
Radius, neck and shaft below: supinator (from ulna) 
66 Muscles arising from radius and ulna, posterior aspect. 
Ulna, shaft: abductor longus pollicis (to metacarpal of 
thumb) 
Ulna, shaft: extensor longus pollicis (to terminal phalanx of 
th umb) 
Ulna, shaft: extensor indicis (to index finger) 
Radius, shaft: abductor longus pollicis (to metacarpal of 
thumb) 
Radius, shaft: extensor brevis pollicis (to proximal phalanx 
of thumb) 
Superficial anatomy. Palpate and identify the following: 
the shaft of the ulna ; the shaft of the radius; the styloid process- 
es of radius and ulna (the former extending one-half inch lower 
than the latter). Note the position of the flexor tendons and the 
radial and ulnar arteries at the wrist. 
Superficial veins. These are the radial, median, and ulnar 
veins already mentioned which arise on the dorsal side of the 
hand and wind around to the anterior side of the limb above the 
wrist. 
Superficial nerves. On the radial side the skin is supplied 
by branches of the musculocutaneous, and on the ulnar side by 
branches of the internal cutaneous nerves. 
Superficial muscles. These arise from the internal epicon- 
dyle of the humerus by a sort of common origin. Along the 
radial side of the arm the brachioradialis muscle, a member of 
the extensor-supinator group, extends from the external epi- 
condyloid ridge of the humerus to the styloid process of the 
radius. This is the only member of this group which will be 
be dissected from the front. On the ulnar side the superficial 
members of the pronator-flexor group are: (1) the pronator radii 
teres going obliquely across the arm to the middle of the radius; 
(2) the flexor carpi radialis passing to the wrist to the second 
metacarpal bone; (3) the palmaris longus (when present) going 
to the palmar fascia; and (4) the flexor carpi ulnaris along the 
innermost side of the arm going to the fifth metacarpal and un- 
ciform bones. In addition to its humeral origin, the pronator 
radii teres has a deep head of origin from the coronoid process of 
the ulna. The median nerve passes between the two heads and 
67 the ulnar artery under the deep head of this muscle. The flexor 
carpi ulnaris also has a deep origin from the shaft of the ulna, 
and the ulnar nerve passes from the posterior to the anterior 
aspect of the arm between these heads. 
Deep muscles. The most superficial muscle of this deep 
group is the flexor sublimis digitorum, which arises from the 
common origin mentioned above, from a deep attachment from 
the coronoid process of the ulna, and from the shaft of the ra- 
dius. The latter origin may be quite extensive. Along the front 
of the ulna lies the flexor profundus digitorum, arising from that 
bone and from the interosseous membrane. Both of these flexors 
divide into four tendons at the wrist; those of the sublimis in- 
sert into the second phalanges, while those of the profundus in- 
sert into the terminal phalanges of the fingers. Along the front 
of the radius is the flexor longus pollicis, passing with one ten- 
don only to the terminal phalanx of the thumb. The pronator 
quadratus lies across the lower fourth of both bones under all 
the other muscles. 
Arteries and Nerves. First clean the superficial layer to the 
wrist, and then the tendons of the deeper flexors at that level so 
as to get a clear view of all these tendons together at that point. 
It is important to distinguish the various tendons here. Befpre 
going deeper, secure the radial and ulnar arteries at the wrist. 
By turning outward the brachioradialis, the radial artery can be 
followed from the cubital space to the wrist, where it passes to 
the back of the hand above the styloid process. Note a branch 
from it over the ball of the thumb. The radial branch of the 
musculospiral nerve lies to the outer side of the artery and 
passes also to the back of the arm. By turning the flexor carpi 
ulnaris inward, part of the ulnar artery and the ulnar nerve to its 
inner side will be found. Note that these structures pass to 
the palm of the hand. The upper part of the vessel and nerve 
will be exposed later. The median nerve will be found at the 
wrist beneath or a bit to the inner side of the tendon of the pal- 
maris longus. This nerve runs about in the midline from the 
cubital space to the wrist between the superficial and deep 
muscles. It is the most important motor nerve of the forearm, 
68 and supplies all the pronator flexor group except the flexor carpi 
ulnaris, and part of the flexor profundus digitorum, which are 
supplied by the ulnar nerve. 
Deep dissection. To expose the deep muscles in the upper 
half of the forearm it will be necessary to cut the pronator radii 
teres. Secure the median nerve in the cubital space and follow 
that nerve to the pronator muscle. Cut through the muscle 
until the nerve is exposed. This will mean that the superficial 
origin of the muscle has been cut. Beneath the nerve will be 
the much smaller deep head. Cut through this and the ulnar 
artery will be displayed beneath it. The two ends of the prona- 
tor radii teres can then be turned in and out. This will probably 
be sufficient to expose the upper part of the flexor sublimis and 
profundus digitorum muscles. The ulnar artery passes beneath 
the superficial layer of muscles to reach the inner side of the arm, 
where it will be found lying on the flexor profundus digitorum 
as far as the wrist. Secure the ulnar nerve above the internal 
condyle of the humerus. Follow it behind the condyle and then 
through or between the two heads of origin of the flexor carpi 
ulnaris muscle to the front of the limb. It will join the ulnar 
artery about half way down the arm. Just before reaching the 
hand it sends a dorsal branch under the tendon of the flexor 
carpi ulnaris muscle to the dorsal side of the wrist and hand. 
The median nerve lies chiefly on the flexor sublimis digitorum. 
Near the cubital space it gives off the anterior interosseous 
branch which runs with an artery of the same name (a branch of 
the ulnar artery) on the anterior aspect of the interosseous mem- 
brane as far as the wrist. The fibers of origin of the flexor pro- 
fundus digitorum from the interosseous membrane can be re- 
moved sufficiently to show this nerve and artery. Probably some 
of the fibers of origin of the flexor sublimis from the ulna and 
radius will have to be cut at the same time. Just above the hand, 
covering over approximately the lower quarter of both bones 
in the forearm, will be found the pronator quadratus, the deepest 
of all the muscles. 
Musculospiral nerve. The musculospiral nerve ends in the 
floor of the cubital space between the brachialis anticus and the 
69 origin of the extensor muscles from the outer condyle. Here the 
nerve divides into the radial and posterior interosseous. The 
radial nerve has already been seen along the outer side of the 
radial artery, lying with that vessel beneath the brachioradialis 
and resting on the flexor sublimis and the flexor longus pollicis. 
The radial nerve is a cutaneous nerve and is distributed to the 
skin on the dorsal side of the wrist and hand. The posterior 
interosseous is a purely motor nerve and supplies the greater 
part of the extensor and supinator muscles on the dorsal side 
of the arm and hand. This branch can be traced from the cubi- 
tal space into a thin flat muscle, the supinator brevis, which aris- 
es from the ulna below the lesser sigmoid cavity and is wrapped 
practically all around the neck of the radius. The nerve passes 
obliquely through this muscle around the outer aspect of the 
radius where it will be picked up in the dissection of the back 
of the arm. That portion of the supinator brevis on the front 
of the radius will be more or less covered up by the tendon of 
the biceps and by the extensor muscles from the outer condyle. 
The best view of this muscle will be found in the deep dissection 
of the back of the arm. The ulnar artery gives off a short branch 
just about at its origin in the depth of the cubital space. This 
is the interosseous artery, which divides almost at once into the 
anterior branch mentioned above, and into a posterior interos- 
seous branch which passes over the upper border of the inter- 
osseous membrane just below the elbow joint to reach the pos- 
terior surface of that membrane. 
70 DISSECTION OF THE HAND, PALMAR SURFACE 
Bones of the hand. The skeleton of the hand is made up of 
three parts: the carpus or carpal bones, which form the frame- 
work of the wrist; the metacarpal bones, forming the frame- 
work of the palm of the hand; and the phalanges, forming the 
skeleton of the thumb and fingers. The phalanges are the most 
important part and form nearly one-half of the total length of 
the hand. 
The carpus is made up of eight small bones arranged in a 
proximal and distal row of four bones each. The proximal row 
consists of the scaphoid (navicular), semilunar, cuneiform 
(triquetrum), and pisiform; the distal row of the trapezium 
(great multangular), os magnum (capitatum), and unciform 
(hamate). The various bones are very irregular in shape and 
have many articular surfaces. They also give attachment to the 
ligaments of the wrist. In general, the bones at the ends of each 
row have three articular and three non-artictilar surfaces, while 
those in the middle of the rows have four articular and two non- 
articular surfaces. This is a rough classification and does nor 
apply to the pisiform. 
In the proximal row the scaphoid and semilunar bones artic- 
ulate above with the radius, the cuneiform with the disk below 
the ulna. The pisiform is merely a sesamoid bone in the tendon of 
the flexor carpi ulnaris muscle and articulates with the cunei- 
form. The scaphoid lies obliquely at the outer end of the row. 
The chief point in connection with it is a tubercle on the palmar 
surface for the transverse carpal ligament. The semilunar lies 
between the scaphoid and cuneiform. The cuneiform lies 
obliquely at the ulnar end of the row and supports the pisiform 
on its palmar surface. The latter bone also gives attachment to 
the carpal ligament. The proximal surface of the first row is 
convex to fit the concavity of the lower end of the radius. The 
distal surface is convex towards the radial and deeply concave 
towards the ulnar side. 
The first bone at the radial end of the second row is the 
trapezium. This is marked on its palmar surface by a groove 
71 for the tendon of the flexor carpi radialis muscle and by a ridge 
for the attachment of the transverse carpal ligament. The tra- 
pezium and trapezoid are placed beneath the scaphoid and carry 
below the 1st and 2nd metacarpal bones. The os magnum is 
the largest of the carpal bones, and has a head, neck, and body. 
The head occupies the deep concavity on the inner side of the 
first row, and the body supports below the 2nd, 3rd, and 4th 
metacarpal bones. The unciform, at the ulnar end of the row, 
is characterized by a hook-like process on its palmar surface, 
to which the carpal ligament is attached. With the os magnum 
it completes the large convex surface which occupies the con- 
cavity of the under side of the first row. Below, the unciform 
carries the 4th and 5th metacarpal bones. The distal aspect of 
the second row forms a horizontal surface to articulate with the 
bases of the metacarpal bones. The carpus as a whole is slight- 
ly convex on the dorsum and concave on the palmar side. This 
concavity is deepened by'the elevations on the bones at the ends 
of each row, which support the transverse carpal ligament. This 
ligament forms the roof of the carpal tunnel, in which lie the 
long flexor tendons of the fingers and some of the vessels and 
nerves of the hand. 
The metacarpal bones are five in number. They articulate 
above with the distal row of the carpus and diverge slightly as 
they extend downwards to articulate with the phalanges. They 
form a sort of grill which is slightly convex on the dorsal side 
and concave on the palmar side of the hand. The proximal ends 
or bases are expanded and present articular surfaces at the ends 
for articulation with the carpal bones, and one or more articular 
surfaces at the sides for articulation with each other. Each base 
has distinctive peculiarities. The shafts are three-sided, with 
a flat surface towards the dorsum and a smooth ridge towards 
the palm of the hand. The distal ends or heads are large and 
rounded, the articular surface being carried further on the palmar 
than on the dorsal surface. There are tubercles on each side 
for the lateral ligaments of the metacarpophalangeal joints. The 
metacarpal bone of the thumb is broader and shorter than the 
others and has no lateral facets. 
72 The phalanges. There are two phalanges for the thumb, 
and three for each finger. The phalanges of the first and second 
rows are curved slightly like the metacarpal bones. The palmar 
surface of their shafts is smooth with lateral ridges for the at- 
tachment of the fibrous sheaths of the flexor tendons. The prox- 
imal ends of the first phalanges are broad with a concave articu- 
lar surface for articulation with the heads of the metacarpal 
bones. Their distal ends have two articular elevations or con- 
dyles divided by a median depression. The second phalanges are 
shorter than the first. The proximal ends have an articular sur- 
face with a central elevation and lateral depressions to fit the 
articular surfaces on the distal ends of the first phalanges. The 
distal ends are similar to those in the first row. The proximal 
ends of the terminal phalanges have articular surfaces similar 
to those of the second row and have flat expanded extremities 
Muscle attachments of wrist and fingers. The long flexor 
and extensor muscles of the wrist and fingers arise from the 
humerus, radius, and ulna. The muscles acting on the wrist are 
inserted into the second row of the carpus and the base of the 
metacarpal bones; the muscles acting on the fingers are inserted 
into the middle and terminal phalanges. The short flexors and 
extensors and the adductors and abductors of the thumb and 
fingers arise from the carpus and metacarpal bones and are in- 
serted chiefly into the proximal phalanges. 
Muscles inserted into the carpus and metacarpus, anterior sur- 
face. 
1st metacarpal, shaft: opponens pollicis (from carpus, radial 
side) 
2nd metacarpal, base : flexor carpi radialis 
flexor carpi ulnaris 
(from internal 
epicondyle of 
humerus) 
Pisiform, unciform 
5th metacarpal, base 
5th metacarpal, shaft: opponens digiti quinti (from carpus, 
ulnar side). 
73 Muscles arising from carpus and metacarpus, posterior surface. 
abductor pollicis 
flexor brevis pollicis 
opponens pollicis 
(to 1st phalanx 
. , . , . 
of thumb, base) 
. 
(to 1st metacar- 
shaft) 
„ .. . . . 
Carpus, radial side : 
Carpus, 2nd row 
3rd metacarpal 
adductor pollicis (to 1st phalanx of 
thumb, base). 
Carpus, 
ulnar 
side: 
abductor digiti quinti 
flexor brevis digiti quinti 
opponens digiti quinti 
(to 1st phalanx, little 
finger, base) 
(to 5th metacarpal, 
shaft) 
2nd, 4th, and 5th metacarpals: palmar interossei (to 1st 
phalanges, base, 2nd, 4th, and 5th fingers) 
Muscles inserted into carpus and metacarpus, posterior surface. 
1st metacarpal, base: abductor longus pollicis (from radius 
and ulna) 
2nd metacarpal, base: extensor carpi radialis longior 
3rd " " extensor carpi radialis brevior 
5th " " extensor carpi ulnaris 
(from lateral supracondyloid ridge and epicondyle of 
humerus) 
Muscles arising from carpus and metacarpus, posterior surface. 
All metacarpals: dorsals interossei (to 1st phalanges, base, 
2nd, 3rd, 4th fingers) 
Muscles inserted into phalanges, anterior surface. 
(from carpus radial 
side 
(from carpus second 
row; third metacar- 
pal) 
Proximal 
phalanx 
of thumb 
abductor pollicis brevis 
flexor pollicis brevis 
adductor pollicis 
Proximal phalanx of 5th finger: 
abductor digiti quinti 
flexor brevis digiti quinti 
(from carpus, ulnar side) 
74 Middle phalanges: flexor sublimis digitorum (from humerus, 
ulna, and radius) 
Terminal phalanx of thumb: flexor longus pollicis (from 
radius) 
Terminal phalanges of fingers: flexor profundus digitorum 
(from ulna) 
Muscles inserted into phalanges, posterior surface. 
Proximal phalanx of thumb: extensor pollicis brevis (from 
radius) 
Proximal phalanges of fingers, dorso-lateral surface: 
lumbricales 
palmar interossei 
dorsal interossei 
(from flexor profundus digitorum) 
(from 2nd, 4th, and 5th metacar- 
pals) 
(from all metacarpals) 
Middle and terminal phalanges of fingers: 
extensor communis digitorum 
extensor minimi digiti 
extensor indicis 
(from external epicon- 
dyle of humerus) 
I from ulna) 
Terminal phalanx of thumb: extensor pollicis longus (from 
ulna) 
Surface anatomy. Note the two elevations caused by the 
short muscles of the thumb and little finger. The tubercle of 
the scaphoid bone and the vertical ridge of the trapezium can 
be felt just above the elevation formed by the short muscles of 
the thumb along the outer side of the carpus. On the inner 
side of the carpus the pisiform bone can be moved slightly, but 
the hook of the unciform bone just distal to it is felt with con- 
siderable difficulty. Note also the transverse furrows crossing 
the palm of the hand. The position of the metacarpophalangeal 
joints corresponds to a line midway between the most distal 
furrow and the web of the fingers. 
Incisions. Make a median incision as far as the base of 
the middle finger and then two transverse incisions inward and 
outward from this point. The superficial fascia of the palm 
of the hand is extremely thick and contains much fibrous tissue. 
It is adherent to the skin and resembles the corresponding fascia 
in the sole of the foot. 
75 Palmaris brevis. In some cases this small cutaneous muscle 
will be seen lying beneath the skin over the eminence formed by 
the muscles of the little finger. 
Deep fascia. The palmar fascia, like the corresponding 
deep fascia of the foot, is extremely dense and aponeurotic over 
the central part of the palm of the hand. Its proximal end is 
more or less pointed and blends with the anterior annular liga- 
ment, which lies in front of the carpus. The tendon of the 
palmaris longus muscle when present is inserted into this part 
of the fascia. Towards the fingers the fascia broadens out and 
is attached by two slips on either side of the bases of the phal- 
anges. On either side of this aponeurotic portion the deep 
fascia is exceedingly thin and covers over the short muscles of 
the thumb and little finger. Cut the proximal attachments of 
the fascia from the annular ligament and from the tendon of the 
palmaris longus and turn it down towards the fingers. The 
thin lateral portions may be left in place temporarily, but the 
central portion of the fascia must be reflected with great care, 
as the superficial arteries and nerves in the palm of the hand 
lie immediately beneath it. The digital branches of these ves- 
sels and nerves will be seen emerging between the slips of the 
aponeurotic part of the fascia at the clefts between the fingers. 
They will be dissected later along the sides of the fingers. 
Anterior annular (transverse carpal) ligament. This is a 
strong fibrous band about an inch in width which stretches 
across the front of the carpus from the pisiform bone and hook 
of the unciform bone on the inside, to the scaphoid and trapezium 
on the outside of the wrist. It blends with the deep fascia and 
receives part of the tendon of the palmaris longus. The short 
muscles of the thumb and little finger also arise partly from it. 
The ulnar nerve and artery and the superficialis volae branch of 
the radial artery pass either superficial to it or partly through 
its superficial fibers. The median nerve and the long flexor ten- 
dons enveloped in their synovial sheaths pass beneath it. 
Superficial palmar arch. The ulnar artery having crossed 
superficially to the anterior annular ligament, swings across the 
palm of the hand forming an arterial arch with the convex side 
76 toward the fingers. When the thumb is in extreme abduction, 
a line drawn across the palm of the hand parallel to the thumb 
marks approximately the position of the arch. The superficialis 
volae branch of the radial artery, which is often small and in 
many cases lacking, communicates with the radial side of the 
arch and completes it. From the convexity of the arch, branches 
pass opposite the spaces between the metacarpal bones to the 
clefts between the fingers, where each divides into a digital 
branch passing along the contiguous sides of the fingers. In the 
palm of the hand the arch lies superficial to the branches of 
the median and ulnar nerves and the long flexor tendons. Along 
the sides of the fingers the branches of the nerves, however, 
become superficial to the corresponding arteries. Remove the 
skin from one finger and follow the vessels and nerves to the 
tip of the finger. 
Ulnar nerve. The ulnar nerve crosses superficial to the 
anterior annular ligament, lying between the ulnar artery and 
pisiform bone. In the palm of the hand its superficial branches 
are cutaneous to the little finger and usually to the ulnar side 
of the ring finger. A deep branch pierces the short muscles of 
the little finger accompanied by a corresponding branch from 
the ulnar artery. These deep branches pass underneath the long 
flexor tendons, the arterial branch helping to form the deep pal- 
mar arch while the branch of the nerve supplies the deep muscles 
of the hand to be described later. In cleaning the branches of 
this nerve the fascia can be removed from the short muscles of 
the little finger, but take care to avoid injuring the deep branches 
just mentioned. 
Median nerve. This nerve passes underneath the anterior 
annular ligament in the middle of the wrist. It breaks up at 
once into a set of digital branches which supply the skin of the 
radial side of the ring finger and both sides of the other two 
fingers and thumb on the palmar surface. It is the most impor- 
tant cutaneous nerve in the palm but supplies four muscles only, 
which will be mentioned later. 
Long flexor tendons. Having cleaned the branches of the 
superficial palmar arch and of the median and ulnar nerves, the 
77 tendons of the flexor sublimis and flexor profundus digitorum, 
which lie beneath these vessels and nerves, are next to be dis- 
sected. Note that the vessels and nerves lie opposite the spaces 
between the metacarpal bones, while the flexor tendons lie di- 
rectly opposite the metacarpal bones. In the palm of the hand 
the flexor sublimis tendon lies superficial to the corresponding 
flexor profundus tendon. On reaching the phalanges these ten- 
dons will be found to be held firmly against each phalanx by 
strong fibrous sheaths. These sheaths are lined with synovial 
membrane, which is also reflected over the tendon, thus forming 
the synovial sheaths. In the case of the tendons to the thumb 
and the tendons to the little finger, these synovial sheaths are 
usually prolonged from the distal end of the thumb and little 
finger to a point about one inch above the anterior annular 
ligament. In the case of the tendon to the first, second, and 
third fingers, the synovial sheaths usually terminate near the 
metacarpal phalangeal joint. There is then an interruption in 
the sheaths of these tendons to about the lower border of the 
anterior annular ligament. Here there begins a common sheath 
which incloses these six tendons and extends upward for about 
an inch above the annular ligament. Very often beneath and 
just above the anterior annular ligament there may be a common 
synovial sheath for all nine flexor tendons from which one pro- 
longation will extend down the little finger and another down 
the thumb. It is not easy to demonstrate these sheaths in an 
ordinary dissection, but they should be studied carefully owing 
to their practical importance in infections of the fingers. The 
fibrous sheath over one finger should first be exposed and cleaned 
and then opened up to demonstrate the synovial sheath and 
flexor tendons in it. Note particularly the peculiar plan of 
insertion of the tendons of the flexor sublimis and profundus. 
The tendon of the sublimis opposite the first phalanx splits in 
two and allows the tendon of the profundus to pass through it. 
The split portion of the sublimis reunites and attaches to the 
second phalanx, while the profundus passes to the base of the 
terminal phalanx. The action of these tendons on the second 
and third phalanges should be carefully noted. 
78 Lumbrical muscles. In cleaning the tendons of the flexor 
profundus digitorum the little lumbrical muscles should be 
noted. They have little muscular bellies, one attached to each 
tendon of the flexor profundus digitorum. They are inserted on 
the lateral sides of the dorsal surface of the proximal phalanges 
of the fingers. 
Short muscles of the thumb. The two superficial muscles 
of this group are: on the outer side, the abductor pollicis; and 
on the inner side, the flexor brevis pollicis. Separate these two 
and beneath them appears a deeper muscle layer, the opponens 
pollicis. These muscles arise in a general way from the anterior 
annular ligament and from the carpus. The two superficial ones 
are inserted into the base of the proximal phalanx, the deep one 
to the metacarpal bone of the thumb. They are supplied by the 
median nerve. 
Short muscles of the little finger. The same three muscles 
are found on this side in approximately the same position, aris- 
ing from the anterior annular ligament and carpus, and have the 
same insertion as the thumb muscles into the proximal phalanx 
of the little finger and the metacarpal bone of the little finger. 
They are supplied by the deep branch of the ulnar nerve. 
Deep dissection of the palm of the hand. To expose the 
deeper portions of the palm of the hand it will be necessary to 
cut the anterior annular ligament in the middle and to lift out 
the median nerve and the long flexor tendons. The remains of 
the synovial sheaths should be thoroughly removed from these 
tendons. It will probably be necessary to cut the superficialis 
volae artery if that is present, so that the superficial arch can be 
drawn downward and inward. This method will probably ex- 
pose sufficiently the deep palmar arch, the adductor muscles of 
the thumb, and the palmar interosseous muscles. 
Deep palmar arch. Just above the wrist the radial artery 
winds around the base of the styloid process of the radius to 
reach the dorsal side, where it will be picked up in the dissection 
of that region. On the dorsal side the artery passes forward be- 
tween the first and second metacarpal bones to reach the palm 
of the hand, where it lies on the interosseous muscles and under- 
79 neath the long flexor tendons. Here it passes to the ulnar side 
in the palm, forming the deep palmar arch which is usually com- 
pleted by the deep branch of the ulnar artery mentioned above. 
The deep arch lies from one-half to three-fourths of an inch near- 
er the wrist than the superficial arch, and the two arches 
are separated by the long flexor tendons and the median and 
ulnar nerves. From the deep palmar arch, vessels are given 
off usually to supply the thumb and the radial side of the fore- 
finger, and in addition two or three smaller arteries which anas- 
tomose with the branches of the superficial arch at the clefts of 
the fingers. The deep branch of the ulnar nerve lies in close 
relation to this deep arch. 
Adductor muscles of thumb. These consist of a transverse 
and an oblique portion arising partly from the carpus and partly 
from the metacarpal bones and inserting into the base of the 
proximal phalanx of the thumb. This muscle partly conceals 
the deep palmar arch. 
Interosseous muscles. In the palm of the hand there are 
three of these muscles, which act as adductors of the index, ring, 
and little fingers towards the middle finger. They arise from 
the metacarpal bone of the finger on which they act. The first 
is inserted on the ulnar side of the base of the first phalanx of 
the index finger, and the second and third on the radial sides of 
the corresponding phalanx of the ring and little fingers. 
Nerve supply of muscles in the palm of the hand. The me- 
dian nerve supplies the abductor pollicis, the flexor brevis pol- 
licis, the opponens pollicis, and the two lateral lumbrical muscles 
usually. All the other muscles in the palm of the hand are 
supplied by the ulnar nerve. 
80 DISSECTION OF DORSAL SIDE OF SHOULDER, AND 
ARM TO ELBOW 
Review the bony landmarks and the two superficial layers 
of muscles on the back, as given in the early pages of this sylla- 
bus. 
Incisions. The skin has already been reflected over the 
dorsal surface of the scapula. Make an incision from the tip of 
the acromion process down the midline of the arm to the olecran- 
on process of the ulna and turn the flaps inward and outward. 
The cutaneous nerves over the back of the arm may be disre- 
garded and there is nothing special to note about the fascia. 
Note especially the relations of the trapezius and latissimus dorsi 
muscles to the scapula. The remains of the trapezius muscle 
can be detached from the spine of the scapula. Note the fibrous 
layer of fascia attached to the borders of the scapula, which hold 
the dorsal scapular muscles against that bone. Review the dor- 
sal surface of the scapula, especially muscular attachments. 
Dorsal scapular muscles. The supraspinatus muscle covers 
the scapula above the spine, its tendon passing underneath the 
acromion process to the great tuberosity of the humerus. This 
tendon lies immediately above the shoulder joint. Below the 
spine of the scapula, the infraspinatus muscle covers the greater 
part of the dorsal surface of the scapula. This tendon passes 
directly behind the capsule of the shoulder joint to the great 
tuberosity of the humerus. Along the upper part of the axillary 
border of the scapula arises the teres minor muscle which often 
seems fused with the infraspinatus. Its tendon also passes be- 
hind the capsule of the shoulder joint to the great tuberosity. 
From the lower part of the axillary border arises the teres majo , 
much larger than the teres minor. Note the relations of this 
muscle to the tendon of the latissimus dorsi. The teres major 
and the latissimus dorsi tendon pass together around the medial 
aspect of the surgical neck of the humerus to reach the bicipital 
groove of that bone. 
Deltoid muscle. The deltoid muscle covers over a large 
portion of the muscles above mentioned. It will be advisable 
81 to clean the deltoid and then detach a considerable portion of its 
origin from the spine of the scapula and turn the muscle for- 
ward. This will open up the muscles mentioned above more 
completely and will facilitate their dissection. In turning up 
the edge of the deltoid, care should be taken not to injure the 
circumflex vessels and nerves which enter the deep surface of 
that muscle. Do not wholly detach the deltoid from its origin. 
Note carefully the insertion of the deltoid on the outer aspect of 
the shaft of the humerus, and the origin from the two bones of 
the shoulder girdle. 
Triceps muscle. The long head of the triceps muscle arises 
just below the glenoid fossa of the scapula, while the outer and 
inner heads cover the dorsal surface of the humerus above and 
below the musculospiral groove. Note the relation of the long 
head of the triceps to the teres major and teres minor muscles. 
When these muscles are completely dissected, two artificial 
spaces are found between them. The quadrilateral space lies 
between the surgical neck of the humerus externally and the long 
head of the triceps internally, while the teres minor and teres 
major bound it above and below. Imbedded in the areolar tissue 
in this space will be found the posterior circumflex artery from 
the axillary artery, and the circumflex nerve from the posterior 
cord of the brachial plexus. The artery and nerve lie close 
against the surgical neck of the humerus. The artery is distri- 
buted to the muscles in this region and the nerve to the teres 
minor, deltoid, and skin over the deltoid muscle. The chief im- 
portance of the quadrilateral space is the artery and nerve just 
mentioned. The triangular space is relatively unimportant, and 
lies internal to the long head of the triceps and between the 
two teres muscles. The dorsal scapular branch of the subscapu- 
lar artery reaches the posterior surface of the scapula in this 
space. 
Clean the triceps muscle to its insertion in the olecranon 
process of the ulna, and note how the three bellies end in a broad 
flat tendon. The musculospiral nerve should be picked up on 
the inner side of the arm and followed around the back of the 
humerus through the musculospiral groove. Make an incision 
82 between the inner and outer heads of the triceps muscle to ex- 
pose the nerve in th,e groove as it lies against the bone at this 
point. The nerve should be completely dissected down in the 
cubital space. A few cutaneous branches may possibly be found 
passing from the nerve down the outer side of the arm and fore- 
arm. 
83 DISSECTION OF THE DORSAL AND LATERAL SUR- 
FACE OF THE FOREARM AND DORSAL SURFACE 
OF THE HAND 
Incisions. Remove the skin from the olecranon process 
above to the bases of the fingers below. 
Cutaneous veins. In the superficial fascia on the dorsum of 
the hand will be found the cutaneous veins, which pass to the 
front of the limb just above the wrist to form the radial and ulnar 
veins. 
Cutaneous nerves. Over the outer side of the forearm 
branches of the musculocutaneous and musculospiral nerve may 
be traced to the wrist, while branches of the internal cutaneous 
nerve will be found along the inner aspect of the arm. Over 
the dorsum of the hand the ulnar nerve supplies the same area 
of skin as it did on the palm, its dorsal cutaneous branch winding 
from the front to the back a short distance above the wrist. The 
radial nerve passes from the front to the back of the forearm 
about two inches above the wrist, and supplies the same cutan- 
eous area on the dorsum of the hand that the median nerve did 
on the palmar surface. Secure the main trunks of these nerves 
and of the veins. 
Deep fascia. The deep fascia on the back of the forearm is 
much thicker and more aponeurotic than that on the anterior 
surface, especially in the upper part where the superficial muscles 
of the extensor group arise freely from it. Over the dorsal as- 
pect of the wrist there is a transverse thickening in the fascia, 
the so-called posterior annular ligament which does not have as 
definite attachments or limits as the anterior annular ligament. 
Cut through the deep fascia along the outer side of the arm and 
dissect it as carefully as possible from the underlying muscles. 
Leave the posterior annular ligament in place in order to steady 
the muscles while they are being cleaned, but its dissection will, 
however, be distinctly artificial. 
Superficial layer of muscles. Along the outer side of the 
forearm will be found the brachioradialis which has already been 
cleaned in a previous dissection. Just beneath the brachioradia- 
84 lis lie the extensor carpi fadialis longior and still deeper the ex- 
tensor carpi radialis brevier. The first two of these three 
muscles arise from the humerus well above the outer condyle, 
'while the third springs from the common origin of the extensor 
group from the outer condyle. These three muscles form the 
greater part of the muscular prominence on the lateral part of 
the forearm. The brachioradialis has been traced to its insertion 
in the styloid process of the radius. The extensor carpi radialis 
longior and brevier pass downward on the posterior aspect of 
the forearm beneath the posterior annular ligament and are in- 
serted respectively into the bases of the second and third meta- 
carpal bones. The next muscle from the common tendon of 
origin is the extensor communis digitorum. This occupies the 
greater part of the middle aspect of this region. Just above the 
wrist it divides into four tendons that pass under the posterior 
annular ligament and are inserted into the phalanges of the 
fingers. This insertion will be studied later. Along the ulnar 
side of the extensor communis, and in many cases apparently 
fused to it, is the small extensor minimi digiti which passes with 
the corresponding tendon of the extensor communis to the little 
finger. Along the ulnar side of the back of the palm lies the ex- 
tensor carpi ulnaris, which passes to the base of the fifth meta- 
carpal bone. In addition to the muscles just mentioned is the 
anconeus muscle, which extends from the back of the external 
condyle of the humerus to the outer surface of the olecranon 
process of the ulna, in the same plane with the insertion of the 
triceps muscle. 
Deep muscles. The deep muscles of the back of the fore- 
arm are the three extensor muscles of the thumb, the extensor 
of the index finger, and the supinator brevis. The first four 
of these muscles arise partly from the interosseous membrane 
and partly from the shaft of both radius and ulna. The first 
of the thumb extensors is the extensor ossis metacarpi pollicis 
(abductor longus pollicis). The latter term is probably the 
better, as the action of this muscle is rather to abduct than to 
extend the thumb. The abductor pollicis mentioned previously 
with the short muscles of the thumb on the palmar side had bet- 
85 ter be referred to as the abductor brevis pollicis. The abductor 
longus pollicis on the dorsal surface of the arm lies just above 
the extensor brevis pollicis, the two muscles coming partly from 
the radius and ulna and partly from the interosseous membrane. 
Just above the wrist the tendons of these muscles lie superficial 
to the lower end of the tendons of the extensor carpi radialis 
longior and brevior and pass to the outer aspect of the thumb, 
the abductor inserting into the base of the first metacarpal bone, 
the extensor brevis into the base of the first phalanx. The ex- 
tensor longus pollicis lies a little deeper and a little lower down 
than the two just mentioned coming from the interosseous mem- 
brane and the ulna. Its tendon at the wrist turns very sharply 
outward, crossing the insertion of the two radial extensors, and 
passes to the base of the terminal phalanx of the thumb. With 
the thumb in extreme extension and abduction these three ten- 
dons can be seen beneath the skin and should be carefully noted. 
The extensor indicis arises from the ulna and interosseous mem- 
brane beneath the tendons of the extensor communis. Its ten- 
don passes with the corresponding tendon of the communis to 
the index finger. 
The supinator brevis muscle. This muscle is wrapped 
around the upper end of the radius and extends down about to 
the origin of the thumb extensors just mentioned. To expose 
the deep layer of muscles it will be necessary to divide or separ- 
ate longitudinally the radial extensor muscles from the extensor 
communis and also to cut part of the origin of the communis 
from the common tendon and turn it towards the ulnar side. Do 
this sufficiently to expose the deep muscles just mentioned. 
Posterior interosseous nerve and artery. The posterior in- 
terosseous nerve is practically the direct continuation of the mus- 
culospiral. It should have been traced into the anterior portion 
of the supinator brevis muscle with the dissection of the front of 
the forearm. The nerve should be followed through the fibers 
of the supinator brevis and will be found running down the arm 
more or less between the superficial and deep layers of muscles 
It is the chief motor nerve of this group. In close relation to 
the nerve will probably be found the artery of the same name, a 
86 branch of the ulnar which reaches the back of the arm by pass- 
ing between the two bones above the upper border of the 
interosseous membrane. It passes more or less in relation to 
the nerve as far as the wrist, where it anastomoses with some of 
the small dorsal arteries of the wrist. 
87 Having demonstrated the above structures in the arm, they 
should be followed into the hand. Clean the various tendons 
just mentioned as far as the fingers, leaving the posterior annular 
ligament for the moment in place. The extensor tendons to one 
finger should be followed out. Note how the tendon of the 
extensor communis is more or less expanded over the dorsal sur- 
face of the first phalanx. With this expansion are connected 
the insertions of the lumbricales and the interosseous muscles. 
The expansion of this tendon then divides in a general way into 
three slips, the two lateral of which are inserted in the base of 
the terminal phalanx while the median slip is inserted into the 
second phalanx. The tendon of the extensor minimi digiti prac- 
tically blends with the expansion of the tendon of the extensor 
communis to the little finger, and the extensor indicis does the 
same with that of the index finger. Note the aponeurotic or 
tendinous slips which as a rule pass between the extensor ten- 
dons of the little finger and the ring finger, between the ring 
finger and the middle finger, and occasionally one between the 
middle finger and the index finger. 
The posterior annular ligament should now be cut and the 
tendons lifted out and cleaned. These tendons lie in synovial 
sheaths underneath the posterior annular ligament which holds 
them firmly against the back of the radius and ulna and the back 
of the carpus. Grooves can be seen usually on the radius and 
ulna for the various tendons, and the position of these grooves 
and the tendons contained in each should be carefully noted. 
The abductor longus pollicis and the extensor brevis pollicis oc- 
cupy a groove on the outer surface of the styloid process of the 
radius enveloped usually in a common synovial sheath. Pass- 
ing towards the ulnar side the next groove contains the two 
radial extensor tendons either in a common or separate synovial 
sheaths. A deep narrow cleft supports the tendon of the exten- 
sor longus pollicis. The four tendons of the extensor communis 
digitorum and the extensor indicis come next in a common 
sheath. The tendon of the extensor minimi digiti lies in its 
DISSECTION OF THE HAND 
88 synovial sheath against the ligament connecting the lower ends 
of the two bones of the forearm, while lastly against the back 
of the ulnar styloid process is the extensor carpi ulnaris in its 
synovial sheath. 
Under the extensor tendons on the dorsum of the hand are 
found small arterial branches from the so-called dorsal carpal 
arch, which pass between the metacarpal bones to the fingers 
and there anastomose with the digital arteries of the fingers. This 
dorsal, carpal arch is formed by branches from the radial and 
ulnar arteries. It usually is quite small and poorly injected. 
Note carefully the position of the radial artery on the dorsal as- 
pect of the wrist and hand. It reaches this region by winding 
around the base of the styloid process of the radius, passing 
under the tendons going to the dorsal and outer aspect of the 
thumb. It then passes forward between the first two metacarpal 
bones to form the deep palmar arch. On the dorsum of the hand 
it gives off the digital branches to the thumb and forefinger. 
Dorsal interosseous muscles. These are four in number. 
They arise in a bipenniform manner from the contiguous sur- 
faces of the metacarpal bones. Their action is to abduct the 
fingers, and they are inserted into the bases of the proximal 
phalanges of the fingers, the first on the radial side of the index 
finger, the second on the radial side of the middle finger, the 
third on the ulnar side of the middle finger, and the fourth on 
the ulnar side of the ring finger. 
89 DISSECTION OF THE JOINTS OF THE 
UPPER EXTREMITY 
The study of the joints should be left until the dissection 
of the whole limb has been finished. They will serve as a review 
of the skeleton, and their relations to the muscles and to the 
deeper parts will be better understood. The joints are an impor- 
tant part of the anatomy of any region and their dissection 
should be done with care. The joints will be opened on only 
one limb of each subject. The dissection of a joint necessitates 
much destruction of surrounding parts, and it is advisable to 
keep one limb relatively intact for study and review. The best 
dissection should be selected for preservation, and the worst 
used for the dissection of the joints. The student should begin 
with the joints of the shoulder girdle and study them with the 
shoulder joints. The elbow, forearm, and hand joints can be 
dissected in that order. 
In dissecting and studying the joints on the cadaver, the 
student should first get a good idea of the muscles which sur- 
round a joint. These can then be dissected away to expose the 
capsule in its whole extent. The attachment of the capsule to 
the bones and any strengthening bands or accessory ligaments 
should be studied. The capsule can then be opened. In the 
upper extremity it will be most convenient to open the capsule 
from the front, leaving the posterior part in place to hold the 
bones together. The joints should not be wholly separated, and 
if some of the capsule is left to preserve the connection between 
the bones, the joints can be dislocated and then replaced. They 
can also be kept for study and review. The joint ends of the 
bones should be carefully studied and their relation to the line 
of reflection of the capsule inside of the joint carefully noted. 
The more important bursae should be identified if possible. 
Sternoclavicular joint. This joint is made up of the sternal 
end of the clavicle and the articular surface on the upper border 
of the manubrium. It is the only joint which connects the skel- 
eton of the upper extremity to that of the trunk. It is a com- 
pound joint, the articular cavity being divided into two separate 
90 parts by a disk of cartilage or meniscus. The articular surfaces 
of both sternum and clavicle are poorly adapted to each other. 
The disk helps to improve their adaptation and also permits of 
different types of motion in each half of the joint. The disk is 
attached above to the upper edge of the clavicle and below to 
the cartilage of the first rib. It is included within the capsule, 
which is attached to the periphery of the articular surfaces. The 
capsule is strengthened by the interclavicular ligaments, which 
run from the top of the sternal ends of the clavicles to the upper 
border of the manubrium and partly fill the interclavicular notch, 
and by the costoclavicular (rhomboid ligament), which attaches 
the sternal end of the clavicle to the first rib. 
Movements. Antero-posterior movements of the shoulder 
take place chiefly between the disk and the sternum; up and 
down movements chiefly between the clavicle and the disk. 
Movements of circumduction take place probably in both parts 
of the joint simultaneously. The joint depends principally for 
its support on the interclavicular and costoclavicular ligaments; 
it has to support the leverage of the whole upper extremity in 
all movements involving the shoulder, and is subjected to a great 
strain. It is a very strong joint and is rarely dislocated. 
The tissues may be dissected off the anterior aspect of the 
joint to expose the capsule. Care should be taken to avoid in- 
jury to the origin of the sternomastoid muscle from the clavicle. 
Incisions may be made into the joint on either side of the disk 
to show both joint cavities. The joint must not be disarticulat- 
ed at present; this will be done in the deeper dissection of the 
neck. 
Acromioclavicular joint. This is a simple true joint be- 
tween the outer end of the clavicle and the acromion process of 
the scapula. Each bone has a small oval articular surface, and 
the joint may be subdivided by a disk. The capsule is reinforced 
above and below, but is of no great strength, and the chief union 
between the bones is the strong coracoclavicular ligament which 
runs from the clavicle to the coracoid process. This little joint 
is important, as it increases the elasticity of the shoulder girdle 
and absorbs shock from falls or blows on the shoulder. It also 
allows of limited movement between the bones. This movement 
91 permits the scapula to be held firmly against the thoracic wall 
as it moves forward and back or up and down, and enables the 
glenoid fossa to be always directed forward in line with the head 
of the humerus. The coracoclavicular ligament should be de- 
fined under the outer end of the clavicle. No other dissection of 
this joint is necessary. 
Shoulder joint. The shoulder joint is formed by the glenoid 
fossa of the scapula and the head of the humerus, and is a ball 
and socket joint. The glenoid fossa is too small and shallow to 
receive or support the large rounded head of the humerus; con- 
sequently the joint derives no real support from the adaptation 
of its articular surfaces. 
Ligaments. A ring of fibrocartilage, the cotyloid ligament, 
about half a centimeter deep, is attached around the rim of the 
glenoid fossa. It makes a feeble attempt to deepen the fossa, 
but it is too limited to grasp the head of the humerus. It really 
acts as a buffer between the two bones. The capsule is thin and 
loose. It is attached above beyond the rim of the glenoid fossa, 
often extending well back on the neck of the scapula. The 
cotyloid ligament is wholly within the capsule. Below it is at- 
tached to the anatomical neck of the humerus. A poorly marked 
band of fibers, the corachumeral ligament, is prolonged from the 
base of the coracoid process over the front and top of the capsule. 
It is really a part of the capsule and offers some slight reinforce- 
ment to it. On the deep aspect of the capsule are three thicken- 
ings, the glenohumeral ligaments. These are hard to demon- 
strate and. have but little strength. The synovial membrane 
lines the deep surface of the capsule and covers the cotyloid 
ligament. It is prolonged over the biceps tendon as the 
structure passes through the joint and ends at the periphery of 
the articular surfaces. 
The coraco-acromial ligament is an accessory ligament and 
is not a part of the capsule. It stretches between the coracoid 
and acromion processes and with them forms a strong overhang- 
ing roof to the joint, which prevents upward displacement of the 
humerus. A transverse humeral band or ligament is stretched 
between the tuberosities and supports the biceps tendon. 
Muscles. Several muscles are in immediate relation to the 
92 capsule of the joint and greatly strengthen it. On the medial 
aspect is the subcapularis muscle inserting into the lesser tuber- 
osity of the humerus. The supraspinatus passes above the 
capsule to the top of the greater tuberosity, and the infraspinatus 
and teres minor pass behind it to the back of the tuberosity. The 
origin of the long head of the triceps strengthens the under side 
of the capsule. Inside the capsule the long head of the biceps is 
of great assistance in steadying and supporting the head of the 
humerus in all positions of the joint. The tendon lies on the deep 
surface of the capsule and is covered by synovial membrane. As 
it leaves the capsule a portion of the synovia is prolonged around 
it into the upper part of the bicipital groove under the transverse 
humeral ligament. Covering all the above muscles is the deltoid, 
which forms a sort of cap over the joint. 
Bursae. There is a small bursa under the insertion of the 
subscapularis muscle, which often communicates with the joint. 
There is a large subacromial or subdeltoid bursa over the top of 
the joint. This lies under the deltoid, the acromion, and the 
coraco-acromial ligament, and facilitates the movements of the 
head of the humerus. It is of practical importance when in- 
flamed. 
Movements. The shoulder joint is capable of all movements 
and has probably the most extensive range of movements of any 
joint in the body. Its weak capsule and poorly adapted joint 
surface give no strength to the joint, and it depends for its real 
support on the surrounding muscles. These provide a mobile 
and elastic support, an arrangement admirably adapted to permit 
of the wide and varied range of movement which is so essential 
to the proper function of the human arm and hand. What is 
gained in mobility is lost in stability and strength, and the 
shoulder is very liable to dislocation. Movements of the should- 
er joint are closely associated with those of the shoulder girdle, 
which greatly increases the range of motion. 
Dissection of the shoulder joint. Note the coraco-acromial 
ligament above the joint. Open the subacromial bursa and define 
its limits. Then dissect the various muscles from the capsule, 
cutting them so as to leave stumps about two inches long at- 
tached to the tuberosities. Look for any traces of the coraco- 
93 humeral ligament. Open the interior part of the capsule by 
following the biceps tendon through the joint, observing its 
relation to the capsule. The head of the humerus can be 
displaced from the joint and the glenoid fossa and cotyloid liga- 
ment displayed. Note carefully the attachment of the capsule 
to the bones, the synovial lining, and the appearance of the first 
articular cartilage. 
Elbow joint. This joint encloses the ends of three bones, the 
lower end of the humerus and the upper ends of the ulna and the 
radius. The humerus and ulna form the chief part of the artic- 
ulation ; the radius takes only an insignificant part in the elbow 
joint proper and merely follows the ulna in the movements of 
flexion and extension. The elbow joint is a modified hinge 
joint, as the axis of rotation is oblique to the long axes of both 
humerus and ulna, and the ulna has to revolve in a spiral course 
around the humerus. 
Joint surfaces. The sigmoid cavity of the ulna adapts itself 
closely to the trochlea. The olecranon and coronoid processes 
support the bones and prevent either forward or backward dis- 
placement of the ulna or the humerus. The shape of the articular 
surfaces determines the character of the movement; it permits 
of flexion and extension only, and reduces any lateral movement 
to a minimum. Seen from the front or in frontal section, the 
capitellum and trochlea present a series of alternating elevations 
and depressions which fit closely the opposing series represented 
by the head of the radius and the sigmoid cavity of the ulna. The 
real strength of the joint lies in this excellent adaption of its 
articular surfaces. 
Ligaments. The capsule is attached on the front of the 
humerus along a line which runs just above the coronoid and 
radial fossae and then just below the epicondyles. Behind, the 
line of attachment does not include all the olecranon fossa. On 
the ulna it is attached to the margins of the olecranon and coro- 
noid processes; on the radius to the annular ligament, which 
holds the radial head in the radial notch of the ulna, and to the 
neck of the radius below. The radial and ulnar collateral liga- 
ments are merely thickenings in the capsule. They are attached 
above to the epicondyles of the humerus, below to the annular 
94 ligament of the radius and to the medial side of the olecranon and 
coronoid processes. These ligaments are tense and tend to check 
any lateral movements. The front and back of the capsule are 
relatively weak and are supported by the brachialis muscle 
anteriorly and by the triceps posteriorly. 
The synovial membrane lines the deep part of the capsule, 
is prolonged around the head of the radius and lines the annular 
ligament; small synovial folds project into the intervals between 
the bones. There are also fatty pads between the synovia and 
the capsule on the front and back of the joint. 
Muscles. The capsule is reinforced in front by the brachi- 
alis, and behind by the triceps, both of which are adherent to the 
capsule. On either side the extensor and flexor groups cover in 
the lateral portions of the capsule. 
Movements. The movements are those of flexion and ex- 
tension, which are determined by the configuration of the joint 
surfaces and by the lateral ligaments. The ulna revolves around 
the lower end of the humerus in a spiral course corresponding to 
the shape and axis of the trochlea. No joint surfaces are ever 
mathematically exact, and, while the above movements predom- 
inate, there is a little lateral movement between the ulna and 
humerus which becomes apparent in pronation and supination of 
the hand. 
Dissection of the elbow joint. Cut the biceps just above the 
epicondyles and turn the lower end down. The vessels and 
nerves in the cubital space can be drawn aside. Then cut the 
brachialis and dissect it carefully away from the capsule. The 
triceps can then be treated in a similar fashion. The back of the 
capsule is especially thin, and the triceps must be separated from 
it with great care. The origin of the flexors and extensors can 
be cut at the epicondyles and separated from the sides of the 
capsule. Note the radial and ulnar collateral ligaments. The 
anterior surface of the capsule can then be opened. Observe its 
attachment to the bones and then displace the lower end of the 
humerus. This will be more difficult, as the bones fit so closely. 
Note the head of the radius, its annular ligament, and the rela- 
tions of the synovial membrane to all parts of the joint. 
The superior radio-ulnar joint lies between the lateral surface 
95 of the head of the radius and the radial notch of the ulna. The 
annular ligament surrounds the head of the radius like a collar and 
is attached to the anterior and posterior borders of the notch. 
This joint is included in the elbow joint. 
The shafts of the radius and ulnar are connected by the 
interosseous membrane, which consists chiefly of fibers directed 
downward and inward from the interosseous border of the radius 
to that of the ulna. The membrane has an oblique free border 
above, over which vessels pass from the anterior to the posterior 
surface of the limb. This gap is bounded above by an oblique 
band of fibe; s running from the ulna to the radius just below the 
bicipital tubercle. The membrane gives attachment to the flexor 
and extensor muscles. 
The inferior radio-ulnar joint lies between the head of the 
ulna and the ulnar notch on the lower end of the radius. It is 
shut in below by the disk of cartilage between the styloid process 
of the ulna and the lower margin of the ulnar notch of the radius; 
it is entirely separated by the disk from the wrist joint. The 
capsule of the joint is strengthened in front and behind by fibers 
passing from the radius to the ulna, and a prolongation of the 
synovial membrane may extend upwards between the lower ends 
of the radius and ulna for some distance. The synovial cavity 
extends horizontally below between the disk and the head of the 
ulna. 
Movements of pronation and supination. These occur in 
the two radio-ulna joints, the radius revolving around the lower 
end of the ulna on a ve: tical axis represented by a line passing- 
through the head of the radius above and the head of the ulna 
below. In the position of supination, the palm of the hand is 
directed forward or upward; the bones of the forearm are sepa- 
rated and parallel to each other. As the motion of pronation 
begins, the head of the radius rotates in its collar in the radial 
notch of the ulna, and the lower end of the radius, carrying the 
whole hand with it, revolves around the head of the ulna. The 
fibrocartilage between the lower ends of radius and ulna acts as a 
pivot for the lower end of the radius in this movement. When 
the movement of pronation is completed, the shaft of the radius 
crosses the ulna, the head of the ulna is prominent at the back of 
96 the wrist, and the dorsal side of the hand is uppermost. In this 
movement there is some slight movement of the lower end of the 
ulna laterally, due to a slight lateral movement at the elbow joint. 
Dissection of inferior radio-ulnar joint. Clean the muscles 
oft' both sides of the interosseous membrane to demonstrate its 
attachments and the gap above it. Clear the lower end of radius 
and ulna and cut into the lower joint. Note the right angle shape 
of its cavity and its extent upward. Be careful not to injure the 
triangular fibrocartilage. which will be seen more clearly when 
the radiocarpal joint is open. 
Joints of hand. The joints of the hand may be divided into 
three groups: 1. The wrist and carpal joints; 2. The metacarpo- 
phalangeal joints; 3. The interphalangeal joints. 
Wrist and carpal joints. This group includes the radiocar- 
pal joint between the first row of carpal bones below, and the 
radius and disk of cartilage above (this forms an oval ball and 
socket (egg-shaped) joint) ; the mid-carpal joint between the 
first and second rows of the carpus (a concave-convex line of 
articulation) ; and the carpometacarpal joint between the distal 
row of the carpus and the metacarpal bones (a horizontal line of 
articulation). The carpal bones are held together by several 
interosseous ligaments which pass between their adjacent sur- 
faces. The bases of the metacarpals are connected in the same 
manner, with the exception of the metacarpal bone of the thumb, 
which is not connected with the others. The wrist joint can 
be conveniently regarded as a compound joint, the first row of 
carpal bones being the meniscus. Movements occur above and 
below this row. The second to the fifth metacarpals for all 
practical purposes follow the second row in all movements. The 
carpometacarpal joint of the thumb is independent of this com- 
pound joint in action, though included in the common capsule. 
The ligaments which are attached to the palmar and dorsal 
surfaces of the bones can be regarded as a common capsule. 
The capsule is attached above to the lower ends of radius and 
ulna where it blends with the capsule of the inferior radio-ulnar 
joint, and below to the bases of the metacarpal bones. The fibers 
are also attached to the dorsal and palmar aspects of the carpal 
97 bones. On either side the fibers are condensed to form the 
radical and ulnar collateral ligaments. The capsule is reinforced 
on both sides by the sheaths of the flexor and extensor tendons. 
The transverse carpal ligament also supports the wrist joint. 
Synovial cavities. The following separate synovial cavities 
are contained in the common capsule: 1. Inferior radio-ulnar. 
2. Radiocarpal. 3. Between trapezium and metacarpal bone 
of the thumb. 4. Between all the other bones included in this 
joint. 
Movements. Flexion and extension occur in both the radio- 
carpal and the mid-carpal joints. Flexion is rather more marked 
in the upper, and extension rather freer in the lower. Lateral 
movements are adduction or ulnar flexion, and abduction or 
radial flexion. In ulnar and radial flexion the movement is 
centered at the head of the os magnum, the distal row of the car- 
pus with the bases of the metacarpal bones moving as one piece 
from side to side on this central point. At the same time the 
proximal row of carpal bones is also displaced. In radial flexion, 
the first row is pushed to the ulnar side, and a large gap is 
opened up between the fibrocartilage and the cuneiform bone. 
In ulnar flexion, the first row is much displaced to the radial 
side, and the cuneiform bone is pushed close against the cartilage 
disk. Circumduction is a combination of the above movements, 
and takes place simultaneously in both the radiocarpal and mid- 
carpal joints. In all movements the 2nd to 5th metacarpal bones 
move practically as one piece with the distal row of the carpus. 
The 5th and possibly the 4th may be slightly flexed, as can be 
seen in the approximation of the radial and ulnar sides of the 
palm of the hand (cupping the hand). The numerous articular 
surfaces between the carpal bones permit of a considerable 
amount of gliding and yielding, which is hard to analyze. These 
well defined movements add to the elasticity and mobility of the 
wrist and act as shock absorbers in falls or blows on the wrist 
and hand. 
Carpometacarpal joint of thumb. This is a saddle-shaped 
joint between the trapezium and 1st metacarpal bone, and is 
■capable of all movements except rotation. Owing to the position 
98 of the thumb, the movements are not in the same plane as the 
corresponding movements in the fingers. Flexion of the meta- 
carpal carries the thumb towards the palm. Flexion is therefore 
combined with adduction, and extension with abduction. The 
synovial cavity is entirely independent. 
Metacarpophalangeal joints. Thumb. This is practicallv 
a hinge joint and is capable of hardly any lateral movement. 
Flexion and extension are free. There are two sesamoid bones 
connected with this articulation. The extensive movements of 
the thumb, which are such an important feature in the move- 
ments of the hand, are due to the mobility of the carpometacarpal 
joint. 
Fingers. The heads of the metacarpal bones are received in- 
to the hollow bases of the first phalanges. The heads of the 
metacarpals are bound together by the transverse metacarpal 
ligament. This blends with the capsules of the joints, which 
are also strengthened by collateral ligaments. A dense fibrous 
plate, the volar collateral ligament, strengthens the volar or an- 
terior surface of the capsule. These joints allow free flexion 
and extension. Adduction and abduction, separation of the 
fingers, are also permitted when the fingers are fully extended. 
The collateral ligaments are tense in flexion and prevent any 
lateral motion. 
Interphalangeal joints. These are pure hinge joints, with 
strong lateral ligaments, and flexion and extension are the only 
movements possible. 
Dissection of the joints of the hand. The flexor tendons can 
be cut above the wrist and turned down. Clean the anterior 
surface of the common capsule and then the posterior surface, 
cutting the extensor tendons if necessary. Remove any por- 
tion of the short muscles of the thumb and little fingers that 
are in the way. Then open the radiocarpal joint and dislocate 
the lower ends of the radius and ulna forward. Note the egg- 
shaped surface offered by the first row of carpal bones, the articu- 
lar surface of the radius, and the triangular cartilage. Pronate 
and supinate .the forearm and observe the position of the cartilage 
and the lower end of the radius in the different positions. 
99 Next open the mid-carpal and then the carpometacarpal 
joints. Note the opposing articular surfaces in each. Open the 
carpometacarpal joint of the thumb and observe its saddle-shaped 
articular surfaces. One of the metacarpophalangeal and one of 
the interphalangeal joints should be dissected to show the lateral 
ligaments and the interior arrangements. 
100 ACTION OF MUSCLES: UPPER EXTREMITY 
Shoulder girdle. The following muscles act directly on the 
shoulder girdle. Movements of the girdle are caused by other 
muscles which act directly on the arm below. These will be 
considered in the movements at the shoulder joint. 
Elevation: trapezius (upper part), levator scapuli, rhomboids 
(upper fibers). 
Depression: pectoralis minor. 
Forward movement: serratus anterior, pectoralis minor. 
Backward movement: rhomboids, trapezius (middle part). 
Shoulder joint. 
Flexion: raising the arm forward to the horizontal: deltoid 
(clavicular), pectoralis major (clavicular), biceps, coraco- 
brachialis. 
Flexion: raising the arm above the horizontal: serratus an- 
terior, trapezius (acromial). 
Extension: carrying the arm back of the body : latissimus dorsi, 
teres major and minor, infraspinatus, triceps, deltoid (scapu- 
lar). 
Abduction: raising the arm laterally to the level of the should- 
er: deltoid (middle), supraspinatus, biceps. 
Abduction: raising the arm above the level of the shoulder: 
trapezius, serratus anterior. 
Adduction: bringing the arm to the side: latissimus dorsi, 
triceps, infraspinatus, teres major and minor, pectoralis 
major, deltoid, coracobrachialis. 
Horizontal adduction: arm carried forward at shoulder level: 
coracobrachialis, pectoralis major, deltoid (anterior half). 
Horizontal abduction: arm carried backward at shoulder level: 
deltoid (middle and posterior), latissimus dorsi, teres major 
and minor, infraspinatus, triceps. 
Medial rotation: turning the arm in: deltoid (clavicular), pec- 
toralis major, subscapularis, teres major, latissimus dorsi. 
Lateral rotation: turning the arm out: deltoid (posterior), in- 
fraspinatus, teres minor. 
101 In all movements which involve the shoulder only, the 
shoulder girdle is fixed by the trapezius, rhomboids, serratus 
anterior and pectoralis minor. When the shoulder girdle comes 
into play, these muscles relax and contribute to the movement. 
Movements of the shoulder girdle greatly increase the range of 
movement of the shoulder joint. 
Elbow joint. 
Flexion: biceps, brachialis, brachioradialis, pronator teres, 
flexors of wrist and fingers, extensors of wrist and fingers 
(in pronation). The biceps is a flexor supinator; the pro- 
nator teres is a flexor pronator. 
Radio-ulnar joints. 
Pronation: pronator radio teres, pronator quadratus, flexor 
carpi radialis. 
Supination: biceps, supinator (brevis), extensors of wrist and 
thumb. Brachioradialis is probably a flexor, though it may 
have some slight action in supination. 
Wrist joint. 
Flexion: flexor carpi radialis, flexor carpi ulnaris, palmaris 
longus, long flexors of thumb and fingers. 
Extension: extensor carpi radialis, longior and brevior, exten- 
sor carpi ulnaris, abductor longus pollicis, extensors of the 
thumb and fingers. 
Abduction (radial flexion) : flexor carpi radialis, extensor carpi 
radialis longior and brevior, abductor longus pollicis, exten- 
sor longus pollicis. 
Adduction (ulnar flexion) : flexor carpi ulnaris, extensor carpi 
ulnaris. 
Joints of fingers. 
Flexion and extension only occur at the interphalnageal 
joints. 
Flexion and extension, adduction and abduction, occur at 
the metacarpophalangeal joints. 
Flexion: third phalanx, flexor profundus digitorum, second 
phalanx, flexor sublimis digitorum, first phalanx, lumbricales 
and interossei, flexor digiti and abductor digiti quinti brevis 
(little finger). 
102 Extension: third and second phalanges, interossei, lumbricales, 
all phalanges, extensor communis digitorum, extensor indi- 
cis, extensor digiti quinti. 
Abduction: dorsal interossei, abductor digiti quinti brevis 
(little finger). 
Adduction: palmar interossei. 
Joints of thumb. 
Flexion: opponens pollicis (carpometacarpal joint), flexor 
brevis, adductor, abductor brevis pollicis (carpometacarpal, 
and metacarpophalangeal joints), flexor longus pollicis (all 
joints). 
Extension: abductor pollicis longus (carpometacarpal joint), 
extensor pollicis brevis (carpometacarpal and metacarpo- 
phalangeal joint), extensor pollicis longus (all joints). 
Abduction: (carpometacarpal joint), abductor pollicis longus 
and brevis, extensor pollicis longus and brevis. 
Adduction: (carpometacarpal joint), adductor flexor brevis, op- 
ponens pollicis, first dorsal interosseus. 
103 Skull. The skull consists of the cranium and the face. The 
cranium forms the protective case for the brain and the auditory 
apparatus, and contributes to the wall of the orbits and nasal 
cavities. The face contains the jaws, which support the teeth 
and represent the beginning of the digestive tract. It also con- 
tributes to the formation of the nasal cavities and the orbits. 
The cranium. The cranium is rather arbitrarily divided into 
the vault and the base. The vault forms the rounded arched wall 
of the cranial cavity which surrounds and protects the brain, and 
is covered by the layers of the scalp externally. The base sup- 
ports the brain and provides foramina for the exit of the cranial 
nerves and for the vessels entering or leaving the cranium. It 
surrounds the delicate auditory apparatus. The bones which 
form the vault are flat bones, but are curved and arched in a 
very characteristic manner. They are reinforced along certain 
lines by ridges, which are of great importance in strengthening 
the skull and in diverting the course of impact from external 
blows. These bones consist of two plates, the external and the 
internal tables, joined by the diploe. In the meshes of the diploe 
are found numerous veins. The bones are articulated together 
by means of sutures, which are peculiarly characteristic of the 
skull. They greatly increase the elasticity of the skull and aid 
in the absorption of shock. The deep surface of the bones of 
the cranium is grooved by the middle meningeal artery, which 
supplies them, and is covered by a thick membrane, the dura 
mater. The membrane not only surrounds the brain but acts 
also as the internal periosteum of the bones of the skull. 
The bones which form the base are more uneven and broken 
up than those of the vault. They are harder and more brittle 
and are separated by sutures and pierced by numerous foramina. 
They are also covered by the dura, which is more firmly adherent 
to the base than to the vault. The bones that form the base also 
contribute to the formation of the vault. That portion found in 
the vault is usually known as the squamous portion of such a 
bone. There are two bones of the vault which do not enter into 
DISSECTION OF THE HEAD AND NECK 
104 the base. The line of demarcation between the vault and base 
is an arbitrary one, but is of some practical importance. It is 
represented on the lateral aspect of the skull by a line that runs 
along the upper border of the zygoma to the external auditory 
meatus, and from that point to the external occipital protuber- 
ance. 
The study of the separate cranial bones is difficult and tedi- 
ous, and the student should study the skull as a whole, taking 
up the various bones as they are found in the principal regions 
of the skull. This method can be readily followed on the speci- 
men which is given to each student. The temporal bones will 
require more special treatment in the study of the ear. the eth- 
moid in the study of the nasal cavity, and the jaws in the study 
of the face. 
Superior aspect of the skull. This region is formed anterior- 
ly by the vertical part of the frontal bone, and posteriorly by 
the squamous part of the occipital bone. On either side are 
the parietal bones, separated by the sagittal suture. The coronal 
suture separates the frontal from the parietals, and the lambdoid 
suture separates the parietals from the occipital bone. Near the 
posterior medial angle of the parietal bones is the parietal fora- 
men for an emissary vein. The point of meeting of the coronal 
and sagittal sutures is known as the bregma; where the sagittal 
joins the lambdoid suture is the lambda. While a detailed de- 
scription of the maxillae and the small bones of the face is given 
here, the position and relations of these bones will be reviewed 
in the dissection of the superficial and deep parts of the face, the 
orbits, and the nasal cavities. 
The maxilla. The two maxillae unite to form the upper 
jaw. They form the greater part of the skeleton of the upper 
portion of the face, part of the lateral wall and floor of the nasal 
cavity, the greater portion of the floor of the orbits, and part of 
the roof of the mouth. They contain the maxillary sinuses, 
which communicate with the nasal cavities. Each maxilla con- 
sists of a body and four processes-zygomatic, frontal, alveolar, 
and palatine. 
The body is pyramidal and hollow. It contains the maxil- 
105 lary sinus and has four surfaces. The anterior or facial surface 
appears on the face. On it are the infra-orbital foramen, just 
below the lower margin of the orbit, and the canine and incisive 
fossae, overlying the roots of the canine and incisor teeth. The 
zygomatic process separates this surface from the posterior or 
infratemporal surface, which is directed towards the infratempo- 
ral and pterygo-palatine fossae. The orbital surface lies in the 
floor of the orbit and is traversed by the infraorbital groove and 
canal for the maxillary nerve. The nasal or medial surface forms 
part of the lateral wall of the nasal cavity. From before back- 
ward is a crest, to which the inferior turbinate bone is attached; 
the lachrymal groove, containing the lachrymal canal; the open- 
ing of the maxillary sinus and the palatine groove, covered by 
the palate bone, in which the descending palatine vessels and 
nerves pass from the pterygo-palatine fossae to the roof of the. 
mouth. 
The zygomatic process projects laterally between the an- 
terior and posterior surfaces. It is blunt and rough, and sup- 
ports the zygomatic or malar bone. The frontal process pro- 
jects upward from the upper and anterior part of the body. It 
forms the inner margin of the orbit, part of the lateral wall of 
the nose, and on its anterior border supports the nasal bone. The 
alveolar process projects downward from the inferior part of the 
body and carries the sockets for the teeth of the upper jaw. The 
palatine process projects horizontally from the lower part of the 
medial surface and forms the anterior two-thirds of the hard 
palate. Its smooth upper surface lies in the floor of the nasal 
cavity; its rough inferior surface forms the roof of the mouth. 
At the anterior end of its medial border are the incisor crest and 
anterior nasal spine, which support the nasal septum. The in- 
cisive canal leads into a groove, which becomes the incisive for- 
amen when the two maxillae are in place, just behind the crest. 
Through this opening vessels and nerves pass from the nose to 
the mouth. 
The maxilla articulates with several small bones, which can 
be regarded as practically parts of the maxilla and add the finish- 
ing touches to it. The zygomatic or malar bone is attached to 
106 the zygomatic process. It forms part of the prominent outer 
border arrd wall of the orbit, and articulates with the external 
angular process of the frontal above and with the zygoma of the 
temporal bone behind. It lies in the broadest part of the face, 
and, with the zygoma, forms a supporting buttress along the side 
of the face and cranium. 
The lachrymal bone is a simple grooved plate which com- 
pletes the lachrymal canal of the maxilla and contributes to the 
inner wall of the orbit. The nasal bones are two small oblong 
bones which articulate with each other and are carried on the 
frontal processes of the maxilla. They form the bony bridge of 
the nose. Their upper ends form the nasofrontal suture with the 
frontal bone, and their lower ends give attachment to the carti- 
lage of the nose. 
The inferior turbinate resembles the ethmoid turbinates, but 
is larger. It articulates with the nasal surface of the maxilla 
and partly closes the large opening of the maxillary sinus. The 
palate bone consists of a vertical and horizontal portion. The 
vertical part covers the posterior portion of the nasal surface 
of the maxilla, and partly closes the opening of the maxillary 
sinus. Its inner surface lies in the lateral wall of the nasal cavi- 
ty; its outer in the floor of the pterygo-palatine fossa. The 
sphenopalatine foramen is in the upper part, and transmits ves- 
sels and nerves from this fossa to the nasal chamber. The hor- 
izontal or palate portion forms the posterior third of the hard 
palate, part of the floor of the nose, and part of the roof of the 
mouth. Its free posterior border gives attachment to the soft 
palate. 
Anterior aspect. Skull and face. The line of separation be- 
tween skull and face corresponds to the supra-orbital ridges. 
The anterior aspect of the skull is formed wholly by the vertical 
or squamous part of the frontal bone. The lower border of the 
vertical portion forms the thick supra-orbital ridges and ends 
laterally in the prominent external angular process, which is a 
landmark of practical importance. From this point the temporal 
ridges run upward and backward. The supraorbital notch is 
found in the supraorbital margin for the supraorbital vessels and 
107 nerves. Between the inner angles of the orbits is a flat area, the 
glabella, below which is the articulation with the nasal bones. 
Above the orbits are the supercilliary ridges, and over the most 
prominent part of the forehead are the frontal eminences. 
Face. The openings of the orbits occupy the upper lateral 
part of the face. Between them is the opening into the nose with 
the nasal bones above it. The boundaries of the orbit will be 
taken up later in the dissection of that region. The outer and 
lower borders of the orbits are formed by the malar, the inner 
border by the maxillary bones. These bones, with the nasal, 
form the main part of the skeleton of the upper region of the 
face. The infra-orbital foramen, for the infraorbital vessels and 
nerves, opens just below the lower border of the orbits. The 
opening into the nose is bounded by the nasal bones above and 
by the maxillae on either side and below. At the lower border 
of the maxillae are the alveolar processes for the upper teeth. 
The lower part of the face and the chin are formed by the 
mandible. The symphysis of the mandible forms the point of the 
jaw. The body of the mandible supports the alveolar process 
for the lower teeth, and has the two mental foramina on either 
side of the symphysis for branches of the mental nerve. The 
body ends behind in the ascending process, which will be found 
on the lateral aspect of the face. 
Lateral aspect of skull and face. The line of separation be- 
tween skull and face corresponds to the posterior border of the 
malar bone from the external angular process to the zygoma, 
and the upper border of the zygoma as far as the external audi- 
tory meatus. From before backwards the lateral surface of the 
skull is made up of the following bones: The squamous part of 
the frontal bone occupies the anterior and upper part of this re- 
gion. The external angular process articulates with the malar 
bone and lies at the outer angle of the orbit. From it the tem- 
poral ridges run upward and backward over the parietal bones. 
Below the frontal bone, is found the great wing of the sphenoid 
bone. Behind the frontal is the parietal bone, which occupies 
the upper lateral part of this region. The two parietal bones are 
joined in the midline by the sagittal suture; they articulate an- 
108 teriorly with the frontal bone by the coronal suture, and behind 
with the occipital bone by the lambdoid suture. At the most 
prominent part of the parietal bone is the parietal eminence. 
The anterior inferior angle of the parietal bone articulates with 
the great wing of the sphenoid, and lower border with the squa- 
mous part and the posterior angle with the mastoid process of 
the temporal bone. 
The squamous portion of the temporal bone completes the 
lower part of this area, and is connected by its anterior border 
to the great wing of the sphenoid. From the lower border of th A 
part of the temporal bone arises the zygoma, a narrow bony 
process, which runs horizontally forward to articulate with the 
malar bone of the face. This forms an important connection 
between the skeleton of the face and cranium, and strengthens 
the lateral part of the skull. Just below the origin of the zygoma, 
is the external auditory meatus to which is attached the carti- 
lage of the external ear. The lower and posterior part of this 
lateral region is formed by the the mastoid process of the tem- 
poral and the squamous part of the occipital bones. The mastoid 
process lies just behind the external auditory meatus and forms 
a prominent landmark on the lateral aspect of the skull. It gives 
attachments to important muscles of the head and neck, and is 
connected with the auditory apparatus. The mastoid foramen 
for an emissary vein lies near its posterior border. It articulates 
above with the posterior inferior angle of the parietal bone. The 
squamous part of the occipital bone forms the posterior part of 
this region. It is roughened for the attachment of muscles of 
the neck and of the back. At the center of this portion of the 
bone in the midline, is the external occipital protuberance, an 
important landmark on the posterior aspect of the skull. That 
part of the squamous portion below the protuberance lies in the 
base of the cranium. 
Sutures. The lambdoid suture ends below at the upper 
border of the mastoid process. This point is called the asterion. 
The coronal suture ends below at the middle of the upper border 
of the great wing of the sphenoid. This point is called the pte- 
rion. This suture, with those which separate the frontal from the 
109 sphenoid and the sphenoid and temporal from the perietal, are 
arranged in the shape of the letter H. The pterion is a point of 
great importance in the surgery of the cranium. 
Temporal fossa. This is the deep space between the malar 
bone and the zygoma anterolaterally, and the side of the skull 
medially. The medial wall of the fossa is made up of the lower 
part of the frontal, the anterior inferior angle of the parietal, the 
great wing of the sphenoid, and the squamous part of the tem- 
poral bones. The medial wall is bounded below by the infra- 
temporal crest, a ridge on the outer surface of the sphenoid. The 
fossa is bounded in front by the frontal and the malar bones, 
laterally by the zygoma, and above by the temporal crest or ridge 
of the parietal bone. The wall of the skull is very thin in this 
region and is protected by the thick temporal muscle which arises 
from the medial wall and fills the whole fossa. Below, the fossa 
communicates with the infratemporal fossa. 
The Infratemporal fossa is continuous with the temporal 
fossa and extends downward medial to the neck and ramus of 
the mandible. The medial wall is formed by the lateral ptery- 
goid plate of the sphenoid bone. The superior wall is formed 
by the under surface of the body of the sphenoid and contains 
the openings of the foramen ovale, for the mandibular nerve, and 
the foramen spinosum for the middle meningeal artery. The an- 
terior wall is formed by the infratemporal surface of the maxilla. 
A vertical slit, the pterygomaxillary fissure, leads from the me- 
dial wall into a deep cleft between the maxilla and sphenoid 
bones. This cleft is the pterygopalatine fossa, which is closed 
medially by the palate bone. The foramen rotundum for the 
maxillary nerve, and the pterygoid (vidian) canal for the vidian 
nerve, open into the posterior part of this fossa. The sphenopal- 
atine foramen opens on the medial wall into the nose, and the 
pterygopalatine canal leads down from the space to the region 
of the palate and roof of the mouth. The infratemporal fossa is 
to be associated with the mandibular nerve, the internal maxil- 
lary artery, and the pterygoid muscles. It will be exposed in 
the deep dissection of the face. The pterygopalatine fossa is to 
be associated with the maxillary nerve and the terminal branches 
110 of flie internal maxillary artery. Branches from the maxillary 
nerve and the internal maxillary artery are given off in this 
little fossa and pass to the nose, palate, and mouth. 
Face. The lateral region of the face is formed above by the 
malar bone and by the zygoma, which are the most prominent 
and superficial portions. The malar bone articulates with the 
maxilla, and the latter lies below the malar on a deeper level. 
The lower lateral part of the face is completed by the mandible, 
and the whole external surface of this bone lies in this part of 
the face. A more detailed account of the mandible is given here, 
but its medial surface should be reviewed in the dissection of 
the deep parts of the face and of the mouth. 
The mandible. The mandible consists of a horseshoe- 
shaped body and two flat broad rami extending up from the pos- 
terior part of the body. The right and left halves of the bone 
are fused together at the symphysis, which forms the prominent 
part of the chin. On either side of the symphysis are the mental 
tubercles. The upper border of the body carries the alveolar 
processes for the lower teeth. The lower border is smooth and 
rounded. On the lateral aspect of the body is the incisive fossa 
below the incisor teeth, and about one inch from the symphysis 
the mental foramen for the terminal branches of the mandibular 
nerve. An oblique line is carried up onto the anterior border of 
the ramus. 
The ramus begins at the prominent angle of the jaw, which 
is roughened for the insertion of the internal pterygoid muscle. 
The ramus is flat and expanded, and is covered by the insertion 
of the masseter muscle. The upper border of the ramus has two 
projections separated by a notch. The anterior is the coronoid 
process for the insertion of the temporal muscle; the posterior 
forms the neck and condyle of the jaw. The head, or condyle, 
articulates with the mandibular fossa on the inferior aspect of 
the temporal bone. The joint lies just below and in front of the 
external auditory canal, and the head of the jaw can be felt by 
the finger in the ear when the mouth is opened and shut. The 
alveolar processes of the upper and lower jaws with the teeth 
complete the bony framework of this part of the-face. 
111 The medial surface of the body is crossed by the mylohyoid 
line which gives origin to the mylohyoid muscle. There is a de- 
pression below the posterior part of this ridge for the submaxil- 
lary gland. Above the anterior end of the ridge the bone is 
smooth and is in relation to the sublingual gland. At the back 
of the lower part of the symphysis are the mental spines, which 
give origin to the genioglossi and geniohyoid muscles. The 
medial aspect of the ramus is marked by a rough area on the 
deep side of the angle for the insertion of the internal pterygoid 
muscle. At the center of the ramus is the opening of the inferior 
dental or alveolar canal for the inferior dental vessels and nerves. 
This opening is bounded by a sharp elevation, the lingula, to 
which the sphenomandibular ligament is attached. The mylohy- 
oid groove runs down and forward from the foramen, and con- 
tains the mylohyoid artery and nerve. 
Posterior aspect of the skull. This includes the posterior 
parts of the parietal bones above, the squamous part of the oc- 
cipital bone below, and the posterior borders of the mastoid 
processes below and laterally. The sagittal suture joins the lamb- 
doid suture at the bregma; the lambdoid suture runs downward 
and laterally to the mastoid process. This suture is irregular 
in outline and often contains numerous wormian bones. The 
lower part of this area is bounded by the superior curved lines 
of the occipital bone which run laterally from the external oc- 
cipital protuberance in the midline. This proturberance is called 
the inion. These lines give attachment to the muscles of the 
back of the neck. The parts of the occipital bone below the su- 
perior curved lines belong to the base of the skull. 
Superficial anatomy of the cranium. Identify and palpate 
the following: external angular processes, supra-orbital crest, 
and supra-orbital foramen or notch of the frontal bone; nasal 
bones; malar bone; zygomatic process, mastoid process, and 
external auditory meatus of the temporal bone; external occipi- 
tal protuberance of the occipital bone. Note the position of the 
temporal artery in front of the external ear. This can easily be 
felt on the living and in the cadaver when injected. 
Surface anatomy of the face. Identify the following: the 
112 malar bone and zygoma; the superior maxilla, especially the 
alveolar processes for the incisor and canine teeth; the mandible, 
especially the symphysis, body and the angle of the jaw. Note 
also the position of the foramina through which the terminal 
branches of the fifth nerve pass to enter the skin and fascia of the 
face. These are the supraorbital notch and foramen for the first 
division, the infra-orbital foramen for the second division, and 
the mental foramen for the third division. 
Surface anatomy of the neck. Palpate and identify the fol- 
lowing: in the median line from above downward, the hyoid 
bone, the thyroid cartilage (Adam's apple), the cricoid cartilage, 
and the trachea. The upper part of the trachea is covered by 
the thyroid cartilages. This gland is very noticeable when en- 
larged (in goitre). On the lateral aspect note the supraclavicu- 
lar fossa above the clavicle, the prominence of the sternomastoid 
muscle from the mastoid process to the sternal end of the clavicle 
and the anterior border of the trapezius. 
113 SUPERFICIAL DISSECTION OF HEAD AND NECK 
The muscles of expression form a subcutaneous muscle layer 
over the side of the neck, the face, and the scalp. This whole 
layer will be dissected at first. The scalp is the name given to 
the soft parts which cover the top and sides of the cranium. The 
layers of the scalp and the temporal fascia and the temporal 
muscle, which fills the temporal fossa, will then be studied. 
After that dissection, the calvaria will be removed and the con- 
tents of the cranium dissected. The student should be careful 
to dissect only the subcutaneous muscles over the neck and face. 
The deep dissection of these regions will be undertaken later. 
Incisions. 1. From the middle of the clavicle upward just 
in front of the ear to the midline of the head. 2. From the 
angle of the jaw forward to the point of the chin. 3. From the 
external auditory canal forward along the zygoma to the outer 
angle of the orbit, and around the margins of the orbit to the 
nose. The three anterior flaps should be turned forward about 
to the midline, but they should not be detached, as they must 
be stitched back in place during the dissection of the interior of 
the cranium. The posterior flap will probably not have to be 
touched. It may be necessary to free it a little above the ear to 
see the temporal artery, and below to free it a little from the 
clavicle to see all of the platysma muscle. Great care must be 
taken in making these incisions to cut through the skin only, 
and not to include the subcutaneous muscles of the face and 
scalp. In turning up the skin flaps it will be necessary to clean 
the deep surface of the skin to avoid injuring these muscles 
which lie in the superficial fascia just beneath the skin. 
The superficial fascia of the head and neck has several pe- 
culiar features which should be noted before beginning the dis- 
section. In the scalp it is tough and fibrous and closely adherent 
to the skin above and to the epicranial aponeurosis beneath. It 
contains the superficial vessels and nerves. In the face, beneath 
the skin of the eyelids, it is very loose and thin and has no fat. 
•Over the face and neck it is thicker, may contain a good deal of 
114 fat, and is separated by the subcutaneous muscles from the deep 
fascia. On the face it is continuous with a thick pad of fat which 
lies between the masseter and buccinator muscles. 
Superficial fascia of the neck. This is usually a rather thin 
layer, the fatty elements being best marked in the lower part of 
the neck and under the chin. The superficial muscle, the platys- 
ma. lies in or under this layer and often its fibers are so pale that 
it is difficult to distinguish them from the fascia. The incision 
must be made here with special care. 
Muscles of expression. These muscles lie immediately be- 
neath the skin and are attached at one end to bone or fascia, at 
the other to the integument. They are below or imbedded in 
the superficial fascia. They are divided into the muscles of the 
scalp, face, and neck. 
The muscles of the scalp consist first of the epicranius. 
which is composed of a frontal and occipital portion. The frontal 
belly is attached to the muscles about the eyelids, the occipital 
belly to the superior curved line of the occipital bone. The two 
bellies are connected by a layer of fascia, the epicranial aponeu- 
rosis (galea). This aponeurosis forms the second layer of the 
scalp. It is prolonged over the sides of the scalp and is con- 
nected with the subcutaneous muscles about the ear. The auric- 
ular muscles are the superior, anterior, and posterior auricularis. 
They arise from the surrounding fascia or from the temporal 
bone, and are inserted into the cartilage of the external ear. 
They are poorly developed and often cannot be seen. No special 
attention need be paid to them. 
The muscles of the face form three groups, associated with 
the orbit, nose, and mouth. The muscles about the orbits lie 
in the eyelids. The chief muscle is the orbicularis oculi, which 
forms a series of loops passing around the lids from the inner to 
the outer angles. It forms a sort of sphincter muscle about the 
lids. The corrugator is really a part of it and lies at the medial 
end of the eyebrow under the orbicularis. 
The muscles of the nose consist of longitudinal fibers run- 
ning along the sides of the nose continuous above with the epi- 
cranius, and of fibers passing horizontally over the bridge of the 
115 nose and about the nostrils. These latter can compress or dilate 
the nostrils. 
The muscles of the mouth are more numerous and more 
complicated. They are continuous with the platysma in the 
neck and with the buccinator, the deep muscle of the cheek, 
which will be seen in the deep dissection of the face. One group 
of these muscles arises from the maxilla or malar bone and 
passes to the upper lip and angle of the mouth; another group 
arises from the mandible below and runs up to the lower lip or 
angle of the mouth. The first set comprises the quadratus labii 
superioris, zygomaticus, and caninus. The second comprises the 
quadratus labii inferioris, triangularis and mentalis. These 
muscles either raise or depress the lips or angles of the mouth. 
Their fibers blend together about the lips, and this complex 
forms the orbicularis oris which acts as a sphincter muscle for 
the mouth and lips. At the angle of the mouth all these fibers 
are joined by the platysma, a part of whose fibers are known 
as the risorius. The anterior fibers of the buccinator blend with 
these muscles and contribute to the general muscle complex 
about the lips. 
The muscle of the neck is represented by the platysma, a 
thin quadrilateral sheet of muscle, which arises from the deep 
fascia over the clavicle and pectoral region. The muscles do not 
meet in the median line of the neck, but are directed upward 
and forward across the body of the jaw and spread out over the 
side of the face. A few fibers insert into the mandible, but the 
greater part join the muscle complex about the mouth. 
The dissection of these muscles is usually not very satis- 
factory. The superficial vessels of the scalp should be secured 
if possible and then the frontal bellies of the epicranius cleaned. 
They are often pale and hard to demonstrate. The posterior 
bellies can be left to the dissection of the back of the neck. In 
the face, the orbicularis oculi can be easily demonstrated. Work 
down along the side of the nose and from the lower border of the 
orbit to the upper lip. Do not attempt to remove the superficial 
fascia behind the angles of the lips, as there is danger of injur- 
ing the fascial nerves and vessels. Then work down from the 
116 lower lip to the chin. The superficial fascia must be carefully 
removed, as the fibers of the muscles blend closely with it. In 
the neck the platysma can usually be readily seen. It should be 
cleaned from below upward to the mouth. Do not go beneath 
the muscle, as the superficial nerves and veins of the neck lie 
under it and will be dissected later. 
Scalp. This term is given to the soft parts which cover the 
top and sides of the vault of the skull, and consists of three 
definite layers. 
Superficial layer. This is formed by the skin and superficial 
fascia together. The fascia is here unusually dense and is so 
closely adherent to the skin that the separation of the two is 
difficult. It contains much fibrous tissue intermingled with the 
fatty elements. The vessels and nerves of the scalp ramify in 
this fibro-fatty fascia. Secure the temporal artery in front of 
the ear and follow its branches as far as possible, removing the 
fascia to expose the vessels. This artery is one of the terminal 
branches of the external carotid which supplies branches to the 
scalp and face. Lying usually along the posterior side of the 
temporal artery is the auriculotemporal nerve, a branch of the 
third (mandibular) division of the fifth cranial nerve. This nerve 
is small and, like the other nerves in the scalp, is much obscured 
by the fibrous tissue in the fascia. The supra-orbital artery, a 
branch of the ophthalmic, will be found in the supra-orbital 
notch or foramen passing up over the forehead. With it lies 
the supra-orbital nerve, a branch of the first (ophthalmic) divi- 
sion of the fifth nerve. There are small frontal arteries and a 
small supratrochlear nerve at the inner angle of the orbit. The 
posterior auricular artery and small occipital nerve from the 
cervical plexus and the great occipital artery and nerve supply 
the skin behind the ear, back to the external occipital protuber- 
ance. It is not easy to secure them at this time and they will be 
seen with the dissection of the back of the neck. 
Second layer of the scalp. This lies in the plane of the deep 
fascia elsewhere and is continuous below with the deep fascia 
of the face and neck. It consists of a dense layer of tissue known 
as the epicranial aponeurosis, which connects the anterior and 
117 posterior parts of the occipitofrontalis (epicranius) muscle. 
The anterior bellies of this little muscle are usually pale and not 
easy to demonstrate. The anterior portions arise from the 
muscle fibers about the upper margin of the orbits, and are two 
or three inches in length. The posterior bellies arise from the 
occipital bone, and can usually be shown later. Laterally this 
aponeurosis passes to the face and neck and becomes continuous 
with the deep fascia of these regions. If the arteries in the su- 
perficial fascia have been thoroughly cleaned, the greater part 
of that layer will have been removed and the aponeurosis dis- 
played. Cut through the aponeurosis in the midline above and 
turn it down. Beneath it is a collection of very thin and loose 
tissue which connects the second layer with the third layer of 
the scalp. It is in the plane of this loose tissue that the scalp is 
detached in accidents, and where fluid can collect. This loose 
tissue is not worthy to be called a real layer, and gradually fades 
away towards the face and neck. 
Third layer. This is simply the periosteum covering the 
external surface of the skull, and is sometimes called the peri- 
cranium. Raise it for a short distance. It is rather loosely at- 
tached to the surface of the cranial bones, but more firmly along 
the line of the sutures. 
Temporal fascia and temporal muscle. These two struc- 
tures are found over the temporal fossa of the skull, where the 
bone is very thin. They are situated just above the zygoma 
between the second and third layers of the scalp. The temporal 
fascia is a very definite pearly layer which arises above from 
the superior temporal line and ends below at the zygoma. It 
will come into view as the first two layers of the scalp are turned 
down to the level of the zygoma. Having demonstrated this 
layer, cut into it and turn the flaps forward and backward. The 
temporal muscle arises beneath it from the inferior curved line 
of the temporal bone, and from the temporal fossa, and passes 
beneath the zygoma to insert into the coronoid process of the 
lower jaw. This insertion cannot be seen until a later dissection. 
Having thoroughly cleaned this muscle, the vault of the skull 
can next be removed, the brain taken out, and the structures at 
118 the base of the skull dissected. Make a circular incision through 
all soft parts with the cartilage knife about one inch above the 
level of the orbits in front, and about the same distance above 
the external occipital protuberance behind, and saw through the 
skull at this level. The skull is cpiite thin except just in front 
and behind, so one must be careful not to carry the saw cut too 
deep. The top of the skull can easily be lifted off the dura mater. 
Dura mater. This membrane is continuous with the dura 
of the spinal canal, but is thicker and consists of two layers. 
The outer layer is loosely connected with the bones of the vault, 
but is much more adherent to the prominences and foramina ar 
the base where it is carried out on the sheaths of the cranial 
nerves. At the edge of the foramen magnum it is continuous 
with the periosteum lining the spinal canal. The inner or deep 
layer is placed against the pia-arachnoid, and at the foramen 
magnum is continuous with the spinal dura. The two layers 
separate along certain lines and inclose between them the im- 
portant intracranial venous sinuses, which drain the cranial cav- 
ity and the brain, and are continued into the internal jugular 
vein. The two layers of the cranial dura also form partial folds 
or partitions which support and separate various parts of the 
brain. The outer surface is covered by the branches of the 
middle meningeal vessels. 
Middle meningeal artery. This vessel is derived indirectly 
from the external carotid artery, and lies between the dura and 
the inner aspect of the cranial bones. It enters the cranial cav- 
ity by the foramen spinosum in the sphenoid bone, runs laterally 
in the floor of the middle fossa of the base of the skull, and di- 
vides into anterior and posterior branches. The anterior branch 
runs in a groove on the deep side of the anterior inferior angle 
of the partial bone. The posterior branch runs backward on 
the deep surface of the scpiamous part of the temporal bone. 
These vessels lie on the deep side of the medial wall of the tem- 
poral fossa, where the cranial bones are very thin and are liable 
to be ruptured in fractures of the skull in this region. The 
branches of the middle meningeal artery make numerous small 
grooves on the inner table of the skull. 
119 Superior sagittal sinus. There is a longitudinal groove in 
the midline on the deep aspect of the vault of the cranium with 
small irregular depressions on either side. This groove marks 
the position of the superior longitudinal (sagittal) sinus and that 
fold of the dura known as the falx cerebri, which is placed be- 
tween the two halves or hemispheres of the brain. The sinus 
just mentioned lies in the upper or attached edge of the falx. 
The small irregular depressions are made by little bunches of 
arachnoid tissue which are placed in the lateral wall of this longi- 
tudinal sinus, and are part of the drainage system for the cere- 
brospinal fluid. They are called the Pacchionian bodies (arach- 
noid granulations). Cut into the dura along the midline and lay 
open the superior longitudinal sinus. Note the openings of the 
cerebral veins into it on either side. 
Removal of the brain. Cut through the dura on either side 
of the superior longitudinal sinus. Then make a lateral incision 
from the mid-point of the former downward to just above the 
ear, and turn the four triangular flaps downward. The central 
strip of dura, which represents the attached border of the falx 
and contains the superior sagittal sinus, will be left in place. 
The convolutions on the surface of the brain, covered by the thin 
pia-archnoid and the cerebral vessels, will be exposed. The ar- 
teries are more numerous at the base, and lie deep in the fissures, 
while the veins are more numerous at the upper aspect of the 
brain, and lie more superficial. Next cut the attachment of the 
falx at the crista galli and turn it backward between the hemis- 
pheres. The head of the subject should now be hung well over 
the edge of the table. While one student supports the brain with 
the calvarium, the other should gently raise the tips of the fron- 
tal lobes and separate the olfactory bulbs from the floor of the 
anterior fossa with the handle of the knife or the tips of the scis- 
sors. The tiny branches of the olfactory nerve will be torn from 
the bulb and remain in the cribriform plate of the ethmoid bone, 
but they are so small that it is hard to see much of them. Allow 
the brain to fall gently backward by its own weight, and the 
round white optic nerves (second pair) next appear. They are 
joined together by the optic commissure and should be cut close 
120 to that structure, leaving their peripheral stumps in the optic 
foramina of the sphenoid bone. Just behind the nerves appear 
the internal carotid arteries, and a little behind and between 
them in the midline a small stalk passes from the base of the 
brain to the hypophysis or pituitary body. The little stalk will 
probably break off itself, and the pituitary body will not be seen 
at present as it is buried under the dura at this point. Cut the 
internal carotid artery close to the foramen, but leave all arterial 
branches on the under side of the brain. Just behind the stalk 
of the pituitary body is a bony prominence on the sphenoid bone, 
the dorsum sellae, at the lateral borders of which the third or 
ocular motor nerve lies. This is a good sized nerve and is easily 
seen. Close to it lies a tiny threadlike nerve, the fourth or troch- 
lear nerve. This latter, however, is usually concealed under the 
sharp crescentic edge of the tentorium, one of the folds of the 
dura that forms a partial roof to the posterior fossa of the skull. 
This structure will be fully exposed when the brain is removed. 
Hold the frontal lobes in their present position with the left 
hand, and with the right raise the temporal lobe at the right side 
by passing the fingers of the right hand between it and the lateral 
wall of the cranial cavity. As the temporal lobe is tilted inward, 
the free edge of the tentorium is exposed, and the brain stem 
will appear ascending from the posterior fossa from beneath the 
tentorium. Support both the frontal and temporal lobes with the 
left hand, and with the right insert the knife above the level of 
the third nerve into the side of the brain stem and cut inwards 
towards the midline and backwards through the stem, carrying 
the knife above the parallel to the plane of the tentorium. Then 
drop the brain back in place, turn to the left' side, raise both 
frontal and temporal lobes as before, and make the same incision 
on the left side of the brain stem. A large artery, the basilar, 
lies in the median line on the under surface of the brain stem and 
divides at about this level into two large vessels. Endeavor to 
cut this artery behind its point of bifurcation, so that its branches 
may be left on the under surface of the brain. Both hemispheres 
can then be turned back. A large vein coming from the depths 
of the brain will probably have to be cut in the midline behind 
121 the cut stem. The hemispheres can then fall back into the cal- 
varium and be placed to one side. 
Falx cerebri. Restore this to its place, and notice how it 
forms an incomplete median septum in the cranial cavity, with 
an attached upper border, in which lies the superior longitudinal 
sinus, and a free sickle-shaped lower border, in which is placed 
the smaller inferior longitudinal sinus. This latter should be 
opened with the scissors and traced backward to the free edge 
of the tentorium. The blood current in these sinuses is from 
before backward. Note particularly the attachment of the falx 
to the tentorium. The inferior longitudinal sinus receives the 
large deep vein mentioned above, is prolonged backward between 
the attached border of the falx and the tentorium, and is known 
as the straight sinus. 
Tentorium cerebelli. This fold, like the falx, consists of 
two layers of the dura, and forms an incomplete roof to the pos- 
terior fossa of the skull. Medially it has a free crescentic border 
which surrounds the brain stem. Note the anterior attachments 
of the tentorium to the sphenoid bone. If its external or attached 
border is followed backward, it will be found to be attached to 
the upper borders of the petrous portions of the temporal bones 
and then to the grooves for the lateral sinuses on the deep sur- 
face of the occipital bones. In the midline on its superior aspect 
is the attachment of the falx. Open up the lateral sinuses along 
the attached border of the falx. On reaching the temporal bone, 
the sinus turns down towards the jugular foramen and passes 
out of sight. The superior petrosal sinus, which runs along the 
upper border of the petrous portion of that bone, enters the 
lateral sinus at this point. The superior longitudinal sinus can 
be traced behind into the beginning of the right lateral sinus, 
while the inferior longitudinal sinus and the straight sinus can 
be followed into the left. Follow carefully the position and 
course of these sinuses. 
Removal of the brain stem. Cut through the tentorium on 
either side of the attachment of the falx, and continue the inci' 
sions laterally, following the course of the lateral sinus to the 
temporal bone, but leave the sinus itself in place in its groove 
122 on the occipital bone. The two parts of the tentorium can then 
be turned out and the median piece turned back. The cerebellum 
is now exposed, and its relation to the tentorium should be noted. 
To remove it and the stem, let the head again fall backward. 
One man should steady the cerebellum as before, and the other 
gently raise the end of the stem and cut the nerves as close as 
possible to the brain. Cut first the third nerve. Just behind 
and external to it, partly under the edge of the tentorium, will 
be found the tiny thread-like fourth nerve. Next comes the very 
large fifth nerve passing forward and outward over the upper 
border of the petrous part of the temporal bone. Below and 
medial to the fifth, will be found the much smaller sixth nerve 
passing forward to the lateral border of the dorsum selae. A 
short distance behind the trunk of the fifth nerve, are the fac a' 
or seventh and the auditory or eighth nerves, passing through 
the internal auditory meatus in the petrous portion of the tem- 
poral bone. Just below these, are found the ninth, tenth, and 
eleventh nerves passing out through the jugular foramen. The 
twelfth nerve is low down and far back, and leaves the skull 
through the anterior condyloid foramen. When the brain stem 
has been turned back to this point, the vertebral arteries should 
be cut at the foramen magnum, the brain stem cut through at the 
same level, and removed. 
The intracranial aspect of the base of the skull. In order 
to appreciate the position and arrangement of the structures at 
the base of the cranium, the student should study carefully the 
macerated skull, and compare the appearance of the macerated 
base with that in which the dura remains m place. The base 
of the cranium is divided into three fossae which are arranged 
in a series of terraces. The anterior fossa is the highest, and 
the posterior the lowest. All the bones which form the vault 
of the cranium, with the exception of the parietal bone, con- 
tribute to a certain extent to the floor of these fossae. In study- 
ing them, note particularly the bony boundaries, the foramina 
with the structures passing through them, and the vessels and 
nerves found in each fossa. It is also important to get an idea 
of the general relations of each fossa to the parts of the face and 
123 neck which lie below them, though these relations will be seen 
to better advantage later. 
Anterior fossa. This fossa is formed by the frontal, eth- 
moid, and sphenoid bones. It is bounded anteriorly by the ver- 
tical part of the frontal; behind by the posterior border of the 
lesser wings of the sphenoid. The floor is made up of the orbital 
plates of the frontal, the cribriform plate of the ethmoid, and 
of the lesser wings of the sphenoid. 
The frontal bone forms the whole of the anterior and a 
portion of the lateral part of the vault, and the greater por- 
tion of the floor of the anterior fossa of the base of the cran- 
ium. It also forms the larger part of the roof of the orbits 
and contributes to the roof of the ethmoid cells which com- 
municate with the nose. It contains the frontal sinus, which 
communicates with the nasal cavity. The frontal bone is made 
up of two parts-a vertical or frontal, and a horizontal or 
orbital. The vertical part forms the whole of the anterior 
portion of the vault of the skull and part of the temporal fossa. 
Below it forms the upper margin of the orbits, and ends later- 
ally in the prominent external angular or zygomatic process. 
The horizontal part is composed of the two orbital plates, 
concave on their orbital, convex and irregular to correspond 
to the convolutions of the frontal lobes of the brain, on the 
cranial surface. The plates are separated in the center by a 
notch, which is filled by the ethmoid bone. The frontal sinus, 
one of the accessory air sinuses, lies between the tables of the 
frontal bone above the orbits. 
The ethmoid bone forms the greater part of the skeleton 
of the nose and will be described with that region. It has a 
vertical plate which divides the bone into two lateral halves. 
The upper anterior part of this plate forms a triangular eleva- 
tion, the crista galli, which projects in the middle of the an- 
terior fossa and gives attachment to the anterior end of the 
falx. The cribriform plate is horizontal and is perforated by 
many small openings for the olfactory nerves and for 
the nasociliary nerve. It forms part of the roof of the nasal 
124 cavity. The lesser wings of the sphenoid are thin flat plates and 
will be described with the middle fossa. 
Foramina. 1. Foramen caecum near the crista galli for an 
emissary vein to the nasal cavity. 2. Openings in the cribri- 
form plate for filaments of the first or olfactory nerve, which 
pass from the olfactory area of the mucosa in the nose to the ol- 
factory bulb of the brain. 3. For the nasal branch of the oph- 
thalmic division of the fifth nerve to the mucosa of the nose 
and to the skin of the nose. 
Inferior relations. In the midline this fossa forms part of 
the roof of the nasal cavities and laterally the greater part of 
the roof of the orbits. 
Middle fossa. This fossa is formed by the sphenoid and 
temporal bones. It lies at a lower level than the preceding. 
The central part is narrow and somewhat elevated; the lateral 
parts are expanded and lie at a lower level. 
The sphenoid bone contributes, to the lateral part of the 
vault and forms a large part of the middle fossa of the base of 
the cranium. This bone, with the frontal and occipital, extends 
across the whole width of the base of the skull and plays an im- 
portant role in strengthening both base and vault. The sphen- 
oid forms part of the outer wall and roof of the orbits, and part 
of the roof and lateral wall of the nasal cavity. The bone pro- 
vides the optic foramen, for the optic nerve and ophthalmic 
artery, the wide fissure, by which the first division of the fifth 
and the motor nerves, to the eye muscles enter the orbit, and 
also the foramina for the second and third divisions of the fifth 
nerve and the middle meningeal artery. 
The sphenoid has a body, which is hollow and contains the 
sphenoidal sinuses; a pair of lesser wings, and a pair of greater 
wings, which extend laterally from the body; two pterygoid 
processes, which project downward from either side of the under 
surface of the body. The body forms the central part of the 
middle fossa of the cranium. The front part of the body is 
elevated, forming the tuberculum sellae, between the optic fora- 
mina. The dorsal part forms an elevated ridge, the dorsum 
sellae, with small projections, the posterior clinoid processes, at 
the upper corners. The fossa on the body between the tuber- 
125 culum sellae and dorsum sellae is the sella turcica or pituitary- 
fossa and lodges the pituitary body. The body contains two 
cavities of unequal size divided by a septum. These are the 
sphenoidal sinuses, accessory air sinuses, which communicate 
anteriorly with the nasal cavity. Behind, the body fuses with 
the occipital bone. The under surface of the body forms the 
posterior part of the roof of the nose and gives origin to the pter- 
ygoid processes, which complete the lateral walls of the nasal 
chambers. 
The lesser wings are flat and pointed, and extend laterally 
from the front of the body. They articulate with the posterior 
border of the orbital plates of the frontal. The anterior clinoid 
processes are on the posterior border of the lesser wings near 
the body of the sphenoid. Both sets of clinoid processes give 
attachment to the tentorium. The greater wings of the sphen- 
oid extend laterally from the body and are expanded. They 
articulate laterally with the parietal and squamous part of the 
temporal; posteriorly with the petrous portions of the temporal 
bones. They have three openings, the foramen rotundum, fora- 
men ovale and foramen spinosum. Between the lesser and 
greater wings is the sphenoidal or superior orbital fissure leading 
to the orbit. 
The temporal bone contributes to the lateral area of the 
vault of the skull and forms part of the floor of the middle and 
part of the anterior wall of the posterior fossa of the base of the 
cranium. It contains the greater part of the auditory apparatus, 
provides the socket for the joint of the jaw, and the canals for 
the internal carotid artery, the facial nerve and the auditory 
nerve. It has three parts, squamous, petromastoid, and tym- 
panic. 
The squamous portion extends upwards. Its extracranial 
surface forms part of the floor of the temporal fossa and is 
smooth and covered by the temporal muscle. It gives origin 
to the zygomatic process, which runs forward to the face. That 
part of this surface below the zygoma is directed downward 
and supports the mandibular fossa for the joint of the jaw. The 
fossa is bounded in front by an eminence, the articular tubercle 
ar eminentia articularis, which forms part of the socket. Be- 
126 hind, the fossa is separated from the tympanic plate by the petro- 
tympanic (Glaserian) fissure. The intracranial surface forms 
part of the floor and lateral wall of the middle fossa, is grooved 
by the middle meningeal artery, and exhibits elevations and 
depressions coresponding to the convolutions of the temporal 
lobes of the brain. The squamous portion articulates with the 
great wing of the sphenoid and the parietal bones. 
The tympanic portion consists of a plate, the outer edge of 
which is curved and rolled on itself to form the anterior, inferior, 
and part of the posterior wall of the external auditory meatus. 
The incomplete part of the meatus above is closed in by the 
squamous portion of the bone. The main part of the plate lies 
behind the socket for the jaw, is limited by the glaserian fissure, 
and on its superficial aspect is in relation to the parotid gland. 
Its deep surface forms the bony part of the anterior wall of the 
external auditory canal. 
The petromastoid portion is in the form of a four sided 
pyramid with a base and an apex. The base is formed by the 
mastoid process on the lateral aspect of the skull. This process 
contains many small spaces, the mastoid cells, which communi- 
cate with the cavity of the tympanum. The intracranial surface 
of the mastoid is deeply grooved by the sigmoid sinus, which is 
separated by a very thin wall from the mastoid cells. The re- 
lation of the mastoid cells to the tympanic cavity and to the 
sinus is of great importance in the surgery of the ear. The apex 
of the pyramid lies on either side of the body of the sphenoid 
bone. The intracranial opening of the carotid canal lies be- 
tween the apex and the body of the sphenoid. The superior sur- 
face of the body of the petromastoid portion forms part of the 
floor of the middle fossa. From within outward on this surface 
are found, a depression for the Gasserian ganglion of the fifth 
cranial nerve; a groove and small foramen, hiatus fallopi for the 
large superficial petrosal nerve; an elevation, marking the su- 
perior semicircular canal of the internal ear; and a flat area 
which forms the roof of the antrum of the mastoid. 
The posterior surface looks backward into the posterior 
fossa and contains the internal auditory meatus and canal for 
the facial and auditory nerves. The canal conducts the audi- 
127 tory nerve to the internal ear, and the facial nerve to the facial 
canal. The facial canal passes through this part of the temporal 
bone, arches over the tympanic cavity, and opens on the lower 
surface of the petromastoid portion at the stylomastoid foramen. 
The inferior surface is directed downward onto the extracranial 
aspect of the base and will be described with that region. The 
anterior surface is of limited extent and cannot be seen from the 
surface. It lies between the petromastoid and tympanic por- 
tions and under the tegmen tympani. A glimpse of it can be 
obtained by looking down the external auditory canal. It forms 
part of the boundary of the tympanic cavity and is closely asso- 
ciated with parts of the middle and internal auditory apparatus. 
It will be described with the account of the organ of hearing. 
The petromastoid part articulates medially with the great wing 
and body of the sphenoid, posteriorly with the basilar process, 
the condyloid and squamous parts of the occipital, and above 
with the parietal bones. 
The middle fossa is bounded anteriorly by the borders of 
the lesser wings of the sphenoid and a ridge between the anterior 
clinoid processes; posteriorly by the dorsum sellae, and the su- 
perior border of. the petrous portion of the temporal bone. The 
floor is formed by the body of the sphenoid mesially, and laterally 
by the great wings of the sphenoid, and the squamous and pet- 
rous portions of the temporal. 
Foramina. 1. Optic foramen for the second or optic nerve 
from the retina of the eye to the optic commissure and optic 
tract of the brain, and the ophthalmic branch of the internal 
carotid artery to the orbit. 2. Sphenoidal fissure, for the oph- 
thalmic vein from the orbit; first or ophthalmic division of the 
fifth nerve, the sensory nerve of the orbit; third or motor oculi, 
fourth of trochlear; and sixth or abducens, the motor nerves 
of the orbit. 3. Foramen rotundum for the second or maxillary 
division of the fifth nerve to the region the upper jaw. 4. Fora- 
men ovale for the third or mandibular division of the fifth nerve 
to the region of the lower jaw. 5. Foramen spinosum for the 
middle meningeal artery. 6. Hiatus fallopii for the superficial 
petrosal nerve. 7. Carotid canal for the internal carotid artery. 
128 8. Middle lacerated foramen is filled with cartilage and only a 
small vein passes through it. 
Sinuses. 1. Cavernous. These lie on either side of the 
body of the sphenoid bone. The ophthalmic vein passes from 
the orbit via the sphenoidal fissure to the cavernous sinus. The 
blood is then drained from the cavernous sinus by the (2) su- 
perior petrosal and (3) inferior petrosal sinuses into the internal 
jugular vein. The internal carotid artery passes through the 
cavernous sinus. The third and fourth nerves and first division 
of the fifth nerve lie in that older in the outer wall of the sinus 
on their way to the sphenoidal fissure. The sixth nerve runs 
through the sinus just lateral to the internal carotid artery. 
The petrosal sinuses lie on the upper and lower borders respec- 
tively of the petrous portion of the temporal bone. The infer- 
ior petrosal sinus lies in the posterior fossa and will be followed 
in the dissection of that region. 4. Circular sinus. This con- 
nects the two cavernous sinuses but is not readily demonstrated. 
Pituitary body (hypophysis). This structure lies on the 
sella turcica between the two cavernous sinuses. It is covered 
by a layer of dura pierced in the center by the stalk which con- 
nects the hypophysis with the brain. Its relations should be 
carefully noted. 
Gasserian ganglion. This is the sensory ganglion of the 
fifth nerve, and lies in a pocket of dura mater on the superior 
surface of the petrous portion of the temporal bone. The clin- 
oid process of the sphenoid bone should be noted and the at- 
tachment to them of the anterior ends of the tentorium. 
Arteries. 1. The internal carotid artery enters the middle 
fossa through the carotid canal in the petrous part of the tem- 
poral bone, passes through the cavernous sinus and appears on 
either side of the body of the sphenoid bone. It then gives off 
the anterior and middle cerebral arteries to the brain and the 
ophthalmic arterj , which enters the orbit with the optic nerve 
in the optic forai ten. 2. The middle meningeal artery arises 
from the internal maxillary branch of the external carotid, enters 
the middle fossa Trough the foramen spinosum and runs out- 
ward towards th* anterior inferior angle of the parietal bone. 
Here it divides in o an anterior and posterior division. The for- 
129 mer runs chiefly over the deep surface of the squamous portion 
of the temporal. The relations of this vessel to the skull and 
dura are of practical importance in injuries to the temporal re- 
gion of the skull. 
Inferior relations of the middle fossa. The sphenoidal sin- 
uses lie below the floor of the pituitary fossa in the middle. Lat- 
erally the antrum of the mastoid lies below the outer part of the 
superior surface of the petrous part of the temporal bone. The 
transverse ridge on this surface marks the position of the semi- 
circular canals; the vestibule and cochlea, the other portions of 
the inner ear lie between this ridge and the internal auditory mea- 
tus. Below the squamous portion, just lateral to the superior sur- 
face of the petrous part, lies the tympanic cavity, or middle ear, 
with the external auditory canal running outward from it to the 
external auditory meatus. The joint of the jaw lies under the 
squamous portion just in front of the external auditory canal 
and meatus. The inferior surface of the body of the sphenoid 
lies jn the roof of the nasopharynx; the under surface of the 
greater wings lie over the infratemporal fossa; the inferior sur- 
face of the petrous part of the temporal bone lies over the upper 
end of the great vessels in the lateral part of the neck. 
The posterior fossa. This is the largest and deepest of the 
three fossae, and is fqrmed by the occipital, temporal, sphenoid 
and parietal bones. It is covered by the tentorium and lodges 
the cerebellum, medulla and pons. This fossa is bounded an- 
teriorly in the midline by the dorsum sellae of the sphenoid, the 
basilar portion of the occipital bone, and more laterally by the 
posterior surface of the petromastoid portion of the temporal 
bone. The squamous portion of the occipital bone forms the 
posterior boundary. The floor is formed wholly by the occi- 
pital. 
The occipital bone forms the whole of the posterior portion 
of the base and the vault of the skull. It contains the foramen 
magnum, through which the cord, the spinal part of the acces- 
sory nerves, and the vertebral arteries enter the skull. It also 
has the foramen for the hypoglossal or twelfth cranial nerve. 
The occipital bone consists of three parts: a basilar portion in 
front of the foramen magnum, lateral portions on either side, 
130 and a squamous portion behind the foramen. The basilar por- 
tion is a thick strong mass. It is fused anteriorly with the pos- 
terior surface of the body of the sphenoid. Its intracranial sur- 
face is smooth and slightly concave, and supports the medulla 
and pons. It articulates laterally with the temporal bone. The 
lateral or condyloid portions form the lateral boundaries of the 
foramen magnum. They carry the condyles of the occiput on 
their inferior surface. The hypoglossal canal for the twelfth 
cranial nerve pierces the bone at the base of the condyles. A 
small posterior condyloid canal for a vein is sometimes present. 
The sides of the condyloid portion form the jugular process 
which contains a notch, the jugular notch. This notch, with a 
con esponding notch on the temporal bone, completes the jug- 
ular foramen. The jugular process is grooved by the sigmoid 
sinus as it passes out of the foramen. The squamous part of the 
occipital bone forms the posterior part of the base of the vault 
of the skull. About the center of its intracranial surface is the 
occipital protuberance. A vertical and a horizontal ridge meet 
at this point, and divide the surface into four hollows; the two 
upper receive the posterior cerebral lobes, the lower two the 
cerebellar lobes of the brain. The superior part of the vertical, 
and the transverse ridges are grooved by the superior sagittal 
and lateral or sigmoid sinuses. The groove of the superior sinus 
usually is continuous with the right lateral sinus. The vertical 
ridge below the internal occipital protuberance is the internal 
occipital crest. 
The posterior surface of the petromastoid part of the tem- 
poral bone lies in the antero-lateral wall of the middle fossa, 
and presents the following features: the internal auditory 
meatus near the center, for the facial and auditory nerves; below 
this opening is the jugular notch forming part of the jugular fora- 
men; postero-lateral to this foramen is the deep surface of the 
mastoid process grooved by the sigmoid sinus. The posterior 
part of the sella turcica and the body of the sphenoid complete 
the anterior wall of the fossa in the midline, and with the basilar 
process of the occipital support the medulla and pons. The tip 
of the postero-inferior angle of the parietal bone just touches the 
groove for the sigmoid sinus and completes the dorso-lateral wall 
of the fossa. 
131 Foramina. 1. Foramen magnum for the upper end of the 
spinal cord, the spinal portion of the eleventh nerve, and the 
vertebral arteries. 2. Internal auditory meatus for the seventh 
or facial nerve, the motor nerve of the face, and for the eighth 
or auditory nerve from the internal ear. 3. Jugular foramen for 
the inferior petrosal and lateral sinuses which here form the 
internal jugular vein; the ninth or glossopharyngeal nerve to 
the tongue and pharnyx; the tenth or vagus nerve to the viscera 
of the neck, thorax and upper abdomen; and the eleventh or 
spinal accessory nerve to the sternomastoid and trapezius 
muscles. 4. Anterior condyloid foramen for the twelfth or hy- 
poglossal nerve, the motor nerve to the tongue. 5. Posterior 
condyloid foramen for an unimportant emissary vein. 
Sinuses. 1. The termination of the superior longitudinal 
and the straight sinuses at the internal occipital protuberance and 
the formation at the point of the (2) lateral sinuses. 3. The oc- 
cipital sinus joins the above at the same point, but it is unimpor- 
tant. 4. The termination of the superior petrosal sinus in the 
lateral sinus at the outer part of the fossa. 5. Inferior petrosal 
sinus. 
The extracranial aspect of the base of the skull can be divid- 
ed into three parts. The anterior part (excluding the mandible) 
consists of the palate and alveolar arch, divided in the midline by 
a suture. The anterior two-thirds of the palate is formed by the 
maxilla; the posterior third by the palate bone. A line of suture 
divides these two parts. Anteriorly in the midline is the incisive 
foramen, with canals opening into it from each side. It transmits 
nerves from the nose to the palate. Near the posterior free mar- 
gins of the palate on each side are the openings of the pterygo- 
palatine canals, which transmit vessels and nerves from the 
pterygopalatine fossa to the palate. The nasal cavity and orbits 
separate this region from the anterior fossa inside the skull. 
The middle division extends back to the foramen magnum 
and lies under the middle fossa of the skull and the petrous 
parts of the temporal bones. In the midline from before back, 
are the under surface of the body of the sphenoid, covered partly 
by the base of the vomer, which forms the posterior part of the 
nasal septum; and the basilar process of the occipital, with its 
132 pharyngeal tubercle. On either side of the posterior border of 
the vomer are the posterior openings into the nose. These 
openings are bounded laterally by the pterygoid processes of 
the sphenoid. Each process consists of an external and internal 
plate, joined in front but separated behind to inclose the ptery- 
goid fossa. These processes articulate with the palate bones. 
The inferior surfaces of the petrous part of the temporal bones 
run outward and backward from the sides of the basilar process. 
From within outward they present a rough area for the origin 
of the palate muscle; the beginning of the carotid canal; the 
styloid process of the temporal bone, a slender bony process 
which gives attachment to the styloid group of muscles and the 
stylohyoid ligament; and the stylomastoid foramen, through 
which the facial nerve leaves the skull. The opening of the bony 
portion of the Eustachian tube, which leads from the middle ear 
to the nose, appears just anterior to the opening of the carotid 
canal. The cartilage portion of the tube is attached to this open- 
ing. Antero-lateral to the petrous part of the temporal bone is 
the inferior surface of the great wing of the sphenoid bone with 
the foramen ovale and foramen spinosum. This portion forms 
the roof of the infratemporal fossa. Behind and external to this 
region is the tuberculum auriculare and the mandibular fossa of 
the temporal bone, and the joint of the jaw. 
The posterior division lies beneath the floor of the posterior 
fossa. It contains the foramen magnum in the center. On 
either side of the foramen are the condyloid portions of the 
occipital bones. The condyles of the occiput lie on either side of 
the anterior half of the foramen. They are elliptical elevations 
covered by hyaline cartilage, and are directed forward and 
inward. They articulate with the superior articular surfaces of 
the first cervical vertebra. Just lateral to the condyle is the 
hypoglossal canal, and lateral to the canal the jugular foramen. 
At the extreme lateral portion of this region are the occipital 
groove for the occipital artery, the digastric notch for the di- 
gastric muscle, and the under side of the mastoid process of the 
temporal bone. Behind the foramen magnum is the extracranial 
surface of the lower part of the squamous portion of the occipital 
bone. This regie n is divided by a median ridge, the external 
133 occipital crest, which ends above at the external occipital pro- 
tuberance. The inferior nuchal or curved line runs laterally 
from the middle of the crest. These lines and rough areas 
marked off by them, are for the insertion of the axial muscles 
of the neck. 
Inferior relations of the posterior fossa. The inferior sur- 
face of the basilar process lies above the pharynx and gives at- 
tachment to part of the pharyngeal wall. The foramen magnum 
and the condyloid portions of the occipital are in relation with 
the upper end of the vertebral column. The under surface of 
the mastoid process and the extracranial surface of the squamous 
part of the occipital give attachment to the mass of muscles in 
the dorsal part of the neck. 
134 Anterior fossa. No special dissection is required in this 
fossa. 
Middle fossa. The nerves to the orbit should be followed 
first. Cut into the roof of the cavernous sinus just external 
to the carotid artery and turn the outer wall laterally. The 
blood in the sinus can be carefully removed to expose the 6th 
nerve running along the outer side of the artery in the middle 
of the sinus. The 3rd, 4th, and 1st division of the 5th nerve 
can then be dissected from the deep surface of the outer wall, 
and the various nerves followed forward to the sphenoidal fis- 
sure. Remove the dura from the Gasserian ganglion. Do this 
with care, as the ganglion is very soft. Having exposed the 
ganglion, dissect out its three branches from the dura and trace 
them to their respective foramina. Then follow the 6th nerve 
through the sinus and expose at the same time the internal 
carotid artery. The dura over the pituitary body can then be 
removed and that structure displayed. Finally dissect out the 
middle meningeal artery in the floor and lateral wall of the fossa. 
Posterior fossa. Demonstrate the connection of the petrosal 
sinuses with the cavernous sinus and trace their course with 
the probe to the lateral sinus. All the sinuses can then be split 
open and fully demonstrated. All nerve trunks in all the va- 
rious openings in each fossa should, of course, be identified. 
Cerebral arteries. These vessels will be found chiefly at 
the base of the brain where they form an elaborate anastomosis 
in the pia mater, which is known as the "Circle of Willis." The 
two vertebral arteries in the posterior fossa join to form the 
basilar. This in turn divides into the posterior cerebral, which 
sends forward the two posterior communicating arteries to join 
the middle cerebral branches of the internal carotid. From 
the carotid are given off the anterior cerebral arteries, which 
pass forward and are united beneath the frontal lobes by the 
anterior communicating arteries to complete the anastomosis. 
From this circle branches are given off to the deep substance of 
the brain, which end in the form of terminal arteries. If the 
brain is firm enough, the general distribution of the main 
branches can be followed over the surface and in the fissures. 
DISSECTION OF THE FOSSAE 
135 The auditory apparatus consists of three parts: 
1. External ear. The external ear consists of a plate of 
fibrocartilage called the auricle or pinna, and the external audi- 
tory canal. The outer third of the canal is cartilaginous and is 
the direct continuation of the cartilage of the pinna. The inner 
two-thirds are formed by the tympanic and squamous portions 
of the temporal bone. This canal is bounded at its mesial or 
internal end by the membrance tympani, or the drum membrane. 
The external auditory canal lies below the lateral part of the 
middle fossa of the skull. Inferiorly is the articulation of the 
jaw, posteriorly the mastoid process, and anteriorly the parotid 
gland. The relations to the gland and the jaw will be exposed 
with the dissection of the face. 
2. Middle ear. The middle ear, or cavity of the tympanum, 
is a narrow slit situated between the petrous and tympanic 
portions of the temporal bone. It is approximately 20 mm. in 
length, 15 mm. in vertical depth, and from 2 to 5 mm. broad. 
The superior boundary of this cleft is a thin plate of bone 
belonging to the squamous part of the temporal bone, and is 
called the tegmen tympani. This plate lies in front of the ele- 
vation for the superior semicircular canal. Below the cavity of 
the middle ear is the jugular fossa and the beginning of the 
internal jugular vein. In front the cavity of the middle ear 
is bounded by the tympanic plate of the temporal bone, and 
behind by the anterior surface of the petrous portion of the 
temporal bone. Internally the cleft is prolonged into the Eus- 
tachian tube, which passes downward and inward to the naso- 
pharynx. Externally and a bit posteriorly, the cleft communi- 
cates with the mastoid antrum and with the cells of the mastoid 
process. The student should understand that the long axis of 
this narrow cavity is parallel to the long axis of the petrous 
portion of the temporal bone, and hence is placed somewhat 
obliquely. In the cavity of the middle ear are found three small 
bones or ossicles: 1. Malleus, which is attached directly to 
the inner surface of the drum membrane. 2. incus. 3. stapes. 
These three bones are connected by two small true joints, and 
AUDITORY APPARATUS 
136 the stapes at its internal encl is embedded in an opening, the 
foramen ovale, on the posterior wall of the space. On the pos- 
terior wall of the cavity of the middle ear, which is in reality 
the anterior surface of the petrous portion of the temporal 
bone, are found the following: 1. Promontory, a swelling formed 
by the cochlea, a part of the internal ear. 2. Just above the 
promontory the foramen ovale closed by the stapes. This open- 
ing communicates with the vestibule, a portion of the internal 
ear. 3. Just above the foramen ovale is an elevation formed 
by the canal for the seventh or facial nerve. Below the pro- 
montory is the foramen rotundum communicating with the in- 
ternal ear, but closed by the secondary drum membrane. There 
are two tiny striated muscles in this space, the stapedius and 
the tensor tympani, which are inserted into the ossicles. 
Mastoid process. The cavity of the middle ear extends above 
the upper limit of the drum membrane, forming the so-called 
epitympanic recess or attic. This recess is just above the level 
of the canal for the facial nerve, and is prolonged backward 
over this elevation into the mastoid antrum, a space at the base 
of the mastoid process. The mastoid antrum is placed just 
external to the elevation on the superior surface of the petrous 
portion of the temporal bone, formed by the superior semi- 
circular canal previously mentioned. On the surface of the 
skull it corresponds to a point at the upper and posterior mar- 
gin of the external auditory meatus and lies at a depth of about 
one-half inch from that point. The mastoid antrum communi- 
cates with the various cells in the mastoid process, and repre- 
sents a communication between the middle ear on the one hand 
and the spaces of the mastoid process on the other. The posi- 
tion of the mastoid process has already been noted on the ex- 
ternal surface of the skull. The internal or deep aspect of the 
mastoid process is deeply grooved by the lateral sinus, an im- 
portant practical relation in inflammation of the mastoid process. 
Eustachian tube. The Eustachian tube simply represents 
the prolongation of the cavity of the middle ear inwards and 
downwards to the nasopharynx. This can be studied and ex- 
plored with a probe when the head and neck have been split at 
a later dissection. 
137 3. Internal ear. The internal ear is composed of a com- 
plicated series of bony canals embedded in the hardest and 
densest part of the petrous portion of the temporal bone. These 
bony canals form the bony labyrinth of the internal ear. They 
are lined by a membrane which forms a series of tubes known 
collectively as the membranous labyrinth. Between the walls 
of the bone and the membranous labyrinth is a fluid called the 
perilymph. Inside the membranous labyrinth is a second col- 
lection of fluid, the endolymph. The fibers of the auditory nerve 
arise in the walls of the membranous labyrinth and emerge from 
the internal ear through the internal auditory canal on the 
posterior surface of the petrous portion of the temporal bone. 
Sub-divisions of the internal ear: 
1. Semicircular canals, three in number, known as the 
lateral, posterior and superior semicircular canals. These are 
placed just posterior to the antrum and can be located in the 
petrous part of the temporal bone by the elevation of the supe- 
rior canal previously mentioned. 
2. Vestibule. The semicircular canals empty into the ves- 
tibule. This lies just behind the foramen ovale and immediately 
above the promontory. 
3. Cochlea. The cochlea appears much like a snail's shell, 
and consists of a bony tube which makes two and one-half 
turns around a central shaft. The first turn of the cochlea forms 
the promontory previously mentioned on the posterior wall of 
the cavity of the middle eai. If a probe should be passed 
inward through the external auditory canal, and then through 
the drum membrane, it would strike the promontory or the 
foramen ovale above it. If this line should be continued, it 
would pass through the vestibule or the cochlea, and go through 
the internal auditory meatus with the auditoiry nerve into 
the posterior fossa of the skull. If a line could be drawn from 
the base of the mastoid process along the anterior of the petrous 
portion of the temporal bone, this line would approximately pass 
through the mastoid antrum, the epitympanic recess, the cavity 
of the middle ear, and down the Eustachian tube to the naso- 
pharynx. These two lines would intersect in the tympanic 
cavity approximately at the promontory. 
138 Position and boundaries of the orbit. The orbits lie below 
the anterior fossa of the skull on either side of the nasal cavities. 
The orbits are pyramidal in shape, the base of the pyramid being 
at the orbit margins, the apex at the optic foramen and inner 
end of the sphenoidal fissure. The inner walls of the two orbits 
are parallel with each other, and form the lateral wall of the 
nasal chamber. The lateral walls, however, diverge so that the 
long axis of the spaces is directed forward and outward. The 
upper wall is formed by the orbital plates of the frontal bone 
and by the lesser wings of the sphenoid; the floor by the 
maxilla and malar bones, and by a bit of the palate bone near 
the apex; the medial wall by the frontal process of the maxilla, 
the lachrymal, ethmoid, and body of the sphenoid; the lateral 
wall by the malar and sphenoid. The superior orbital (sphen- 
oidal) fissure runs from the apex outward between the roof and 
lateral wall. It communicates with the middle fossa of the 
skull. The inferior orbital (sphenomaxillary) fissure lies be- 
tween the lateral wall and floor, and communicates with the 
infratemporal and pterygopalatine fossae. On the inner wall 
are: the lachrymal groove leading into the nasolachrymal canal, 
which communicates with the nose, and two smaller openings, 
the anterior and posterior ethmoid canals. The supra-orbital 
notch or foramen lies in the upper margin at the base of the 
orbit and the optic foramen at the apex, medial to the sphenoidal 
fissure. The orbits are in relation above to the anterior fossa 
of the skull; beloW with the maxillary sinuses; medially with 
the nasal cavities ; laterally with the temporal fossa on the lateral 
surface of the skull. 
139 DISSECTION OF THE ORBIT 
Break through the thin orbital plate of the frontal bone and 
rhe lesser wing of the sphenoid, taking care not to encroach on 
the cribriform plate of the ethmoid. Immediately below the 
roof will be found a dense layer of periosteum which lines the 
cavity of the orbit. This is continuous with the dura mater at 
the optic foramen and at the sphenoidal fissure. When this layer 
is thin a good sized nerve can be seen shining through it in the 
midline. This is the frontal branch of the ophthalmic division 
of the 5th nerve. Place the blow pipe in the stump of the optic 
nerve and try to inflate the eyeball. If this is successful the 
deeper dissection will be made more conveniently. Cut through 
the periosteum along the nerve, and turn the two layers to either 
side. Beneath the periosteum is a mass of firm fat in which 
are embedded all the structures found in the orbit. In general 
the following structures will be found in the orbit: 1. Nerves. 
The second cranial nerve, or optic nerve, passing to the eyeball. 
This is the nerve of special sense. 2. The ophthalmic or first 
division of the 5th cranial nerve. This is the nerve of ordinary 
sensation, and divides into three branches just before entering 
the orbit. These branches are (a) the nasociliary, distributed 
to the mucous membrane of the nose and skin over the nose, 
(b) the frontal nerve to the skin of the upper lid and the fore- 
head. (c) the lachrymal nerve to the lachrymal gland and the 
eyelids. 3. The motor nerves to the muscles of the eyeball and 
the upper eyelid. These are the 3rd, 4th, and 6th nerves. 4. 
Vessels. The ophthalmic artery from the internal carotid. The 
ophthalmic veins which drain chiefly into the cavernous sinus 
and also anastomose with the veins of the face. 5. The lachry- 
mal gland, which secretes a fluid that keeps the conjunctive of 
the eyeball and the lids moist. 6. Nasolachrymal duct, draining 
the above secretion from the orbit to the nose. 7. The ocular 
muscles. 
Immediately beneath the periosteum in the midline is found 
the frontal nerve, which divides near the middle of the space 
into the supra-orbital and the supratrochlear nerves. The supra- 
140 orbital nerve passes out of the orbit in the supra-orbital notch 
or foramen with an artery of the same name, and is distributed 
to the forehead. The supratrochlear branch, much smaller in 
size, with several tiny frontal arteries, passes out at the inner 
angle of the orbit to the skin just above the nose. Along the 
outer margin of the orbit will be found the lachrymal nerve. 
This small nerve lies just above the superior border of the 
external rectus muscle and can be traced into the lachrymal 
gland, a pinkish brown structure about the size of the tip 
of the»finger, which lies in the upper outer angle of the orbit. 
Along the inner wall of the orbit lies the nasociliary nerve. 
This nerve passes between the superior oblique and superior 
rectus muscles, leaves the orbit by a foramen in the inner wall 
of the space, and runs to the cribriform plate. Here the 
nerve lies for a very short distance in the anterior fossa of 
the skull, and then passes through the cribriform plate into 
the anterior part of the nose, where is supplies the mucous 
membrane. Its terminal branches end in the skin on the 
tip of the nose. Just before leaving the orbit, the nasal nerve 
gives off a small infratrochlear branch which passes to the 
inner angle of the orbit. With the lachrymal nerve and with 
the nasal nerve are the corresponding arteries, and if there has 
been a good injection, these arteries are often a convenient 
guide to these nerves. The small veins can be disregarded in 
this dissection. 
All the muscles in the orbit, with one exception, arise from 
the neighborhood of the optic foramen and the inner end of 
the sphenoidal fissure, where they form a sort of muscular circle. 
From the narrow origin the muscles pass horizontally forward, 
one going to the upper eyelid and the remainder to the eyeball. 
In the midline, immediately beneath the frontal nerve, will be 
found two muscles, one above the other. The most superficial 
of the two is the levator palpebrae superioris, which is inserted 
into the tissues of the upper lid. Immediately beneath this 
muscle is the superior rectus, which is inserted into the upper 
surface of the eyeball. In the outer part of the orbit, immedi- 
ately below the lachrymal nerve and vessels, will be found the 
external rectus muscle passing to the outer aspect of the eyeball. 
141 On the medial surface of this muscle is found the sixth nerve, 
which supplies this muscle only. Along the inner wall of the 
orbit, in close relation to the nasal nerve and vessels is the 
superior oblique muscle, which passes forward to the upper 
inner angle of the orbit. Here its tendon passes through a 
little loop or hook of fibrocartilage, turns sharply outward, form- 
ing almost a right angle, and passes to the upper surface of the 
eyeball to be inserted under cover of the insertion of the supe- 
rior rectus. Just below the superior oblique is the internal 
rectus muscle. The nasal nerve passes between these two muscles 
to leave the orbit. Entering the medial surface of the superior 
oblique muscle well back in the orbit, is the fourth nerve. The 
third cranial nerve on entering the orbit breaks up into branches 
which supply all the muscles (except the superior oblique and the 
external rectus). Its branches enter the muscles on their deep 
surfaces. Having secured and cleaned the structures above men- 
tioned, the dissector should next remove a portion of the outer 
margin of the orbit. Cut through the upper border just external 
to the supra-orbital angle so as to leave the supra-orbital nerve in 
place. Make a second cut obliquely downward and inward 
through the external angular process The greater part of the 
anterior margin of the orbit can then be turned forward and 
downward. This will give more room for the deeper dissection. 
The levator palpebrae superioris and the superior rectus, 
with the frontal nerve on top of them, can then be drawn to one 
side, and the orbital fat removed, until the optic nerve and the 
eyeball are exposed. Note particularly the large white optic nerve 
passing into the posterior surface of the eyeball. Surrounding the 
optic nerve are a number of small ciliary arteries and several 
small ciliary nerves. These ciliary nerves are derived from the 
ciliary ganglion and the nasal nerve, and with the corresponding 
arteries supply the deep structures of the eyeball. The main 
trunk of the ophthalmic artery lies beneath the optic nerve in 
the optic foramen. Just inside the orbit the artery winds around 
to the upper surface of the nerve, where it breaks up into its 
terminal branches. The ciliary vessels are derived from this 
artery. Besides the arteries already mentioned, there are numer- 
ous branches going to the muscles and to the eyelids. Clean the 
142 ciliary vessels and nerves and the optic nerve thoroughly, also 
the internal and external rectus. Beneath the optic nerve, lying 
on the floor of the orbit, is the inferior rectus. The last muscle 
to be dissected is the inferior oblique. This muscle arises from 
the inner wall of the orbit close to the floor, well forward in the 
space, and passes horizontally outward beneath the eyeball to 
be inserted in its under and outer side. This muscle can be 
reached most conveniently by making an incision through the 
lower eyelid just above the floor of the orbit. A branch of the 
third nerve can be traced to this muscle. As the roof of the 
orbit is being removed, some of the ethmoid cells will be ex- 
posed along the edge of the cribriform plate. Do not injure these 
any more than can be helped, as they will be studied later with 
the nasal cavities. The ophthalmic veins can be disregarded in 
the dissection. The smaller branches of these veins unite into 
a superior vessel in the upper part of the orbit, and a correspond- 
ing inferior vessel below. These two eventually form the oph- 
thalmic vein, which passes through the sphenoidal fissure to 
the cavernous sinus. 
Deep fascia of the face. The deep fascia of the face is con- 
tinuous above with the second layer of the scalp, and below the 
jaw with the deep fascia of the neck. It is usually a fairly thin 
but well marked layer. The deep fascia of the face closely in- 
vests the superficial aspect of the parotid gland, and with the 
corresponding fascia in the neck forms a more or less complete 
capsule for the gland. In most subjects the lobules of the 
gland may be seen through the deep fascia just in front of the 
ear and below the zygoma. 
Parotid gland. Facial nerve. To remove the deep fascia, 
cut through it in front of the ear onto the surface of the parotid 
gland. This structure is grayish pink in color, and can easily 
be identified by the peculiar appearance of the gland lobules. 
Dissect the fascia with great care from the parotid gland from 
behind forward, and as the anterior border of the gland is ap- 
proached, look out for branches of the facial nerve. This nerve 
leaves the base of the skull at the stylomastoid foramen and 
passes through the parotid gland. Its branches are given off in 
the gland substance and emerge along the anterior border. From 
143 this point they spread upward, forward, and downward over the 
sides of the scalp, face, and upper part of the neck. As the 
fascia is raised from the anterior border of the gland, blunt dis- 
secting with the back of the blade of the knife along the general 
course of the nerve fibers will be the safest method to follow. 
Special care should be taken in tracing out the branches of this 
nerve, and as soon as they come into view each branch can be 
dissected out independently, and the fascia removed more or 
less piece-meal. Among the fibers of the facial nerve at the an- 
terior border of the gland will be found the duct of the gland 
known as Stensen's duct. This is a relatively large whitish 
structure running horizontally across the face about a finger's 
breadth below and parallel to the zygoma. It pierces the tissues 
of the cheek to open into the mouth. 
Facial artery and vein. The facial artery and vein cross the 
lower jaw about one inch anterior to its angle. The artery can 
be felt here pulsating in the living, or when well injected on the 
cadaver. The vein lies a little posterior to the artery and rather 
more superficially. The facial arte y has a distinctly tortuous 
course from this point towards the angle of the mouth, and up- 
ward to the inner margin of the orbit. It gives off numerous 
branches to the eyelids, mouth, and nose. The facial vein as- 
sumes an almost st aight course f om the inner angle of the 
orbit to the angle of the jaw, and its main trunk only need be se- 
cured in the dissection. The b anches of the facial nerve as they 
are traced forward through the cheek will pass superficial to 
those vessels. 
Muscles. The muscles of expression can be removed in the 
dissection of the facial vessels. There are two other muscles 
which should, however, be carefully cleaned up. (a) Masseter. 
This is one of the muscles of mastication and extends from the 
zygoma above to the angle of the jaw below. It is covered to a 
large extent by the parotid gland and its duct, and by the 
branches of the facial nerve. Clean the muscle as far as possi- 
ble without injuring these structures, (b) Buccinator muscle. 
This consists of a thin layer of muscle fibers passing between 
the alveolar process of the upper and lower jaw. It forms the 
muscular layer of the cheek, and lies at a distinctly deeper plane 
144 than the masseter. It is usually covered up by a pad of fat 
continuous with the fascia, which forms the rounded contour of 
the cheek. The muscle will be more or less obscured by the 
facial vessels and nerves. The long buccal branch of the 3rd 
division of the 5th nerve supplies the skin over this muscle and 
its main trunk should be secured. 
Trifacial, fifth cranial nerve. This is the great sensory nerve 
of the face, and arises in the gasserian ganglion. The peripheral 
part of the nerve divides into three divisions. The ophthalmic 
or first division has been studied in the dissection of the orbit, 
and supplies sensation to the nose, eyelids, and forehead. The 
maxillary or second division leaves the skull by the foramen 
rotundum, passes through the pterygopalatine fossa where it 
sends branches to the nose, palate, and roof of the mouth, and 
enters the infra-orbital groove in the floor of the orbit. Here it 
sends dental branches to the teeth of the upper jaw and emerges 
onto the face through the infra-orbital foramen, just below the 
lower margin of the orbit. This terminal part is the infra-orbi- 
tal nerve and supplies the skin of the lower lid, side and tip of 
the nose, and of the upper lip. A few branches are sent to the 
temporal region. 
The mandibular or third division leaves the skull at the 
foramen ovale and enters the infratemporal fossa. Here it gives 
off an auriculotemporal branch, which supplies the skin in the 
temporal region; the long buccal branch, which supplies the 
skin over the buccinator muscle; the lingual branch, which sup- 
plies the anterior part of the mucosa of the tongue,. and an in- 
ferior dental branch to the teeth of the lower jaw. This latter 
nerve gives off the terminal or mental branch which reaches the 
face by the mental foramen of the mandible and supplies the skin 
over the lower jaw. The only motor fibers which are found with 
the 5th nerve accompany the third division, and supply the 
muscles of mastication (temporal, masseter, internal and external 
pterygoid). The student can only dissect the infra-orbital and 
mental branches at this stage. The other branches will be found 
in the deep dissection of the face and in the nasal cavity. Many 
of the smaller deep branches run in bony canals and cannot be 
readily dissected. The terminal branches of the infra-orbital 
145 and mental nerves are very small as they pass through the 
muscles of expression to the skin. Secure the main trunks as 
they emerge from the foramina and follow the branches from 
that point. Both nerves adjoin the branches of the facial. 
Seventh or facial nerve. The terminal branches of this nerve 
have been noted as they emerge at the anterior border of the 
parotid gland and pass to the muscles of expression. These 
branches should now be traced backward into the substance of 
the parotid gland, the gland tissue being dissected away until 
the main trunk of the nerve is reached in the depths of the gland. 
The branches of the facial nerve in the substance of the gland 
lie superficial to the external carotid artery and its temporal and 
internal maxillary branches, and also to the corresponding veins. 
These veins unite at the lower border of the gland to form the 
external jugular vein of the neck. The course of the facial 
nerve from the internal auditory meatus through the facial canal 
in the petrous part of the temporal bone, and particularly in the 
relation of this canal to the cavity of the middle ear, should be 
carefully studied. 
Parotid gland. This is the largest of the three salivary 
glands. Note carefully its superficial relations; the zygoma is 
above, the external auditory canal, the tympanic plate of the 
temporal bone, and the mastoid process lie behind. Beneath the 
superficial part of the gland, is the masseter muscle and the 
ramus of the mandile. The anterior limits of the gland vary 
considerably, but usually the duct arises from its extreme an- 
terior portion. The course of the duct and its relation to the 
branches of the facial nerve have already been noted. The deep 
portion of the gland is thrust into the depths of the upper part 
of the neck, between the posterior border of the ramus of the 
jaw in front, and the tympanic plate of the temporal bone be- 
hind. The deep or medial aspect of this portion rests on the 
styloid process of the temporal bone, and on the great vessels 
and nerves of the neck in this region. These important deep 
relations will be partly exposed as the gland is removed piece- 
meal in the dissection of the facial nerve, and more particularly 
at a later stage with the deep dissection of the neck. 
146 Dissection of the infratemporal fossa. This region is situ- 
ated medial to the ramus of the jaw. The fossa is continuous 
medially with the sphenomaxillary or pterygopalatine fossa, a 
narrow cleft between the maxilla and the sphenoid bone. This 
latter fossa in turn communicates with the orbit and nasal 
cavities. This whole area should be carefully studied on the 
skull before beginning the dissection. The infratemporal region 
contains two of the muscles of mastication, the external and in- 
ternal pterygoids; the internal maxillary artery; and a large 
part of the branches of the mandibular division of the fifth nerve. 
In the sphenomaxillary fossa will be found the termination of 
the internal maxillaiy aitery and a part of the maxillary division 
of the fifth nerve. 
To expose this region it will be necessary to remove part of 
the zygomatic process and the upper half of the ascending ramus 
of the mandible. Before removing these bones the temporo- 
mandibular joint should be studied. A bit of the posterior 
border of the masseter muscle and the remains of the parotid 
gland will have to be removed to expose the capsule of this joint. 
Care should be taken to avoid injuring the auriculotemporal 
nerve, which is just behind the neck and dondyle of the jaw. 
The temporomandibular joint is a compound joint and is 
formed by the condyle of the mandible below and the mandibular 
fossa of the temporal bone above. The condyle of the mandible 
is cylindrical with its long axis running forward and outward. 
The articular surface on the temporal bone includes the mandib- 
ular fossa and the articular eminence in front of it. This gives 
a concave-convex surface from behind forward. The articular 
capsule is thin and reinforced laterally by the so-called temporo- 
mandibular ligament, a sort of collateral ligament. The joint is 
subdivided into two separate synovial cavities by a disk which 
improves the adaptation of the articular surfaces. On the medial 
side of the joint is an accessory band of tissue, the sphenoman- 
dibular ligament, from the sphenoid to the inner surface of the 
mandible, and also the stylomandibular ligament, from the 
styloid process of the temporal bone to the angle of the mandible. 
Neither of these are connected with the joint, but they help to 
support the mandible. 
147 Movements of the mandible are depression and elevation, 
protraction and retraction, obliqne and grinding movements. 
The disk follows the condyle in all movements as it moves for- 
ward or backward when the mouth is opened or shut, or the jaw 
thrust forward and drawn back. At the same time the condyle 
revolves on the under surface of the disk. After the capsule has 
been cleaned, cut into it to demonstrate the disk and the two 
separate synovial cavities. Do not disarticulate the joint, as the 
head and neck of the jaw are needed to support the external 
pterygoid muscle. 
Clean the deep surface of the zygoma by blunt dissection 
with the handle of the knife or forceps. Dissect all tissues off 
its superficial aspect including the temporal branches of the 
facial nerve, leaving enough tissue near the orbit to support 
these branches. Then clear the posterior and anterior borders 
of the masseter from the parts beneath by blunt dissection so that 
the muscle can be easily turned down towards its insertion. Cut 
the origin of the masseter from the zygoma and turn it down 
until the upper half of the ascending ramus of the jaw is exposed. 
The facial nerve should be preserved and turned down with the 
muscle. It may be necessary to sacrifice some of its temporal 
branches and those going to the muscles of the eyelids in order 
to turn the nerve down far enough with the masseter. As the 
masseter is reflected, note its nerve, which emerges in the notch 
at the upper border of the ramus of the jaw and enters the deep 
surface of the muscle. The nerve will have to be cut. Then cut 
through the zygoma just in front of the joint of the jaw and 
close to the malar bone, and remove the piece. Clear away some 
fatty tissue to expose the insertion of the temporal muscle into 
the anterior border and deep surface of the ramus of the jaw. 
The coronoid process must next be detached from the ramus 
either with the saw or with bone forceps, and it with the tem- 
poral muscle turned upward. Try to show the nerves which 
enter the deep surface of the muscle to supply it. The deepest 
fibers of the insertion of the muscle must be carefully raised 
as the internal maxillary artery and the external pterygoid 
muscle lie beneath imbedded in loose areolar tissue. This tissue 
148 contains numerous tiny veins which form the pterygoid plexus. 
These can be disregarded, however, and removed with the sur- 
rounding tissue. The external pterygoid muscle arises by two 
heads from the great wing and from the external pterygoid plate 
of the sphenoid bone. The muscle passes horizontally backward 
and is inserted into the neck of the jaw, blending closely with 
the capsule of the temporomandibular joint. Only the upper 
part of the muscle will be seen at present, and it will be more 
fully displayed when more bone has been removed. The inter- 
nal maxillary artery passes under the neck of the jaw and usually 
runs forward and inward on the superficial aspect of the external 
pterygoid. It passes between its two heads to enter the spheno- 
maxillary fossa. It is, therefore, cpiite superficial in this dissec- 
tion. Often, however, it runs under the external pterygoid and 
will not be seen at this stage. Clean the artery and as much 
of the external pterygoid as is possible. 
To expose more fully the infratemporal region, the dissector 
must remove that part of the ascending ramus of the mandible 
above the level of the inferior dental foramen. Care must be 
taken to keep just above the level of this opening so as to pre- 
serve the inferior dental vessels and nerves. The cut with the 
saw or bone forceps should therefore be made at about the mid- 
dle of the ramus. Before making the cut clear the underlying 
tissues along the anterior and posterior borders of the ramus by 
blunt dissection. The condyle and neck of the jaw must be 
left in place to support the external pterygoid muscle. Cut 
through the neck first and then through the ramus, and remove 
the piece of bone. The internal maxillary artery and all of the 
external pterygoid muscle can then be cleaned. The buccinator 
nerve from the third division of the fifth passes through the two 
heads of the external pterygoid muscle and runs forward and 
downward to the skin over the buccinator muscle. It should be 
looked for in cleaning the external pterygoid. 
The internal pterygoid muscle arises by two heads from the 
maxilla and the pterygoid fossa of the sphenoid bone, and passes 
downward to be inserted into the angle of the jaw. It runs at 
almost a right angle to the external pterygoid muscle and with 
149 the masseter muscle forms a sling to support the jaw. The re- 
lations of the two heads of these muscles to each other should be 
noted. 
The internal maxillary artery gives off branches to the 
muscles of the mastication and to the teeth in the upper and 
lower jaw. The inferior dental branch enters the inferior dental 
canal in the lower jaw with the corresponding nerve. The mid- 
dle meningeal branch passes upward to the foramen spinosum of 
the sphenoid. The terminal branches of the vessel are given off 
in the sphenomaxillary fossa to the nose and palate. The cor- 
responding veins form the pterygoid plexus, which drains into 
the internal maxillary vein. This vein joins the temporal vein 
in the parotid gland, and with the posterior auricular forms the 
external jugular vein. 
The mandibular or third division of the fifth nerve leaves 
the cranium through the foramen oval. It consists of a large 
sensory and a small motor branch. The latter supplies the 
muscles of mastication. Its branches to the temporal and mas- 
seter muscles have already been mentioned, but its pterygoid 
branches will not be seen, as they enter the deep surface of those 
muscles. The sensory branch divides into the auriculotemporal, 
lingual, and inferior dental nerves. The auriculotemporal usu- 
ally has two roots which surround the middle meningeal artery. 
It passes backward and then turns upward behind the jaw to 
accompany the temporal artery. It supplies the skin of the scalp 
in the temporal region, the skin of the external auditory canal, 
and sends some branches to the parotid gland. 
The lingual and inferior dental nerves run downward be- 
neath the external pterygoid muscle and lie on the internal 
pterygoid. The lingual is a little anterior to the inferior dental; 
it runs forward, and enters the mouth close to the alveolar pro- 
cess of the last molar tooth of the lower jaw. It goes on to the 
region of the floor of the mouth where it will be followed later. 
It supplies the mucosa of the anterior two-thirds of the tongue. 
The inferior dental nerve, with the corresponding artery, enters 
the inferior dental canal, supplies the teeth of the lower jaw, 
and sends its terminal or mental branch through the mental 
150 foramen to supply the skin of the face. The optic and submax- 
illary ganglia are two small sympathetic ganglia associated with 
the third division of the fifth nerve. 
The lingual and inferior dental nerves and inferior dental 
artery should be cleaned, and also the superficial surface of the 
internal pterygoid muscle. The remains of the capsule of the 
joint of the jaw should then be dissected away, and the condyle, 
with the external pterygoid muscle attached to it, carefully 
raised. This will give the dissector a chance to secure the auric- 
ulotemporal nerve and to follow the lingual and inferior dental 
nerves nearly to the base of the skull. If the lingual nerve is 
followed upwards with care, the small chords tympani will be 
found joining it about one-half inch below the base of the cra- 
nium. This nerve is derived from the facial and sends branches 
along the lingual trunk to the submaxillary and sublingual 
glands and to the mucosa of the tongue. 
The maxillary division of the fifth nerve and the terminal 
branches of the internal maxillary artery in the sphenomaxillary 
fossa are not accessible in the dissection, and can be more easily 
seen when the head is split in the midline. 
151 DISSECTION OF THE MOUTH AND 
SUBLINGUAL REGION 
Saw through the mandible between the middle and lateral 
incisor teeth. Cut away the attachment of the buccinator mus- 
cle from the lower jaw. Cut the mucous membrane that is 
reflected from the tongue to the gums close to the latter. Final- 
ly cut the inferior dental artery and nerve at the inferior dental 
foramen and turn the jaw downward and outward. The lingual 
nerve passes forward close to the last molar tooth and should 
be secured before the jaw is turned. This dissection should be 
done on one side only, as the other half of the jaw is needed to 
support the tongue. An excellent view will now be obtained 
of the sublingual region, the floor of the mouth, and of the 
tongue. This dissection will be connected later with the dis- 
section of the submaxillary region from the side of the neck 
which should be done on both sides. 
Sublingual gland. The gland is the smallest of the salivary 
glands and lies just below the mucosa on the floor of the mouth. 
It is liable to injury as the mucosa is being cut. Lateral to it is 
the mandible, and on its medial aspect are the hyoglossus and 
genioglossus muscles, two of the muscles of the tongue. Their 
origin can be seen better when the submaxillary region is dis- 
sected. They insert into the sides and under surface of the 
tongue. 
Lingual nerve. Follow this nerve forward. It lies on the 
hyoglossus muscle, passes medial to the sublingual gland, and 
supplies sensation to the anterior two-thirds of the tongue. As 
the nerve turns forward, small branches pass down to the tiny 
submaxillary ganglion and to the submaxillary gland and to its 
duct. 
Mylohyoid muscle. This muscle forms the floor of the 
mouth and is sometimes known as the diaphragm of the mouth. 
All above it belongs to the mouth, all below it to the submaxil- 
lary region of the neck. It passes from the jaw to the hyoid bone 
and also joins its fellows in the midline. The best view of it 
will be obtained in the dissection of the neck. At this stage the 
152 student will see its buccal surface and the fibers running ob- 
liquely down and in from the median side of the mandible. At 
its posterior border there may appear a bit of the submaxillary 
gland. 
Submaxillary gland. This gland lies chiefly in the neck 
on the outer surface of the mylohyoid muscle, but its deep part 
winds around the posterior border of the muscle, reaches its 
deep or buccal side, and here gives off its duct (Wharton's). 
This duct runs across the hyoglossus muscle below the lingual 
nerve and disappears under the sublingual gland to open in the 
floor of the mouth. The branches of the lingual nerve to it are 
a convenient guide. Just below the duct lies the hypoglossal or 
12th cranial nerve, which is the motor nerve to the tongue and 
its extrinsic muscles. 
Hypoglossal nerve. This nerve crosses the hyoglossus 
muscle and then turns upward on the genioglossus to the tongue. 
The lingual artery, which lies under the hyoglossus muscle, ap- 
pears on the genioglossus and follows the hypoglossal nerve. 
These structures pass medial to the sublingual gland and can 
be followed to better advantage in the dissection of this region 
from below. The position of the lingual nerve, the submaxillary 
gland and its duct, the sublingual gland and their relations to 
the tongue and floor of the mouth are the most important points 
to establish. The other structures, especially the muscles, can 
be studied better in the dissection of the submaxillary region 
from the neck. 
When the dissection has been completed on one side only, 
restore the jaw to its proper place and tie the incisor teeth to- 
gether with a ligature. This will support the jaw and the tis- 
sues below it in the neck, and will aid their later dissection. 
153 DISSECTION OF THE NECK 
Before beginning the dissection of this region, endeavor to 
get a general idea of the topographical arrangement of the vari- 
ous structures, and the plan of the fascial compartments in the 
neck. In the midline of the neck in front, just beneath the skin 
and subcutaneous layers, are the larynx and the trachea. Pos- 
terior to these structures are the pharynx and the oesphagus, 
which rest directly on the anterior surface of the vertebral 
column. Owing to the marked forward convexity of the cer- 
vical vertebrae, the anterior surface of the vertebral column lies 
fully half way, or more than half way, between the anterior and 
posterior surfaces of the neck. On either side of the trachea and 
the oesophagus, in the anterolateral portions of the neck, lie the 
carotid arteries and their branches; the internal jugular vein and 
its tributaries; the ninth to the twelfth cranial nerves; the sym- 
pathetic nerve; and branches of the cervical nerves forming the 
cervical and upper part of the brachial plexus. The deep fascia 
of the neck forms a septum running from side to side in front of 
the vertebral column, known as the prevertebral fascia. This 
layer separates the structures above mentioned from the dorsal 
musculature of the neck. The deep fascia sends a second septum 
from side to side, which passes directly in front of the trachea, 
and is known as the pretracheal fascia. Both the pretracheal 
and the prevertebral fascia send off prolongations which sur- 
round the great vessels of the neck, forming the so-called carotid 
sheath. This general topographical arrangement is well shown 
in horizontal sections through the neck. 
Removal of the platysma. Carry the incision in the skin 
-of the neck upward behind the ear. Turn the posterior skin flap 
back as far as the outer border of the trapezius muscle over the 
whole length of the neck, taking care to keep the knife close to 
the deep surface of the skin. Then raise the posterior border 
of the platysma and turn it forward, cleaning its deep surface. 
If this has been carefully done, the superficial veins and the deep 
fascia, which lie just beneath the platysma, will be preserved 
intact. 
154 Deep cervical fascia. Superficial layer. This is a thin mem- 
branous layer which begins behind at the spines of the vertebrae. 
It covers the trapezius muscle, and passes forward over the 
posterior triangle of the neck to the sternomastoid muscle, which 
it encloses in a sort of sheath. From the anterior border of this 
muscle the fascia crosses the anterior triangle to the midline in 
front. Below, the fascia is attached along the upper anterior 
border of the clavicle and the manubrium. Above, in the mid- 
line, the fascia is attached to the body of the mandible, to the 
mastoid process, and to the superior curved line of the occipital 
bone. It then passes over the face, covers the parotid gland 
(parotid fascia), and is attached to the zygoma. Above this 
region it is continuous with the epicranial aponeurosis of the 
scalp. It surrounds the submaxillary gland just below the angle 
of the jaw and sends a process inward to the angle of the jaw 
between the submaxillary and parotid glands. It also sends pro- 
longations inward around the parotid, which forms a partial 
sheath for that gland. This superficial layer is connected under 
the sternomastoid with the middle or pretracheal layer and with 
the deep or prevertebral layers of the cervical fascia, and with 
the carotid sheath. These deep layers will be studied in the 
deeper dissections of the neck. 
Superficial veins. These veins lie chiefly beneath the 
platysma and on the superficial aspect of the deep fascia of the 
neck. They form the system of the external jugular vein, which 
drains the scalp, the superficial parts of the neck, and portions of 
the superficial and a large part of the deep region of the face. 
The temporal vein of the scalp enters the parotid gland and there 
unites with the internal maxillary vein, which drains the deep 
parts of the face. The posterior auricular vein of the scalp joins 
this trunk near the lower border of the parotid gland to form the 
external jugular vein, which passes down the neck from the 
angle of the jaw to the middle of the clavicle. A short distance 
above the clavicle it pierces the deep fascia and empties into the 
internal jugular or subclavian vein. The external jugular vein 
receives tributaries from the front and back of the neck and a 
communication from the facial vein (posterior facial vein). The 
155 facial vein often empties directly into the external jugular vein. 
The anterior jugular vein is a small and less constant vessel, 
which lies near the midline and begins just below the chin. It 
empties below into the jugular vein. There is a good deal of 
variation in the external formation of these superficial veins. 
Clean the main trunks of the external and anterior jugular 
veins, which lie above the fascia and note where the veins pierce 
it. Then clean the deep fascia to demonstrate the whole of 
the superficial layer of the deep fascia. Note the trunks of the 
nerves, which often can be seen through the fascia, especially 
if it is made tense. Note if possible the points where the nerves 
come through the fascia to the surface. 
Superficial nerves. These are branches of the cervical plexus, 
which is formed by the first four cervical nerves. The superfi- 
cial branches are distributed to the skin and reach the surface 
at about the middle point of the posterior border of the sterno- 
mastoid muscle. They run from that point upward towards the 
ear, forward to the midline of the neck, and downward to the 
clavicle and upper part of the pectoral region. The ascending 
branches are the great auricular and small occipital nerves. The 
latter runs along the posterior border of the upper part of the 
sternomastoid muscle to supply the skin of the scalp behind the 
ear. The great auricular nerve is a large nerve, which runs 
obliquely across the sternomastoid muscle to the region of the 
ear and the parotid gland. It runs close to the external jugular 
vein. The transverse cervical nerve is small and runs medially 
and slightly upward across the sternomastoid muscle to supply 
the skin of the middle part of the neck. The descending branches 
form several trunks called the supraclavicular nerves. These 
are at first rather more deeply placed beneath the deep fascia, 
come to the surface just above the clavicle, and are distributed 
to the skin along the clavicle from the tip of the shoulder to the 
sternum. The superficial branches of the cervical plexus should 
now be dissected. Start at the middle o,f the posterior border of 
the sternomastoid muscle and follow each nerve from this point. 
The fascia can be removed as far as is necessary, but be care- 
ful to avoid disturbing the deeper parts of the neck. Only the 
superficial branches of nerves need attention at this time; the 
156 deeper branches will be found in the deep dissection of the tri- 
angles. 
Triangles of the neck. The sternomastoid muscle extends 
from the occipital bone and mastoid process of the temporal bone 
to the top of the sternum and the sternal end of the clavicle. 
This muscle divides the neck into an anterior and a posterior 
triangle, the base of the anterior triangle corresponding to the 
line of the lower jaw, while the base of the posterior triangle cor- 
responds to the line of the clavicle. 
The posterior triangle is bounded in front by the sternomas- 
toid, behind by the trapezius and below by the clavicle. The 
muscles found in this space lie in the following order, from above 
downward ; the splenius, the levator scapulae, the scalenus posti- 
cus, medius and anticus. The splenius arises from the spines of 
the thoracic vertebrae and inserts into the transverse processes 
of the upper cervical vertebrae and into the occipital bone and 
mastoid process. The levator scapulae arises from the trans- 
verse processes of the upper cervical vertebrae and passes to the 
upper angle of the scapula. Below the levator scapulae are the 
three scalene muscles. The posticus is inserted into the second, 
the medius and anticus into the first rib. The posterior belly of 
the omohyoid muscle passes obliquely through the triangle just 
above the subclavian artery to the upper border of the scapula 
This muscle divides the space into a large occipital triangle above 
and a small subclavian triangle below, between it and the clav- 
icle. This subdivision is convenient topographically but it is not 
necessary to attempt to give definite contents to these subdivi- 
sions. 
Cervical fascia. The middle layer of the cervical fascia sur- 
rounds the infrahyoid muscles of the anterior triangle. It en- 
velops the posterior belly of the omohyoid muscle in a sheath, 
which extends throughout the posterior triangle. This layer 
is prolonged downward from the posterior belly to the clavicle, 
where it is continuous with the costocoracoid membrane. Be- 
tween this layer and the superficial layer of the cervical fascia 
is the supraclavicular space. This space is closed below by the 
attachment of the middle layer of fascia to the lower border of 
the clavicle; above by the fusion of the middle and superficial 
157 layers above the posterior belly of the omohyoid muscle. Me- 
dially the space communicates beneath the sternomastoid muscle 
with the suprasternal space. The supraclavicular space con- 
tains the lower end of the external jugular vein and the termina- 
tion of the transverse cervical and transverse scapular veins 
from the lower and back part of the neck. 
Nerves and vessels. The cervical nerves are to be associ- 
ated with this triangle. The first four form the cervical plexus, 
which gives off its branches in this triangle; the last four and 
the first thoracic, which form the brachial plexus, are found in the 
lower part of the triangle. The spinal portion of the spinal ac- 
cessory nerve passes through the middle of the space to the tra- 
pezius muscle. A part of the subclavian artery and vein lie in 
the triangle just above the clavicle and give off branches, which 
pass through the lower part of the space to the back of the neck. 
Anterior triangle. The anterior triangle is bounded by the 
sternomastoid muscle behind, by the midline of the neck in front, 
and by the line of the lower jaw above. It is subdivided into 
three smaller triangles, the muscular and carotid triangles below 
and the digastric triangle above the hyoid bone. 
The muscular triangle is bounded in front by the midline, be- 
hind by the sternomastoid and above by the anterior belly of the 
omohyoid. The carotid triangle is bounded behind by the stern- 
omastoid, below by the anterior belly of the omohyoid and above 
by the posterior belly of the digastric muscle. The digastric 
or submaxillary triangle is bounded by the two bellies of the 
digastric muscle in front and behind, and by the body of the 
mandible above. Seen from the front the two anterior triangles 
may be divided by the hyoid bone into an infrahyoid and a supra- 
hyoid triangle, with their bases together at the hyoid bone and 
their apices at the sternum and chin respectively. 
The small subdivisions of the anterior triangle are of some 
topographical convenience, but much time is wasted in trying to 
learn the contents of each as given in books. The student will 
find it more convenient and more practical to group the various 
structures in the infra and suprahyoid regions only. 
Contents of infrahyoid region. Muscles. These form the 
infrahyoid group. They arise above from the hyoid bone and 
158 insert below in the sternum and scapula. The sternohyoid lies 
next to the median line and runs straight down the neck to the 
top of the sternum. The omohyoid lies beside it, and passes ob- 
liquely downward and outward. This anterior belly disappears 
under the sternomastoid, where it is united to the posterior belly 
by a small tendon. The posterior belly runs through the pos- 
terior triangle as already described. Beneath these muscles is 
the thyrohyoid, passing between the hyoid bone and the thyroid 
cartilage, and its continuation, the sternothyroid, which runs 
from the thyroid cartilage to the sternum. 
Cervical fascia: middle layer. The middle layer of the cer- 
vical fascia invests the sternohyoid and omohyoid muscles in a 
sheath and covers over the superficial surface of the sterno- 
thyroid. Above, this layer of fascia is attached to the hyoid 
bone; below it is attached to the posterior border of the man- 
ubrium. This middle layer fuses with the superficial layer of the 
cervical fascia in the midline of the neck between the hyoid bone 
above and the isthmus of the thyroid gland below. Below this 
point there is a shallow cleft between it and the superficial layer, 
which contains the communicating branch between the anterior 
jugular veins, a lymph gland and some loose tissue. This is r'nd 
suprasternal space. It is limited below by the top of the man- 
ubrium. Laterally, the middle layer of the fascia fuses with the 
superficial layer at the edge of the sternomastoid muscle. That 
part which surrounds the omohyoid muscle is carried with the 
muscle into the posterior triangle and is prolonged from its pos- 
terior belly to the the clavicle, where it forms the deep boundary 
of the supraclavicular space. The suprasternal space is pro- 
longed laterally above the sternoclavicular joints under the stern- 
omastoid muscle, and this lateral recess is practically continuous 
with the supraclavicular space. 
Viscera. In the midline, from above downwards, are found 
the thyroid cartilage, the cricoid cartilage, the thyroid gland, 
and the trachea. Posterior to these structures are the lower 
end of the pharynx and the upper part of the oesophagus. The 
cricoid and thyroid cartilages form part of the wind pipe and 
larynx and are superficial. The trachea begins at the lower bor- 
159 der of the cricoid and recedes from the surface as it descends to 
the thorax. The upper part is covered by the thyroid gland, the 
lateral parts of which run up on either side of the cricoid and 
thyroid cartilages. The gland is covered by the infrahyoid mus- 
cles and is in relation laterally with the great vessels. The po- 
sition of the gland is of great practical importance. These mid- 
line organs rest behind on the prevertebral fascia and muscles 
and the cervical vertebrae. 
Vessels. The common carotid artery begins behind the 
sternoclavicular joint and runs up to the level of the hyoid bone, 
where it divides into the external and internal carotids. On its 
lateral side is the internal jugular vein, the two vessels lying in 
a sheath formed by prolongations of the middle and deep layers 
of the cervical fascia. In the lower part of the neck (muscular 
triangle) the vessels and all other structures are covered by the 
muscles and are deeply placed. In the upper part (carotid tri- 
angle) they are comparatively superficial. In addition to the 
common carotid, this triangle contains the inferior thyroid ar- 
tery from the subclavian artery, and the superior thyroid, from 
the external carotid. These arteries supply the thyroid gland. 
The thyroid veins pass to the internal jugular or the innominate 
veins. 
Nerves. The hypoglossal or twelfth cranial nerve lies for 
a short distance in the upper part of this region just below the 
digastric muscle. It communicates with the cervical plexus and 
these communicating branches, in the form of a loop, li£f in 
front of the sheath and supply the infrahyoid muscltes. The 
■vagus or tenth cranial nerve lies in the carotid sheath behind 
the vessels. The sympathetic nerve lies behind the sheath on 
the prevertebral muscles. These vessels and nerves lie chiefly 
under the sternomastoid muscle on either side of the organs, 
which are situated in the midline of the neck. 
The suprahyoid region lies between the hyoid bone and the 
posterior belly of the digastric muscle below, and the body-of 
the mandible above. Behind the angle of the jaw, the space is 
continued into the retromandibular fossa. This space lies be- 
tween the ramus of the jaw in front, the sternomastoid behind, 
160 and the posterior belly of the digastric below. The suprahyoid 
region consists of a superficial portion, which lies on the super- 
ficial surface of the mylohyoid muscle, and a deep portion which 
lies beneath that muscle. The deeper part forms the sublingual 
region and belongs to the floor of the mouth; the superficial part 
belongs to the neck. 
Contents of the suprahyoid region (superficial part). Mus- 
cles. The digastric is a two bellied muscle; the posterior belly 
arises from the mastoid process, the anterior belly from the 
symphysis of the jaw. The two bellies are united by a tendon, 
which is bound down by fascia to the hyoid bone. In close re- 
lation to the posterior belly is the stylohyoid muscle, which 
arises from the styloid process of the temporal bone, and is in- 
serted with the posterior belly of the digastric into the hyoid. 
Beneath these muscles is the mylohyoid muscle, which arises 
from the mylohyoid ridge of the mandible. The two halves of 
the muscle meet in the median line between the symphysis of 
the jaw and the hyoid bone, and are also attached to the hyoid. 
This muscle forms the diaphragm or floor of the mouth and sepa- 
rates the neck from the mouth. 
The submaxillary gland lies on the mylohyoid muscle be- 
low the angle of the jaw. It is surrounded by a sheath formed 
by the superficial layer of the deep cervical fascia. The parotid 
gland occupies the retromandibular fossa, but its tip often ex- 
tends down to this region. The two glands are separated by a 
prolongation of cervical fascia, which is attached to the mandible 
at the angle. 
The facial artery, from the external carotid, enters the digas- 
tric triangle under the posterior belly of the digastric muscle, 
runs under the gland, and over the body of the mandible to the 
face. The facial vein lies usually superficial to the gland. The 
submental branch of this artery and the mylohyoid artery and 
nerve, from the inferior dental artery and nerve, lie deeper in 
the anterior part of the triangle. 
The retromandibular fossa is occupied by the parotid gland 
and the structures which run through the gland. The upper part 
of the external carotid and its posterior auricular branch and the 
posterior fascial vein, are found here also. 
161 DISSECTION OF THE CERVICAL TRIANGLES 
After the superficial veins and nerves have been dissected, 
the muscles which form the boundaries and subdivisions of the 
triangles should be cleaned on their superficial surfaces only. 
The dissector must avoid any dissection of the contents of the 
triangles at the present time. What he needs at this stage is a 
view of the superficial musculature of the neck and the actual 
size of the triangles. After the muscles have been cleaned or 
disturbed they shrink and the triangles are much distorted. 
Clean first the sternomastoid, trapezius and posterior belly of the 
omohyoid and then turn to the anterior triangle and clean the 
two bellies of the digastric. The small stylohyoid muscle lies 
close to the posterior belly and should be cleaned with it. The 
submaxillary gland overlaps somewhat the posterior belly of 
the digastric. Clean the fascia off the superficial aspect of the 
gland and then raise it just enough to expose the posterior belly. 
The facial artery lies on the deep aspect of the gland. Disturb 
these parts as little as possible as they will be dissected later. 
Then clean the infrahyoid muscles to the sternum and the 
omohyoid to the point where it passes under the sternomastoid. 
Take particular care to leave both the anterior and posterior 
borders of the sternomastoid undisturbed. If this dissection is 
successfully done, a good view of the outline of the various tri- 
angles and of the superficial musculature of the neck will be 
obtained. 
162 DISSECTION OF THE POSTERIOR TRIANGLE 
The spinal accessory or 11th cranial nerve appears from 
under the posterior border of the sternomastoid about at the 
middle of the triangle and communicates freely with the cervical 
nerves. It runs through the triangle and disappears under the 
trapezius, which it supplies. Numerous lymph glands lie along 
the posterior border of the sternomastoid and are often enlarged. 
They can be removed as the triangle is cleaned. The superficial 
cervical artery, from the thyrocervical artery, with its vein, runs 
towards the back of the neck in the lower part. The deep 
branches of the cervical plexus pass chiefly to the muscles in 
the floor of the triangle. They should be cleaned with the mus- 
cles in the floor. It is safer to clean these structures from above 
down, as the nerves are imbedded in the fascia which covers 
the muscles. 
The lower portion of the triangle, the subclavian triangle, 
should next be dissected. When the posterior belly of the om- 
ohyoid is in place this is a very limited area. As soon as the 
muscle is loosened the space is artificially enlarged. The trans- 
verse cervical and superficial cervical arteries are found here 
and should be traced back until they disappear under the tra- 
pezius muscle; they supply the muscles in the back of the neck, 
and are derived from the subclavian or from its thyrocervical 
trunk. The lower cervical nerves are much larger than the up- 
per and form a large nerve mass, which passes just external 
to the subclavian artery to the axilla. 
The third part of the subclavian artery will be found be- 
tween the posterior belly of the omohyoid and the clavicle. It 
is covered by the superficial veins already mentioned. These 
should be removed to show the vessel, and the brachial nerves 
on its outer aspect. Clean all structures as far as the clavicle 
but do not cut that bone. 
163 This region can be dissected next to connect the structures 
seen in the floor of the posterior triangle with the deep parts of 
the back of the neck. The student should review the general 
plan of the muscles of the back before beginning the dissection. 
The posterior bellies of the epicranius muscle and the occipital 
and posterior auricular arteries and nerves to the posterior re- 
gion of the scalp can be seen in favorable subjects. Turn the 
subject over and review the attachments of the trapezius muscle. 
The occipital artery and the great occipital nerve should be 
cleaned over what is left of the occipital bone. The trapezius 
muscle can now be reflected by cutting its origin from the oc- 
cipital bone. Beneath the trapezius will be found the levator 
scapulae and towards the midline the splenitis. Clean these 
muscles and then reflect the splenitis by cutting its origin from 
the vertebrae. Beneath the splenitis lies a large broad muscle, 
the semispinalis capitis (complextis). This muscle really repre- 
sents the tipper end of the spinalis portion of the sacrospinalis 
ami of the semispinalis muscles. Note the great occipital nerve 
coming through the tipper part of the complextis. Cut the in- 
sertion of the complextis from the occipital bone and turn it 
down. Beneath it is found the suboccipital triangle, a small re- 
gion immediately posterior to the arch of the atlas. The triangle 
is bounded medially by the rectus capitis posticus, major and 
minor, below by the inferior oblique and above by the superior 
oblique. In the depths of the triangle are the occipital artery 
and the tiny posterior division of the first cervical nerve, which 
appears between the artery and the arch of the atlas. The ar- 
tery can easily be found, but the nerve is so small that it is 
usually lost. The arteries to the back of the neck should be 
followed into the dorsal muscles if the injection is good enough. 
When the trapezius is removed from the clavicle, the posterior 
belly of the omohyoid can be followed to the scapula. Do not 
cut the levator scapulae. 
Dissection of the anterior triangle. Infrahyoid region. To 
demonstrate the contents of the anterior triangle it will be neces- 
DISSECTION OF THE BACK OF THE NECK 
164 sary to turn back the sternomastoid pivoting it on its posterior 
border. Cut about half of the origin of the muscle from the 
clavicle, raise the anterior border and turn it back. It will be 
safer to clean the deep surface of the muscle. Two little arteries, 
branches of the superior thyroid and occipital arteries, enter its 
deep surface. The carotid sheath will now be exposed. This 
appears as a mass of rather loose tissue, in which can be felt 
the injected artery. Crossing the lower part of the sheath is the 
little tendon of the omohyoid muscle and still lower the inser- 
tions of the other infrahyoid muscles overlap the sheath. The 
origin of the sternomastoid from the mastoid process can now be 
partly divided to show the upper end of the posterior belly of 
the digastric and the stylohyoid muscles. These lie just super- 
ficial to the sheath at the angle of the jaw. The hypoglossal 
nerve (12th cranial) lies just behind and below the posterior 
border of the digastric and stylohyoid muscles. Secure the nerve 
at this point and trace it forward till it disappears under the di- 
gastric muscle. It sends a tiny branch down to the thyrohyoid 
muscle, which should be secured at this point. Here it gives 
off its descendens hypoglossi branch which runs down in front 
of and partly in the sheath to unite with a communicans hypo- 
glossi branch from the cervical nerves. This branch usually 
winds around the posterior border of the sheath about half way 
down the neck. From the loop thus formed little branches can 
be traced to the infrahyoid muscles. Clean up the loop and its 
branches, doing as little injury as possible to the sheath. Near 
the tip of the hyoid bone several veins enter the sheath to reach 
the jugular vein. These are the common facial, lingual, and 
superior thyroid veins. There is a good deal of irregularity in 
their arrangement. The middle thyroid veins enter the internal 
jugular lower down. 
Contents of the carotid sheath. The carotid sheath should 
now be opened and its contents displayed. The terminal branch- 
es of the hypoglossal loop can be cut and the loop turned up and 
saved. In opening the sheath be careful not to cut into the vein, 
whose walls are very thin. The vein is external, the common 
carotid is internal, and the vagus nerve is between and behind 
165 the two. The tendon of the omohyoid can be cut and the sheath 
opened from below upwards. Go deep enough to secure the 
vagus nerve but do not dissect into the posterior wall of the 
sheath. Clean the vessels up to the bifurcation of the common 
carotid, also the oesphagus and cartilages of the larynx. The 
recurrent laryngeal branch of the vagus nerve lies between it and 
the trachea. The thyroid gland lies on the medial side of the 
artery and overlaps it in front. Behind is the sympathetic nerve 
in the prevertebral fascia over the prevertebral muscles, and the 
inferior thyroid branch of the subclavian artery. These struc- 
tures will be seen later. The infrahyoid muscles should now be 
cut just above the sternum and carefully turned up. The small 
thyrohyoid muscle can be left in place. It is continued by the 
sternothyroid, which should be removed to expose the thyroid 
gland. 
Thyroid gland. The position and relations of the thyroid 
gland are especially important. The gland consists of 
a median part, an isthmus, and two lateral lobes. 'The isthmus 
lies opposite the 2nd, 3rd, and 4th rings of the trachea and 
the lateral lobes run upward along the sides of the cricoid and 
thyroid cartilages. These lobes lie internal to the carotid artery 
and overlap it somewhat anteriorly. The recurrent laryngeal 
nerves run along under the lower border of the lateral lobes in 
close relation to the inferior thyroid artery. Anteriorly the 
gland is covered by the infrahyoid muscles and is closely in- 
vested by the pretracheal fascia. The inferior thyroid artery, 
from the subclavian, enters the gland along its lower border, 
and the superior thyroid, from the external carotid, is found 
along the upper border. The inferior thyroid veins run down- 
ward from the isthmus in front of the trachea to the innominate 
veins, while the superior and middle thyroid veins drain into the 
internal jugular vein. There are two superior and two inferior 
parathyroid glands, about the size of a pea, which lie behind the 
lateral lobes near their upper and lower borders respectively. 
The thyroid and cricoid cartilages and the trachea lie in the 
midline. The thyroid and cricoid cartilages inclose the vocal 
cords and muscles of the larynx, which will be dissected later. 
166 The trachea begins at the lower border of the cricoid and runs 
down into the superior mediastinum. It is covered anteriorly 
by the thyroid gland and the inferior thyroid veins. Behind the 
trachea lies the oesophagus, and the recurrent laryngeal nerves 
run upward along the side of these two structures. Follow the 
superior thyroid vessels to the tip of the lateral lobe of the thy- 
roid gland and dissect the infrahyoid muscles carefully off the 
anterior surface of the gland. The muscle and gland tissue 
often are rather hard to distinguish from each other. Deter- 
mine with care the relations of the gland and the distribution 
of the vessels to it. The recurrent laryngeal nerve and the 
trachea below the gland can be worked out with the dissection 
of the subclavian artery. 
The subclavian artery lies behind the scalenus anticus mus- 
cle and is divided into three parts by that muscle. The artery 
ends at the outer border of the first rib. The first part of the 
vessel, medial to the scalenus anticus, lies deep in the neck and 
is covered by the subclavian and internal jugular veins, and 
crossed by the vagus and phrenic nerves. The second part lies 
behind the scalenus anticus muscle and the third part extends 
from the outer border of the scalenus anticus to the outer bor- 
der of the first rib. The artery and vein arch over the apex of 
the lung and pleura. The brachial plexus lies along the outer 
side of the third part of the artery and accompanies it to the 
axilla. 
The subclavian artery gives off the following branches, 
though there is much variation. From the first part arise: (1) 
the vertebral artery, which runs up through the foramina in the 
transverse processes of the cervical vertebrae, enters the foramen 
magnum and supplies the posterior part of the brain. (2) The 
thyrocervical trunk arises at the medial border of the scalenus 
anticus and gives off (a) the inferior thyroid to the thyroid 
gland; this vessel gives off the ascending cervical, which runs 
upwards on the scalenus anticus with the phrenic nerve; (b) 
the superficial cervical, and (c) the transverse scapular artery 
to the back of the neck and to the dorsum of the scapula; (3) the 
internal mammary to the inner aspect of the anterior thoracic 
167 wall. From the second part arises (4) the costocervical trunk, 
which gives off the (a) superior intercostal artery to the upper 
intercostal spaces, and (b) the deep cervical artery to the back 
of the neck. (5) The transverse cervical arises from the third 
part of the artery and runs between the brachial nerves to the 
lateral and back parts of the neck. 
Subclavian vein. The subclavian vein lies under cover of 
the clavicle and anterior to the artery. The artery arches up- 
ward for at least one-half inch above the level of the clavicle and 
it is therefore considerably higher than the vein. The vessels 
are separated by the scalenus anticus muscle, the vein being 
anterior and the artery posterior to this muscle. The vein is 
the continuation of the axillary vein and begins at the first 
rib. It joins the internal jugular vein behind the sternoclavicular 
joint to form the innominate vein. On the left side the thoracic 
duct empties into the junction of these vessels. This structure 
looks much like a small vein and can often be seen by inflating 
the duct below in the thorax. 
168 The subclavian vessels arch upward above the clavicle under 
the sternomastoid muscle, which must therefore be cut from the 
clavicle and turned up. Reflect the lower end carefully as the 
great veins lie just beneath and are easily cut. The muscle can 
be turned up as far as the hyoid bone, and the infrahyoid region 
can in this way be connected with the greater part of the pos- 
terior triangle. The whole of the scalenus anticus muscle will 
be exposed when the sternomastoid is turned up. The phrenic 
nerve, the most important branch of the cervical plexus, from 
the 3rd, 4th and 5th cervical, lies in the fascia over the muscle. 
The nerve should be at once cleaned and secured. It runs be- 
tween the subclavian artery and vein into the thorax. The first 
part of the artery and its relation to the common carotid artery 
and jugular vein should now be demonstrated. Draw the lower 
end of the internal jugular vein to one side. Just behind it is a 
fairly large vein, the vertebral vein, and behind the vertebral 
vein lies the first part of the subclavian artery. The subclavian 
vein is wholly anterior to the scalenus anticus, note how the 
artery arises considerably above the clavicle, while the vein is 
mostly behind the clavicle. In addition to the vertebral vein 
the vagus nerve crosses the front of the artery and also several 
smaller fibers from the sympathetic nerve, which form a loop 
about the vessel. Secure these if possible and they can be 
traced to the main sympathetic trunk later. As the right vagus 
nerve crosses the front of the subclavian artery, it gives off the 
inferior or recurrent laryngeal branch, which hooks around the 
artery, runs up behind it and the lower end of the common 
carotid and along the side of the trachea to the larynx. The 
nerve lies behind the lateral lobes of the thyroid gland. On the 
left the nerve winds around the aortic arch. These nerves can 
now be dissected from the subclavian artery up under the thyroid 
gland. At the inner edge of the scalenus anticus is a short trunk 
arising from the subclavian, the thyrocervical (thyroid axis). 
From this run out laterally the superficial cervical and the supra- 
scapular branches to the posterior triangle. Passing upward 
DISSECTION OF THE SUBCLAVIAN ARTERY 
169 and curving medially towards the lower end of the thyroid gland 
is the inferior thyroid artery, which disappears behind the com- 
mon carotid. The small ascending cervical artery springs from 
the inferior thyroid and runs up along side of the phrenic nerve. 
There is a good deal of variation in the origin of these and other 
branches from the subclavian. The vertebral artery is deeply 
placed and is in close relation to the sympathetic nerves in this 
part of the neck. This artery and the deeper part of the sympa- 
thetic nerve can be left for the deeper dissection of this part 
of the neck. The third part of the subclavian artery has been 
seen in the dissection of the posterior triangle. 
The clavicle should now be removed in order to connect 
the subclavian vessels and the brachial nerves with the axilla, 
and the structures in the anterior triangle with the superior 
mediastinum. Disarticulate the sternal end of the clavicle. It 
must be separated with great care from the great vessels, es- 
pecially the veins. The subclavius muscle must also be dissected 
off its inferior surface, and at the outer end the costoclavicular 
ligament between it and the coracoid process of the scapula must 
be cut and the acromioclavicular joint disarticulated. The clav- 
icle can then be removed and full relations with the axilla es- 
tablished. The transverse scapular branch from the thyro- 
cervical artery, which lies behind the clavicle, can be followed 
to the scapula, the insertion of the scalenus anticus into the 
first rib demonstrated, and the subclavian artery and the brachial 
plexus connected with the axillary vessels and the nerves in the 
axilla. 
Brachial plexus. The last four cervical and first thoracic 
nerves emerge between the scalenus anticus and medius. These 
large nerve trunks lie on the floor of the posterior triangle and 
just above the first rib are concentrated into a large bundle that 
lies along the outer side of the subclavian artery and passes on 
to the axilla. These nerves represent the supraclavicular por- 
tion of the brachial plexus and the following branches are given 
off in the neck: long or posterior thoracic; suprascapular; nerves 
of the rhomboids, scalene, prevertebral and subclavius muscles. 
The suprascapular branch can be easily followed and will be 
170 found running outward and backward with the posterior belly 
of the omohyoid and the suprascapular artery to the upper bor- 
der of the scapula. The upper serrations of the serratus anterior 
can now be seen. The long thoracic nerve, from the 5th, 6th, 
and 7th cervical nerves, appears between the anterior and middle 
scalene muscles in the lower part of the neck, and should be 
followed behind the axillary artery over the upper serrations of 
the serratus. 
The origin of the innominate vein can next be dissected and 
these veins traced to the superior cava. The left innominate 
vein can then be cut near the cava and turned to the left to 
expose the origin of the great branches of the aortic arch. This 
region was hidden by the upper part of the manubrium when 
the thorax was dissected, but now can be thoroughly cleaned up. 
The heart should be restored to the thorax and the aorta and 
superior cava temporarily sutured so as to restore the parts, 
and give a view of the anterior aspect of the heart, the great 
vessels in the superior mediastinum, and in the neck up to the 
thyroid gland. 
171 DISSECTION OF THE SUPRAHYOID REGION 
Superficial part. The structures in the digastric triangle 
should now be studied. Clean the submaxillary gland and the 
facial artery beneath it. Follow the artery to the jaw and face 
and look for its submaxillary or submental branch close to the 
body of the jaw. This vessel runs forward to the chin. In the 
fascia over the mylohyoid muscle lie the tiny mylohyoid nerve 
and artery. Secure them and then clean the mylohyoid muscle 
with the digastric still in place. Follow the posterior belly of 
the digastric to its origin from the mastoid and clean the stylo- 
hyoid at the same time. The hypoglossal nerve should be no- 
ticed along the inferior border of the posterior belly. The ves- 
sels in the infrahyoid region should be thoroughly cleaned up 
to the posterior belly of the digastric. The posterior belly and 
the stylohyoid can then be cut near their origin, and turned 
down to the hyoid bone. This will expose the external carotid 
and its branches and part of the internal carotid and the deep 
nerves. 
172 DISSECTION OF THE EXTERNAL AND INTERNAI 
CAROTID ARTERIES 
The common carotid artery divides into the external and 
internal carotids. The former leaves the sheath, while the latter 
is continued up in the sheath to the base of the skull. The bi- 
iurcation of the artery is usually at the level of the hyoid bone. 
The external carotid artery is relatively superficial at its origin 
and runs up towards the angle of the jaw. It is covered an- 
teriorly by the veins from the thyroid gland, face, and tongue, 
by the 12th nerve and the posterior belly of the digastric and 
stylohyoid muscles. It ends in the parotid gland. On its deep as- 
pect are the styloglossus and pharyngeus muscles, the 9th nerve 
and the pharyngeal branches of the 9th and 10th nerves, which 
separate it from the internal carotid. These deep structures will 
be dissected with the internal carotid. At this time the dissector 
should clean the external carotid and follow out its branches as 
fas as possible. 
The first branch from the external carotid is the superior 
thyroid, which runs downward and inward under the infrahyoid 
muscles to the thyroid gland, and usually sends a small laryngeal 
branch into the larynx at the upper border of the thyroid carti- 
lage. This artery lies close to the superior laryngeal branch of 
the vagus nerve. The lingual artery comes off just above the 
superior thyroid and runs forward and inward just above the 
hyoid bone. It very soon disappears under the muscles of the 
submaxillary region. The facial artery (external maxillary) 
arises close to the lingual and runs upward under the submaxil- 
lary gland to reach the jaw. Just below the mandible it gives 
off a good sized branch, the submental, which runs fowards in 
the submaxillary triangle. The occipital artery arises almost 
opposite the facial, is more deeply placed, and runs backward 
under the sternomastoid muscle in front of the jugular vein 
towards the mastoid process. It passes under this process and 
becomes superficial in the occipital region of the scalp. The 
small posterior auricular branch arises above the occipital artery 
and runs up behind the ear. The two terminal branches, the 
173 temporal and the internal maxillary, are given off in the parotid 
gland. A tiny ascending pharyngeal branch lies along the side 
of the pharynx. The dissection can now be connected up with 
the deep dissection of the parotid region. Cut through the stern- 
omastoid muscle to follow the occipital artery under the mastoid 
process to the occipital region of the scalp, but do not wholly 
detach the upper end of the muscle. The spinal accessory nerve 
will probably be seen entering the deep surface of the sterno- 
mastoid a short distance below the mastoid process. It passes 
either anterior or posterior to the internal jugular vein. 
Internal carotid artery. Draw the external carotid to one 
side and clean up the structures between it and the internal 
carotid. First dissect the styloglossus and pharyngeus muscles 
and note their origin from the styloid process. The glosso- 
pharyngeal nerve lies along the posterior border of the stylo- 
pharyngeus muscle, and passes forward either anterior or pos- 
terior to this muscle to the tongue. It gives off some branches 
to the pharynx. Close below it are the pharyngeal branches 
of the vagus, which join the pharyngeal branches of the glosso- 
pharyngeal, and pass to the pharynx. The ascending pharyngeal 
artery from the external carotid runs along side of the internal 
carotid. The vagus nerve and the jugular vein have the same 
relation as to the common carotid. 
Cranial nerves. The relations of the glossopharyngeal, 
vagus, spinal accessory and hypoglossal nerves to the carotid 
vessels should be carefully checked up at this time. The hypo- 
glossal is the most superficial. It lies at first between the jugu- 
lar vein and the internal carotid artery, turns forward super- 
ficial to both carotids and passes under the digastric muscle to 
supply the muscles of the tongue. The loop formed by the com- 
municans and descendens hypoglossi consists wholly of fibers 
derived from the 1st, 2nd and 3rd cervical nerves, and lies super- 
ficial to the common carotid artery and jugular vein. 
The glossopharyngeal nerve lies at first between the internal 
carotid and jugular veins, turns forward between the external 
and internal carotids, lies in close relation to the stylopharyn- 
geus muscle and supplies the dorsal part of the tongue (sensa- 
174 tion only). It gives off pharyngeal branches, which are in 
close connection with the pharyngeal branches of the vagus. 
These two sets of pharyngeal nerves pass between the two car- 
otid arteries to the lateral wall and muscles of the pharynx. 
The vagus nerve lies first between the internal carotid arterv 
and jugular vein and lower, between the common carotid and 
the jugular vein in the carotid sheath. It enters the thorax be- 
tween the subclavian vein and artery. High up in the neck it 
gives off the pharyngeal branches just mentioned and also the 
superior laryngeal branch. This nerve passes behind the internal 
and external carotids to the upper border of the thyroid carti- 
lage, where it enters the larynx. It is the chief sensory nerve of 
the larynx. Just before it enters, it gives off an external branch 
which runs down on the outer side of the thyroid cartilage to 
supply the cricothyroid muscle. It sends pharyngeal branches 
to the pharynx. The inferior laryngeal (recurrent) branch is 
given off below the subclavian or aortic arch. It passes behind 
the lower end of the right common carotid and then lies on the 
medial side of both common carotids until it enters the larynx 
at the lower border of the cricoid cartilage. It is the chief motor 
nerve of the larynx. 
The spinal accessory nerve leaves the skull with the 9th and 
10th nerves, lies between the internal carotid and jugular vein, 
and turns outward either in front or behind the jugular vein to 
enter the deep surface of the sternomastoid muscle. It passes 
through this muscle, supplies it (together with some branches 
from the cervical nerves) and ends in the trapezius. 
The sympathetic nerve lies behind the internal carotid artery 
above, and behind the common carotid below. It lies in the 
prevertebral fascia behind the carotid sheath. It is characterized 
by an oval enlargement about an inch and a half long, which lies 
just above the tip of the hyoid bone. The main trunk of the 
sympathetic is quite small and is easily lost in the prevertebral 
fascia. If the superior cervical ganglion is found, it will be easy 
to trace the nerve down the neck to the subclavian artery. In 
the lower part of the neck are two tiny enlargements, the middle 
175 and inferior cervical ganglia. These lie near the inferior thyroid 
and vertebral arteries. Many small branches to the other nerves 
of the neck and to the heart are given off from these three 
ganglia. 
176 SUPRAHYOID REGION; DEEP DISSECTION 
Cut the anterior belly of the digastric and clean the whole 
of the mylohyoid muscle. The submaxillary gland should be 
raised and tinned back. This muscle separates the region of 
the neck from the floor of the mouth or sublingual region, which 
was paitly shown in the deep dissection of the face and mouth. 
To open up the floor of the mouth from the neck, the mylohyoid 
muscle must be cut from the jaw and turned down. On the 
side where the jaw has already been turned down, it will be 
only necessary to cut between the two halves of the muscle 
from the jaw to the hyoid bone, and allow the jaw and the muscle 
to fall down out of the way. This will open up the whole sub- 
lingual region and it can be connected up with the structures 
just seen in relation to the internal carotid artery. The mylo- 
hyoid muscle can be cut from the jaw on the side where the 
jaw was left in place and turned down on the hyoid bone. That 
half of the jaw must not be removed, so as to keep some sort 
of support to the tongue. 
Sublingual region. This region lies on the deep aspect of 
the mylohyoid muscle and contains the vessels, nerves and 
muscles of the tongue and part of the submaxillary and sub- 
lingual glands. The following muscles will be found here. The 
geniohyoid extending from the symphysis of the jaw to the 
hyoid bone. The hyoglossus extending from the hyoid bone 
to the side of the tongue. The genioglossus, fan-shaped muscle, 
between these two and on a deeper plane, running from the 
symphysis of the jaw to the under surface of the tongue and 
to the hyoid bone. The styloglossus, blending with the hyo- 
glossus along the side of the tongue. 
On the superficial aspect of the hyoglossus from above 
downward lie the lingual nerve, the deep part of the submaxil- 
lary gland and its duct (Wharton's) and the hypoglossal nerve. 
Follow these forward to the floor of the mouth and to the 
tongue. The hypoglossal nerve is the motor nerve to all these 
muscles and to the muscular substance of the tongue. The 
lingual nerve is sensory to the anterior two-thirds of the tongue. 
177 Wharton's duct opens in the floor of the mouth just beneath 
the tip of the tongue. This duct and the lingual nerve run on 
the medial aspect of the sublingual gland. Note the position 
of this gland beneath the mucosa of the floor of the mouth, and 
between the body of the mandible and the genioglossus muscle. 
On the deep aspect of the hyoglossus muscle lie the glosso- 
pharyngeal nerve and below it the lingual artery. The vessel 
turns upward anterior to the hyoglossus and runs on the genio- 
glossus to the tongue. The glossopharyngeal nerve supplies the 
stylopharyngeus muscle, runs under that muscle and the hyo- 
glossus to supply sensation to the posterior one-third of the 
tongue. 
Cranial and sympathetic nerves. These nerves are grouped 
about the internal jugular vein and the carotid arteries, and lie 
on the anterior surface of the prevertebral muscles. These nerves 
and the great vessels should be followed upward as near the base 
of the skull as possible. Cut the styloid process and turn the 
styloglossus and pharyngeus forward. This will expose the upper 
ends of the nerves and vessels. The nerves are all wrapped up 
together in a sort of common sheath between the artery and vein. 
They should be separated as far as possible, but this is a difficult 
dissection. Finally check up on the relations of all the vessels 
and nerves throughout the whole neck. 
The upper part of the posterior triangle should now be con- 
nected with the dissection of the deeper part of the anterior tri- 
angle. Note the position and relations of the muscles, which 
arise from the transverse processes and run into the floor of the 
posterior triangle, to the prevertebral muscles, which lie on the 
aspect of the bodies of the vertebrae. The position of the upper 
cervical nerves and their connections with each other remain to 
be seen. Follow all the cervical nerves inward to the point where 
they disappear at the outer edge of the scalenus anticus and the 
prevertebral muscles. The second nerve lies just below the prom- 
ontory formed by the transverse process of the atlas. The first 
nerve is very small and lies just above this prominence. Note 
how all the cervical nerves are connected together by a series of 
loops a short distance beyond their point of appearance. 
Pharynx. The lateral wall of the pharynx will finally be 
178 exposed. The pharyngeal wall consists chiefly of the three 
constrictor muscles, which arise from the under surface of the 
skull, the lower jaw, side of the tongue, the hyoid bone and the 
thyroid and cricoid cartilages, and meet behind in the median 
line of the pharynx. These muscles can usually be dissected 
better when the whole head is removed and the pharynx can 
be approached from behind. In those cases where the head 
will be split in the median sagittal plane, it will be necessary 
to study them here. Begin below and follow the constrictor 
muscles upward, noting how each in turn overlaps the next one 
above. The upper border of the superior constrictor is deficient 
and the gap is filled by the pharyngeal fascia which lies in the 
pharyngeal wall on the deep side of the constrictors. This 
gap is also partly occupied by the levator and tensor palati 
muscles as they pass from their origin at the under side of 
the petrous portion of the temporal bone to the soft palate. 
These muscles will be seen better from the inside of the pharynx. 
Note the relation of the stylopharyngeus to the superior and 
middle constrictors and that of the two laryngeal nerves to the 
upper and lower borders of the inferior constrictor muscle. 
Prevertebral fascia and muscles. The prevertebral fascia 
is the deepest layer of the cervical fascia. It blends with the 
carotid sheath and the middle layer of the fascia beneath the 
sternomastoid muscle and forms a strong fascial covering across 
the neck in front of the prevertebral muscles. Laterally it is 
prolonged over the muscles in the floor of the posterior triangle. 
The prevertebral muscles extend from the base of the skull 
to the 4th thoracic vertebra. The longus capitis arises from the 
transverse processes of the 3rd to 6th cervical vertebrae and is 
inserted into the basilar process of the occipital bone. The 
longus colli lies medial to it on either side of the midline. It 
consists of several sets of fasciculi attached to the front and 
sides of the vertebrae and its upper extremity terminates at the 
ventral arch of the atlas. Two small muscles, the rectus capitis 
anterior and the rectus capitis lateralis, run from the transverse 
process of the atlas to the basilar process and condyloid portion 
of the occipital bone. 
179 REMOVAL OF THE HEAD AND PHARYNX 
Cut the ligament between the occipital bone and the poste- 
rior arch. Carry the knife forward and disarticulate the condyles 
of the occipital bone from the superior articular processes of 
the atlas. This will be difficult owing to the convexity of the 
condyle and the concavity of the articular process. The check 
ligaments between the odontoid and the occiput, as well as the 
anterior occipito-atlantal ligaments, must be cut. If this is 
done successfully, the skull with the pharynx and the great ves- 
sels and nerves of the neck on either side of the pharynx can 
be separated from the vertebral column. Care should be taken 
in disarticulating the occiput not to drive the knife forward 
into the posterior wall of the pharynx. Separate the pharynx 
and the great vessels from the cervical vertebrae as far as the 
lower border of the thyroid gland. Cut through the pharynx 
and trachea and all other structures in the neck at this level, 
and stuff the pharynx from below upward with cotton or tow. 
The great vessels and the nerves of the neck on either side of 
the pharynx can then be cleaned from behind and followed up 
to the base of the skull. 
Pharynx. The pharynx is a fibromuscular tube which is 
attached above to the basilar portion of the occipital bone and 
ends below at the level of the 6th cervical vertebra. The 
pharyngeal wall is surrounded behind and on the sides by loose 
areolar tissue, which is continuous posteriorly with the preverte- 
bral fascia and laterally with the carotid sheath. Pharyngeal 
veins and nerves are scattered through this loose tissue on the 
dorsum of the pharynx. The pharyngeal wall is complete behind 
and laterally, but anteriorly the wall is deficient and the pharynx 
communicates freely with the nose, mouth and larynx. The 
pharyngeal wall is formed externally by the three constrictor 
muscles of the pharynx. These are striated muscles, which 
arise laterally from the under aspect of the skull, from the 
medial aspect of the mandible, from the hyoid bone, and the 
thyroid and cricoid cartilages of the larynx. The fibres pass 
transversely and obliquely backward and meet in the midline 
180 behind in a fibrous seam or raphe. The inferior constrictor 
overlaps the middle constrictor and that in turn overlaps the 
superior constrictor muscle. The upper border of the superior 
constrictor does not cover in the last inch of the wall of the 
pharynx. Here the musculature is deficient and the wall is 
formed by a layer of fibrous tissue, the so-called pharyngeal 
fascia, which lies between the constrictor muscles and the 
mucous lining of the tube. Having cleaned these muscles, lay 
open the pharyngeal wall in the midline from behind. Turn the 
two flaps to either side and study the anterior relations of the 
pharynx. 
Nasopharynx. This is the upper part of the pharynx and 
lies behind the posterior opening of the nose down to the lower 
border of the soft palate and uvula. In the lateral wall note 
particularly the shape and position of the opening of the 
Eustachian tube, especially its relation to the posterior border 
of the hard palate. Note also the deep lateral recess behind the 
opening of the tube. Study the position and relations of the 
Eustachian tube at this stage. 
Muscles of palate. The two principal muscles of the soft 
palate are the levator palatini and the tensor palatini. These arise 
from the inferior surface of the petrous portion of the temporal 
bone and from the Eustachian tube. The two muscles practi- 
cally surround the tube, pass with it over the upper border of 
the superior constrictor muscle and enter the substance of the 
soft palate. The levator palatini lies just beneath the mucous 
membrane behind the opening of the Eustachian tube and can 
be easily demonstrated by cutting into the mucosa. The tensor 
palatini lies more external and anterior to the levator. It makes 
a right angle turn around the hook-like tip of the external 
pterygoid plate. This little tip can be felt usually with the finger 
and is a guide to the muscle. These muscles should be dis- 
played before the head and palate are split. The levator is easily 
demonstrated, the tensor is more difficult to reach owing to its 
depth. Cut lateral to the levator and above the tip of the 
pterygoid plate. The thin edge of the tensor muscle and its 
tendon will be found at a deeper level to the levator. 
188 Oropharynx. This is the portion of the pharynx lying 
behind the mouth and tongue. It is bounded above by the free 
edge of the soft palate and below by the tip of the epiglottis. 
Note in the median section the relation of the tip of the uvula, 
the tip of the epiglottis and the posterior surface of the tongue 
to the vertebral column. In the lateral wall of the oropharynx 
note the anterior and posterior pillars of the fauces. These are 
folds of mucous membrane reinforced by striated muscle fibers 
passing from the under surface of the soft palate to the side of 
the tongue and the side of the pharynx respectively. By raising 
the soft palate with the forceps these folds will stand out more 
prominently. The anterior fold is the line of demarcation be- 
tween mouth and pharynx, and between the two folds or pillars 
will be found the faucial tonsil. Study carefully the position 
and relations of the tonsil to the pharynx, tongue and vessels in 
the neck. Observe the papillae on the dorsal surface of the 
tongue the three folds of mucous membrane, the glosso-epiglot- 
tic folds, passing from the tongue to the epiglottis and the two 
little fossae between these folds. 
Laryngopharynx. This is the lowest part of the pharynx 
extending from the tip of the epiglottis to the 6th cervical 
vertebra below. Note particularly its relation to the larynx. 
This can be seen best in the view from behind. The opening 
into the larynx is bounded anteriorly by the epiglottis, posteriorly 
by the tip of the arytenoid cartilages of the larynx and laterally 
by the arytenoepiglottic folds. Note the pouch or fossa at the 
lateral aspect of these folds, between them and the upper bor- 
der of the thyroid cartilage. On looking down through the open- 
ing into the larynx from above the vocal cords can be seen. 
Compare this view from above with that of the larynx in median 
section. 
182 DISSECTION OF THE LARYNX 
The larynx should be studied as a whole and its muscles 
dissected before the head is split. Later it can be studied in 
the median section. Study first the hyoid bone and then the 
thyroid and cricoid cartilages. Also note the position and rela- 
tions of the arytenoid cartilages on the upper surface of the 
cricoid. Pay particular attention to the boundary of the open- 
ing into the larynx and the view of the vocal cords from above. 
Seen from above, the false vocal cords form two rounded eleva- 
tions on either side and are simply folds of mucous membrane. 
Deeper down and closer together will be seen the sharper, 
thinner folds of the true vocal cords, consisting of thin bands 
of connective tissue reinforced by muscles and covered by 
mucous membrane. The position of the two cords should be 
particularly noted in the view from above and in the median 
section. Note later in the median section the laryngeal pouch 
or sinus which lies between the cords and extends upward on 
the lateral aspect of the false cords. The relation of the superior 
and inferior laryngeal nerves and the corresponding arteries to 
the cartilages of the larynx should be carefully noted. 
Muscles of the larynx. One set of these muscles lies on 
the superficial aspect of the thyroid, cricoid and arytenoid carti- 
lages. A deeper set lies on the deep aspect of the thyroid 
cartilages. Of the superficial muscles, the cricothyroid will be 
found on the superficial surface of the cricoid and thyroid cart- 
ilages more or less under cover of the infrahyoid group of 
muscles and the lateral lobes of the thyroid gland. It is sup- 
plied by the superior laryngeal nerve. The muscles on the pos- 
terior aspect of the cricoid and arytenoid cartilages can be 
demonstrated only on the specimens where the head has not been 
split. Cut through the anterior wall of the laryngopharynx, and 
the posterior cricoarytenoid muscles can be shown passing from 
the posterior surface of the cricoid to the muscular processes of 
the two arytenoid cartilages. On the posterior aspect of the 
two arytenoid cartilages the oblique and transverse fibres of 
the arytenoid muscle will be seen. The oblique fibres are pro- 
183 longed into the arytenoepiglottic folds which bound the open- 
ing into the larynx. To demonstrate the muscles under cover 
of the thyroid cartilages, it will be necessary to remove one-half 
of that cartilage. The lateral crico-arytenoid muscle passes 
from the upper border of the cricoid to the muscular processes 
of the arytenoid cartilage. Superior to this, forming a thin 
flat sheet of muscle, is the thyro-arytenoid passing from the 
arytenoid cartilage behind to the anterior border of the thyroid 
cartilage in front. This sheet of muscle lies lateral to the vocal 
cords and a special part of it forms the muscular reinforce- 
ments of the true vocal cords. Note particularly the nerve sup- 
ply of the above muscles. The inferior or recurrent laryngeal 
nerve supplies all the above muscles except the cricothyroid 
which is supplied by the superior laryngeal nerve. 
The head and neck can now be split in the midline. The 
saw cut should pass between the lateral and medial incisor teeth 
so as to leave the nasal septum on the left half. The cut should 
be carried through the midline of the vertebral column down to 
about the level of the 6th or 7th thoracic vertebra, where the 
column can be divided transversely. The object of carrying 
the section to this level is to preserve the axilla and its contents 
on each lateral half. 
184 NASAL CAVITY AND ACCESSORY SINUSES 
The ethmoid bone forms part of the roof, lateral wall and 
septum of the nose. It also enters into the floor of the anterior 
fossa of the skull and the medial wall of the orbit. It contains 
the ethmoid cells, accessory air sinuses, which communicate 
with the nasal cavity. It is composed of two plates of bone, 
one vertical, the other horizontal, and a cellular portion, the 
ethmoid labyrinth. The vertical plate forms the upper and 
posterior part of the septum of the nose, which is completed by 
the vomer below and behind, and by the septal cartilage below 
and in front. Its upper border is prolonged into a triangular 
process, the crista galli, which gives attachment to the falx 
cerebri in the anterior cranial fossa. The horizontal, or cribri- 
form plate, forms part of the nose and floor of the anterio 
fossa. It contains many small opening's for the olfactory nerve 
and one for the nasociliary nerve. 
The ethmoid labyrinth is composed of very thin bone, en- 
closing a number of air cells, arranged in three irregular groups, 
anterior, middle and posterior. These communicate with each 
other and with the nasal cavities. The frontal above, the maxilla 
below, the lacrymal in front, and the sphenoid bones behind 
complete the walls of the labyrinth. The lateral walls of the 
labyrinth forms a flat plate, the orbital plate, which lies in the 
medial wall of the orbit. The medial aspect of the labyrinth 
carries two curved bony plates, the superior and middle tur- 
binates or conchae. The space beneath the superior is the 
superior meatus, that beneath the middle, the middle meatus 
of the nose. The middle concha is larger than the inferior. 
The inferior concha or turbinate bone is an independent bone, 
and articulates with the medial aspect of the maxilla below the 
middle concha. It is the largest of the three. 
The vomer is a flat, thin plate of bone which forms the 
posterior inferior part of the septum of the nose. The upper 
border articulates with the under surface of the body of the 
sphenoid; the lower border with the hard palate; the anterior 
border supports the cartilage of the septum ; the posterior border 
185 is free and directed backward, between the posterior nares, to 
the nasopharynx. 
The septum of the nose divides that cavity into a right 
and left chamber. The anterior opening is bounded by the 
nasal bones above and the maxillae laterally and below. The 
lateral and alar cartilages, which form the nostrils and tip of 
the nose, are attached to the borders of this opening. The pos- 
terior openings are bounded above by the body of the sphenoid, 
laterally by the internal pterygoid plate of the sphenoid, below 
by the palate and medially by the vomer. They are symmetrical 
and open into the nasopharynx. 
Each nasal chamber forms a narrow vertical cavity higher 
in the middle than at either end. The anterior portion in rela- 
tion to the cartilages is known as the vestibule. The medial 
wall is formed by the septum, the space between the vomer and 
vertical plate of the ethmoid being filled by a plate of fibro- 
cartilage. The lateral wall from before backward is made up 
of the following bones; the nasal, the maxilla, the lacrymal, 
the ethmoid and inferior turbinate, the palate and the internal 
pterygoid plate of the sphenoid. This wall is characterized 
by the three turbinate bones with the space known as the 
meatus under each. The roof contains the nasal, frontal, cribi- 
form plate of ethmoid and body of the sphenoid bones. The 
roof slants upward in front under the nasal bones, and down- 
ward behind under the sphenoid. The floor is formed by the 
palatine processes of the maxilla and palate bones. 
The accessory air sinuses have important relations to the 
nasal cavity and with the meati in its lateral wall. The frontal 
sinuses lie on either side above the anterior end of the roof and 
open either directly into the middle meatus or into the anterior 
ethmoid cells. The ethmoid labryinth lies in the upper lateral 
wall. The anterior and middle cells open into the middle 
meatus; the posterior cells into the superior meatus. The 
maxillary sinus lies in the lower lateral wall and opens into 
the middle meatus. The sphenoid sinus lie above the posterior 
part of the roof and open into the superior meatus or into the 
sphenoethmoidal recess. The lacrymal canal, from the orbit 
186 opens into the inferior meatus; the sphenopalatine foramen, from 
the pteryopalatine fossa, opens into the lateral wall just pos- 
terior to the superior turbinate. The roof contains the open- 
ings for the filaments of the olfactory and nasociliary nerves. 
187 DISSECTION OF THE NASAL CAVITY 
The lateral wall of the nasal cavity should be studied on 
the skeleton noting particularly the relation of the ethmoid 
bone and the frontal, sphenoidal, and maxillary sinuses to the 
upper and outer wall of the cavity. Having studied the lateral 
wall with the parts in situ, the inferior turbinate can be parti- 
ally cut with the scissors and turned upward. The only open- 
ing beneath it will be that of the naso-lacrymal duct passing from 
the orbit. Follow the course of this duct with the probe. 
Next cut the middle turbinate in the same method. Beneath 
this bone there is a large swelling in the lateral wall known as 
the bulla of the ethmoid, which contains one of the ethmoidal 
air cells. Below and in front of the bulla is a deep narrow gutter 
which communicates in about 50% anteriorly and above with 
the frontal sinus. Endeavor to explore this communication 
with the probe. In the bottom of the gutter are one or two 
small openings communicating with the maxillary sinus and 
with the anterior and middle set of ethmoidal cells. The open- 
ings into the ethmoidal cells are, however, rather varied and 
there may be a special opening above the bulla. Next cut 
the superior turbinate bone and beneath this there is found a 
connection with the posterior ethmoid-cells. In some cases 
there may be more than three turbinate bones. The recess in 
the upper part of the nasal cavity just beneath the sphenoidal 
sinus is known as the sphenoethmoidal recess, and usually con- 
tains an opening into the sphenoidal air sinus. Cut through 
the thin palate bone just posterior to the turbinate bones to 
lay open the palatine canals. Here will be found the palatine 
branches from the second division of the fifth nerve and the 
corresponding arteries from the internal maxillary. Trace the 
nerves into the mucosa of the hard and soft palate. If the 
nerves are followed up in the canal they will lead to the 
sphenopalatine ganglion of the second division of the fifth nerve 
and just above the ganglion is the main trunk of this division. 
This dissection connects the nasal cavity with the pterygo- 
palatine fossa. 
188 Eustachian Tube. Eustachian tube can be dissected in the 
wall of the lateral recess of the pharynx. Cut through the 
mucosa at the orifice of the tube and dissect the mucosa off the 
tube upwards and backwards to the roof of the naso-pharynx. 
This will display the cartilaginous portion of the tube. The 
mucosa can be turned back along the dorsal border of the tube 
and the levator palatini muscle cleaned. The tensor palatini lies 
on a deeper level and will be found just anterior to the lower 
end of the levator and below the opening of the tube. Note 
the relation of the tube to these two muscles. By removing the 
mucosa a little farther back the deep side and upper free border 
of the superior constrictor will be seen. 
189 ACTION OF MUSCLES OF THE HEAD AND NECK 
Muscles of the scalp and face. The muscles of the auricle 
are usually not under the control of the will. The occipital 
bellies of the epicraneus steady the scalp and allow the frontal 
bellies of the muscles to act in raising the eyebrows and in 
puckering the skin over the forehead. 
The orbicularis closes the lids either gently or forcibly, and 
acts also on the lachrymal sac in winking. The orbicular mus- 
cles depress the eyebrows and are the antagonists of the frontal 
muscle. 
The pyramidalis draws down the skin of the forehead; the 
transverse fibres about the nostrils compress or dilate the 
nostrils. 
The orbicularis oris compresses the lips. The buccinators 
perform the action of suction, regulate the forced expulsion of 
air in blowing, and flatten the cheeks during mastication. The 
zygomaticus and quadratus labii superioris raise the corners of 
the mouth, the upper lip, and the ala of the nose. Their action 
is associated with the expression of mirth, disdain, or grief. 
The quadratus labii inferioris and the triangularis depress 
the lower lip and angle of the mouth. Their action expresses 
depression, grief, or ill-humor. The levator menti protrudes 
the lower lip in the expression of disdain. The platysma raises 
the skin of the neck and shoulder, and draws down the angle 
of the mouth. Its action is stimulated by sudden apprehension 
or fear. 
Muscles of mastication. The lower jaw is depressed by 
the geniohyoid, mylohyoid, and digastric muscles. The in- 
frahyoid muscles fix the hyoid bone to enable the suprahyoid 
muscles to act. The jaw is raised by the temporal, masseter, 
and internal pterygoids. The jaw is drawn forward by the 
external pterygoids acting together; the masseter and internal 
pterygoids may assist in this movement. The jaw is drawn 
back by the posterior part of the temporal muscles and by the 
digastric. When the hyoid bone is fixed, grinding movements 
are performed chiefly by the alternate action of the external 
pterygoids assisted to some extent by the elevators of the jaw. 
190 Muscles of the tongue. The genioglossus protrudes, re- 
tracts, and depresses the tongue, by the action of its posterior, 
anterior or middle fibers respectively. The styloglossus ele- 
vates the base and draws the tongue back. The hyoglossus 
retracts and depresses the tongue. The genioglossi and stylo- 
glossi acting together produce a concavity on the dorsum of 
the tongue; the hyoglossi make the dorsum convex. 
Muscles of palate and pharynx. The constrictor muscles 
contract the walls of the pharynx on its contents. The middle 
and inferior constrictors and the stylopharyngeus draw the 
hyoid bone and larynx upward and backward. The palatoglossi 
depress the palate and draw the palatoglossal folds together 
to shut the mouth off from the pharynx. The palatopharyngei 
have a similar action on the palatopharyngeal folds and tend 
to separate the nasal and buccal parts of the pharynx. The 
levator palatini raises, the tensor palatini steadies the palate. 
The latter opens the orifice of the Eustachian tube in swallow- 
ing. 
The act of swallowing is performed by the combined action 
of the muscles of the pharynx and palate, and those of the tongue 
and hyoid bone. The tongue is pressed against the palate and 
the food carried back through the isthmus of the fauces by the 
mylohyoid, styloglossus, and palatoglossus; the hyoid bone is 
raised by the mylohyoid, geniohyoid, digastric, and stylohyoid; 
the larynx is carried up and back under the hyoid bone by the 
thyrohyoid and stylopharyngeus; the base of the tongue is 
drawn back by the styloglossi and the epiglottis carried back 
over the opening into the larynx. The passage of food into 
the nasophraynx is prevented by the simultaneous action of the 
palate muscles, which raise and steady the soft palate and draw 
the posterior pillars of the fauces together. The food passes 
into the pharynx, the constrictors contract on it from above 
downward, and force it on to the gullet below. 
Muscles acting on the head. Flexion (nodding) of the 
head on the spine is performed by both sternomastoid muscles, 
by the longus capitis and rectus capitis anterior and lateralis. 
The hyoid muscles acting on the jaw may aid in this movement. 
If the muscles of one side act alone, the head is inclined ob- 
191 liquely. Extension of the head is performed by the trapezius, 
splenius, upper parts of the sacrospinalis and the deeper dorsal 
muscles, and by the rectus capitis posticus major and minor. 
Movements of rotation (turning the head from side to side) are 
performed by the sternomastoid and part of the trapezius of 
one side, and by the splenius, platysma, and omohyoid of the 
other. 
The prevertebral muscles and the scaleni are flexors of the 
cervical part of the spine when both act together. When those 
of one side act alone the spine is bent to that side. The whole 
spine may be flexed by the combined action of the abdominal 
muscles below the thorax, and the scaleni and prevertebral 
muscles above the thorax. 
Hyoid muscles. The suprahyoid muscles, the myohyoid, 
geniohyoid, digastric, and stylohyoid elevate the hyoid bone and 
depress the jaw (except the stylohoid). The mylohyoid raises 
the floor of the mouth and presses the tongue upwards against 
the palate in the first stage of swallowing. The infrahyoid 
muscles fix the hyoid bone, so that the suprahyoids can act on 
the jaw and depress it after it has been raised in the act of 
swallowing. The thyrohyoid raises the larynx and produces 
the descent of the epiglottis on the opening into the larynx dur- 
ing deglutition. 
192 DISSECTION OF THE ABDOMINAL CAVITY 
Structures below the diaphragm. Before opening the ab- 
dominal wall, the diaphragm should be partially removed to 
show the position of the abdominal organs below it. 
Incisions. Cut through the attachment of the diaphragm 
at the junction of the seventh left costal cartilage and the 
sternum, insert the finger into the opening and slightly raise the 
diaphragm to avoid injuring the organs beneath it. Carry the 
incision to the left along the costal attachments of the muscle 
to the ninth or tenth costal cartilages and then straight back to 
the dorsolateral wall. Carry the hand to the right beneath the 
diaphragm and about at the median line it will be arrested by a 
layer of peritoneum which passes from the superior surface of the 
liver to the under surface of the diaphragm. This is the left side of 
the falciform ligament of the liver. Carry the hand backward 
along this fold. The layer of peritoneum will turn to the left 
and end in a free edge. This is known as the left lateral or tri- 
angular ligament. The finger can only reach the posterior side 
of the left lobe by passing around the free edge of this ligament. 
On the right side make the same incisions. Carry the hand along 
the right side of the falciform ligament, which is formed by two 
layers of peritoneum placed back to back. The finger is pre- 
vented from passing over the posterior border of the right lobe 
by the prolongation of the right side of the falciform ligament, 
which turns to the right and runs along the superior surface to 
the right margin of the liver. This layer is much longer than 
the one on the left, is called the coronary ligament, and ends in 
a free border, the right lateral (triangular) ligament. The falci- 
form ligament divides the superior and anterior surfaces of the 
liver into the right and left lobes and is continued down on the 
deep side of the anterior abdominal wall as far as the umbilicus. 
Cut backward along each side of the falciform ligament, leaving 
a strip of diaphragm about an inch wide to support its dia- 
phragmatic attachment. The incisions should be carried as far 
as the opening of the vena cava inferior or to the point where 
the two layers of the falciform ligament diverge to form the 
193 coronary and lateral ligaments. Do not cut into the opening of 
the cava or injure the coronary and lateral ligaments. 
On the right, the liver occupies all the area immediately be- 
low the diaphragm. Its left lobe extends a variable distance to 
the left of the median line, usually about half way between it and 
the lateral abdominal wall, it is subject to variation and often 
touches the wall on the left side. The size of this lobe deter- 
mines how much of the stomach and spleen come' in contact with 
the left half of the diaphragm. There is a good deal of variation 
in the size of these organs. Just below the diaphragm, the lower 
end of the oesophagus grooves the posterior border of the left 
lobe of the liver and a part of the anterior surface of the stomach 
is seen below and to the left of the liver. Behind and to the left 
of the stomach lies the spleen. It will be well to examine a num- 
ber of the subjects in the dissecting rooms and note the varia- 
tions in these organs, thus getting a clear idea of the relations of 
the structures above and below the diaphragm. The overlap be- 
tween the organs above and below accounts for the changes in 
the percussion note, and is of the utmost importance in the clin- 
ical examination of the thorax and upper part of the abdomen. 
Before opening the abdominal wall, the sternum should be 
put in place, its upper end sutured to the upper part of the manu- 
brium and its lower end to the stump of the xiphoid cartilage. 
This will restore as far as possible the normal position of the 
costal borders and will show their proper relations to the liver 
and stomach when the abdomen is opened. Later the sternum 
can again be removed, and the costal borders cut away, to give, 
more room for the dissection of the upper part of the abdominal 
cavity. Make the first incision in the anterior abdominal wall 
from the xiphoid cartilage to the umbilicus just to the left of the 
mid line. Make a second incision horizontally across the abdom- 
inal wall from side to side just below the umbilicus. A third in- 
cision can then be made from the umbilicus upwards along the 
right side of the falciform ligament to the costal border. The 
two flaps can then be turned up and secured. There will be left 
a very narrow strip of the anterior abdominal wall in the mid- 
line supporting the falciform ligament, and continuous above 
with the similar strip over the diaphragm. This central piece 
194 can be turned from side to side and the extent and connections 
of the falciform ligament noted. The two layers of peritoneum 
which compose this ligament have a crescentic free margin look- 
ing downward and backward. Inclosed in this free margin is a 
soft rounded cord, the round ligament of the liver, which passes 
from the umbilicus to a notch in the inferior surface of that or- 
gan. This cord is the remains of the umbilical vein of the foetus, 
which becomes obliterated shortly after birth. The lower flap 
of the abdominal wall can be turned downward towards the 
pubes. Cuts can be made downward at the outer ends of the 
flap toward the crest of the ilium to facilitate this. The folds 
and fossae on the deep aspect of the anterior belly wall should be 
noted, especially their relation to the internal ring and the in- 
guinal canal. Later, if more room is needed, this flap can be 
divided in the mid line. 
Three folds run downward from the umbilicus on the deep 
aspect of the abdominal wall. The median fold is formed by the 
remains of the urachus and passes to the apex of the bladder. It 
is the medial umbilical ligament. The lateral folds pass from the 
umbilicus to the lateral aspect of the bladder and are the lateral 
umbilical ligaments. They are formed by the remains of the um- 
bilical arteries of the foetus. On either side of the lateral um- 
bilical ligaments are the epigastric folds containing the deep epi- 
gastric arteries. The lateral inguinal fossa lies on the outer side 
of the epigastric fold and marks the position of the internal ab- 
dominal ring. The spermatic vessels run upward and backward 
from this fossa under the peritoneum, the spermatic cord turns 
downward and inward from the fossa and passes into the pelvis. 
This fossa is the seat of indirect inguinal hernia. The middle in- 
guinal fossa lies between the epigastric fold and the lateral um- 
bilical ligament. This fossa lies in relation to the deep aspect 
of Hesselbach's triangle and to the outer edge of the conjoined 
tendon. It is the seat of a direct inguinal hernia. 
Abdominal viscera in situ. There is much variation in the 
shape and size of the abdominal organs with a corresponding 
variation in their position and relations, and this fact should be 
borne in mind in opening an abdomen and examining its con- 
tents. 
195 Liver. Only a part of the anterior surface and the inferior 
border of the liver are seen when the abdomen is opened. The 
upper limit of the right lobe is on a level with the upper border 
of the fifth rib. It crosses the mid line about at the junction of 
the sternum and xiphoid, and the upper limit of the left lobe is 
usually at the lower border of the fifth rib. On the right side, in 
the midaxillary line, the liver usually extends to the eleventh rib, 
then turns forward and follows the lower costal border to the tip 
of the ninth costal cartilage. Here it leaves the costal border, 
crosses obliquely the midline about half way between the lower 
end of the sternum and the umbilicus, and disappears under the 
left costal border at the level of the eighth costal cartilage. Two 
notches are found in the lower border of the liver. The umbili- 
cal notch is near the midline and into it passes the round liga- 
ment. The notch for the gall bladder contains the fundus of the 
gall bladder and lies at the level of the ninth costal cartilage at 
the outer border of the rectus muscle. The falciform ligament is 
attached to the anterior surface of the liver and separates it into 
the right and left lobes. 
Stomach. Like all hollow organs there is much variation in 
its size and shape, depending on the degree of distention. When 
moderately full, part of the anterior surface and greater curva- 
ture is seen below the inferior border of the liver. This part of 
the organ has an area of contact with the anterior abdominal 
wall bounded above by the lower border of the liver, to the left 
by the left costal border, at the ends of the eighth and ninth cos- 
tal cartilages. This lower limit is variable, and is carried lower 
down as the stomach becomes more fully distended. 
Great Omentum. Along the lower border of the stomach 
or the greater curvature are attached two layers of peritoneum 
which are continuous with the peritoneum over its anterior and 
posterior surfaces. Below the greater curvature these two layers 
are fused together, appear as one layer, and are prolonged down- 
ward over the anterior surface of the intestines, almost to the 
pubes. This structure is known as the great omentum, and more 
or less fat is usually found in its two layers, so much so that at 
times it resembles a sort of fatty blanket spread over the abdom- 
inal contents below the stomach. In many cases the omentum 
196 is much more limited in extent and often is more or less rolled 
up and tucked away in the upper left part of the abdominal cav- 
ity. Blood bessels are contained between the two layers of peri- 
toneum. These run about an inch below the stomach, forming 
an arterial arch along its greater curvature, and send smaller 
branches upward to the stomach and downward to the lower 
part of the omentum. The arteries are branches of the first vis- 
ceral branch of the abdominal aorta, the coeliac axis, and the 
veins are tributaries of the portal system of veins. 
Intestines. Occasionally the great omentum is so large 
that it wholly covers the intestines below the stomach. Usually 
some coils of small intestine will be seen below its lower border, 
and on the extreme right and left a part of the large intestine is 
usually visible. The large intestine or colon is distinguished 
from the small intestine not only by its size, but also by its pe- 
culiar sacculated appearance and by the presence of three longi- 
tudinal bands of smooth muscle fibers on its surface. The por- 
tion to the right is the ascending colon and that to the left is the 
descending colon. Great variation is, however, to be expected 
in the size and position of the great omentum and in the amount 
of small and large intestine exposed below it. 
Having noted the position of the various organs in situ, re- 
move the sternum and trim away the costal borders as far back 
as the tenth ribs. This will open up much more extensively the 
whole upper part of the abdominal cavity, will expose more of 
the superior and anterior surfaces of the liver and of the anterior 
surface and greater curvature of the stomach. A portion of the 
anterior margin of the spleen may also be shown, especially i-f 
the organ is at all enlarged as is often the case. 
Inferior surface of liver. Turn up the lower border of the 
liver to expose its inferior surface. The pear-shaped gall bladder 
extends from the inferior border obliquely inward and backward 
on the inferior surface of the right lobe. To the right of the gall 
bladder is a shallow depression which lies over the hepatic flex- 
ure of the colon; behind this area is the larger renal depression 
which is in relation to the right kidney. To the left of the gall 
bladder is a quadrilateral shaped area, the quadrate lobe, which 
lies just above the pyloric end of the stomach and the first part 
197 of the duodenum. This lobe is bounded on the left by the um- 
bilical fissure, which separates the right and left lobes on the 
inferior surface. The inferior aspect of the left lobe presents a 
concavity, which lies above the anterior surface of the stomach, 
and an elevation, the omental tubercle, which is adapted to the 
lesser curvature of the stomach and the lesser omentum. 
Stomach and oesophagus. About an inch of the oesopha- 
gus is found below the diaphragm curving to the left to open into 
the cardiac orifice of the stomach. The upper part or fundus of 
the stomach rises beneath the diaphragm above the cardiac orifice. 
The greater curvature begins at the oesophagus behind the fundus, 
and runs downward, forward, and to the right to end at the pyloric 
end of the organ. The lesser curvature also begins at the oesoph- 
agus, passes at first almost straight downward along the verte- 
bral column, and its lower end turns abruptly to the right to 
reach the pyloric end at, or to the right of, the midline. Note 
the attachment of the lesser omentum all along the lesser curva- 
ture and of the great omentum all along the greater curvature. 
The lower part of the stomach is narrower and more tubular 
than the fundus and is known as the pylorus. It opens by the 
pyloric orifice into the first part of the duodenum, which repre- 
sents the beginning of the small intestine. The position of the 
opening is often marked by a small vein or a groove around the 
gut, and on palpation a circular thickening can always be felt, 
which marks the pyloric sphincter muscle. Beyond the stomach 
about three inches only of the duodenum can be seen, in the 
present stage of the dissection. The lesser omentum is pro- 
longed for a short distance along the upper border of the duo- 
denum. 
The cardiac orifice of the stomach lies on the left side of the 
tenth thoracic vertebra, or one inch to the left of the junction 
of the seventh left costal cartilage and the sternum. This repre- 
sents the most fixed portion of the organ. When the stomach is 
empty, the fundus is always more or less distended, and is adapt- 
ed to the under surface of the left half of the diaphragm, while 
the pyloric end is more tubular and contracted. The pyloric end 
is the most movable part, and its position and that of the great 
curvature vary greatly, depending on the degree of distention of 
198 the organ. When the stomach is empty, the pyloric orifice lies 
in the transpyloric plane (midway between the top of the ster- 
num and pubes) close to the midline and on a level with the first 
lumbar vertebra. When moderately distended, the pyloric ori- 
fice moves somewhat to the right of the midline at the level 
given above, and the greater curvature would probably be at the 
level of the tenth left costal cartilage. In extreme distention, the 
lower border of the greater curvature may descend below the 
umbilicus down to the crest of the ilium, and the pyloric extrem- 
ity may be two or three inches to the right of the midline. The 
position of the pyloric end of the stomach has a marked effect 
on the position of the first part of the duodenum. With the 
empty stomach the duodenum passes almost horizontally to the 
right, but when the stomach is fully distended the duodenum 
may extend almost straight backwards with its gastric end two 
or three inches from the mid line. All degrees of distention and 
of variation in size and shape are to be expected in the stomach, 
as seen in the dissecting room. One of the commonest variations is 
that of the "hour glass" stomach, where there is a more or less 
well marked constriction between the fundus and pylorus. An- 
teriorly, the stomach is in relation to the left lobe of the liver 
and the anterior abdominal wall, while posteriorly it is in rela- 
tion to the lesser peritoneal cavity and to the structures of the 
dorsal wall of that space. These will be exposed later when the 
stomach is removed. 
Lesser omentum. Carry the finger backward over the sur- 
face of the quadrate lobe of the liver and it will be stopped by a 
layer of peritoneum which forms the posterior boundary of this 
lobe. The inner end or neck of the gall bladder disappears be- 
hind this layer. This layer of peritoneum has a second layer 
behind it, and the two are fused together and form the lesser 
omentum. The lesser omentum consists of two layers of peri- 
toneum, which are for the most part fused together like the two 
layers of peritoneum of the great omentum. These fused layers 
are attached below and to the left to the lesser curvature of the 
stomach, where they separate to inclose the gastric and pyloric 
vessels which supply that part of the stomach. The two layers 
then pass on either side of the stomach, meeting again along the 
199 greater curvature, where they are continuous with the layers of 
the great omentum. If the lesser omentum is traced to the right, 
its two layers show a free border which forms the anterior boun- 
dary of the foramen of Winslow, (epiploic foramen). In this 
border lie the portal vein, the bile duct, and the hepatic artery. 
Above, the lesser omentum can be traced to the portal or trans- 
verse fissure on the inferior surface, and to the fissure of the 
ductus venosus on the posterior surface of the liver. At these 
fissures the two layers of the omentum separate. The anterior 
layer passes forward over the inferior and anterior surfaces of 
the liver and thence on to the anterior abdominal wall and under 
surface of the diaphragm, contributing to the formation of the 
falciform, coronary and lateral ligaments. The posterior layer 
passes backward over a part of the posterior surface, helps to 
form the coronary and lateral ligaments, and then is reflected 
onto the posterior abdominal wall. Here it passes downward over 
the pancreas, forms the upper part of the dorsal wall of the lesser 
peritoneal cavity, and meets the superior of the two layers of the 
peritoneum in the dorsal wall of the great omentum, thus com- 
pleting the peritoneal covering of the dorsal wall of the lesser 
peritoneal cavity. 
Foramen of Winslow and lesser peritoneal cavity. Place 
the finger on the under surface of the gall bladder and carry it 
backward to its neck. Here the finger will strike the right edge 
of the lesser omentum on the under surface of the liver. This 
edge is rounded and free towards the right. The finger will slip 
under this edge and enter an opening, the Foramen of Winslow 
(epiploic foramen), which leads from the general peritoneal cav- 
ity into the lesser peritoneal cavity. This space lies behind the 
lessed omentum and stomach, and is prolonged down into the 
great omentum. As the finger passes into the foramen of Wins- 
low, the free edge of the lesser omentum lies directly in front of 
it. It is rounded and thickened owing to the presence of the 
portal vein, common bile duct and hepatic artery between its two 
layers. These vessels pass to the liver and will be exposed in a 
later stage of the dissection, but their position in the omentum 
and their relations to the foramen should be carefully noted at 
200 this time. The Huger in the foramen will lie just above the first 
part of the duodenum. 
Great omentum. This structure forms a sort of bag, with 
anterior and posterior walls and a free lower border. The an- 
terior wall is formed by the two layers of peritoneum which sur- 
round the stomach. These layers meet and fuse into one layer 
along the greater curvature where they inclose the epiploic ves- 
sels that supply the greater curvature. At the lower border of 
the omentum these fused layers are continued upward as the 
posterior wall of the sac to the level of the second lumbar verte- 
bra where they are attached along a transverse line to the pos- 
terior abdominal wall. At this line of attachment the fused lay- 
ers again separate into two distinct layers, which are reflected 
up and down over the posterior abdominal wall. Turn up the 
whole omentum over the liver and stomach and examine its pos- 
terior wall and especially its line of attachment. The great 
omentum forms a sort of shelf along the line of attachment to 
the posterior abdominal wall, which is of topographical impor- 
tance in dividing the abdominal cavity into an upper and lower 
region. Between the fused layers of the posterior wall of the 
omentum lies the transverse colon. The transverse colon is 
usually attached about at the middle of the posterior wall of the 
great omentum, and it can be traced to the right into the hepatic 
flexure just below the liver, and to the left into the splenic flex- 
ure just below the spleen. Note that the splenic flexure is higher 
up and more posterior than the hepatic flexure. 
Lesser peritoneal cavity. The extent of this space and its 
relations to the surrounding organs should be carefully studied. 
Pass a probe into the foramen of Winslow and carry it down 
behind the stomach below the level of the greater curvature. The 
tip of the probe can be felt through the anterior wall of the 
great omentum. Cut through the anterior wall of the omentum 
below the level of the large vessels running along the greater 
curvature, and the probe will emerge through the opening. 
Carry the incision in the anterior wall of the omentum to the 
right and left as far as the points where the right and left gastro- 
epiploic arteries run from the dorsal wall onto the greater curv- 
ature of the stomach. These vessels can usually be felt through 
201 the peritoneum if they are injected and must not be cut. Turn 
the stomach up and the anterior wall of the omentum down. This 
dissection will expose the dorsal wall of the lesser peritoneal sac. 
The pancreas can usually be seen through the peritoneum on the 
dorsal wall. If the splenic artery is injected, it can be felt 
through the peritoneum above the pancreas. The left kidney 
and adrenal body form a slight elevation on the dorsal wall just 
above the pancreas. To the left, the spleen can be felt in the lat- 
eral wall of the omentum. 
The finger or probe can be carried down between the an- 
terior and posterior layers, showing that the lesser cavity is pro- 
longed down below the greater curvature of the stomach into 
the peritoneal bag formed by the anterior and posterior layers 
of the great omentum. Occasionally the space will extend down 
to the very bottom of the bag, but more frequently there is an 
adhesion between the omental layers, and the space rarely ex- 
tends below the level of the transverse colon. It is not uncom- 
mon to have the space more or less obliterated by pathological 
adhesions, and then it is difficult to demonstrate the extent of 
the cavity. Note carefully the boundaries of the lesser peritoneal 
sac. Above is the spigelian lobe of the liver; in front from above 
downward are the lesser omentum, the posterior surface of the 
stomach, and the anterior layers of the great omentum. Behind 
from below upward are the posterior layers of the great omen- 
tum, the transverse colon and its mesocolon. Above the line of 
attachment of the transverse mesocolon is the dorsal wall, where 
lie the pancreas and other structures, which will come into view 
when the stomach is removed. The bottom and sides of the 
omental bag bound the space below and laterally. 
Spleen. This organ usually lies to the left and well behind 
the stomach. The spleen lies opposite the ninth, tenth, and 
eleventh ribs on the left side and in normal conditions should not 
appear below the left costal border. Enlargement of the spleen, 
however, is very common. Pick up the great omentum at the 
greater curvature and trace it to the left to the spleen. The two 
layers of the omentum pass to the medial surface of the spleen 
and split to surround the organ. The term gastrosplenic liga- 
ment is often given to that part of the great omentum between 
202 the stomach and spleen, and between these two layers branches 
of the splenic artery pass to the greater curvature of the stom- 
ach. Pass the hand around the spleen and palpate its convex 
diaphragmatic surface and note that the organ is almost wholly 
surrounded by peritoneum. 
Small intestine. Before disturbing the colon further, exam- 
ine the coils of small intestine. This part of the gut consists of 
the duodenum, which is about ten inches long, and of the jeju- 
num and ileum, which form the rest of the small intestine. The 
greater part of the duodenum is deeply placed, being covered in 
front by the transverse colon and its mesentery, and by the mes- 
entery of the jejuno-ileum. Its general shape and position can 
be demonstrated by inflating it from below at the beginning of 
the ileum or from above at the lower end of the oesophagus. 
When its position has been established, it and the stomach 
should be emptied, as the distended stomach will be in the way. 
The great mass of intestines now exposed are both the jejunum 
and ileum, the former being about two-fifths and the latter about 
three-fifths of this part of the gut. Draw the small intestine over 
to the left to expose the ascending colon. The lower end of the 
ileum opens into the colon at the level of the right sacro-iliac 
joint. 
Large intestine. The colon begins in a dilatation known as 
the caecum. This structure should be wholly surrounded by 
peritoneum and can be raised from the posterior wall. Its upper 
limit behind is marked by the level at which the peritoneum 
passes from its posterior surface to the posterior abdominal wall. 
Above this point the ascending colon begins, and is fused to the 
posterior wall so that it cannot be raised. The three bands which 
characterize the colon meet at the under side of the caecum and 
at this point is the origin of the vermiform appendix. This organ 
is about three inches in length and usually lies under cover of 
the caecum either pointing upward and inward, or downward 
and inward. There are several little pockets or fossae in the per- 
itoneum of the dorsal wall behind the caecum and the beginning 
of the ascending colon, in one of which the appendix often lies. 
This is a favorite spot for adhesions by which the appendix is 
often more or less concealed. Follow the ascending colon upward 
to the hepatic flexure. It is only about four or five inches long, 
203 is usually rather dilated, and is fused to the posterior wall. At the 
hepatic flexure it passes forward and to the left into the transverse 
colon, which is suspended several inches from the dorsal wall by a 
part of the great omentum. That part of the omentum from the trans- 
verse colon to the dorsal wall was originally part of the mesentery of 
the colon and is called the transverse mesocolon. Follow the trans- 
verse colon and its mesocolon over to the spleen. Here the gut 
turns downward, loses its mesentery and becomes fixed to the 
posterior abdominal wall. This marks the beginning of the de- 
scending colon, which is longer than the ascending, and is usu- 
ally much contracted. Draw the small intestine well over to the 
right to expose the descending colon. Trace this part of the 
colon downward, and a short distance below the iliac crest it 
will recover its mesentery and form a fairly long loop. This loop, 
the sigmoid colon or flexure, passes over the brim of the pelvis 
and at the third sacral vertebra becomes fused again to the pos- 
terior wall. Here is the beginning of the rectum, the last part 
of the large intestine. 
Mesentery of small intestine. Examine last of all the mes- 
entery of the jejunum and ileum. Draw the small intestines 
over to the right to expose the left side of the mesentery. It be- 
gins at the left side of the second lumbar vertebra and runs 
obliquely downward and to the right to the level of the sacro- 
iliac joint. Turn the intestines to the left and expose the right 
side of the mesentery. The termination of the ileum will be seen 
lying along the medial side of the caecum and entering the colon 
just above the caecum. Branches of the superior mesenteric 
artery lie in this mesentery. This vessel supplies the jejuno- 
ileum, caecum and appendix, and ascending and transverse 
colon. In thin subjects, with a clear peritoneum and a good ar- 
terial injection, the branches to the gut stand out very clearly, 
and their general distribution can be noted at this stage. They 
will be dissected later. Turn back the intestines to the rig'ht and 
examine the beginning of the jejunum just below the line of 
attachment of the transverse mesocolon. The terminal part of 
the duodenum seems to spring from the depths of the dorsal 
wall just below the mesocolon and passes directly over into the 
beginning of the jejunum forming the duodenojejunal flexure. 
204 DISSECTION OF THE REGION ABOVE TRANSVERSE 
MESOCOLON 
The organs above the line of attachment of the transverse 
mesocolon form a topographical whole in their development, re- 
lations and blood supply. They are developed from that part 
of the primitive digestive tube which is supplied chiefly by the 
coeliac axis, and are grouped about the lesser peritoneal cavity. 
Having studied and followed out the layers of peritoneum that 
enter into the walls of the lesser peritoneal sac, the vessels in 
the greater and lesser omentum should be dissected. As they 
lie between the two layers of peritoneum of each omentum, it 
will only be necessary to remove the superficial layer and leave 
the deeper one to support the vessels. 
Vessels in the lesser omentum. The structures to be ex- 
posed in this dissection are the hepatic, cystic and common bile 
ducts; the hepatic artery, the pyloric and gastric arteries and 
veins, and the portal vein. With the exception of the pyloric 
and gastric vessels, which lie along the lesser curvature of the 
stomach, these structures lie chiefly between the layers of the 
omentum at its free right border, and enter or leave the liver at 
the portal fissure. Cut through the anterior layer of peritoneum 
along this border to expose the structures in the margin. The 
injected hepatic artery can usually be felt through the perito- 
neum and it is best to start with this vessel. It should be cleaned 
from the peritoneum and traced down as far as the level of the 
top of the pylorus and first part of the duodenum and upward to 
the transverse fissure of the liver. 
Coeliac plexus. The hepatic artery is surrounded by a plexus 
of nerves, which are branches of the coeliac ganglia and belong to 
the sympathetic system. The ganglia lie on either side of the 
coeliac artery; the branches from the ganglia form a plexus on 
the hepatic, gastric and splenic arteries and supply the various 
organs to which those vessels are distributed. The hepatic artery 
should be cleaned carefully in order to display some of the 
nerves, which usually are fairly large. The same procedure should 
be followed when the gastric and splenic vessels are dissected. 
205 Bile Ducts. External to the artery lies the bile duct, which 
is soft and cannot be felt with the fingers. The tissues are usu- 
ally stained a greenish brown by the bile pigments, which filter 
through the wall of the gall bladder, and the duct is thus often 
obscured. The best procedure is to start at the neck of the gall 
bladder and secure the cystic duct, which drains the gall bladder. 
This duct enters the lesser omentum and joins the hepatic duct, 
which represents the union of the right and left hepatic ducts 
from the right and left lobes of the liver. These two hepatic 
ducts join to form the common hepatic duct well up in the portal 
fissure. The common hepatic duct joins the cystic duct to form 
the common bile duct somewhere between the fissure above and 
the top of the duodenum below. The common bile duct will be 
traced later to its opening in the second part of the duodenum. 
The duct and the artery lie about on the same plane, and behind 
the two is the portal vein. This vessel is formed lower down 
behind the pancreas by the union of the splenic and superior 
mesenteric veins. If there is difficulty finding the bile ducts, a 
blow pipe can be inserted into the fundus of the gall bladder and 
the duct inflated, or the blow pipe can be tied into the duodenu- 
jejunal flexure and the duct and gall bladder inflated from below 
to demonstrate the connection between the duodenum and bile 
ducts. This latter method is often ineffective on account of the 
plugging up of the duodenal opening of the bile duct by intes- 
tinal contents. 
The ducts, artery and vein should be thoroughly exposed 
from the liver down to the top of the pyloric end of the stomach 
and the duodenum, and, if the dissection has been properly done, 
the anterior layer of the lesser omentum and the connective tis- 
sue about these vessels only will have been removed, while the 
posterior layer of peritoneum will have been left intact behind 
them. Note again at this stage the boundaries of the foramen 
of Winslow. Above is the spigelian lobe of the liver, which 
sometimes can be seen shining through the lesser omentum; be- 
low is the duodenum; anteriorly the vessels just dissected; and 
behind on the dorsal wall of the abdomen is the inferior vena 
-cava, though this vessel cannot yet be clearly seen. 
206 Coeliac artery. The hepatic artery gives oft a small branch, 
the pyloric, which passes to the pyloric end of the stomach, and 
anastomoses with the gastric artery. The hepatic and gastric ar- 
teries are both branches of the coeliac artery. The coeliac artery 
is a short vessel which arises from the abdominal aorta just be- 
low the diaphragm and lies behind the lesser omentum. Its ori- 
gin will be seen later in the dissection of the dorsal wall of the 
lesser peritoneal cavity. The gastric artery runs upward towards 
the oesophagus in a fold of peritoneum, the gastropancreatic 
fold, just inside the foramen of Winslow. On reaching' the 
oesophagus, it sends a few branches to that structure and then 
runs down along the lesser curvature to the pylorus. From the 
arterial arch formed by the gastric and pyloric arteries, branches 
are given off to the stomach. Remove the anterior layer of the 
lesser omentum along the course of these arteries and clean 
them along the lesser curvature, but leave the posterior layer of 
the lesser omentum intact to support them behind. 
Vessels in the great omentum. Turn next to the greater 
curvature and dissect out the vessels which form the correspond- 
ing arterial arch along that side of the stomach. Begin at the 
pyloric end and work over to the left. A large vessel will be 
seen in the great omentum just below that pylorus running to 
the left. This is the right gastro-epiploic artery, a branch of the 
gastroduodenal artery. The latter lies behind the pyloric end of 
the stomach or the first part of the duodenum and arises from 
the hepatic artery. Its origin may have been exposed in the dis- 
section of the hepatic artery above the duodenum, but if not, it 
can be seen later. The right gastro-epiploic artery anastomoses 
with the left gastro-epiploic artery, a branch of the splenic ar- 
tery. The splenic artery arises from the coeliac axis, lies on the 
dorsal wall of the lesser peritoneal sac, and passes to the spleen. 
At the hilum of the spleen the gastrosplenic portion of the great 
omentum splits to surround that organ and the artery sends 
branches through this part of the great omentum to the greater 
curvature of the stomach. These are the vasa brevia, which go 
to the upper part of the greater curvature, and the left gastro- 
epiploic, which runs along the greater curvature. From this 
207 arch, formed by the right and left gastro-epiploic arteries, which 
lies a little below the greater curvature, branches are sent to 
both sides of the stomach. The veins along both curvatures cor- 
respond to the arteries. They are tributaries of the portal sys- 
tem of veins and terminate eventually in the portal vein. Re- 
move only the anterior layer of peritoneum from the vessels, and 
leave the posterior layer to support the vessels. 
208 DISSECTION OF THE DORSAL WALL OF THE LESSER 
PERITONEAL CAVITY 
A large part of the lesser peritoneal cavity is situated pos- 
terior to the stomach and that organ is in close relation to the 
structures in the dorsal wall of the lesser sac, the potential 
space of the cavity and the peritoneum over its dorsal wall in- 
tervening. The peritoneum on the dorsal wall of the lesser 
peritoneal cavity is reflected down from the posterior surface of 
the liver. At the lower border of the pancreas this layer is con- 
tinuous with the superior layer of peritoneum in the dorsal wall 
of the great omentum. The line of attachment of the great 
omentum, or in other words of the transverse mesocolon, is 
along the inferior border of the pancreas, so that the latter or- 
gan is practically confined to the lesser sac and is there fused to 
the dorsal wall with peritoneum on its anterior surface only. 
Pancreas. This is the most important organ in the dorsal 
wall of the lesser sac. The line of attachment of the transverse 
mesocolon runs along its lower border and its anterior surface 
stands out beneath the peritoneum of the dorsal wall. The body 
of the organ only is seen at this stage. Along the upper border 
of the organ parts of the splenic artery can be felt or seen pass- 
ing to the left towards the spleen. The gastric artery can be fol- 
lowed up to the oesophagus and the hepatic artery into the lesser 
omentum just above the pyloric end of the stomach. If the peri- 
toneum is thin all these can be easily felt and seen and should be 
carefully identified. Just above the tail of the pancreas near the 
spleen a part of the left kidney will be felt deeper in the dorsal 
wall. The position of the spleen in the lateral wall of the lesser 
sac will not be apparent. The enlarged head of the pancreas is 
embraced by the four parts of the duodenum and is partly cov- 
ered by the attached border of the transverse mesocolon. It will 
be exposed later. The body of the pancreas passes to the left 
and a little upward on the dorsal wall of the lesser sac and its 
left end or tail is usually in contact with the spleen. Cut into 
the peritoneum along its upper border and dissect this mem- 
brane off its anterior surface, but do not destroy the line of at- 
209 tachment of the mesocolon along its lower border. It is desir- 
able that this be preserved intact until the dissection of the dor- 
sal wall of the lesser cavity is completed. 
Vessels in the dorsal wall. Next following the splenic artery 
along the upper border of the pancreas to the spleen. It lies 
against the posterior wall partly above and partly behind the 
pancreas, having a rather tortuous course. The artery enters the 
hilum of the spleen and gives off at this point branches to the 
greater curvature of the stomach. The two layers of the great 
omentum pass from the greater curvature of the stomach and 
surround the spleen. This part of the omentum is the gastro- 
splenic ligament of omentum. The two layers meet at the hilum 
of the spleen, and pass to the kidney on the dorsal wall, forming 
the lienorenal ligament or omentum. On the kidney the two 
layers separate, the left passing outward over the posterolateral 
wall of the general peritoneal cavity, the right passing inward 
over the kidney, pancreas and dorsal wall of the lesser perito- 
neal sac. The splenic artery runs behind the peritoneum along 
the upper border of the pancreas, crosses the anterior surface of 
the left kidney, and passes between the two layers of the lie- 
norenal ligament to the spleen. The branches to the stomach pass 
between the layers of the gastrosplenic omentum to the greater 
curvature of the stomach. The vasa brevia go to the upper part 
of the greater curvature; the left g,astro-epiploic runs along the 
lower part of the greater curvature and forms an arterial arch 
with the right gastro-epiploic artery. 
The gastrosplenic and lienorenal ligaments of the great 
omentum form the left lateral wall of the lesser sac above the 
line of attachment of the transverse mesocolon. The splenic 
artery and its branches to the spleen and stomach should be 
carefully dissected to their distribution on these organs. The 
gastric artery should also be dissected out of the gastropancre- 
atic fold up to the oesophageal end of the stomach and connected 
to the arterial arch along the lesser curvature. The hepatic ar- 
tery gives off the gastroduodenal branch, which runs down be- 
hind the pylorus or first part of the duodenum. This in turn 
gives off the right gastro-epiploic to fhe greater curvature of the 
stomach and the superior pancreaticoduodenal artery to the 
210 head of the pancreas and duodenum. The right lateral wall of 
the lesser sac above the line of attachment of the transverse 
mesocolon is formed by the fusion of the great omentum with 
the duodenum and by the first and second parts of the duode- 
num itself. Immediately above the duodenum the lateral wall 
is lacking and here is situated the foramen of Winslow. The 
right gastro-epiploic artery passes from the dorsal wall of the 
lesser sac between the layers of the omentum which extend from 
the duodenum to the pyloric end of the greater curvature and 
anastomoses with the left gastro-epiploic artery. The hepatic 
artery should be followed from the coeliac axis to the pyloric 
end of the stomach and connected with that part of the vessel 
already dissected between stomach and liver. The gastroduo- 
denal and right gastro-epiploic arteries should then be followed 
to the greater curvature. The superior pancreaticoduodenal 
artery can be followed later. 
Coeliac ganglia. The right and left coeliac ganglia lie on 
either side of the coeliac artery and are connected together by 
branches which surround the vessel. The ganglia are irregular- 
ly semilunar in shape, and lie on the crura of the diaphragm. 
The right ganglion is thrust in behind the inferior vena cava; 
the left lies in the dorsal wall of the lesser sac just above the 
splenic artery. A mass of branches are given off from the gan- 
glia, which surround all branches of the coeliac artery and travel 
on these vessels to the various organs. The nerves and connec- 
tive tissue about the vessels are often so matted together that 
the dissection is difficult, but the ganglia are so large that they 
can be secured without difficulty. Clean the left ganglion only at 
this stage; the right can be got at more conveniently later. En- 
deavor to demonstrate some of the branches of the plexus on the 
three main branches of the coeliac artery when those vessels are 
being cleaned. When the coeliac axis is exposed, the crura of 
the diaphragm will come partially into view and the two phrenic 
arteries, which arise either just above the coeliac axis from the 
aorta or sometimes from the axis itself, may be seen. They can 
be followed up to the under side of the diaphragm later when 
the liver is removed. The splenic vein lies mostly behind the 
pancreas, but part of it will be exposed towards the tail of the 
211 pancreas and at the hilum of the spleen. It will be traced to the 
portal vein later when the pancreas is removed. 
Left kidney and suprarenal gland (adrenal). The upper 
end of the kidney rises above the upper border of the pancreas. 
The suprarenal gland is placed partly on the upper and partly 
on the inner aspect of the kidney. The kidney is solid and can 
easily be felt through the peritoneum on the dorsal wall, but the 
suprarenal body is often soft and poorly preserved, and can be 
easily lost in the dissection, unless special care is taken to se- 
cure it at this stage. The adrenal body and kidney will be more 
fully exposed when all the other organs are removed. The pan- 
creas and the splenic vessels lie across the anterior surface of the 
kidney. 
Spleen. This organ will be now thoroughly exposed and 
can be studied in situ. It has a convex diaphragmatic surface 
opposite the ninth, tenth and eleventh ribs; a concave gastric 
surface on which is situated the hilum directed toward the dor- 
sal side and greater curvature of the stomach, and a smaller 
renal surface directed inward and backward towards the left kid- 
ney. This latter surface will be seen better when the organ is 
removed. The great omentum can be cleared away about the 
spleen to expose the hilum and the splenic vessels, but the vessels 
are not to be cut and the organ is to be left in place. 
Stomach bed. The structures in the dorsal wall of the 
lesser sac above the line of attachment of the transverse meso- 
colon, together with the transverse mesocolon and transverse 
colon itself all lie behind the stomach and form a sort of concav- 
ity, which is called the stomach bed. If the line of attachment 
of the mesocolon has been kept intact, this bed will now be fully 
displayed, and the position of the contents and their relation to 
the stomach should be carefully checked up, as they will be 
much disturbed in the next stage of the dissection. 
This completes for the moment the dissection of the upper 
region of the abdomen above the shelf formed by the tran'sverse 
mesocolon. The duodenum and head of the pancreas cannot be 
fully exposed until the transverse colon and its mesocolon have 
been removed, and the liver cannot be taken out until the bile 
■duct has been thoroughly dissected. The transverse mesocolon 
212 will now be turned up and the dissection of the lower region be- 
low it begun. 
Small intestine. Duodenum. The duodenum is the first ter. 
or twelve inches of the small intestine. It has already been in- 
flated but its general position and subdivisions should be ob- 
served at the present time before the parts about it have been 
further disturbed. The duodenum is usually somewhat like the 
letter U in shape, and is described as having four parts. In 
many cases it is more V-shaped and then has three parts, the 
third part corresponding to the third and fourth part of the U- 
shaped form. The first part of the duodenum is somewhat egg- 
shaped and is about three inches in length. Its position with 
the empty or distended stomach has already been mentioned. 
Note its relations to the foramen of Winslow and the vessels in 
the edge of the lesser omentum. Above and in front is the liver 
and gall bladder and below the head of the pancreas. The second 
part of the duodenum descends along the right side of the ver- 
tebral column to about the bottom of the third or the top of the 
fourth lumbar vertebra. It is crossed anteriorly by the begin- 
ning of the transverse colon and its mesocolon and is in contact 
above with the gall bladder. The bile duct opens into its poster- 
omedial wall. It lies in front of the inferior vena cava, right 
renal vessels and hilum of the right kidney. The third part 
turns to the left and runs obliquely across the vertebral column, 
the vena cava, and the aorta. In front it is covered by the at- 
tached border of the mesentery of the jejuno-ileum, containing 
the superior mesenteric vein and artery. The fourth part, if it 
exists, turns up in front of the aorta and passes into the duode- 
nojejunal flexure on the left side of the second lumbar vertebra. 
The head of the pancreas is embraced in the curve of the duode- 
num and tends to overflow the surrounding gut either in front 
or behind. The peritoneal relations of each part of the duode- 
num should be noted. The first part, being the continuation of 
the stomach, is surrounded wholly by peritoneum, except along 
the line of attachment of the greater and lesser omentum to this 
part of the duodenum. The other three parts have lost their 
peritoneum behind and are fused to the dorsal wall. The sec- 
ond part has lost its peritoneum in front, where the transverse 
213 mesocolon crosses it, and the third part also, where it is crossed 
anteriorly by the mesentery of the jejuno-ileum, and the su- 
perior mesenteric vessels. The dorsal relations will be followed 
out later but the anterior relations, especially the peritoneal, 
should be noted now. 
Duodenojejunal fossae. There are several small peritoneal 
pockets or fossae which should be looked for here. The most 
constant are the superior and inferior duodenojejunal fossae on 
the left side of the duodenojejunal flexure. Turn the intestine 
over to the right and in most cases two little peritoneal folds 
will be seen running from the gut to the dorsal wall. The in- 
ferior mesenteric vein lies in the base of the superior fold. They 
will usually admit the tip of the finger, and form the anterior 
wall of the fossae. Another may sometimes be found above the 
flexure up under the attached border of the mesentery of the 
transverse colon. Sometimes these may be so enlarged that part 
of the intestine is buried in them, forming a retroperitoneal her- 
nia. Follow the line of attachment of the mesentery of the small 
intestine along its left side. It extends from the left side of the 
second lumbar vertebra to the right iliac fossa and is about six 
inches in length at its attached border and over twenty feet on 
the intestinal border. 
Jejuno-ileum. The small intestine is usually about twenty 
to twenty-three feet long in the cadaver, but is probably some- 
what shorter in the living. The jejunum is the first two-fifths, 
and is of rather larger caliber, thicker walls, and more vascular 
than the ileum, which is the terminal three-fifths of the gut. 
When the gut is removed later from the mesentery and opened 
up more striking differences in the two parts are seen in the 
mucosa. That of the jejunum is raised in numerous well-marked 
circular folds, the valvulae conniventes, while in the ileum these 
become more scattered and poorly developed. There are large 
collections of lymphoid tissue in the ileum called Pey- 
er's patches, which are very scanty in the jejunum, but it is not 
easy to see these patches in the dissecting room specimens. The 
terminal part of the ileum runs along the medial side of the cae- 
cum, turns sharply to the right, and enters the colon just above 
the caecum, the opening being guarded by a valve, the ileocae- 
214 cal valve, which prevents regurgitation of contents from colon 
to ileum. 
Meckel's diverticulum. This is a small pouch about two 
inches long which projects from the gut two and one-half or 
three feet above the termination of the ileum. It is present in 
about 2 per cent of cases and is the persistent proximal end of 
the vitelline duct. 
Caecum and appendix. The caecum lies usually on the 
right iliopsoas muscle close to the brim of the pelvis and just 
above the outer part of Poupart's ligament. It is sometimes 
arrested in its descent and may lie up under the right lobe of 
the liver. The caecum should normally be wholly surrounded 
with peritoneum. The longitudinal bands of the colon meet on 
the posteromedial aspect of the caecum at the root of the appen- 
dix. The appendix lies usually under cover of the caecum, as 
has already been mentioned. It also is normally surrounded by 
peritoneum and has a little mesentery of its own, which is at- 
tached to the termination of the ileum and its mesentery. The 
anterolateral wall of the caecum should be opened to demon- 
strate the ileocaecal valve and the opening of the appendix. 
Fossae about ileum and caecum. There are several peri- 
toneal fossae about the caecum similar to those about the duo- 
denojejunal flexure. There is a retrocaecal fossa up behind the 
caecum and the beginning of the ascending colon; a superior 
ileocaecal fossa just above the entrance of the ileum into the 
caecum; and an inferior ileocaecal fossa between the lower side 
of the termination of the ileum and the mesentery of the appen- 
dix. The appendix may be curled up or buried in one of these 
fossae. 
Blood supply of small intestine and caecum. The superior 
mesenteric artery supplies the intestine from the lower half of 
the duodenum above to the splenic flexure of the colon below. 
This vessel lies behind the body of the pancreas, crosses in front 
of the third part of the duodenum, and enters the mesentery of 
the jejuno-ileum. It lies near the attached border of the mesen- 
tery and extends to the caecum. From the main trunk, arteries 
are given off at intervals, which anastomose to form one tier of 
arches and then send terminal branches to the walls of the gut. 
215 Towards the lower end of the jejunum and beginning of the 
ileum there appears a second tier of arches, and finally at the 
lowest part there may be four or more of these tiers of arches 
before the terminal vessels are g'iven off. Dissect out the ves- 
sels as they pass from under the pancreas over the duodenum, 
cutting through the transverse mesocolon and follow the main 
trunk down to the caecum. Dissect out the branches to the gut 
in the upper part of the mesentery by simply removing the peri- 
toneum of the right side of the mesentery for about six inches. 
Then do the same at the lower end to compare the arrangement 
of arches, and follow the branches to the caecum and the mesen- 
tery of the appendix. In many cases these vessels can be ex- 
posed by simply stripping off one layer of peritoneum in the 
mesentery. Note the branches of the superior mesenteric nerve 
plexus which follow the vessels in the mesentery to the gut. 
These nerves come from the coeliac and superior mesenteric 
ganglia and follow the arteries to all parts of the intestine. Be 
sure to turn the intestines and mesentery to the left and dissect 
on the right side of the mesentery. 
Ascending colon. This part of the colon begins just above 
the ileocaecal valve and runs to the hepatic flexure below the 
liver. It is fused to the posterior wall against the psoas muscle 
and in front of the lower end of the right kidney. 
Transverse colon. This extends from the hepatic flexure to 
the splenic flexure. The line of attachment of its mesentery has 
been noted and mention made of the difference in levels and po- 
sition of the two flexures. This part of the colon is subject to 
much variation in length and in the position of its loop. The 
splenic flexure is attached to the left lateral wall by a shelf-like 
band of peritoneum, the costocolic ligament, on which, in some 
cases, the lower end of the spleen may rest. 
Descending colon and sigmoid flexure. The colon from the 
splenic flexure to the rectum (third sacral vertebra) is composed 
of the above two parts. This is much the simplest subdivision, 
and should be followed rather than the more complicated one of 
descending, iliac, and sigmoid colon. The descending colon is 
fused to the dorsal wall, lies along the outer border of the left 
216 kidney and on the left psoas muscle. It is usually much con- 
tracted as compared with the right. The differences in relation 
of the two kidneys to the ascending and descending colon should 
be noted. The descending colon begins to recover its mesentery 
near or a little below the iliac crest. Here it becomes the sig- 
moid flexure, which passes to the brim of the pelvis, turns sharp- 
ly backward and inward along the brim and enters the true pel- 
vis to end in the rectum at the third sacral vertebra. The sig- 
moid flexure varies from a very short loop to one over two feet, 
in length ; it and the transverse colon are the most variable por- 
tions of the large intestine. Great displacements may be often 
found in the position of these parts of the colon, and a long sig- 
moid may overlie the caecum and appendix on the right side. 
Blood supply of the colon. As the superior mesenteric ar- 
tery passes into the mesentery of the small intestine, it gives off 
the midcolic branch which passes into the transverse mesocolon 
to supply the right half of the transverse colon. The right colic 
branch leaves the main artery lower down and passes trans- 
versely to the right to reach the ascending colon. Here it di- 
vides into an ascending branch which anastomoses with the mid- 
colic at the hepatic flexure, and into a descending branch which 
joins the ileocolic branch at the top of the caecum. These ves- 
sels lie behind the peritoneum on the posterior abdominal wall, 
where they can easily be felt and often clearly seen. Remove 
enough of the peritoneum to trace these vessels to the gut, dis- 
turbing the posterior wall as little as possible. Note especially 
the ileocolic and the arteries to the caecum and appendix. 
Then turn the small intestine and mesentery to the right to 
expose the splenic flexure, descending colon and sigmoid flexure. 
The inferior mesenteric artery arises from the aorta several 
inches below the superior mesenteric. This vessel inclines to 
the left, lying behind the peritoneum on the dorsal wall, and 
gives off the left colic, the sigmoid and superior hemorrhoidal 
arteries, which supply the colon from the splenic flexure to the 
rectum. These arteries are connected by ascending and descend- 
ing branches. The hemorrhoidal arteries cross the pelvic brim 
and run down between the rectum and sacrum. The terminal 
branches should be dissected in the same way as the correspond- 
217 ing vessels on the right side, with as little damage as possible 
to the posterior wall. 
Removal of the stomach. Open the anterior wall of the 
stomach to study the mucosa, but do not cut the sphincter. Cut 
the gastric vessels at the point where they pass on to the lesser 
curvature near the oesophagus, and trim off any remains of the 
lesser omentum as far as the pylorus. Cut the pyloric artery 
and vein and free with care the pylorus from the vessels behind 
it. Cut the right gastro-epiploic artery at the greater curvature 
and trim off any omentum along that curvature. The left gas- 
tro-epiploic and vasa brevia arteries will have to be cut also. 
Cut through the oesophagus close to the stomach and the pylo- 
rus on the stomach side of the sphincter (so that the sphincter 
can be left with the duodenum) and remove the stomach. 
Removal of the transverse colon. Tie two ligatures about 
the colon close to the hepatic and splenic flexures and cut be- 
tween them. Dissect the beginning of the transverse colon from 
the anterior surface of the second part of the duodenum, so as 
to leave the lines of peritoneal reflection intact on the gut. Cut 
the attached border of the transverse mesocolon along the lower 
edge of the pancreas over to the splenic flexure and remove the 
transverse colon and its mesentery. 
Pancreas and duodenum. Observe the pyloric sphincter in 
situ; then pass a ligature around it and inflate the duodenum 
again; Follow carefully the various parts of this piece of gut, 
noting especially the relations of the gall bladder and foramen 
of Winslow to the first part; the relations of the transverse co- 
lon and the mesocolon to the second part, and the mesentery of 
the jejlmoileum to the third art. Clean all tissue off the head 
of the pancreas to expose the head and to demonstrate its rela- 
tions to the duodenum. Look for the superior pancreaticoduo- 
denal artery (from the gastroduodenal) and the inferior pancre- 
aticoduodenal (from the superior mesenteric) which form an 
arch around the head of the pancreas and duodenum. The veins 
corresponding to these vessels usually join the right gastro- 
epiploic vein over the head of the pancreas, or empty separately 
into the superior mesenteric vein. The bile duct and portal vein 
can now be cleaned down to the upper border of the pancreas. 
218 It will be advisable to leave the duct at the upper border of the 
head of the pancreas, and its further course behind the head and 
its opening into the second part of the duodenum can be worked 
out later. 
This dissection connects the upper and lower parts of the 
abdominal cavity. The duodenum is really in relation to both, 
as the mesocolic shelf crosses the middle of the second part of 
the duodenum. The origin of the coeliac artery from the aorta, 
the coeliac ganglia, the crura of the diaphragm, the phrenic ar- 
teries and the suprarenal body should all be thoroughly cleaned 
up to complete the dissection of the dorsal half of the lesser sac. 
Pancreatic and bile ducts. The pancreatic ducts should now 
be dissected. The main duct (Wirsung) runs transversely 
through the organ from the tail to the head and receives many 
small lateral branches from the lobules of the gland. It passes 
obliquely through the wall of the duodenum and opens with the 
common bile duct on the dorsomedial wall of the second part of 
the duodenum. This opening lies on the summit of a papilla in 
the mucosa. The accessory pancreatic duct (Santorini) may 
open by a separate orifice at a somewhat higher level in the duo- 
denum. This duct drains the lower part of the head and there 
is usually a connection between it and the main duct. The com- 
mon bile duct passes behind the first part of the duodenum and 
upper part of the head of the pancreas. It then runs obliquely 
through the head and joins the pancreatic duct at the postero- 
medial wall of the second part of the duodenum. 
Cut through the pancreatic tissue half way between the up- 
per and lower borders over that part of the pancreas that lies in 
front of the spine. The duct is usually greyish white in color 
and can readily be distinguished from the pinkish pancreatic tis- 
sue. Follow it to the right to the duodenum. Try to locate the 
accessory duct, though this is not so easy to dissect. Then fol- 
low the duct to the left as far as possible. When the whole pan- 
creatic duct has been displayed cut through the head of the 
pancreas at the point where the common bile duct disappeared 
behind the upper border and follow this duct to its junction with 
the pancreatic duct. The duodenum may be slit open and washed 
out to demonstrate the openings of these ducts. If there is any 
219 difficulty in locating it, the bile duct can be again inflated from 
the gall bladder and this will clear the opening. It will be best 
to open the duodenum and locate the papilla before cutting into 
the pancreas. 
Removal of the pancreas. The pancreas should next be re- 
moved to show its posterior relations. Start near the tail of the 
organ and dissect it carefully away from the splenic artery and 
splenic vein. The greater part of the vein lies directly behind 
the gland. Raise the pancreas and turn it gradually towards the 
right, cleaning the splenic vessels. The anterior surface of the 
left kidney and of the adrenal gland will be partly exposed. Next 
a part of the left renal vessels will come into view at the medial 
border of the kidney and close to the duodenum the superior 
mesenteric vessels will be seen lying behind the pancreas and 
entering the mesentery of the jejuno-ileum in front of the third 
part of the duodenum. The renal artery and the superior mesen- 
teric artery are branches of the aorta. The renal vein is a tribu- 
tary of the inferior vena cava, but the splenic and superior mes- 
enteric veins are tributaries of the portal system. The dorsal 
surface of the pancreas is closely moulded over these vessels. 
The remains of the head should then be freed from the duode- 
num and bile duct, the pancreatic duct cut near its entrance to 
the duodenum, and the whole gland removed. The pancreas 
must be separated with great care from the vessels on its deep 
surface. The upper end of the inferior mesenteric vein will now 
be exposed. It empties either into the splenic or superior mes- 
enteric vein. The splenic and superior mesenteric veins unite 
behind the neck of the pancreas to form the portal vein. 
Portal vein. This vein runs up behind the pancreas and 
first part of the duodenum, enters the lesser omentum, where it 
lies posterior to the bile duct and the hepatic artery. It passes 
to the liver, where it receives the cystic vein from the gall blad- 
der and divides in the portal fissure into a right and left branch. 
The portal vein has for immediate tributaries the gastric, pyloric 
and cystic veins. The portal system of veins drains blood from 
all the digestive tract, from the cardiac end of the oesophagus 
to the lower part of the rectum, from the spleen and pancreas, 
and conveys this blood to the liver. After passing through the 
220 sinusoids of the liver, this blood is carried by the hepatic veins 
in the liver substance to the inferior vena cava. The duodenum 
should be left in place to support the bile duct. Clean all struc- 
tures thoroughly in the portal fissure of the liver. The superior 
mesenteric artery should be followed to its origin from the aorta. 
Note the dense mass of sympathetic nerve fibers from the coeliac 
ganglia which spread over it. These may be cleaned away and 
both ganglia should be fully exposed. Note the position of the 
left and right renal vessels, but do not do much to them at this 
stage. The renal veins lie in front of the renal arteries; the left 
lies just below the splenic vein, the right behind the portal vein 
and bile duct. Draw the portal vein to one side and clean the 
inferior cava between the right renal vein and the liver. Note 
where it disappears in the posterior surface of the liver. 
Removal of the intestine. Tie the intestine twice at the top 
of the jejunum and again a few inches from the caecum and cut 
between the ligatures. Then cut the gut close to the intestinal 
border of the mesentery and remove it. It can be opened and 
the difference in the character of the mucosa at various levels 
noted. 
Removal of the large intestine. Remove the caecum and 
the ascending colon. This can best be done by raising the cae- 
cum and the ascending colon from below and cutting its- peri- 
toneal attachments up to the hepatic flexure. Do this as care- 
fully as possible so as to demonstrate its exact position on the 
dorsal wall. Turn the splenic flexure and descending colon from 
above downwards, cutting the peritoneal attachments as on the 
right. Note particularly the point where the descending colon 
begins to recover its mesentery, or in other words, the point 
where the sigmoid flexure begins. Two ligatures can be placed 
around the lower end of the sigmoid below the pelvic brim, the 
colon cut off between them, and removed. Open up a portion 
of the colon to see the character of the mucosa lining it, and 
compare it with that seen in the small intestine. 
Removal of the liver. The superior mesenteric vessels may 
be turned up off the duodenum, and the duodenum separated 
from the aorta, cava and kidney. The portal vein may be cut 
below the portal fissure and the inferior vena cava just below 
221 the liver. Draw the liver downward and forward from the dor- 
sal wall. On the posterior aspect of the right lobe is a non- 
peritoneal area which is bounded in front by the anterior layer 
of the coronary ligament and is in direct contact with the under 
surface of the diaphragm. This can be separated easily with the 
fingers. As the liver falls further forward, the fingers will come 
in contact with the posterior part of the coronary ligament, 
passing from the posterior surface of the organ behind this non- 
peritoneal area to the diaphragm. This should be trimmed off 
close to the liver. Cut the vena cava close to the top of the 
liver, and free the posterior border of the left lobe from the dia- 
phragm. The whole liver can now be removed with its duct 
passing from it to the duodenum. The entire organ should be 
carefully studied. Note particularly the structures on its pos- 
terior surface, which have been concealed from view while the 
organ was in place. The posterior border of the left lobe is thin 
and has a notch for the oesophagus. This is separated from the 
posterior surface of the right lobe by a continuation of the um- 
bilical fissure, which is here called the fissure of the ductus ve- 
nosus. Immediately to the right of this fissure is the spigelian 
(caudate) lobe, an oblong area, which is prolonged into a little 
short projection known as the caudate lobe (compare new and 
old terminology in connection with the lobes of the liver). The 
caudate lobe or process separates the portal fissure in front from 
the fissure of the vena cava behind. The fossa or furrow for the 
inferior vena cava lies to the right of and more or less under 
cover of the spigelian (caudate) lobe. The vena cava is often 
completely buried in liver substance at this point. To the right 
of the inferior vena cava is the non-peritoneal surface, which 
was in direct contact with the diaphragm. The anterior and 
posterior layers of the coronary ligament are reflected from liver 
to diaphragm on either side of this non-peritoneal area, the two 
layers meeting on the right of this area to form the right tri- 
angular (lateral) ligament. The two layers of the lesser omen- 
tum are attached to the liver so as to include between them the 
portal fissure and the fissure of the ductus venosus. Trace care- 
fully the attachments and reflections of the peritoneum to and 
from the various parts of the organ. The structures in the por- 
222 tai fissure should be traced a short distance into the depths of 
the fissure. Follow the branches of the cystic artery to the gall 
bladder, and find the right and left hepatic ducts. 
Removal of the spleen. The spleen can now be removed. 
Cut the splenic vessels and take the spleen out by itself. Study 
carefully the surfaces and the relations of the various parts of 
the spleen. 
Retroperitoneal space. This region is situated behind the 
peritoneum on the dorsal wall of the abdomen. In this area the 
aorta and the inferior vena cava lie side by side in front of the 
spine, the cava just to the right and the aorta to the left of the 
median line. On either side of these vessels are the quadratus lum- 
borum and iliopsoas muscles, which form the dorsal muscula- 
ture of this region resting on these muscles are the kidneys with 
the adrenal glands, the duct of the kidney (ureter), the sper- 
matic vessels, and the branches of the lumbar plexus of nerves. 
Great care should be taken in removing the various organs pre- 
viously described in order to avoid injuring any of the vessels 
or nerves which lie behind them and behind the dorsal peri- 
toneum. 
Aorta and inferior vena cava. It will be best to begin the 
dissection of this region with these two vessels. The aorta lies 
to the left of the midline, and extends down to the fourth lum- 
bar vertebra. The stumps of the visceral branches passing to 
the abdominal organs will be left attached to its anterior sur- 
face. In addition to branches to the organs, the aorta gives off 
the phrenic arteries to the diaphragm and the lumbar arteries, 
usually four on each side, to the dorsal wall. The latter corre- 
spond to the intercostal arteries of the thorax, but are deeply 
placed and not very much will be seen of them. A peculiar tiny 
branch, the spermatic artery, arises from the aorta just below 
the renal arteries, usually from the anterior aspect and often by 
a tiny common stem with the corresponding vessel on the oppo- 
site side. Be careful not to destroy the rather delicate attach- 
ment of these vessels to the aorta. The spermatic artery with 
the corresponding vein passes obliquely downward beneath the 
peritoneum to the internal abdominal ring. The spermatic ves- 
sels lie just in front of the ureter and adhere closely to the peri- 
223 toneum. They should be secured before the peritoneum has 
been much disturbed. The right spermatic vein runs to the in- 
ferior cava, while the left spermatic vein usually joins the left 
renal vein. The inferior vena cava lies to the right of the aorta, 
terminating below at about the same level. Having cleaned 
these vessels and followed the spermatic vessels to the internal 
abdominal rings, trace the renal artery and vein to the kidneys. 
The right renal artery passes behind the cava. The left renal 
vein crosses anterior to the aorta. 
Aortic plexus. Branches of the sympathetic nerves, form- 
ing the aortic plexus, cover the aorta. They connect above with 
the coeliac ganglia, and at the sides with the lumbar chain of 
sympathetic nerves and ganglia on the lateral aspect of the ver- 
tebrae. They send branches into all the visceral branches of the 
aorta and below form the hypogastric plexus of the pelvis. Note 
these branches in cleaning the aorta. 
Iliac arteries and veins. Next clean up the common iliac 
arteries and veins and the external iliac arteries and veins. These 
vessels lie on the psoas muscle along the pelvic brim. The com- 
mon iliac artery divides opposite the sacro-iliac joint into the 
external and internal iliac arteries. The internal iliac artery en- 
ters the true pelvis and will be dissected there later. The ex- 
ternal iliac should be followed along the pelvic brim to Poupart's 
ligament where it passes into the thigh and becomes the femoral 
artery. The iliac veins lie along the posterior and mesial side 
of their arteries. Note carefully the origin of the deep epigastric 
and circumflex iliac vessels. 
Kidney. Remove the peritoneum from the kidney, paying 
particular attention to the suprarenal bodies on the upper and 
inner margin of the kidneys. These are often soft and easilv 
missed. A little branch from the renal artery or vein often is 
of use in leading the dissector to these structures. The kidney 
lies behind the peritoneum on the transversalis fascia and is em- 
bedded in a mass of fatty connective tissue known as the fatty 
capsule of the kidney. This surrounds the vessels at the inner 
margin of the kidney and is prolonged on them into the hilum 
of the kidney. This fatty capsule also surrounds the suprarenal 
gland. Cut through the fatty capsule along the mesial border 
224 of the kidney and turn it outward as far as the outer margin. 
Beneath the fatty capsule is the fibrous capsule lying directly 
against the kidney tissue. 
Note the position of'the kidneys with reference to the verte- 
bral column and the last ribs, also the position of the hilum 
along the inner margin where the vessels and duct will be found. 
The suprarenal glands are triangular or shaped something like 
a cocked hat. They are perched on the upper part of the organ 
and extend down its inner margin almost to the hilum. These 
should be left in place on the tops of the kidneys. Note care- 
fully the anterior relations of the organs on the two sides and 
the portions of the anterior surface which are peritoneal or non- 
peritoneal. On the right side the anterior surface is largely under 
cover of the right lobe of the liver with the hepatic flexure cross- 
ing its lower end and the second part of the duodenum lying in 
front of the hilum. On the left side the pancreas passes across the 
middle of the organ and above the pancreatic area are the spleen 
and stomach. The descending colon lies close to the outer mar- 
gin of the left kidney. The non-peritoneal areas of each kid- 
ney correspond to the position of those organs which have be- 
come fused secondarily to the posterior wall. At the hilum of 
the kidney the branches of the renal veins are more or less in 
front. The arteries occupy rather an intermediate position, and 
the ureter or duct of the kidney is posterior. This appears at the 
hilum in the form of a triangular dilatation, the pelvis of the 
ureter, which narrows rather suddenly to form the main part of 
the ureter. The ureter passes downward on the psoas muscle 
directly behind the peritoneum and the spermatic vessels to 
about the bifurcation of the common iliac arteries, where it en- 
ters the pelvic cavity and will be followed later. Note the rela- 
tion of the ureters to the mesentery of the small intestine and 
the mesentery of the sigmoid flexure. 
Muscles of the posterior abdominal wall. Behind the kid- 
ney lie the psoas and quadratus lumborum muscles. The for- 
mer arises from the side of the lumbar vertebrae, passes down 
along the pelvic brim, and here fuses with the iliacus muscle. 
The iliacus arises from the iliac fossa of the ilium and joins the 
psoas to form the iliopsoas muscle, which is inserted into the 
225 lesser trochanter of the femur. Just at the outer border of the 
kidney is the transversalis muscle, and the crura of the dia- 
phragm lie behind the upper end of the kidney. The quadratus 
lumborum occupies the interval between the last rib and the 
crest of the ilium. 
Fascia of the abdominal wall. The above named muscles 
are covered first by the peritoneum and second by a loose layer 
of connective tissue which lies in the plane between the peri- 
toneum and the transversalis fascia. This loose layer, under the 
diaphragm and on the anterolateral wall of the belly, is so scanty 
as to be negligible, but over the dorsal wall, especially in the 
neighborhood of the kidneys, it assumes much larger propor- 
tions, contains fat and forms the fatty capsule of the kidney. 
The transversalis fascia lies behind the fatty capsule of the kid- 
ney. Lying on or in the muscles of the dorsal wall behind the 
transversalis fascia, are the branches of the lumbar plexus. At 
the pelvic brim the iliac fascia of the posterior abdominal wall 
separates the iliac arteries and veins in front from the branches 
of the lumbar plexus and the muscles behind. 
Nerves. After the dissection of the vessels and kidneys has 
been finished, the muscles of the dorsal wall, together with the 
branches of the lumbar plexus below the level of the kidneys, 
should be cleaned. At the outer border of the kidney are the 
ilio-inguinal and iliohypogastric nerves, which pierce the trans- 
versalis muscle to reach the plant between it and the internal 
oblique. A little above these nerves near the last rib is found 
the last intercostal nerve. Below the level of the crest of the 
ilium, passing obliquely to the anterior superior spine, the ex- 
ternal cutaneous nerve resting on the iliacus muscle. Between 
the iliacus and the psoas is the largest branch of the plexus, the 
anterior crural (femoral) nerve. These two muscles will prob- 
ably have to be slightly pulled apart to demonstrate it. On the 
anterior surface of the psoas muscle, following closely the lower 
part of the spermatic vessels, lies the genitocrural (lumbo-in- 
guinal) nerve. This is often not much larger than a coarse 
thread, and is easily lost when the muscle is being cleaned. The 
spermatic vessels should be the best guide to it, especially in 
the neighborhood of Poupart's ligament. At a later dissection 
226 these nerves will be traced toward the vertebral column and will 
be found to disappear under the psoas muscle. At this stage of 
the dissection, however, the kidneys should be left in place and 
the muscles and nerves cleaned only below and to the outer side 
of these organs. 
Removal of the kidney. After the dissection of the muscles, 
vessels and nerves on the posterior wall has been completed as 
previously directed, the kidney should be raised from its fatty 
capsule and turned inward. Dissect away any remains of this 
capsule and follow the nerves behind the kidney to the outer 
edge of the psoas muscle and finish the dissection of that muscle 
and of the quadratus lumborum muscle. The kidney can then 
be split open by an incision along its outer border and the cut 
carried into the pelvis of the kidney and beginning of the ureter. 
Do not, however, detach the renal vessels or ureter. Note the 
gross details of structure, especially the renal cortex and pyra- 
mids and the pelvis of the ureter in the hilum and sinus of the 
kidney. The branches of the lumbar plexus should then be fol- 
lowed into the substance of the psoas muscle to the interverte- 
bral foramina. The muscle can be freely removed as the nerve 
trunks are dissected. The last branch of the lumbar plexus is 
the obturator nerve. This lies, however, just below the brim of 
the true pelvis under the psoas muscle and iliac vessels. It runs 
forward along the lateral wall of the pelvis together with an 
artery of the same name (a branch of the internal iliac artery) 
and leaves the pelvis at the obturator notch in the obturator for- 
amen. It then enters the thigh where it and the other branches 
of the lumbar plexus will be found later. This nerve can easily 
be secured by separating the iliac vessels from the psoas muscle 
and dissecting along the pelvic wall just below that muscle. Do 
not attempt to dissect at this time below the level of this nerve 
in the pelvis. 
227 DISSECTION OF THE PELVIS 
Pelvic girdle. The two innominate bones articulate behind 
with the sacrum and in front with each other. The girdle is. 
therefore, firmly fixed to the lower end of the spine, and there is 
practically no movement between it and the skeleton of the 
trunk. This arrangement provides the strength and stability 
needed by the pelvic girdle in order to support the weight of the 
trunk and transmit it to the thigh bones. The two innominate 
bones, with the sacrum, form the walls of the pelvic cavity. 
The innominate bone, or os coxae, articulates behind with 
the sacrum, in front with the other innominate bone, and later- 
ally with the femur. The bone is constricted in the center and 
expanded above and below. The acetabulum, the socket for the 
head of the femur, is on the outer aspect of the central constrict- 
ed portion. The expanded portion above the socket forms the 
lower lateral part of the abdominal wall; that portion below the 
socket, the wall of the pelvic cavity. The bone is formed from 
three separate pieces, the ilium, the pubis, and the ischium, which 
later are fused into a single bone. 
The ilium forms the upper expanded portion of the innomi- 
nate bone and also the upper two-fifths of the acetabulum. The 
outer or dorsal surface is convex in front and concave behind; it 
is crossed by three lines, the gluteal lines, which run downwards 
and backwards from the upper to the lower border. These lines 
limit the attachments of the gluteal muscles. The inner or ven- 
tral surface is divided into an upper and a lower area by the iliac 
portion of the iliopectineal line. The area above the line is the 
iliac fossa; it is smooth and concave, is covered by the iliopsoas 
muscle, and completes the lower part of the abdominal wall. The 
area below the line has a smooth fiat surface in front, which 
forms part of the lateral wall of the pelvic cavity and a rough 
posterior portion behind. This region presents the articular sur- 
face for the sacrum with an irregular area behind it for the at- 
tachment of the posterior sacro-iliac ligaments. The upper bor- 
der of the ilium forms the prominent iliac crest which is curved 
from before backwards in two directions. There is a medial con- 
228 cavity in the anterior and a lateral concavity in the posterior 
portion of the crest. The crest is bounded in front by the an- 
terior superior spine and behind by the posterior superior spine. 
A short concave anterior border runs down from the anterior 
superior spine to the anterior inferior spine, which lies just 
above the acetabulum. A short posterior border separates the pos- 
terior superior from the posterior inferior spine. The anterior su- 
peior spine is a landmark of importance on the abdominal wall, 
and it and the inferior spine give origin to muscles which pass 
to the anterior and lateral parts of the thigh. The crest gives 
attachment to the abdominal muscles and to the latissimus dor- 
si ; the posterior spines to the sacrospinalis muscle and to the 
sacrosciatic (sacrotuberous and sacrospinous) and sacro-iliac 
ligaments. The inferior border overhangs the great sciatic notch 
behind the acetabulum. 
The pubis forms the anterior wall of the pelvic cavity and 
consists of a flattened body and two rami. The medial border 
of the body forms the pubic symphysis with the opposite bone. 
On its superior border is the pubic crest which ends laterally in 
the pubic spine or tubercle, a landmark of practical importance 
in the inguinal region. The outer surface is rough and gives at- 
tachment to some of the adductor muscles of the thigh ; the in- 
ner or pelvic surface is smooth. The superior ramus is thick and 
runs outward to join the ilium at the iliopectineal eminence. A 
sharp line, the pubic portion of the iliopectineal line, runs out- 
ward from the spine on the upper border of this ramus and joins 
the iliac part of the same line on the ilium. The inferior ramus 
is thin and flat, and runs downward to join the superior ramus 
of the ischium. The pubis forms the anterior fifth of the ace- 
tabulum. 
The ischium forms the inferior portion of the hip bone. The 
body of the bone is thick and strong and bears below a rough 
projection, the tuberosity of the ischium. This supports the 
weight of the body in the sitting position and gives attachment 
to the great sacrosciatic (sacrotuberous) ligament and to the 
flexor muscles of the leg. On the posterior border of the body is 
the spine projecting inward behind the acetabulum. The small 
sciatic notch lies just below the spine. The spine gives attach- 
229 ment to the lesser sacrosciatic (sacrospinous) ligament and to 
the mucles of the pelvic floor. The upper part of the body forms 
the lower two-fifths of the acetabulum. The superior ramus 
runs up to join the inferior ramus of the pubis. The pubis and 
ischium form the boundaries of a large opening in the lateral 
wall of the pelvis, the obturator foramen. The obturator notch 
for the obturator vessels and nerve lies in the upper border of 
the foramen. The foramen is filled by the obturator membrane. 
The ischiopubic ramus gives origin to the adductor muscles of 
the thigh and to the muscles in the urogenital triangle of the per- 
ineum. The margins of the obturator foramen and the inner and 
outer surfaces of the membrane are covered by the obturator in- 
ternus and externus muscles. The iliac crest and its superior 
spines, the spine of the pubis, the perineal margins of the ischio- 
pubic rami, and the tuberosity of the ischium are subcutaneous 
and can be felt. The rest of the bone is deeply covered. 
The acetabulum is a cup-shaped cavity looking outward and 
slightly forward and downward. It has a strong prominent mar- 
gin, which is deficient below, forming the cotyloid or acetabular 
notch. The articular surface is horseshoe-shaped and does not 
cover the bottom of the cavity. The bone here is very thin. The 
notch is filled by the transverse and interarticular ligaments, and 
the non-articular part of the socket by a pad of fat. The acetab- 
ulum surrounds the head of the femur and forms with it a very 
perfect ball and socket joint. 
Pelvis as a whole. The bony pelvis is bounded below and 
in front by the pubic bones; above and behind by the sacrum 
and coccyx; laterally by the greater part of the innominate 
bones. The lateral wall is partially deficient in the region of the 
obturator foramen and the great sciatic notch between the in- 
nominate bone and sacrum. The foramen is filled almost com- 
pletely by the obturator membrane, which is in turn covered on 
both sides by the obturator muscles. The notch is converted 
into two foramina, the greater and lesser sacrosciatic foramina 
by the greater and lesser sacrosciatic ligaments. These open- 
ings are filled by the pyriformis and obturator internus muscles 
as they leave the pelvis to reach the gluteal region. The pelvis 
is divided by the iliopectineal lines, or brim of the pelvis, into 
230 the false pelvis (pelvis major) above, and the true pelvis (pelvis 
minor) below. The false pelvis is to be associated with the ab- 
dominal cavity the true pelvis with the pelvic cavity and the re- 
gion of the perineum. The pelvic brim, or pelvic inlet, is some- 
what heart-shaped and is bounded in front by the pubic symphy- 
sis and crests, laterally by the iliopectineal lines of the innomi- 
nate bones, and behind by the promontory of the sacrum and the 
sacro-iliac joints. The pelvic outlet is diamond-shaped; it is 
bounded in front by the under surface of the pubic symphysis, 
laterally by the ischiopubic rami, the tuberosities of the ischilia 
the great sacrosciatic ligaments, and behind by the tip of the 
coccyx. The axis of the pelvic cavity is curved, conforming to 
the general curve of the sacrum. 
The position of the pelvis. In the erect attitude of the body, 
the pelvis is inclined forward so that the plane of the inlet or brim 
forms an angle of 55 to 60 degrees with the horizontal. It is 
very important to appreciate this inclination of the pelvis in 
order to understand the position and relations of the pelvic con- 
tents. When the pelvis is in its proper position, the anterior su- 
perior spines of the ilia and the spines of the pubes are on the 
same frontal plane, and the lower borders of the acetabular 
notches are in the horizontal plane. The anterior wall of the 
pelvis (the bodies of the pubes and the symphysis) approaches 
the horizontal, and the posterior wall (the sacrum) looks down- 
ward into the pelvic cavity. The inlet of the pelvis is directed 
chiefly forward and upward, and the outlet backward and down- 
ward. 
Sacro-iliac joint. This is a half joint; with its articular sur- 
faces covered by cartilage, and having a joint cavity. The sur- 
faces are concavo-convex and are held in such close contact that 
there is scarcely any movement between the bones. The joint 
is strengthened in front by the anterior sacro-iliac ligaments 
which extend from the front of the sacrum to the iliac and pelvic 
surfaces of the ilium. These fibers blend somewhat with the 
lumbosacral and iliolumbar ligaments, which run from the trans- 
verse process of the fifth lumbar vertebra to the ilium. The 
posterior sacro-iliac ligaments consist of a number of strong 
bundles which extend from the inner aspect of the upper part 
231 of the ilium and its posterior spines to the back of the lateral 
mass of the sacrum. The posterior sacrosciatic ligaments arise 
from the posterior spines of the ilium and from the sacrum, and 
are inserted into the spine and the tuberosity of the ischium. 
They are to be regarded as accessory ligaments which help to 
support the sacrum from tilting forward into the pelvis. 
Symphysis pubis. This is a typical half joint. The pubic 
bones are united by a disk of fibrocartilage which usually has a 
slit-like cavity in it. The joint is reinforced by ligaments on all 
sides of the body of the pubic bones and forms a very strong 
and flexible union between them. 
Mechanics and movements of the pelvis. The pelvis sup- 
ports the weight of the trunk and transmits it to the thigh bones. 
It also forms the bony pelvic canal in the female through which 
the foetus passes during labor. It has to possess great strength 
combined with elasticity and also to permit of a very slight de- 
gree of movement or of yielding in its joints under certain con- 
ditions. The two joints of the pelvis add greatly to its strength 
and to its elasticity. The pelvis is made up of two sets of arches, 
one of which supports the weight of the body in the erect posi- 
tion, the other in the sitting position. The former is called the 
femorosacral arch and each half consists of the lateral mass of 
the sacrum, the sacro-iliac joint, and that part of the ilium be- 
tween this joint and the upper and back part of the acetabulum. 
This is the strongest part of the ilium. The head, neck, and 
upper part of the shafts of the thigh bones complete the arch. 
In sitting, there is a slight flexion of the pelvis on the spine, and 
the line of gravity of the body then falls a little back of the 
standing arch. The sitting arch may be said to consist of the 
sacrum, the sacro-iliac joints, and the bone between them and 
the tuberosities of the ischia. Each of these arches is supported 
by a counter arch to take some of the strain off the main arch. 
The counter arch for the femorosacral arch is represented by the 
horizontal rami and bodies of the pubic bones; that for the 
sitting arch by the rami of pubes and ischia. Both these counter 
arches meet at the symphysis pubis, which is therefore always 
tinder a severe strain. 
232 The sacrum is suspended by the posterior sacro-iliac liga- 
ments between the ilia. The weight of the body tends to force 
the sacrum downwards into the pelvic cavity. This is resisted 
by these ligaments and by the articular surfaces of the two 
bones, which enable the sacrum to act somewhat like the key- 
stone of an arch. The pelvic joints may yield very slightly 
under the strain in order to absorb shock and jar, but there is 
ordinarily no real motion in them. 
In the female pelvis during labor the bony pelvic canal 
offers a very narrow passage for the foetal head. In order to gain 
additional room there is a little movement between th sacrum 
and ilium at the sacro-iliac joint and between the lower end of 
the sacrum and coccyx. These slight movements increase the 
diameters of the pelvic canal and facilitate the passage of the 
foetal head. 
Muscle attachments of innominate bone. The innominate 
bone gives origin to muscles which pass upward to the trunk 
and to the shoulder girdle, and downward to the femur and to 
the bones of the leg. It also gives origin to the muscles which 
form the pelvic floor, and to muscles which surround the geni- 
talia in the perineum. 
Muscles inserted into the innominate bone; lateral surface. 
Iliac crest, outer lip: external oblique (from lower ribs) 
i t;/ I 
Muscles arising from the innominate bone; lateral surface. 
sartorius (to tibia) 
tensor fascial latae (to iliotib- 
ial band of thigh) 
Ilium, anterior superior spine 
anterior inferior spine 
acetabulum 
rectus femoris (to patella and 
tibia) 
gluteus maxim us 
" medius 
minimus 
to great trochanter of 
femur 
gluteal ridges: 
233 Pubis, superior ramus: pectineus (to femur below lesser tro- 
chanter) 
body : rectus abdominis (to ribs and xiphoid) 
pyramidalis (to rectus sheath) 
adductor logus (to femur, linea aspera) 
gracilis (to tibia) 
adductor brevis (to femur, linea as- 
pera) 
: adductor magnus (to femur, linea 
aspera) 
obturator externus (to femur, great 
trochanter) 
inferior ramus 
Ischium, superior ramus 
tuberosity 
quadratus femoris (to femur, 
great trochanter) 
biceps (to fibula) 
semitendinosus (to tibia) 
semimenbranosus (to tibia) 
tuberosity and body: 
body near spine: gemelli (to obturator internus tendon) 
Muscles arising from innominate bone; medial surface. 
internal oblique (to aponeuroses and ribs) 
transversalis (to aponeuroses and ribs) 
quadratus lumborum (to twelfth rib) 
latissimus dorsi (to scapula and humerus) 
Ilium, crest 
crest and posterior superior spine: sacrospinalis (to spine, 
ribs, cranium) 
iliac fossa: iliacus (to femur, lesser trochanter) 
Ilium 
Pubis 
Ischium 
margins of obturator foramen, obturator internus 
(to femur, great trochanter) 
234 Pubis, body : levator ani (to rectum and coccyx) 
inferior ramus 
Ischium, superior ramus 
ischiocavernosus (to penis) 
: compressor urethrae (to urethra and 
opposite ramus) 
tuberosity: transverse perinei (to central point of per- 
ineum) 
spine: levator ani (to coccyx and sacrum) 
" " coccygeus (to coccyx) 
The accent of the bony pelvis has been given here so that 
the student may get an idea of its position and functions before 
beginning t-he study and dissection of the pelvic contents. The 
details of the innominate bone will be appreciated better with 
the dissection of the lower extremity. 
General plan of the pelvic viscera. The rectum lies in the 
posterior part of the pelvis in close relation to the sacrum and 
consists of the rectum proper, and a terminal part, the anal canal. 
The bladder and prostate lie in the anterior part of the pelvis 
in relation to the symphysis pubis. On the posterior surface of 
the bladder are the two vas deferens and the two seminal ves- 
icles. The crura of the penis are attached to the ischiopubic 
rami and the corpus spongiosum of the penis lies in the midline 
between the crura and below the prostate. The urethra passes 
from the bladder through the prostate and corpus spongiosum to 
the head of the penis. The space in the true pelvis is divided 
into an upper and lower part by the pelvic floor or diaphragm. 
The region above the diaphragm is the pelvic cavity proper; the 
region below is the perineum. The perineum is divided into an 
anterior or urogenital triangle and into a posterior or rectal tri- 
angle. The pelvic diaphragm is formed by a layer of muscle, 
the levator ani and coccygeus muscles, covered by a layer of 
fascia. These muscles arise from the lateral wall of the pelvis 
and run downward and inward to the midline. In the anterior 
half of the pelvis the two halves of the diaphragm do not meet 
and the floor here is incomplete. The prostate and bladder lie 
just above this deficient portion of the floor; the crura and the 
235 corpus spongiosum of the penis lie just below it in the urogenital 
triangle of the perineum. This triangle contains several layers 
of muscles and fascia, which surround the different parts of the 
penis, and form a horizontal shelf, the perineal or urogenital dia- 
phragm, which lies immediately beneath the deficient part of the 
pelvic floor and supports the prostate and bladder. 
In the posterior part of the pelvis, the two lateral halves of 
the pelvic diaphragm meet in the midline and here the floor is 
completed and carried back to the sacrum and coccyx. The rec- 
tum proper lies above this part of the pelvic diaphragm, the anal 
canal pierces it, and lies in the rectal triangle below. 
In the female the general plan of the floor is similar to that 
in the male, and the rectum has the same relation to it. In the 
anterior part of the female pelvis, in addition to the bladder and 
urethra, are the uterus, fallopian tubes and ovaries, and the va- 
gina. The bladder, uterus, tubes, and ovaries lie in the pelvic 
cavity above the pelvic floor. The urethra and vagina lie in the 
deficient portion of the floor, and their lower ends are surround- 
ed and supported by the perineal diaphragm and by muscles and 
fasciae of the urogenital triangle corresponding to those of the 
male pelvis. In both sexes those portions of the pelvic organs 
which lie above the pelvic floor are covered by the pelvic peri- 
toneum. The space between this peritoneum and the pelvic 
floor is filled by loose areolar tissue and by the pelvic vessels 
and nerves distributed to the pelvic viscera. Another set of ves- 
sels and nerves lies below the pelvic floor and passes to those 
portions of the pelvic organs which lie in the rectal and urogen- 
ital triangles of the perineum. 
Male pelvis. Peritoneum. The peritoneum lining the pel- 
vic cavity should be carefully studied from above before the ac- 
tual dissection is begun. The medial umbilical fold of peri- 
toneum extends from the umbilicus to the top of the bladder. 
This fold contains the remains of the urachus and is known as 
the superior false ligament of the bladder. Laterally, the peri- 
toneum passes onto the lateral pelvic wall and is known as the 
lateral false ligaments. This lateral reflection forms the floor 
of the shallow paravesical fossae on either side of the bladder. 
The peritoneum covers the superior surface of the bladder and 
236 passes from its posterior border in the form of two folds, the 
sacrogenital or rectovesical folds, which are sometimes called 
the posterior false ligaments. These folds pass backward along 
the side of the pelvis to the sides of the sacrum and rectum, 
where they form the lateral margin of the shallow pararectal 
fossae on either side of the rectum. These fossae communicate 
in front of the rectum and form the rectovesical pouch or fossa 
between the rectum and the bladder. Immediately beneath the 
floor of the rectovesical pouch lie the upper ends of the seminal 
vesicles and part of the vasa deferentia. These folds and fossae 
are not always well marked. They are seen best when the rec- 
tum and bladder are empty. As these organs fill up, the fossae 
and folds are more or less obliterated. 
Rectum. The rectum begins at the third piece of the sac- 
rum and runs downward and forward following the general 
curve of the sacrum and coccyx. A short distance in front of 
the coccyx the terminal part of the rectum turns sharply down- 
ward and backward, pierces the pelvic floor, and becomes the 
anal canal. The rectum proper is about five or six inches long. 
It is curved with the concavity forward, and also has three lat- 
eral curvatures; the upper and lower usually are convex to the 
left, the middle to the right. These flexures are marked on the 
interior of the gut by three transverse folds, the rectal valves. 
The lower end of the rectum is somewhat dilated, forming the 
ampulla which lies directly behind the prostate, bladder, vas 
deferens, and seminal vesicles. The prostate can be palpated 
through this part of the rectum. The upper part of the rectum 
is covered by peritoneum on its anterior and lateral aspects. The 
anal canal lies in the rectal triangle of the perineum and will be 
described with that region. 
The Bladder. This organ varies in shape, depending on its 
degree of distention. Its shape and position can be appreciated 
best in a median sagittal section of the pelvis. The superior 
aspect is directed upward and backward into the pelvic cavity, is 
covered by peritoneum, and is in relation to the intestines. On 
the inferior aspect of the bladder is the opening of the urethra, 
and the area about this opening is in direct relation with the 
prostate. In front of the prostate, the under surface of the blad- 
237 tier is in relation with the prevesical space, between it and the 
pubis. This space is filled with loose tissue and some veins. 
Behind the prostate the inferior surface of the bladder is in re- 
lation with the seminal vesicles, vas deferens, and with the rec- 
tum. The ureters open on the lateral portions of the inferior as- 
pect. When the bladder is empty its upper and lower surfaces 
lie together and are flattened against the pubis. In distention the 
superior surface rises above the pelvic brim. There is a very 
loose connection between the anterior surface of the bladder and 
the back of the pubis, and as the organ distends its upper border 
raises the peritoneum up above the symphysis so that an in- 
strument can be passed into the bladder through an incision 
just over the pubes without opening the general peritoneal cav- 
ity. 
The prostate lies beneath the bladder. It is triangular in 
shape. Its base is directed upward and fused with the under 
surface of the bladder; its apex points downward and is support- 
ed by the urogenital diaphragm. Laterally the prostate rests on 
the two lateral parts of the levator ani muscle and occupies the 
gap in the anterior part of the pelvic diaphragm or floor. Ante- 
riorly the prostate is separated by an interval from the lower 
border of the pubic symphysis; behind it is in close relation to 
the rectum. The prostate and under part of the bladder are sur- 
rounded by veins, the prostatic and vesical plexuses. These re- 
ceive the dorsal vein of the penis in front and drain behind into 
the internal iliac veins. 
The vas deferens passes from the internal ring downward, 
backward and inward across the external iliac vessels, over the 
lateral wall of the true pelvis to the sides and under surface of 
the bladder. It forms a slight fold in the peritoneum along its 
course. By pulling on the vas at the pelvic brim, thie fold will 
be more marked and the course of the vas more clearly indicat- 
ed. It runs beneath the floor of the paravesical fossa and dis- 
appears beneath the rectovesical (sacrogenital) fold at the back 
of the bladder. It enters the upper border of the prostate near 
the midline. At this point it is connected with the seminal ves- 
icle, an oblong sacculated structure about two inches in length, 
which lies just lateral to the vas. 
238 The ureter crosses the common iliac vessels near the pos- 
terior part of the pelvic brim and runs downward and forward 
towards the back of the bladder. Its course is marked by a slight 
fold along the lateral wall of the pelvis, which can be accentu- 
ated by traction on the ureter at the pelvic brim. Compare the 
course of both vas and ureter by simultaneous traction on each. 
They cross each other behind and lateral to the bladder, the vas 
passing medial to the ureter. The ureter enters the bladder just 
lateral to the seminal vesicle, passes obliquely through the wall 
and opens into the inferior surface behind and lateral to the 
urethra. 
If the bladder is collapsed it can be inflated through the 
ureter. Having noted the position of the distended bladder, 
make an incision in the superior wall to examine the interior. 
When the bladder is empty it is more or less contracted and the 
mucosa forms numerous folds which are obliterated with disten- 
tion. In the midline is the internal urethral orifice, and about an 
inch or more behind and laterally are two smaller slit-like open- 
ings, the openings of the ureters. These three openings bound a 
triangular area which is called the trigonum of the bladder, and 
its posterior border is often sharply marked off by a transverse 
fold between the lower ends of the ureters at this point. Imme- 
diately beneath the trigone can be felt the resistant mass of the 
prostate gland, while just above the ridge between the ureters 
the finger will press against the wall of the rectum. Note es- 
pecially the trigone and its relation to the prostate and rectum. 
The vas deferens can next be dissected from the internal 
ring over the pelvic brim by simply cutting through the peri- 
toneum over it. Do the same with the ureter, and show how the 
ureter crosses lateral to the vas deferens at the back of the blad- 
der. The terminal ends of these structures should be followed 
to the base of the bladder. The vas deferens crosses the ureter 
and turns medially to arch over the seminal vesicle. The upper 
ends of the seminal vesicles lie between the vas and ureter in the 
floor of the rectovesical fossa. This dissection will give a good 
view of these relations and of the interior of the bladder. In 
cleaning the ureter and vas, the dissector will come across some 
239 of the branches of the internal iliac vessels. The vesicle branches 
to the bladder may be followed, the others should be left for a 
later dissection. 
Pelvic muscles. The lateral wall of the true pelvis is cov- 
ered by the obturator internus and pyriformis muscles. These 
arise from the bony wall and leave the pelvis by the sacrosciatic 
foramina, to reach the back of the femur. The pelvic floor is 
formed by the levator ani and coccygeus muscles, which arise 
from the lateral wall of the pelvis and meet partially in the mid- 
line. 
The levator ani muscle consists of a right and left portion 
which arise from the pubic symphysis, the spine of the ischium 
and from the white line between these points. Its fibers pass 
downward, inward and backward. In the anterior part of the 
pelvic floor the two halves do not meet, but leave a gap in the 
midline in which lies the prostate gland. In the posterior part 
of the pelvis the two halves meet and form a complete floor. The 
muscle is inserted into the rectum and behind the rectum is pro- 
longed back to the coccyx in the form of a median raphe. The 
muscle is divided into an anterior part, the pubococcygeus and 
into a posterior part, the iliococcygeus. 
The coccygeus muscle is a small affair arising from the 
spine of the ischium and the lesser sacrosciatic ligament and in- 
serting into the coccyx. It helps to complete the hinder part of 
the pelvic floor. These two muscles are completely covered by 
the visceral layer of the pelvic fascia. 
Pelvic fascia. The transversalis fascia of the anterolateral 
abdominal wall and the iliac fascia of the posterior abdominal 
wall form one continuous layer. This layer is prolonged down 
over the brim of the pelvis and becomes the pelvic fascia. The 
pelvic fascia consists of a parietal and a visceral portion. The 
parietal fascia is sometimes known as the obturator fascia. It 
covers the obturator internus and pyriformis muscles on the lat- 
eral wall of the pelvis, and ends below along the ischiopubic rami. 
Here it blends with the deep layer of the triangular ligament 
(urogenital diaphragm), which is the deepest layer of tissue in 
the urogenital triangle of the perineum. About half way down 
the lateral wall of the pelvis there is a thickening in the parietal 
240 pelvic fascia, which runs from the under side of the symphysis 
pubes in front to the spine of the ischium behind, and is known 
as the white line. Along this line arises the second layer of 
fascia, the visceral layer of the pelvic fascia. 
The visceral layer is known also as the diaphragmatic or the 
rectovesical layer of the pelvic fascia. It runs downward and 
inward from the white line, covers the upper or pelvic surface 
of the levator ani and coccygeus muscles and with them forms 
the pelvic diaphragm. The visceral layer of the pelvic fascia 
forms a support to and also the capsule of certain of the pelvic 
viscera. At the pubes the visceral fascia is carried back to the 
anterior surface of the prostate and bladder, forming the pubo- 
prostatic ligaments which form the lower boundary of the pre- 
vesical space. It then surrounds the prostate gland, forming its 
capsule. Above the prostate the visceral layer spreads out over 
the wall of the bladder. Behind the prostate and bladder the vis- 
ceral layer surrounds the seminal vesicles and the vasa defer- 
entia, binds them closely to the back of the bladder, and here 
makes a sort of transverse septum running from side to side be- 
tween the prostate and bladder anteriorly and the rectum pos- 
teriorly. On reaching the rectum, the visceral fascia surrounds 
that organ and is prolonged behind it to the sacrum. In the fe- 
male the pelvic fascia and pelvic floor are arranged on the same 
general plan. The vagina, however, occupies the gap between 
the anterior parts of the levator ani which the prostate occupied 
in the male. The visceral layer of the pelvic fascia invests the 
vagina at this point and then passes back to the rectum. 
Female pelvis. In the female, the peritoneum leaves the 
top and sides of the bladder as it did in the male, but behind, it 
passes in the form of two folds, the vesico-uterine folds, to the 
sides of the uterus. These form the lateral boundaries of the 
vesico-uterine pouch between the bladder and the uterus. The 
peritoneum passes from the bladder in the floor of this pouch 
onto the anterior and superior surface of the uterus and is pro- 
longed laterally from the uterus to the pelvic wall forming the 
broad ligaments of the uterus. These ligaments are composed 
of two layers of peritoneum, between which lie the round liga- 
ments, the fallopian tubes, the ovaries and their vessels. The 
241 upper end or fundus of the uterus rises in the midline between 
and above the upper free borders of the broad ligaments. The 
fallopian tubes are attached to the uterus near its upper border 
and consequently lie in the upper border of the broad ligaments. 
Broad ligament. The lateral and lower borders of the 
broad ligament are attached to the lateral walls and floor of the 
pelvis. Here the blood vessels enter the ligament to reach the 
organs between its folds. The anterior layer of the broad liga- 
ment at the pelvic wall turns forward, passes in the floor of the 
paravesical fossa and becomes continuous with the uterovesical 
folds and lateral false ligaments of the bladder. The posterior 
layer is reflected backward, forming the uterosacral folds. These 
contain some smooth muscle fibers and pass around the pararec- 
tal fossae to the side of the rectum and sacrum. The peritoneum 
passes from the fundus of the uterus over its whole posterior 
surface onto the top of the vagina and there is reflected back- 
ward to the rectum, forming the floor of the pouch of Douglas, 
or recto-uterine fossa. The reflections of peritoneum should be 
studied carefully in median sagittal sections of the pelvis. The 
relations of the peritoneum to the uterus and especially to the 
postero-superior part of the vagina should be carefully noted. 
The uterus is a hollow muscular organ, which lies between 
the rectum and the bladder. The upper end is expanded and 
convex and is known as the fundus; the lower end is rounded 
and tubular, is known as the cervix, and opens into the upper 
end of the vagina. At the upper outer angle of the fundus the 
uterine cavity is continuous with that of the fallopian tube. The 
uterus changes its position freely, depending on the distention 
of bladder and rectum. When these organs are empty the body 
of the uterus lies over the upper surface of the bladder and is 
about horizontal in position. Its posterior surface is in relation 
with the intestines. The neck makes an obtuse angle with the 
body, and is directed downward and backward. The upper end 
of the vagina incloses the neck so that about one-half of it is in 
the vagina. The broad ligaments are attached to the sides of the 
uterus and contain the round ligament of the uterus, the fal- 
lopian tube, the ovaries and their ligaments and the arteries, 
which supply the uterus and these organs. 
242 The round ligament is attached to the upper lateral part of 
the fundus; it runs laterally to the pelvic brim, crosses the ex- 
ternal iliac vessels and enters the internal ring. It is to be as- 
sociated with the anterior layer of the broad ligament. 
The fallopian (uterine) tube runs outward at the top of the 
broad ligament. It arches upward and downward over the 
ovary and, with a piece of the broad ligament, forms a sort of 
hood over that organ. The first part of the tube forms the isth- 
mus ; the terminal part forms the ampulla, and ends in the ex- 
panded fimbriated extremity which opens into the pelvic cavity. 
The ovary is an oval body flattened from side to side. It is 
about one and a half inches long and lies obliquely in a depres- 
sion on the lateral wall of the pelvis between the ureter below 
and the pelvic brim above. Its medial or inferior end is con- 
nected to the upper angle of the uterus by the ligament of the 
ovary. Its outer or upper end is supported at the pelvic brim 
by a peritoneal fold, the suspensory ligament of the ovary. The 
ovary lies between the layers of the broad ligament, but is sur- 
rounded wholly by the posterior layer, and is suspended on the 
posterior aspect of the broad ligament by a sort of mesentery. 
The vagina is a flattened tube about three inches long, with 
its anterior and posterior surfaces in contact. Its lower end 
opens below the labia of the external genitalia; its upper end 
surrounds the cervix of the uterus. It runs forward and down- 
ward, and its posterior wall is fused with the anterior wall of 
the ampulla of the rectum. The urethra lies on its anterior wall. 
The vagina lies in the gap between the lateral halves of the leva- 
tor ani muscles, and below' that level is surrounded by the lay- 
ers of muscles and fasciae of the urogenital triangle. The ex- 
ternal os uteri lies in the upper end of the vagina. The os uteri 
is bounded by two prominent lips (anterior and posterior) which 
can be felt by palpitation through the vagina. The recesses in 
front and behind them at the upper end of the vagina are known 
as the anterior and posterior fornices. The latter forms a deep 
pocket which lies just beneath the peritoneum of the pelvic floor 
in the recto-uterina fossa. 
The rectum and bladder have the same general place as in 
the male pelvis. The rectum is in close relation with the vagina 
243 in front. The bladder is in relation with the vagina below and 
behind. The urethra is a canal about one and a half inches long, 
which runs straight downwards and forwards on the anterior 
wall of the vagina. 
The ureter runs along the lateral wall of the pelvis to just 
below the ovary, and passes under the lower and outer border 
of the broad ligament. It lies just lateral to the upper end of the 
vagina and cervix of the uterus as it enters the inferior aspect of 
the bladder. As it passes under the broad ligament it is crossed 
above by the uterine artery. The relation of the uterus to this 
artery and to the cervix and vagina are of surgical importance 
in gynecological work. The ureter should be followed to the 
bladder, and the bladder opened to compare the interior with 
that of the male bladder. 
Dissection of the broad ligament and ureter. Cut into the 
anterior layer of the broad ligament at the upper angle of the 
uterus to secure the round ligament and then dissect it to the 
internal ring, where it can be followed down the inguinal canal. 
The ovarian vessels can next be followed into the broad liga- 
ment to the ovary. The peritoneum covering the ureter should 
be carefully dissected away and the ureter followed to the point 
where it disappears under the broad ligament. The posterior 
layer of the broad ligament can then be largely removed and the 
ureter followed forward to the bladder. The removal of the 
peritoneum of the broad ligament will expose the uterine artery. 
This vessel should be cleaned and traced inward to the uterus. 
Special care must be taken to verify the relations of the ureter 
to this vessel and to the upper end of the vagina and neck of the 
uterus. The ureter runs under the artery and lies about one- 
half to three-fourths of an inch lateral to the neck of the uterus 
and the vagina. All of the peritoneum of the dorsal side of the 
broad ligament can then be removed, the ligament of the ovary 
followed to the uterus, and if the subject is well injected the 
branches of the uterine artery and ovarian artery fully dissected. 
244 DISSECTION OF THE PERINEUM 
Before beginning the dissection of the perineum, the stu- 
dent should study carefully the pubes and ischia and the boun- 
daries of the pelvic outlet on the skeleton. The outlet of the 
pelvis is roughly diamond-shaped and is divided into two tri- 
angles by a transverse line drawn through the tuberosities of 
the ischia. The anterior triangle is called the urogenital, and 
the posterior the rectal triangle. The triangles are filled by lay- 
ers of muscles and fascia which are closely associated with the 
genitalia and the rectum. Branches of the internal iliac vessels 
and of the sacral plexus of nerves will also be found here. The 
term perineum is now given to the whole region of the pelvic 
outlet and includes both triangles. 
Fhe posterior or rectal triangle contains the lower end of 
the anal canal surrounded by the external sphincter and the 
levator ani muscles. On either side of the anal canal are the 
ischiorectal fossae containing the internal pudic arteries, veins 
and nerves and considerable fat. This triangle and its contents 
are to be associated with the posterior portion of the pelvic floor. 
The anterior or urogenital triangle is bounded in front and at 
the sides by the pubes and ischiopubic rami. It lies wholly an- 
terior to the anal opening. In the male it contains portions of 
the penis and urethra. In the female it contains parts of the ex- 
ternal genitalia, the lower end of the vagina and the greater part 
of the urethra. In both sexes the space is filled by five layers of 
fasciae and muscles which surround and support those portions 
of the genitalia found in this area. The student will find it in- 
structive to compare the structures found in both of the perineal 
triangles with the pelvic floor and pelvic viscera as seen in a 
median sagittal section of the pelvis in the textbook. In the 
pelvic cavity above the posterior triangle is found the rectum in 
both sexes. Above the anterior triangle in the male lie the 
bladder, prostate, seminal vesicles and lower ends of the vasa 
deferentia. In the female, above the anterior triangle lie the 
uterus, the broad ligaments and their contents, the upper end of 
the vagina and the bladder. The layers of muscles and fasciae 
245 have essentially the same position in the triangle in both sexes. 
It should be noted in comparing the structures in the anterior 
triangle in the two sexes that the vagina splits the triangle and 
the layers of tissue in it into a right and left half, which is not 
the case in the male. 
Rectal triangle. It will be most convenient to begin with 
the dissection of the rectal triangle. The body should be placed 
face down, the buttocks elevated and the legs hung over the side 
of the table. Note the relative position of the tuberosities of 
the ischia, coccyx and anus. Make a transverse incision through 
the skin immediately in front of the anus between the two tuber- 
osities of the ischia. From the central point of that incision 
cut through the skin on either side of the anus to the coccyx. 
The two triangular flaps can then be turned laterally as far as 
the tuberosities. 
Ischiorectal fossae. Position. These are two irregularly 
tent-shaped spaces situated between the lower end of the rec- 
tum and lateral wall of the pelvis and immediately beneath the 
pelvic floor, one on either side. Below they are directed to- 
wards the buttock and are filled with a large mass of fat con- 
tinuous with the fatty superficial fascia of the gluteal region. 
Boundaries. Above, origin of the levator ani muscle from the 
wall of the pelvis (white line) ; below, fascia and skin of buttock; 
anterior, contents of urogenital triangle; posterior, gluteus 
maximus muscle; internally, levator ani muscle and external 
sphincter of rectum; externally, obturator fascia, obturator in- 
termus muscle. Contents. Fat prolonged in from the super- 
ficial fascia, the internal pudic artery, vein and nerve, embedded 
in the obturator fascia along the outer wall of the space; the 
inferior haemorrhoidal vessels and nerves. 
The superficial fascia of the gluteal region is extremely 
thick and contains a large amount of fat which fills the ischio- 
rectal fossa. This fat must be removed with some care, as the 
inferior haemorrhoidal vessels and nerves pass through it to the 
anal canal. Make an incision at the inner edge of the tuberosity of 
the ischium through the fat and turn the fat inward towards the rec- 
tum. Feel for the internal pudic vessels along the outer wall of the 
fossa and dissect them out of their fascial sheath. The inferior haem- 
246 orrhoidal branches come off the main branches just after the 
vessels and nerves enter the fossa and rim inward towards the 
anal canal. Trace these little vessels inward towards the rec- 
tum and try to save some of them. The greater number will 
probably have to be sacrificed when the ischiorectal fat is re- 
moved. Separate the fat first from the outer wall of the fossa and 
note the thick parietal pelvic fascia covering over the obturator 
interims muscle. The internal pudic artery and nerve are em- 
bedded in this fascia and should be dissected out of it. The fat 
will separate suite readily from the outer wall of the space. Next 
cut into the fat along the margins of the anus and the fibers of 
the external sphincter of the rectum will come into view. 
External sphincter of rectum. This is a striated muscle and 
must not be confused with the internal sphincter which is merely a 
thickening in the circular smooth muscle layer of the rectum. It arises 
from the coccyx, surrounds the anal canal, where it blends with 
the insertion of the levator ani muscle, and ends just behind the 
bulb of the penis by blending with the superficial muscles of uro- 
genital triangle at the central point of the perineum. Its most 
superficial fibers lie in the subcutaneous tissue about the anus 
and may be prolonged forward to blend with the fascia of Colles. 
The fibers of the sphincter are often pale and difficult to dissect 
in a satisfactory manner. 
The anal canal is barely an inch in length and extends from 
the ampulla of the rectum above to the anal opening between 
the buttocks below. Its wall is thickened by the internal sphinc- 
ter muscle, a thickening of the smooth muscle fibers of the gut, 
and by the external sphincter, a striated muscle. These muscles 
contract the walls of the canal. The mucosa is characterized by 
vertical ridges or columns separated by furrows. These ridges 
contain masses of small veins and this enlargement causes the 
various types of haemorrhoids. 
Dissect the fat off the external sphincter and continue to 
work in deeper, separating the fat from the levator ani muscle. 
The external sphincter and levator ani muscles form the sloping 
inner wall of the fossa. The plug of fat can be gradually sep- 
arated from the inner wall up to the apex of the space which lies 
close to the lateral wall. Remove the fat but try to preserve the 
247 branches of the inferior haemorrhoidal vessels and nerves. The 
internal pudic vessels and nerve should be dissected out of the 
parietal pelvic fascia along the outer wall of the fossa, and car- 
ried forward to the posterior border of the tissues in the an- 
terior or urogenital triangle. Do not injure or encroach on the 
layers of the anterior triangle at this time; the vessels and nerves 
will be taken up again in the dissection of that triangle. Re- 
move the fascia and fat sufficiently to expose the edge only of 
the gluteus maximus muscle at the posterior aspect of the fossa. 
The extent and limits of the fossa can then be explored with the 
finger. The apex of the space corresponds to the line of origin 
of the levator ani muscle from the parietal pelvic fascia along the 
inner aspect of the lateral wall of the pelvis (white line). The 
base of the space is towards the buttock. Carry the finger for- 
ward and it will be arrested by the posterior border of all the 
layers of fasciae and muscles which occupy the urogenital tri- 
angle. These structures therefore constitute the anterior boun- 
dary of the fossa and the finger can be carried a short distance 
over their free posterior borders. 
Urogenital triangle. The body should be placed on its back, 
the buttocks elevated on one or two blocks, and the legs sepa- 
rated and hung over the end of the table. The body must be 
tied in this position. The hips and knees should not be flexed, 
as the flexor muscles of the legs and the adductor muscles of the 
thigh will be injured. The scrotum and penis should be drawn 
well up over the pubes and secured in that position. In making 
this dissection, the arrangement of the parts in alternating lay- 
ers of fasciae and muscle should be borne carefully in mind. 
Make incisions from the tuberosity of the ischium on each side 
forward along the ischiopubic ramus for about three inches. 
Raise the skin and turn it forward over the scrotum, being es- 
pecially careful to leave all fascia in place. 
First layer. Fascia of Colles. The fascia here consists of 
a superficial and a deep layer. The former is continuous with 
the superficial fascia of the gluteal region behind and with the 
superficial fascia of the thighs at the sides. In front it is contin- 
uous with the dartos tunic of the scrotum which in turn is con- 
tinuous with the fascia of the penis and with the superficial 
248 fascia of the anterior abdominal wall. The deeper stratum is thin 
and membranous, similar to the deep fascia elsewhere. An- 
teriorly it also is continuous with the dartos layer of the scro- 
tum, the fascia over the penis and with the deeper part of the 
superficial fascia of the abdominal wall. Laterally it is firmly 
fixed along the ischiopubic rami. The term fascia of Colles is 
given to this deep stratum. The posterior border of the fascia 
of Colles turns around the posterior border of the superficial 
muscular or second layer of tissue in this region, and is continu- 
ous with the third layer or the superficial layer of the triangular 
ligament. This connection can be seen in a deeper dissection, 
but can often be demonstrated at this stage by injecting air or 
water under the fascia of Colles through an incision well for- 
ward on one or both sides of the midline. Then cut through the 
fascia along the midline and again transversely a little anterior 
to the central point of the perineum and reflect the flaps later- 
ally. Do this very carefully, as the superficial perineal vessels 
and nerves lie just below and partly in the fascia. In the female 
this perineal fascia or fascia of Colles is not so well marked, and 
disappears in front under cover of the labia majora. Incisions 
should be made as in the male and the skin and fascia reflected 
forward on either side of the external genitalia. Note the rela- 
tions of the labia to the vulva and the position of the clitoris and 
the external urethral orifice. 
Second layer. Superficial muscles of the perineum. These 
muscles are closely connected to the different parts of the penis 
and the formation of that organ should be studied before the mus- 
cles are dissected. The penis consists of three portions, the two 
corpora cavernosa, which form the dorsum and sides, and the 
corpus spongiosum, which forms the ventral part of the organ. 
The corpus spongiosum anteriorly forms the glans penis or head. 
At its posterior end there is another enlargement, the bulb, 
which lies in front of the anal canal. The spongy (cavernous) 
or third part of the urethra passes through this part of the penis. 
The two corpora cavernosa begin behind the glans penis, and 
lie close together until they reach the lower border of the sym- 
physis pubis, when they diverge to form the crura of the penis. 
These are attached along the rami of the pubis and ischium al- 
249 most as far as the tuberosities and represent the most fixed part 
of the penis. The corpora cavernosa, and the corpus spongiosum 
to a less extent, are composed of erectile tissue, the engorgement 
of which under nervous stimulation causes the erection of the 
organ. The two ischiocavernosus muscles arise from the ischio- 
pubic rami,' cover over and are inserted into the crura of the 
penis. The bulbocavernosus muscle lies in the midline between 
the ischiocavernosi. It arises from the mid point of the peri- 
neum and from a medial raphe along the midline, and its fibers 
surround the bulb and the corpus spongiosum like a hand grasp- 
ing the bulb of a syringe. The transverse (superficial) perinei 
muscles are two slender muscles which arise from the tuberosi- 
ties of the ischia and pass inward and a little forward to meet 
at the central point of the perineum. They are usually very poor- 
ly developed, are often hard to find, and one or both may be ab- 
sent. They correspond to the posterior boundary of the urogeni- 
tal triangle and meet in the midline between the bulbocaverno- 
sus in front and the sphincter ani behind. The external sphincter 
ani muscle really belongs to the posterior triangle where it sur- 
rounds the lower end of the anal canal, but its anterior extremity 
blends with the muscles just mentioned. In some cases its fibers 
are prolonged forward over the bulbocavernosus muscles and 
mingle with the fascia of Colles. 
Central point or tendon of the perineum. This is really a 
small collection of fibrous tissue in the midline between the anal 
canal behind and the bulb of the penis in front. It is the point 
where the two transverse perinei, the anterior end of the ex- 
ternal sphincter ani, the posterior end of the bulbocavernosus and 
some fibers of the levator ani meet and blend together. • 
Superficial vessels and nerves. These are branches of the 
internal pudic artery and nerve. They arise just behind the 
transverse perinei muscles and run either over or under them to 
enter the superficial layer of muscles. Here they lie in the little 
triangular interval between the bulbocavernosus and ischiocav- 
ernosus muscles, supply the skin and the superficial muscles, 
and end in the scrotum. These vessels and nerves are to be in- 
cluded in the second layer of the progenital triangle. 
In the female, the ischiocavernosus muscles are much small- 
250 er, but have the same position as in the male, and surround the 
crura of the clitoris which corresponds to the penis. This organ 
is, however, composed of two small corpora cavernosa only, has 
no corpus spongiosum, and does not contain the urethra. The 
bulbocavernosus muscles surrounds the vagina and has been 
practically split into two lateral parts by that organ. Beneath this 
muscle, on either side of the lower end of the vagina, are two 
masses of venous and erectile tissue, which meet in the mid- 
line above the opening of the urethra, and receive veins from the 
clitoris. These are the bulbs of the vestibule. The opening of 
the urethra is just above the opening of the vagina, between the 
anterior ends of the labia minora. The fossa navicularis, or 
vestibule of the vagina, lies behind the opening of the vagina 
between the posterior ends of the labia minora. The glands 
of Bartholini (vestibular glands) lie partly under the posterior 
extremities of the bulbs of the vestibule and under the bulbo- 
cavernosus muscles. Their ducts open into the vestibule of 
the vagina at the base of the labia minora. The central point 
of the female perineum lies between the lower end of the vagina 
and the anal canal and forms a sort of fibromuscular wedge 
between the lower end of these two tubes. The vessels and 
nerves are in the same position as in the male and supply the 
skin about the labia majora. 
Third layer. Superficial or inferior layer of the triangular 
ligament or urogenital diaphragm. This is a thin layer of fascia 
about the thickness of ordinary thin deep fascia elsewhere, 
which it attached laterally, like the fascia of Colles, to the 
ischiopubic rami. It lies on the deep aspect of the muscles just 
mentioned, and in the midline is pierced by the second or mem- 
branous portion of the urethra. In front there is a little gap 
between its anterior end and the lower border of the symphysis 
pubis, through which the dorsal vein of the penis passes from 
the dorsum of the penis to the veins of the bladder and pros- 
tate. The posterior border of the triangular ligament and the poste- 
rior border of the fascia of Colles meet and fuse together along the 
posterior border of the superficial transverse perinei muscles. As a 
lesult of this fusion, the superficial perineal compartment is 
formed, and its boundaries should be carefully noted as well as the 
251 vontents. The superficial or interior boundary is the first layer of 
this region, or the fascia of Colles; the deep or superior boundary 
is the superficial layer of the triangular ligament. The lateral 
boundaries are formed by the attachments of these two fascia 
layers to the ischiopubic rami. The posterior boundary is formed 
by the fusion of the two layers of fasciae behind the transverse 
perinei muscles. The anterior boundary is lacking, and here the 
compartment is open, because the triangular ligament stops 
just below the pubic symphysis while the fascia of Colles is 
continuous with the dartos of the scrotum. The contents of this 
superficial compartment are the superficial muscles, vessels and 
nerves; the crura of the penis, and the bulb and part of the cor- 
pus spongiosum, which contains a part of the spongy portion 
of the urethra. In the female this layer is in the same plane as 
in the male and like the bulbocavernosus muscle is practically 
split in two by the vagina and urethra, which pass through it. 
Fourth layer. Compressor urethrae muscle. This muscle 
is sometimes divided into a posterior part, the deep transverse 
perinei, and an anterior part, the sphincter urethrae membran- 
aceae, which surrounds the second or membranous part of the. 
urethra. It is, however, simpler to regard them as one contin- 
uous layer of muscle. This compressor urethrae is really a sort 
of muscle complex, its fibers lying in several strata and run- 
ning transversely, obliquely and in circular loops around the 
membranous part of the urethra and between the ischiopubic. 
rami on either side. It fills up the triangular gap between the 
rami, and has the same shape and extent as the superficial layer 
of the triangular ligament. The membranous part of the urethra, 
the second part of that tube, is about three-fourths of an inch 
in length, and passes rather obliquely through the fibers of this 
muscle. On either side of this part of the urethra are two tiny 
glands, Cowper's glands, (bulbo-urethral). They are about the 
size of a pea. and are not easily found in an ordinary dissec- 
tion. In the substance of this muscle lie the deep or terminal 
branches of the internal pudic vessels and nerves. They enter 
the muscle along its posterior border and send an artery inward 
to the bulb of the corpus spongiosum, a branch of each crus, 
and the dorsal artery of the penis, which runs forward to reach 
252 the penis just below the symphysis. The dorsal nerve of the 
penis can be followed with the corresponding artery. In the 
female this muscle surrounds the vagina and urethra and its 
dissection is usually most unsatisfactory. 
Fifth layer. Deep layer of the triangular ligament or uro- 
genital diaphragm. This is the last of the layers in this region, 
and has the same shape and extent as the superficial layer, but 
is on the deep or superior aspect of the compressor urethrae 
muscle. At the posterior border of that muscle the two layers 
of the triangular ligament are fused to form the posterior boun- 
dary of the deep perineal compartment. Laterally this space 
is shut in just as was the superficial by the fusion of the two 
layers of the triangular ligament along the ischiopubic rami, 
while in front, the space is bounded by the under side of the 
symphysis. This deep compartment contains the compressor 
urethrae muscle, Cowper's glands, the deep vessels and nerves, 
and the second or membranous part of the urethra. The posi- 
tion, boundaries and contents of these two compartments should 
be carefully studied as they are of practical importance in rup- 
ture of the urethra. This layer occupies a corresponding posi- 
tion in the female but is of more limited extent. Neither of the 
two compartments is as well marked or is of as much practical 
importance as in the male. 
Urogenital diaphragm. The two layers of the triangular 
ligament with the compressor urethrae muscle between them 
form the urogenital diaphragm, which is placed like a sort of 
shelf below the open or deficient part in the levator ani mus- 
cle or the pelvic diaphragm. This shelf supports directly the 
prostate and bladder. The deep layer of the triangular liga- 
ment is continuous with the capsule of the prostate (visceral 
pelvic fascia) towards the midline and more laterally along the 
rami with the parietal layer of that fascia. It therefore forms 
the connecting link between the tissues of the urogenital tri- 
angle and those in the floor of the pelvis. This important rela- 
tion will be shown in the dissection of the deeper layers of this 
triangle. In the female the diaphragm is split in halves by the 
vagina and is also pierced by the urethra. 
Dissection of the deeper layers. The best way to demon- 
253 strate the superficial layer of the triangular ligament is to first 
remove the bulb of the corpus spongiosum. Begin at the cen- 
tral point and dissect the bulb off the triangular ligament turn- 
ing the bulb forward. The arteries to the bulb and the second 
part of the urethra will be cut. Some of the fibers of the bulb- 
ocavernosus muscle arise from the surface of the ligament and 
must be carefully removed. Then dissect the ischiocavernosi 
muscles from the rami and turn them forward also. This will 
expose the whole extent of the ligament. If it is desirable to 
retain the corpus spongiosum intact for a future median section 
through the whole urethra, the bulb can be left in place and the 
crura only removed. This will give a partial view of the liga- 
ment. 
The compressor urethrae muscle is a very soft pulpy affair 
and its dissection is most unsatisfactory, but something can be 
seen of it by making a careful incision through the superficial 
layer of the triangular ligament. The branches of the artery 
can be found easily if the injection is good. Cowper's glands 
are rarely seen. 
It is of practical importance to demonstrate the relation of 
the urogenital diaphragm as a whole to the deficient part of the 
levator ani muscle and to the prostate. This can be done by cut- 
ting between the levator ani muscle and the central point of the 
perineum. Seize the central point in the forceps and gradually 
turn up the posterior border of the diaphragm. The two halves 
of the levator ani will come into view. On the deep surface of 
the urogenital diaphragm is the thin deep layer of fascia (deep 
layer of the triangular ligament or diaphragm). In the midline 
is the beginning of the membranous urethra and between the 
two medial borders of the levator ani muscles is the anterior 
wall of the ampulla of the rectum covered by that part of the 
rectovesical layer of the pelvic fascia which runs between the 
rectum and prostate. Cut into this layer just behind the ure- 
thra, insert the tip of the scissors and open them to stretch the 
cut and the edges of the levator ani muscle laterally. If the 
cut was made in the right place the instrument will enter the 
plane between the layers of the rectovesical fascia behind and 
the posterior surface of the prostate in front, and the stretching 
254 of the tissues will expose the apex and the posterior surface of 
the prostate. This is a very instructive dissection and should 
be made with care on account of the practical importance of this 
region in the surgery of the prostate. 
It should be clearly understood that all the five layers men- 
tioned above taken together form a triangular mass of muscles 
and fasciae arranged in alternate layers which surrounds the 
second portion of the urethra, the bulb and part of the corpus 
spongiosum and the crura of the penis in the male, and the 
vagina and urethra in the female. The superficial vessels and 
nerves and spongy part of the urethra are in the superficial 
compartment and the deep vessels and the membranous urethra 
are in the deep compartment. The five layers conform to the tri- 
angular space between the rami of the pubes and ischium and 
have necessarily a more or less free posterior border which cor- 
responds to the line dividing the two triangles of the pelvic out- 
let. Note carefully the relations of this triangular mass of tis- 
sue to the anal canal and the ischiorectal fossae. In the midline 
the central point or tendon of the perineum lies like a fibrous 
muscular plug between the bulb of the corpus spongiosum in 
front and the anal canal behind. The ischiorectal fossae lie im- 
mediately behind the posterior borders of the transverse peri- 
neal muscles and the fused posterior borders of the fascia of 
Colles and the two layers of the triangular ligament. 
Dissection of the rectum, bladder and prostate from behind. 
The subject should be turned again face down and the but- 
tocks elevated. Saw transversely through the sacrum at about 
the lower border of the third sacral vertebra. Pull the upper 
border of the detached portion backward and downward, and 
carefully dissect all structures away from its anterior surface. 
The attachments of the levator ani and of the pyriformis mus- 
cles will have to be cut. The posterior surface of the rectum 
will be somewhat obscured by the connective tissue which con- 
nects it to the sacrum, and in this tissue the branches of the 
superior haemorrhoidal artery will be found. Passing laterally 
from the front and sides of the upper part of the rectum is the 
parietal peritoneum of the pararectal fossae of the pelvis, which 
should be carefully preserved intact. Separate the rectum from 
255 this peritoneum with the finger or by blunt dissection, tie the 
rectum in two places near its upper part, and cut between them. 
The rectum can then be turned down and back, pivoting on the 
anal canal. As the rectum is turned back, free its anterior 
surface by dissecting close to the gut so as to avoid any injury 
to the structures at the back of the bladder and prostate. A 
thick layer of fascia will be left in front of the rectum which is 
the transverse septum referred to previously. If the finger is 
carried forward high up in the space in front of the rectum, it 
will simply press against the peritoneum which passes from 
the rectum to the bladder, or in other words, the peritoneum 
forming the floor of the rectovesical pouch. This layer will 
have been cut in the dissection of the vas deferens and ureters 
from above. A little lower down in the midline the finger will 
strike the posterior wall of the bladder between the vasa defer- 
entia. This is the part of the bladder directly in contact with 
the anterior surface of the rectum. Still lower the finger will 
meet the resistant mass of the prostate gland. Having identi- 
fied the position of the prostate, cut into the fascia, which sep- 
arates the rectum and prostate at the midline, and expose the 
posterior surface of the prostate gland. Work upward in the 
midline until the upper border of the gland is reached. By dis- 
secting a little upward and outward from this point the termi- 
nal part of the vasa deferentia can be found. These are soft, 
are embedded in the surrounding fascia, and are easily injured 
unless great care is taken. Just external to each is the seminal 
vesicle, about two inches long and much obscured by its fas- 
cial covering. As the apex of the seminal vesicle is reached, 
look out for the termination of the ureter which passes in front 
of the tip of the vesicle, and also in front and external to the vas 
deferens to enter the posterior border of the bladder. If this 
dissection is done carefully, a very instructive view of the im- 
portant anterior relations of the rectum will be obtained. 
Bladder and prostate, anterior aspect. Make two cuts with 
a saw on either side of the cartilage disk of the symphysis pubis. 
A piece about three-fourths of an inch wide can be removed with- 
out much damage to the adductor muscles which arise from the 
body of the pubis. Separate the cut edges of the pubic bones 
256 and insert a plug to keep them apart. That part of the inferior 
surface of the bladder which is in relation to the pubes and the 
prevesical space will now be exposed. The dorsal vein of the 
penis can be followed into this region and something of the 
prostatic plexus of veins seen. The cut anterior borders of 
each half of the levator ani muscles will be seen on either side. 
Clean the loose tissue and veins away to display the anterior 
aspect of the prostate and note its relation to the two halves 
of the levator ani muscle and to the urogenital diaphragm. 
Urethra. The dorsum of the penis should be split in the 
midline down to the urethra and the urethra opened from the 
glands to the pubes. A sound should be passed into the urethra 
as a guide to the knife. Depress the penis at the pubes and 
carry the cut as far as the bulb. Turn to the bladder and make 
a median incision into the internal urethral orifice and down 
through the anterior wall of the prostatic urethra to connect 
with the cut through the penis. The walls of the bladder, pros- 
tate and penis can now be turned laterally and the whole dorsal 
wall of the urethra displayed. Note the median crest in the 
prostatic urethra; the narrow points at the internal and ex- 
ternal urethral orifices, and in the membranous urethra; the 
dilatations in the glands, bulb and prostatic portions. The cut 
can now be carried back in the midline, the sacrum cut through 
with the saw and the pelvis split in the midline. As most of the 
organs have been partially dissected, the parts will fall more 
or less out of place, and the result is always rather disappoint- 
ing. Note particularly the. median section of the base of the 
bladder, prostate, and as much as possible of the urethra. A 
much better idea of the real position and relation of the pelvic 
organs in this section can be obtained from the pictures in the 
textbooks, and the relations in this view should be carefully 
studied. The most important features to note are the position 
and relations of the bladder, internal urethral orifice, prostate, 
prostatic and membranous urethra to the pubic symphysis, and 
the relation of the rectum and anal canal to the base of the 
bladder and prostate. 
In making a median section through the female pelvis care 
should be taken to cut both uterus and vagina in the midline. 
257 The sacrum and rectum in the female subjects will be in place. 
After the section through the urethra and bladder has been 
made the uterus should be divided in the midline from the fun- 
dus downward. The organ is often somewhat laterally dis- 
placed and must be held in the midline when the cut is made so 
that the incision can be carried downward and forward through 
the middle of the vagina and connected with the incision 
through the bladder. A median cut can then be made through 
the rectum and the sacrum divided in the midline with the saw. 
Lateral wall of pelvis. After studying the position of the 
organs in median section they can be drawn inward and down- 
ward, and the structures in the lateral wall dissected. 
Vessels. The branches of the internal iliac artery will be 
found along the lateral wall. As was the case in the abdomen, 
the branches are partly visceral and partly parietal. The vis- 
ceral are the vesical arteries to the bladder, prostate and semi- 
nal vesicles. These are usually described as superior, middle 
and inferior vesical arteries. The superior vesical artery is 
continued by a fibrous cord which represents the remains of the 
obliterated hypogastric artery, and is prolonged up into the lat- 
eral umbilical fold above the bladder to the umbilicus. The 
vesical arteries are usually represented by several small 
branches. The middle haemorrhoidal artery passes to the rec- 
tum. The dissection of the uterine and vaginal arteries can be 
completed at this stage. They should be followed along side 
of the uterus and vagina. 
The parietal branches are distributed to the pelvic wall, or 
else leave the pelvis through the great sacrosciatic foramen to 
be distributed to the gluteal region and to the perineum. The 
obturator artery runs with the obturator nerve along the lat- 
eral wall just below the pelvic brim, leaves the pelvis through 
the obturator notch and is distributed to the obturator externus 
muscle and deep part of Scarpa's triangle. In many cases this 
vessel arises from the deep epigastric artery. The lateral sacral 
is an unimportant vessel passing to the front of the sacrum. 
The iliolumbar branch runs up into the psoas and quadratus 
lumborum muscles, and need be followed only as far as the 
psoas. The gluteal, sciatic and internal pudic arteries pass to 
258 the pyriformis muscle, and leave the pelvis with that muscle 
through the great sacrosciatic foramen. They should be fol- 
lowed to this opening. The internal iliac artery is usually de- 
scribed as dividing into an anterior and posterior division. From 
the posterior division are given off the iliolumbar, gluteal and 
lateral sacral; from the anterior arise all the other branches. 
There is so much variation, however, and the divisions are 
often so hard to demonstrate that this arrangement can be con- 
veniently disregarded. The student should, however, learn the 
separation of the branches into the visceral and parietal groups. 
The veins that correspond to these vessels are tributaries of the 
internal iliac vein. Preserve the main trunk of this vein and 
let the other branches go. It will be most convenient to begin 
the dissection of the internal iliac artery at the point of bifur- 
cation of the common iliac artery and to trace the visceral 
branches first as far as possible. Then work out the parietal 
branches. 
Nerves. The lower sacral nerves will have been destroyed 
when the sacrum was cut in the dissection of the rectum. The 
lumbosacral cord and the first three sacral nerves should be 
traced with the arteries to the great sacrosciatic foramen. Hav- 
ing cleaned the vessels and nerves, the muscles on the lateral 
wall of the pelvis will be exposed. Part of the origin of the 
pyriformis from the sacrum will have been cut, but the remain- 
der of the muscle can be followed to the great sacroscietic fora- 
men. Note how the nerves lie against the pelvic surface of this 
muscle as they pass out of the pelvis. The parietal vessels and 
nerves should be cleaned to the great sacrosciatic foramen but 
not followed through that opening. They will be picked up 
again in the dissection of the gluteal region. The arteries lie 
on the pelvic or internal side of the pelvic fascia, while the 
(nerves are on its external side. 
Muscles and fasciae. Follow the parietal pelvic fascia down 
the lateral wall of the pelvis to the white line, and note care- 
fully the point where the visceral fascia is given off. If the 
organs are held away from the side of the pelvis to make the 
visceral fascia and the levator ani tense, this will be clearer. 
Note carefully the origin of the levator ani from this white line. 
259 The obturator internus should be cleaned only as far as the 
white line, or otherwise the origin of the visceral fascia and of 
the levator ani will be injured. The lower part of the obturator 
internus should have been cleaned below the white line in the 
dissection of the ischiorectal fossa. 
Action of the muscles of the pelvis and perineum. The 
levator ani and coccygeus support and raise to some extent the 
pelvic floor. They act with the abdominal muscles in forcible 
efforts of expulsion. The pubococcygeus can exert a constrict- 
ing action on the rectum, and can draw it upward and forward. 
The external sphincter, by its tonic contraction, occludes the 
anal orifice and helps to fix the central point of the perineum. 
The transverse perinei muscles also fix and steady the central 
point of the perineum. The ischiocavernosi compress the roots 
of the corpora cavernosa, prevent the outflow of blood, and in- 
crease the tension of the penis or clitoris during erection. The 
bulbocavernosus acts in the same way on the bulb and corpus 
spongiosum. It also helps to empty the urethra at the end of 
micturition or in the emission of semen. These muscles com- 
press the bulbs and erectile tissue of the vagina and act as a 
sphincter muscle for the orifice of the vagina. The compressor 
urethrae supports the perineal diaphragm and prostate and com- 
presses the membranous urethra, helping to empty it at the end 
of micturition and emission. It acts as a sphincter to the ure- 
thra and vagina also. 
260 DISSECTION OF THE LOWER EXTREMITY 
The femur, or thigh bone, is the longest bone in the body. 
It articulates above with the hip bone; below with the patella 
and tibia. In the erect position, the bone inclines inward to- 
wards the median plane so as to approach the lower end of the 
opposite femur. The upper extremity presents a head, neck, 
and two trochanters. The head forms rather more than half a 
sphere, is covered with hyaline cartilage, and has a depression, 
the fovea capitis, a little below and behind its central point. 
This depression gives attachment to the interarticular ligament 
of the hip joint. The neck is triangular in shape, its apex sup- 
ports the head, and its base is continuous with the shaft. The 
head is set on the upper border as well as on the apex of the 
neck, so that the upper border is shorter than the lower. The 
neck forms an angle of about 125 degrees with the shaft and 
inclines a little forward from the shaft. The neck is separated 
from the shaft in front by the intertrochanteric line, and behind 
by the intertrochanteric crest. The trochanteric fossa is a small 
fossa at the junction of the posterior part of the neck and the 
medial side of the great trochanter for the insertion of the ob- 
turator externus muscle. 
The great trochanter is a thick process which lies in line 
with the lateral aspect of the shaft. The intertrochanteric line 
runs down from its anterior border, passes a finger's breadth 
below the lesser trochanter, and joins the linea aspera on the 
back of the shaft. The anterior and lateral surfaces are rough. 
The posterior border is marked by the intertrochanteric crest 
which joins the lesser trochanter, and by a rough ridge, the 
gluteal ridge, which is prolonged downwards to the upper end 
of the linea aspera on the back of the shaft. The great tro- 
chanter provides insertion for the gluteal muscles, the obtura- 
tor muscles, the pyriformis and quadratus femoris. These mus- 
cles come from the innominate bone and are in more or less 
close relation to the hip joint. 
The lesser trochanter is a narrow process on the posterior 
and medial aspect of the bone at the junction of the neck with 
the shaft, and gives insertion to the iliopsoas muscle. 
261 The shaft is slightly curved, with the convexity forward. 
It is cylindrical above, but thick and expanded at the lower end. 
It is reinforced behind in the concavity of the curve by a ridge, 
the linea aspera, which is formed above by the intertrochanteric 
line and the gluteal ridge from the front and back of the great 
trochater. The linea aspera is best marked in the middle third 
of the shaft, and has two sharp lips. In the lower third the lips 
diverge into the lateral and medial supracondyloid lines, which 
end below at the condyles. The medial line ends below at the 
adductor tubercle, a small elevation just above the medial con- 
dyle. It gives attachment to part of the adductor magnus 
muscle. Between these lines, on the posterior surface of the 
lower part of the shaft, is the flat triangular popliteal surface 
which forms the upper part of the floor of the popliteal space. 
The linea aspera gives attachment to the gluteus maximus 
above, and to the adductors below. The anterior surface of the 
shaft is smooth and convex and is covered by the quadriceps 
extensor muscle. 
The lower end supports two oblong elevations, the medial 
and lateral condyles. These are united at the anterior surface 
of the bone, but are separated behind by the intercondyloid 
fossa. The condyles are covered on their inferior surfaces with 
articular cartilage, which is prolonged onto the anterior sur- 
face of the shaft to form an area for articulation with the pa- 
tella. On a fresh bone the patellar surface is limited by two 
slight elevations. This surface is concave in the center with a 
lip on either side, the lateral lip being the most prominent. Be- 
hind the patellar surface the articular cartilage covers the in- 
ferior aspect of the condyles and is carried well up on the su- 
perior surface of each condyle behind. These are the articular 
surfaces for the tibia. The lateral condyle is more prominent 
in front and its long axis is carried straight back. The medial 
condyle is longer and more prominent at the side. Its long axis 
runs with a slight curve inwards and backwards, and its artic- 
ular surface is longer than that of the lateral codyle. When the 
bone is in place, the lower surfaces of the condyles are on the 
same level. On the lateral aspect of each condyle is a tubercle, 
the epicondyle, for the attachment of the collateral ligaments 
262 of the knee joint. There is a groove below the lateral epicon- 
dyle for the insertion of the popliteus muscle. Above the ar- 
ticular area on the upper aspect of each condyle is an impres- 
sion for the origin of the two heads of the gastrocnemius mus- 
cle. The medial aspect of each condyle has an impression for 
the crucial ligaments of the knee joint. 
The great trochanter can be readily felt; the condyles and 
epicondyles are superficial at the knee and can be palpated; 
the outline of the patellar surface can be made out with some 
difficulty under the extensor muscles when the knee is flexed. 
The rest of the bone is deeply imbedded in the surrounding 
muscles. 
The patella, or knee-pan, is the largest sesamoid bone in 
the body and lies in the tendon of the quadriceps extensor mus- 
cle. Its anterior surface is somewhat triangular in shape, is 
slightly rough, and is subcutaneous. The posterior or deep 
surface is covered with hyaline cartilage except at the lower 
end. The articular surface is divided into two areas by a me- 
dian elevation. The lateral areas is the larger and is transverse- 
ly concave; the medial is convex. The infrapatellar tendon or 
ligamentum patellae arises from the lower end of the bone and 
is attached to the tubercle of the tibia. 
Muscle attachments of the femur. The femur provides in- 
sertion for muscles which arise from the pelvis and gives origin 
to others which pass to the bones of the leg and foot. 
Muscles inserted into the femur, anterior aspect. 
Great trochanter, upper border: pyriformis (from sacrum) 
anterior border: gluteus minimus (from 
ilium, lateral surface) 
Muscles arising from the femur, anterior aspect. 
Shaft, front and sides 
vastus lateralis 
vastus medialis 
vastus intermedius 
to patella and 
tibia 
263 Muscles inserted into the femur, posterior aspect. 
Great trochanter, medial side: obturator internus 
" obturator externus 
from in- 
nominate 
>bone, ob- 
turator 
foramen. 
lateral side: gluteus medius 
gluteal ridge : gluteus maximus 
from ilium, 
■lateral sur- 
face. 
intertrochanteric ridge: quadratus femoris 
(from ischium) 
Lesser trochanter: iliopsoas (from spine and ilium) 
Shaft, below lesser trochanter: pectineus (from pubis) 
" linea aspera, inner lip, upper part: adduc- 
tor brevis 
" middle part: ad- 
ductor longus 
" whole length: ad- 
ductor magnus 
from pubis 
and 
ischium 
Muscles arising from the femur, posterior aspect. 
Shaft, linea aspera, inner lip: vastus medialis 
outer lip: vastus lateralis 
to patella and 
tibia 
" " biceps, short head (to fibula) 
Inner condyle, upper surface: gastrocnemius 
Outer condyle, upper surface: 
gastrocnemius 
plantaris 
■to os calcis 
lateral surface: popliteus (to tibia) 
264 DISSECTION OF THE ANTERIOR SURFICE OF THE 
THIGH 
Superficial anatomy. Palpate and identify the following 
bony landmarks. Great trochanter of the femur. This can only 
be felt vaguely in well developed individuals on the dorso-lat- 
eral aspect of the limb. The condyles of the femur on either side 
of knee; the patella; the candyles of the tibia, and the tubercle 
of the tibia. Muscles. Identify the general position of the fol- 
lowing groups. The extensor group on the anterolateral aspect 
of the limb; the adductor group on the medial aspect; the Sar- 
torius muscle crossing the front of the thigh obliquely between 
the two groups just mentioned. Note the position of the quadri- 
ceps tendon above and below the patella and of the iliotibial 
band on the outer side of the knee. Endeavor to identify the 
line of the knee joint. 
Incisions. 1. From the anterior superior spine of the ilium 
along the outer side of the thigh and the outer side of the knee 
to the level of the tubercle of the tibia. 2. From the lower end 
of the first incision transversely inward just below the tubercle 
of the tibia. The skin flap may be raised at its upper outer angle 
and the whole flap turned from without inward. The skin may 
be reflected outward in the upper part of the thigh if more room, 
is required for the dissection. Note the difference in the thick- 
ness of the skin over the outer or extensor surface as compared 
with that over the inner or adductor surface. 
Superficial fascia. In the fascia should be noted; 1, a group 
of lymphatic glands just below Poupart's ligament, which often 
are enlarged; 2, the superficial veins of the lower lateral part of 
the abdominal wall and the region of the pubes which pass over 
Poupart's ligament into the upper part of the thigh. Here they 
meet the large superficial vein of the lower extremity, the long 
or internal saphenous vein, and drain into the femoral vein. The 
internal saphenous vein begins at the inner end of the venous 
arch on the dorsum of the foot and passes along the inner side 
of the leg and knee. It then runs on the inner and anterior as- 
pect of the thigh to a point a short distance below the inner 
265 third of Poupart's ligament. If the fascia is especially thick, 
the vein may be identified by a darkly stained area in the fascia. 
Secure the main trunk and as many of the larger tributaries as 
possible. 3. The small superficial arteries seen in the fascia 
just above Poupart's ligament may be traced below that liga- 
ment to the point where the veins concentrate. They are branches 
of the femoral artery. 4. Cutaneous nerves. These may be 
seen better in the dissection of the deep fascia. Having secured 
the main trunks of the veins throughout the whole area exposed, 
cut through the superficial fascia along the line of the cutaneous 
incisions, turn the whole fascia inward, and remove it. Be care- 
ful not to cut the main trunk of the long saphenous vein and 
nerve at the inner side of the knee in this part of the dissection. 
Great care must be exercised in removing the superficial fascia, 
particularly where the above named veins converge below Pou- 
part's ligament. 
Deep fascia or fascia lata. The connection of the deep fas- 
cia above with Poupart's ligament should be carefully studied. 
Note the thick aponeurotic character of the fascia lata along the 
outer side of the limb and observe how it forms the iliotibial 
band, which extends from the anterior superior spine above to 
the outer part of the tibia below. 
Saphenous opening. This opening lies in the deep fascia 
about one and one-half or two inches below the inner half of 
Poupart's ligament. The superficial vessels of the lower ab- 
dominal wall and the internal saphenous vein of the thigh pass 
through this opening to reach the femoral vessels, which lie 
beneath the deep fascia. The opening is of practical impor- 
tance as it is the place where a femoral hernia appears. Its 
relation to Poupart's ligament and to the external abdominal 
ring should be carefully noted. Between Poupart's ligament 
and the lower margin of the opening the fascia lata divides into 
an outer superficial layer, the iliac fascia, and into an inner 
deeper layer, the pubic fascia. The former is attached above all 
along Poupart's ligament, while the latter is attached to the 
muscles over the iliopectineal line of the pubis. The saphenous 
opening is merely the slit between these two layers through 
which the superficial vessels pass. The opening is closed by a 
266 prolongation of the superficial fascia about the saphenous vein 
something like the intercolumnar fascia about the spermatic 
cord at the external abdominal ring. The best guide to this 
opening is the main trunk of the internal saphenous vein. By 
dissecting along the main trunk of the vein, this fascia may be 
cleared and the edges in the margin exposed. Note carefully 
the peculiar crescentic outer border of the opening. The inner 
portion of the opening has no sharp margin. The iliac portion 
of the fascia lata is thick and strong, and forms the sharp cres- 
centic border seen at the upper and outer margin of the open- 
ing. The thinner and weaker pubic portion of the fascia lata 
forms the insignificant inner border and is prolonged inward 
beneath the superficial veins and beneath the femoral artery 
and vein. The fatty plug in the opening should be carefully 
dissected away to demonstrate the peculiar margins of the 
opening and the relative positions of the two parts of the fascia 
lata at the opening. The saphenous vein can then be followed 
through the opening to the femoral vein and the little arteries 
to the femoral artery. The femoral vein is internal to the ar- 
tery and both vessels are situated immediately beneath the iliac 
portion of the fascia lata, while the pubic portion of the fascia 
lata runs outward behind the vessels. 
Cutaneous nerves. The main trunks of the cutaneous 
nerves are more or less embedded in the deep fascia and should 
be secured if possible before that layer is reflected. The exter- 
nal cutaneous nerve enters the thigh just internal to the an- 
terior superior spine of the ilium and may be searched for just 
below that point. Branches of the middle and internal cuta- 
neous nerves will be found over the front and inner side extend- 
ing down to the knee. The internal saphenous nerve becomes 
cutaneous at the inner side of the knee near the incision through 
the skin. It should be secured here and later followed down 
the leg. 
Reflection of the fascia lata. Cut through the fascia lata 
along the line of the cutaneous incisions. The upper part of 
this cut will expose a muscle embedded in the upper third of 
the iliotibial band, the tensor fasciae latae. The fascia lata may 
also be divided along the line of ligament and the 
267 fascia turned from without inward. The deep fascia should be 
reflected with care, especially in the upper part of the limb, in 
order to avoid injury to the femoral vessels and to avoid dis- 
turbing the superficial muscles. 
Muscles, (a) The quadriceps extensor group forms the 
great mass of muscle on the outer and anterior aspect of the 
limb, (b) The adductor group forms the muscular mass on 
the upper and inner portion of the limb. The muscles of both 
groups should be cleaned on their superficial aspect first in 
order to demonstrate the entire superficial musculature of the 
thigh. Then the deeper dissection of each group can be under- 
taken. First clean the extensor muscles, including the sarto- 
rius muscle with this group. After cleaning this muscle, re- 
move the fascia from the extensor muscles on each side of the 
sartorius. The first of these will be the rectus, beneath which 
will be found the vastus externus (lateralis) and the vastus in- 
ternus (medialis), and still deeper the vastus intermedius. To 
make the fibers of the vasti muscles tense, flex the knee and ab- 
duct the thigh. The rectus arises by two heads from the ilium 
just above the hip joint, while the three vasti muscles arise from 
and surround practically the whole shaft of the femur. These 
four muscles are inserted by a common tendon into the tubercle 
of the tibia. The patella is merely a large sesamoid bone embedded 
in this common tendon. From the margins of the tendon fibrous 
expansions are given off which cover over the anterolateral parts 
of the capsule of the knee joint. The sartorius is in an interme- 
diate position between the extensor and adductor groups. It 
arises from the anterior superior spine of the ilium, crosses the 
thigh obliquely, and is inserted into the inner surface of the 
tibia just below the knee joint. The relation and attachment 
of the fascia lata to the patella, to the quadriceps tendon, and 
to the bony prominences about the knee joint should be noted. 
Next turn to the adductor group. The adductor longus is the 
most superficial and should be cleaned first, and then the gra- 
cilis, which lies along the inner border of the adductor longus. 
The adductor brevis and magnus will be found later beneath 
the longus. The adductor group arises from the body of the 
pubis and from the ischiopubic ramus back to the tuberosity of 
268 the ischium. The group is inserted -along the inner lip of the 
linea aspera of the femur down to the adductor tubercle on the 
inner condyle. The gracilis, however, is inserted on the inner 
aspect of the tibia just below the knee joint in close relation 
with the insertion of the sartorius. If this dissection has been 
properly performed, a good view of the whole anterior muscula- 
ture of the thigh will be secured. The muscles should only 
have been cleaned on their superficial aspect and not otherwise 
disturbed. 
Scarpa's (femoral) triangle. This is the most important 
topographical region of the front of the thigh. It is bounded 
by Poupart's ligament above and by the sartorius and adductus 
longus muscles below. Contents of triangle. From without in- 
ward the anterior crural (femoral) nerve; the femoral artery, 
the femoral vein. The superficial arteries in the skin mentioned 
above spring from the beginning of the femoral artery, and the 
superficial veins terminate in the femoral vein in this region. 
Numerous branches from the anterior crural nerve are found in 
the upper part of the triangle. 
Femoral sheath and femoral canal. The femoral vessels 
are enclosed in a layer of fascia known as the femoral sheath, 
but the nerve is not contained within this sheath. The femoral 
canal is a potential space inside the sheath along the inner as- 
pect of the vein and extends from Poupart's ligament down to 
the lower border of the saphenous opening. The sheath is 
formed by a prolongation of the fasciae on the deep aspect of 
the anterior and posterior abdominal walls, and its relation to 
the femoral canal and saphenous opening is of practical impor- 
tance in femoral hernia. The transversalis fascia on the deep 
aspect of the anterior abdominal wall is prolonged backward 
onto the posterior abdominal wall and is here known as the 
iliac fascia. This iliac fascia covers the iliopsoas and quadratus 
lumborum muscles, but passes behind the aorta, cava, and iliac 
vessels. The transversalis fascia on the anterior, and the iliac 
fascia on the posterior abdominal walls, are attached along the 
whole length of Poupart's ligament except at the point where 
the external iliac artery and vein pass beneath that ligament 
and become the femoral vessels. At this point a prolongation 
269 of the transversalis fascia passes beneath Poupart's ligament 
down into the thigh in front of the femoral vessels, while a sim- 
ilar prolongation from the iliac fascia passes down behind the 
vessels. These layers fuse together on each side and form the 
femoral sheath, in which lie the femoral artery and vein. The 
femoral canal is the potential space in this sheath along the in- 
ner side of the vein. In normal conditions there is practically 
no space here. The sheath, however, is somewhat funnel-shaped 
and fits the vessels loosely, especially along the inner side of 
the vein. This region, therefore, is a relatively weak point, 
which may be selected by a femoral hernia. Such a hernia is 
forced down within the sheath along the inner side of the vein 
and then a real femoral canal is formed. The femoral ring is 
simply the name given to the beginning of this canal and re- 
fers to the space bounded in front by the inner end of Pou- 
part's ligament, behind by the ramus of the pubic bone, inter- 
nally by the edge of Gimbernat's ligament, and externally by 
the femoral vein. The femoral canal never extends below the 
lower border of the saphenous opening because at this point 
the sheath fits the vessels closely and is prolonged down on and 
fused with their outer coats. Any hernia coming down the fem- 
oral canal would, therefore, be arrested at this level and de- 
flected inward through the saphenous opening, which repre- 
sents the line of least resistance. Before cleaning up the saphe- 
nous opening, the student should explore the region of the fem- 
oral ring and the femoral canal from above with the fingers 
or forceps. With a little blunt dissection he can establish a 
canal and demonstrate its relations to the vessels, to the sheath, 
and to the saphenous opening. The femoral sheath with the 
femoral vessels within it should be carefully studied in relation 
to the iliac part of the fascia lata anteriorly, the pubic portion 
of the fascia lata posteriorly, and to the saphenous opening 
along the inner side of the sheath. Do not confuse the iliac 
fascia of the posterior abdominal wall with the iliac portion of 
the fascia lata of the thigh. Study carefully attachments of all 
muscles and fasciae to Poupart's ligament. 
Scarpa's (femoral) triangle. Remove all parts of the fas- 
cia lata and the femoral sheath and clean up the femoral vessels 
270 and the anterior crural (femoral) nerve in this space. Note that 
the nerve is not contained within the femoral sheath. Numer- 
ous branches of the anterior crural nerve can be traced through 
the outer part of the triangle to the sartorius and the extensor 
group of muscles and to the skin. Look out for the internal or 
long saphenous nerve that passes in front of the femoral vessels 
and follows them downward in the thigh. Many of these 
branches can be worked out best by blunt dissection. 
Femoral artery and femoral vein. The femoral vein lies 
along the inner side of the artery and gets well behind it at the 
apex of the triangle. Preserve the attachments of the internal 
or long saphenous vein to the femoral vein and note how the 
superficial veins all drain together at this point. The smaller 
branches of the femoral vein may be disregarded in the dissec- 
tion, but the dissector should secure the profunda vein, which 
enters the femoral vein on its dorsal side about the middle of 
the triangle. The femoral artery gives off the small cutaneous 
branches seen over the inguinal region at the saphenous open- 
ing. The most important branch is the profunda artery which 
leaves the femoral about two inches below Poupart's ligament 
and passes into the depths of the thigh. From the profunda or 
from the femoral at this point arise the external and internal 
circumflex arteries. Follow the branches of the external cir- 
cumflex arteries outward beneath the sartorius muscle into the 
extensor group. The internal circumflex artery disappears in 
the floor of the triangle between the iliopsoas and pectineus 
muscles. 
Floor of Scarpa's triangles. This is formed externally by 
the iliopsoas muscle, which arises from the lumbar vertebrae 
and the ilium and passes to the lesser trochanter of the femur; 
internally by the pectineus muscle which extends from the hori- 
zontal ramus of the pubis to a point just below the lesser tro- 
chanter. By raising the femoral vessels and nerves these mus- 
cles can be cleaned. Take particular pains to make a thorough 
dissection of the triangle before doing anything to the struc- 
tures lower down, and do not cut the main branches of the 
nerves and vessels. 
Extensor group of muscles. The sartorius muscle, for pur- 
271 poses of dissection, may be considered with this group. After 
completing the dissection of Scarpa's triangle, the sartorius can 
be raised and pulled inward to get at the rectus and vasti mus- 
cles beneath it and to its outer side. Do not cut the sarto- 
rius. 
Adductor group. By drawing the sartorius outward, the ad- 
ductor longus and part of the adductor magnus will be exposed. 
Clean the adductor longus, gracilis, and the exposed part of the 
adductor magnus. Note particularly the strong aponeurotic 
layer of fascia extending from the adductor longus to the vastus 
internus in the lower third of the limb and do not cut this until 
later. Cut through the adductor longus muscle about four inches 
below its origin to expose the adductor brevis beneath it. The 
profunda artery will be seen passing beneath the adductor lon- 
gus and continuing down on the adductor magnus muscle. Be 
careful not to cut the superficial branches of the obturator nerve 
which lie beneath the adductor longus and on the adductor 
brevis. 
Obturator nerve. Cut through the pectineus muscle, pull 
the femoral vessels outward, and turn the cut pectineus up and 
down. The obturator externus muscle, with the obturator nerve 
near its upper border and the deeper part of the internal circum- 
flex artery between the obturator externus and the adductor 
brevis, will be exposed. Note the main trunk of the obturator 
nerve emerging from the pelvis through the obturator foramen 
and its division into a superficial and deep set of branches which 
are separated by the adductor brevis muscle. Branches from 
this nerve may be traced to the adductor group and the pec- 
tineus. 
Obturator externus. A part of this muscle will be seen 
under the pectineus. Note its origin from the outer surface of 
the ramus of the pubis, ischium, and obturator membrane, its re- 
lation to the muscles passing from the pelvis to the thigh, and 
its relation to the obturator nerve at the obturator notch. The 
insertion of this muscle into the great trochanter of the femur 
can be seen in the dissection of the back of the limb. Draw the 
femoral nerve and vessels inward, cut the iliopsoas muscles just 
below Poupart's ligament, and turn the lower part down to ex- 
272 pose the capsule of the hip joint lying beneath it. Endeavor to 
locate the bursa beneath this muscle. A portion of the rectus 
may be cut at this same point to facilitate the exposure of the 
capsule of the joint. The dissection of this joint will be com- 
pleted after the dorsal side of the limb has been finished, and 
the capsule must not be opened at present. 
Hunter's (femoral) canal. Hunter's canal is the region oc- 
cupied by the femoral vessels in the lower part of the thigh. It 
extends from the apex of Scarpa's triangle down to the point 
where the femoral vessels pass to the posterior aspect of the 
limb. Note how the sartorius and the strong fascial layer be- 
tween the vastus internus and adductor longus form the super- 
ficial boundary to this space. Cut through this fascia along the 
course of the vessels. The long saphenous nerve may lie super- 
ficial to this aponeurotic layer, or more probably will come, 
through it just above the knee. Be careful to preserve this 
nerve, as it extends down to the foot. Note the position of the 
vastus internus and adductor longus and magnus in the outer 
and posterior boundaries respectively of this space. The fem- 
oral artery lies in front of the femoral vein as they pass 
through the canal with the long or internal saphenous nerve 
more or less superficial to both vessels. Note the opening in 
the lower border of the adductor magnus where the femoral 
vessels pass to the posterior aspect of the limb and become the 
poplital vessels. The insertion of the tendons of the sartorius 
and gracilis should be traced to the inner side of the tibia below 
the knee joint. 
Profunda femoris artery. This vessel lies deep in the 
thigh and passes behind the adductor longus muscle which con- 
sequently separates it from the femoral artery. Below the ad- 
ductor longus the profunda lies on the adductor magnus close 
to the shaft of the femur. It gives off three perforating arteries 
which, with its terminal branch, perforate the adductor magnus 
close to the bone. These vessels will be exposed in the dissec- 
tion of the posterior aspect of the thigh. After Hunter's canal 
has been opened, the femoral vessels can be drawn outward and 
the lower portion of the profunda artery seen on the adductor 
magnus muscle. 
273 Knee joint. The anterior portion of the capsule of the 
knee joint is so thin and so closely adherent to the deep sur- 
face of the aponeurotic expansions from the patella and liga- 
mentum patellae mentioned above that it is impracticable to 
separate them. The joint must not be opened at this stage. It 
will be dissected when the dissections of the popliteal space and 
back of the leg are completed. 
274 DISSECTION OF THE LEG AND FOOT. ANTERIOR 
ASPECT. 
Tibia and fibula. These bones form the framework of the 
leg. The tibia articulates with the femur above at the knee 
joint; the tibia and fibula articulate with each other by the su- 
perior and inferior tibiofibular joints; and both bones together 
articulate below with the astragulus or talus at the ankle joint. 
The tibia is the most important of the two bones and carries 
practically all the weight of the body. It forms the knee joint 
with the femur and the greater part of the socket of the ankle 
joint. The fibula does not enter into the knee joint and forms 
the lateral side only of the socket for the ankle joint. It has no 
special strength, but acts as a lateral support to the tibia and 
provides an additional area for muscle attachments. The two 
bones are so firmly united that only a very slight degree of 
gliding is permitted between them, and they can be regarded 
as one piece of apparatus. 
The upper extremity of the tibia is thick and expanded to 
give a solid support to the condyles of the femur. On either 
side is an expanded tuberosity or condyle which carries the ar- 
ticular surface for the condyle of the femur. On the lateral as- 
pect of the lateral condyle, near the posterior surface, is an oval 
facet for articulation with the head of the fibula; on the medial 
aspect of the medial condyle is a groove for the insertion of the 
semi-membranous muscle. The medial articular surface is oval 
and larger than the lateral, which is more nearly circular. Be- 
tween the articular surfaces is a non-articular area divided in 
the center by an elevation with two tubercles on its summit. 
This is the spine of the tibia and the articular surfaces are pro- 
longed up on its sides. The tubercles and the rough areas in 
front and behind the spine give attachment to the cruciate liga- 
ments and to the interarticular cartilages of the knee joint. Be- 
low the tuberosities, on the anterior aspect of the upper end of 
the bone, is the large tubercle or tuberosity of the tibia into 
which the ligamentum patellae is inserted. 
The upper end of the fibula is slightly enlarged and forms 
275 the head. Its upper surface has an oval facet for articulation 
with the upper end of the tibia. Behind and external to the 
head is the styloid process, to which the fibular collateral liga- 
ment of the knee joint is attached. The head tapers to the shaft, 
forming the neck. The biceps femoris muscle is inserted into 
the head and styloid process of the fibula. 
The shafts of both bones are separated above, but lie close 
together below in the lower third of the leg. The shaft of the 
tibia is three sided, narrows as it descends, and in the lower 
part becomes expanded. It has three surfaces and three bor- 
ders. The anterior border forms the shin and runs in a sinuous 
course down the shaft from the tuberosity above to the malleo- 
lus below. The interosseous border looks towards the fibula 
and gives attachment to the interosseous membrane. The me- 
dial surface is convex and for the most part subcutaneous. The 
anterior or lateral surface is covered by the extensor muscles 
of the foot. The popliteal line runs downward and inward 
across the proximal third of the posterior surface. The popli- 
teus muscle arises from the shaft above this line; the flexor 
muscles of the foot cover the posterior surface below. The shaft 
of the fibula is slender and its surfaces and borders are very ir- 
regularly marked. An interosseous border is directed towards 
the tibia and gives attachment to the interosseous membrane. 
That part of the shaft anterior to the membrane is covered by 
the extensor muscles and that portion behind the membrane by 
the flexor muscles of the foot. The lateral area of the shaft, be- 
tween these two groups of muscles, is covered by the peronei 
muscles. 
The lower extremity of the tibia is expanded transversely 
and its medial surface is prolonged down into a thick process, 
the internal malleolus. It has a quadrilateral concave articu- 
lar surface below, which extends down on the inner aspect of 
the malleolus, and articulates with the astragulus. The lateral 
side of the lower extremity is rough and hollowed out to receive 
the lower end of the fibula. There is no articular surface be- 
tween the two bones at this spot. 
The lower extremity of the fibula is roughly triangular and 
is prolonged into the external malleolus, a larger and longer 
276 process than the internal. On its deep surface is an articular 
facet which completes the socket of the ankle joint. Above 
this articular surface is a rough area where the bone is in direct 
contact with the tibia; below the articular surface is a deep 
groove for the external or fibular collateral ligament of the 
ankle joint. 
Both condyles of the tibia, the greater part of the medial 
surface of the shaft, all of the anterior border, and the internal 
malleolus, are subcutaneous. The head of the fibula can be 
felt at the back and outer side of the knee, below the lateral 
condyle of the tibia. A triangular area just above the external 
malleolus and the malleolus itself can be palpated at the outer 
part of the ankle. 
Muscle attachments of tibia and fibula. These bones re- 
ceive the insertions of muscles which arise from the pelvis and 
femur, and give origin to muscles which are inserted into the 
bones of the foot. 
Muscles inserted into the tibia and fibula, anterior aspect. 
Tibia, tuberosity: quadriceps extensor (from ilium and femur) 
Shaft, below medial condyle: 
sartorius (from ilium) 
gracilis (from pubis) 
semitendinosus (from ischium) 
Fibula, head and styloid process: biceps (from ischium and 
femur) 
Muscles arising from tibia and fibula, anterior aspect. 
Tibia, shaft, lateral surface: tibialis anterior (to 1st cuneiform 
and 1st metatarsal) 
Tibia, lateral condyle 
Fibula, shaft, medial aspect 
extensor longus digitorum (to 
all phalanges of 2nd to 5th toes) 
Fibua, shaft, medial aspect, lower third: peroneus tertius (to 
5th metacarpal, base) 
Fibula, shaft, medial aspect: extensor longus hallttcis (to ter- 
minal phalanx of big toe) 
277 peroneus longus (to 1st cunei- 
form and 1st metatarsal) 
peroneus brevis (to 5th metatar- 
sal, base) 
Fibula, shaft, lateral aspect: 
Muscles inserted into tibia and fibula, posterior aspect. 
Tibia, medial condyle: semimembranosus (from ischium) 
shaft, popliteal surface : popliteus (from femur, lateral 
condyle) 
Muscles arising from tibia and fibula, posterior aspect. 
Tibia, shaft, popliteal line: soleus (to os calcis) 
" posterior surface: flexor longus digitorum (to 
terminal phalanges, 2nd to 
5th toes) 
" posterior surface 
Fibula, shaft, 
tibialis posterior (to all tar- 
sus except astragulus and 
to 2nd to 5th metatarsals, 
base.) 
Fibua, shaft, upper third: soleus (to os calcis) 
" lower two-thirds: flexor longus hallucis (to ter- 
minal phalanx of big toe) 
Skeleton of the foot. The bones of the foot form three 
groups, the tarsal bones or tarsus, the metatarsal bones or meta- 
tarsus, and the phalanges. The primary function of the foot is to 
support the weight of the body and to assist in progression. Its 
power of prehension is negligible. Therefore, the tarsus is the 
predominant part of the foot, forming fully half of it, and the 
phalanges are greatly reduced in size. 
Tarsus. This part of the foot is composed of seven bones 
arranged in two parallel rows, an outer and an inner. The outer 
row is in contact with the ground and is made up from behind 
forwards by the os calcis or calcaneus, the cuboid, and the fifth 
278 and fourth metatarsal bones. The inner row is composed of the 
astragalus or talus, the scaphoid or navicular, the three cunei- 
form, and the third, second and first metatarsal bones. This 
row is elevated above the ground and its hinder end, represented 
by the astragalus, is superimposed on the hinder end of the 
outer row, represented by the os calcis. The inner row touches 
ground at its anterior end only, represented by the head of the 
first metatarsal bone. This peculiar arrangement forms the 
anteroposterior arch of the foot. In addition to this arch there 
is a transverse arch, formed by the three cuneiform and the 
cuboid bones. The two arches are of the greatest importance 
in the anatomy and physiology of the foot, and any weakening 
of these parts causes great discomfort. 
Os calcis. This is the largest of the tarsal bones and has 
four surfaces and two extremities. The dorsal surface carries 
two articular areas separated by a deep groove. These sur- 
faces articulate with the astragalus, and the groove gives at- 
tachment to an interosseous ligament which holds the bones 
together. The inferior surface is rough and at its posterior end 
has the plantar tubercles for the attachment of the plantar 
muscles and ligaments. The lateral surface is flat with a short 
process near the Center which separates the tendons of the per- 
oneus longus and brevis as they pass over the lateral part of 
the foot. The medial surface has a shelf like process, the sus- 
tentaculum tali, under which runs the tendon of the flexor lon- 
gus hallucis. The posterior extremity has a tuberosity for the 
insertion of the tendo achillis, with a smooth area for a bursa 
above. The anterior extremity carries an articular surface for 
the cuboid. 
The cuboid lies between the os calcis behind and the fifth 
and fourth metatarsals in front, and has articular areas for 
these bones on its anterior and posterior surfaces. Medially it 
articulates with the lateral cuneiform, and some times with the 
navicular. On its plantar surface is a ridge with a cartilagi- 
nous area at the outer end. The ridge gives attachment to some 
of the plantar muscles and ligaments. The tendon of the pero- 
neus longus muscle turns around the outer end of the ridge and 
runs across the foot to its inner side. 
279 The astragulus lies on the upper part of the os calcis and 
supports the articular surface for the ankle joint. The bone 
has a body and a head directed forward from the body. The upper 
surface of the body is occupied by the convex articular area for the 
ankle joint. It forms a sort of trochlear surface and the cartilage 
is prolonged down on both sides to articulate with the medial sides 
of the malleoli. The periphery of the articular surface is 
grooved for the attachment of the capsule. On the plantar sur- 
face there are two articular areas separated by a groove. These 
articulate with the os calois, and the ligament which holds the 
bones together is attached to the groove. This arrangement 
allows the astragulus to pivot on the os calcis. The head of the 
bone is separated from the body by a slight neck. It is rounded 
and covered with cartilage. The articular surface is carried 
over onto the plantar surface where it is continuous with the 
anterior facet for the os calcis. The head articulates with the 
navicular bone. This joint is closed below and internally by 
the plantar calcaneonavicular ligament. 
The navicular is oval in shape and is compressed from be- 
fore backward. Its posterior surface is concave to articulate 
with the head of the astragulus; its anterior surface is slightly 
convex and is divided into three parts for articulation with the 
three cuneiform bones. The inner margin of the bone is pro- 
longed downward and inward to form the tuberosity, which is 
prominent at the inner side of the foot, and gives partial inser- 
tion to the tibialis posterior muscle. 
The cuneiform bones are wedge shaped and are so placed 
that the sharp border of the first or internal cuneiform and the 
broad-surfaces of the second and third, the middle and external 
cuneiforms, are directed dorsally. This arrangement contrib- 
utes to the formation of the transverse arch. The cuneiform 
bones articulate behind with the navicular, in front with the 
inner three metatarsal bones. The second cuneiform is shorter 
than the others, and the base of the second metatarsal bone sets 
in between them in a sort of socket. The bones articulate with 
each other and the third with the cuboid. 
The metatarsal bones are five in number and are practically 
the same as those in the hand. Their expanded bases articulate 
280 with the cuboid and cuneiform bones and with each other. The 
line of the tarsometatarsal joint is slightly convex and runs ob- 
liquely outward, but is interrupted at the point where the base 
of the second metatarsal is set back between the three cunei- 
form bones. The shafts are curved with a slight convexity on 
their dorsal surfaces. The heads are rounded, the articular sur- 
face being carried well over onto the plantar surface. The first 
metatarsal is short and stout; the second is the longest. The 
fifth has a prominent process at the base for the insertion of the 
peroneus brevis muscle. 
I'he phalanges are so similar to those in the hand that a de- 
scription is unnecessary. They are much smaller, however, and 
the terminal phalanges are mere nodules of bone. 
The foot as a whole. The foot is narrow behind at the heel, 
but broadens out like a fan towards the toes. The posterior part 
of the longitudinal arch is formed behind by the os calcis and the 
astragulus. This part is short and is composed of the two 
strongest bones, with only one joint between them. This plan 
enables the muscles to act powerfully and promptly on the foot 
when the heel is raised. The anterior part of the arch is longer 
and wider and is interrupted by several joints. This arrange- 
ment provides a broad surface to come in contact with the 
ground at the end of a step, and the numerous joints form a yield- 
ing apparatus which is admirably adapted to absorb shock and 
jar. The outer border of the foot from the heel to the base of 
the fifth metatarsal bone and the heads of all the metatarsal 
bones are in contact with the ground in a well arched foot. This 
can be seen by observing the print of a wet foot. As the arches 
■weaken, more and more of the inner side of the foot comes in 
contact with the ground. 
Muscle attachments to foot. The long flexor and extensor 
muscles of the ankle arise from the tibia and fibula and are in- 
serted into the tarsal bones (except the astragulus, which has 
no muscle attachments) and into the bases of the metatarsal 
bones. The long flexors and extensors of the toes arise from 
the bones of the leg and are inserted into the base of the term- 
inal phalanges of the toes (flexors), and to all three phalanges (ex- 
tensors). The short flexors and extensors, the adductors and 
281 abductors of the toes arise from the tarsal and metatarsal bones 
and are inserted into the bases of the proximal and middle pha- 
langes of the toes. 
Muscles inserted into the foot, dorsal aspect. 
Tarsus 
gastrocnemius 
(from femur) 
plantaris (from fe- 
mur) 
soleus (from tibia 
and fibula) 
Os calcis, posterior surface, tendo achillis 
Metatarsus 
5th metatarsal, base: peroneus brevis (from fibula) 
" peroneus tertius (from tibia) 
Phalanges 
Big toe, 1st phalanx, base: extensor brevis digitorum (from os 
calcis, dorsal surface) 
2nd, 3rd, and 4th toes, 1st phalanges, base: dorsal interossei 
(from 1st to 5th metatarsals, shafts) 
2nd, 3rd, 4th, and 5th toes, 1st phalanges, base: lumbricals 
(from flexor longus digitorum) 
Big toe, terminal phalanx: extensor longus hallucis (from fib- 
ula) 
2nd, 3rd, and 4th toes, all phalanges: extensor brevis digitorum 
(from os calcis dorsal surface) 
2nd to 5th toes, all phalanges: extensor longus digitorum (from 
tibia and fibula) 
282 Muscles arising from the foot, dorsal aspect 
Tarsus 
Os calcis, dorsal surface: extensor brevis digitorum 
(to big toe, 1st phalanx, base) 
(to 2nd, 3rd, and 4th toes, all phalanges) 
Metatarsus 
1st to 5th metatarsals, shafts: dorsal interossei (to 2nd, 3rd, 
and 4th toes, proximal phalanges, base.) 
Muscles inserted in foot, plantar aspect. 
Tarsus 
Tarsus all bones (except astragulus) : tibialis posterior (from 
tibia) 
1st cuneiform: tibialis anterior (from tibia) 
1st cuneiform: peroneus longus ((from fibula) 
Metatarsals 
2nd to 5th metatarsals, base: tibialis posterior (from tibia) 
1st metatarsal, base: tibialis anterior (from tibia) 
1st metatarsal, base: peroneus longus (from fibula) 
5th metatarsal, base: peroneus brevis (from fibula) 
Phalanges 
Big toe, 1st phalanx, base: abductor hallucis (from os calcis, 
plantar tubercle) 
Big toe, 1st phalanx, base: flexor brevis hallucis (from cuboid 
and cuneiforms) 
Big toe, 1st phalanx, base: adductor hallucis (from 3rd, 4th, 
and 5th metatarsals and cuneiforms) 
3rd, 4th, and 5th toes, 1st phalanx, base: plantar interossei 
(from 3rd, 4th, and 5th metatarsals) 
283 Sth toe, 1st phalanx, base: abductor digiti quinti (from os cal- 
cis, plantar tubercles) 
5th toe, 1st phalanx, base: flexor brevis digiti quinti (from 5th 
metatarsal) 
Big toe, terminal phalanx: flexor longus hallucis (from fibula) 
2nd to 5th toes, middle phalanges: flexor brevis digitorum 
(from os calcis, plantar tubercles) 
2nd to 5th toes, terminal phalanges: flexor longus digitorum 
(from tibia) 
Muscles arising from the foot, plantar aspect. 
Tarsus 
Os calcis, plantar tubercles and plantar surface: (abductor 
hallucis (to big toe, 1st phalanx, base) 
flexor brevis digitorum (to 2nd 
to 5th toes, middle phalanges) 
abductor digiti quinti (to 5th toe, 
1st phalanx, base) 
quadratus plantai (to tendon flex- 
or longus digitorum) 
Os calcis, plantar tubercles 
and plantar surface: 
Cuboid 
2nd and 3rd cuneiform 
flexor brevis hallucis (to big toe, 1st 
phalanx, base) 
3rd cuneiform : adductor hallucis (to big toe, 1st phalanx, base) 
Metatarsus 
3rd, 4th, and 5th metatarsals, shafts: plantar interossei (to 
3rd, 4th, and 5th toes, 1st phalanges, base) 
3rd, 4th, and 5th metatarsals shafts: adductor hallucis (to big 
toe, proximal phalanx, base) 
5th metatarsal, base: flexor brevis digiti quinti (to 5th toe, 1st 
phalanx, base) 
284 Surface anatomy. Identify and palpate the following bony 
prominences: the tubercle of the tibia; the internal (subcutane- 
ous) surface and anterior border of the shaft of the tibia; the 
internal malleolus; the head of fibula; the external malleolus. 
Compare the position of both malleoli and their relation to the 
ankle joint. Compare the skeleton of the foot with the undis- 
sected foot to note the position of the tarsus, metatarsus, and 
phalanges. 
Incisions. 1. From the tubercle of the tibia along the an- 
terior border of the tibia just anterior to the internal malleolus 
and along the inner margin of the foot to the base of the first or 
great toe. 2. From the base of the great toe transversely out- 
ward to the base of the little or 5th toe. Turn the skin flap from 
within outward. Do not reflect the skin over the internal sur- 
face of the tibia, as only the area between the anterior border of 
the tibia and the outer border of the fibula will be exposed in 
this dissection. 
Superficial fascia. Dissect the superficial veins from the su- 
perficial fascia. These form a venous arch over the base of the 
toes. Small branches enter the lower convex border of this arch 
from the sides of the toes. From the inner end of the arch the 
blood is carried up the limb by the internal or long saphenous 
vein, which passes upward just anterior to the internal malleo- 
lus, and disappears from this dissection a short distance above 
the internal malleolus. From the outer end of the venous arch 
the blood is carried by the external or short saphenous vein be- 
hind the external malleolus to the back of the limb. Cutaneous 
nerves. Branches of the long or internal saphenous nerve will 
be found with the internal saphenous vein along the inner side 
of the leg and foot. A few branches from the external or short 
saphenous nerve may possibly be seen with the external saphe- 
nous vein along the outer side of the foot, but the dissector need 
not pay particular attention to them. The musculocutaneous 
nerve is the chief cutaneous nerve over the lower third of the leg 
and dorsum of the foot, and pierces the deep fascia at about the 
junction of the lower and middle third of the limb. Its branches 
are distributed to the foot more or less superficial to the cutane- 
ous veins. 
285 Deep fascia. After securing the superficial vessels and 
nerves, the superficial fascia may be removed to expose the deep 
fascia. Note the aponeurotic character of the deep fascia in the 
upper third of the limb where certain muscles take origin from 
its deep surface. Observe also the thickening in the form of a trans- 
verse and oblique band extending between the malleoli which forms 
the anterior annular ligament. In removing the deep fascia 
leave the annular ligament in front of the ankle in place until 
the muscles have thoroughly been cleaned. The dissector will 
find difficulty in removing the deep fascia from the muscles in 
the upper third of the limb, as the fibers arise directly from its 
deep surface, and the dissection will necessarily be somewhat 
ragged. 
Extensor group of muscles. Immediately beneath the deep 
fascia, lying along the outer surface of the tibia, is the tibialis 
anticus (anterior) muscle. Just external to it is the extensor 
longus digitorum, and beneath and partly between the two the 
extensor longus (proprius) hallucis. This group arises from both 
the tibia and fibula, the interosseous membrane, and from the 
deep fascia in the upper part of the limb. The tibialis anterior 
is inserted into the internal cuneiform bone and first metatarsal 
on the inside of the foot. The extensor longus digitorum and 
the extensor longus hallucis are inserted into the dorsal surface 
of the phalanges of the toes. Immediately beneath the tendons 
of the long extensor muscles of the toes will be found the ex- 
tensor brevis digitorum, a small flat muscle which arises from the 
superior aspect of the os calcis, sends one tendon to the base of 
the first metatarsal bone and three tendons to the 2nd, 3rd, and 
4th toes. The insertion of the extensor tendons to the phalanges 
is practically the same as in the forearm and hand. 
Peroneal muscles. The peroneus longus and peroneus brev- 
is will come partially into this dissection. They arise from the 
outer surface of the shaft of the fibula. The tendons of these 
two muscles pass behind the external malleolus and can be seen 
better from the dissection of the back of the leg and sole of the 
foot. The tendon of the peroneus brevis may be traced to the 
base of the. fifth metatarsal bone of the dorsum of the foot. The 
peroneus tertius is so closely blended with the fibers of the ex- 
286 tensor longus digitorum on the lower third of the fibula that 
they cannot he separated. Its tendon can be traced to the base 
of the fifth metatarsal bone in front of the insertion of the pero- 
neus brevis. In cleaning the peroneus longus and brevis, look 
for the main trunk of the musculocutaneous nerve which is em- 
bedded between these two muscles and supplies them. By sep- 
arating the fibers of the two muscles this nerve may be traced 
as high as the neck of the fibula where it will be met again in the 
dissection of the back of the limb. 
Anterior tibial artery and nerve. The anterior tibial artery, 
the main artery of the leg, may he exposed by drawing the tibia- 
lis anticus inward and the long extensor muscles of the toes 
outward. The muscle bellies and their origin from the interos- 
seous membrane may be partly divided to facilitate this separa- 
tion. The anterior tibial artery is given off from the popliteal 
artery at the back of the knee and passes forward to the anterior 
aspect of the limb between the tibia and fibula over the upper 
border of the interosseous membrane. The anterior tibial and 
musculocutaneous nerves are derived from the sacral plexus, 
and are branches of the external popliteal nerve. This nerve 
lies in the popliteal space on the back of the limb, winds around 
the neck of the fibula to reach the anterior aspect of the leg and 
divides under cover of the upper end of the peroneal muscles into 
the anterior tibial and musculocutaneous nerves. The anterior 
tibial nerve is to be associated with the extensor group of mus- 
cles, the musculocutaneous with the peroneal group of muscles. 
(Compare here carefully old and new terminology in regard to 
the sacral plexus and its branches). Follow the anterior tibial 
vessels and nerve on the interosseous membrane beneath the 
extensor muscles. The vessel is prolonged on the dorsum of 
the foot to the point between the first and second toes as the 
dorsal artery of the foot from which small branches run trans- 
versely outward over the tarsus and metatarsus. The termina- 
tion of the dorsal artery of the foot will be found with the ar- 
teries on the plantar side of the foot. The anterior tibial nerve 
follows closely the course of the artery, supplies the extensor 
muscles and terminates in the skin over the dorsum of the first 
and second toes. The anterior annular ligament may be divid- 
287 ed in order to facilitate the dissection of these structures on the 
dorsal side of the foot. Pay particular attention to the tendons 
and their sheaths with reference to the ankle joint. The dis- 
section of the anterior tibial vessels and nerves can then be 
completed and the interosseous muscles cleaned. 
Interosseous muscles. The dorsal interosseous muscles, four 
in number, should be noted between the metatarsal bones be- 
neath the long and short extensor tendons. They arise from 
the opposing surfaces of the metatarsals and insert on the dor- 
sal side of the first phalanges of the 2nd, 3rd, and 4th toes. The 
first two are attached to either side of the 2nd; the third and 
fourth to the lateral side of the 3rd and 4th toes. These can be 
cleaned partially in this dissection by separating the long and 
short extensor tendons. Do not cut any of the long muscles, 
as the deeper parts can be reached by separating the more super- 
ficial structures. In the dissection on the dorsum of the foot 
the venous arch can be partially removed provided enough is 
left to hold in place the origin of the two saphenous veins which 
will be needed in the dissection of the back of the leg. 
288 DISSECTION OF THE GLUTEAL REGION 
Superficial anatomy. Identify and palpate the following 
bony landmarks : the crest of the ilium and the posterior supe- 
rior and posterior inferior spines; the lower end of the sacrum 
and coccyx; the tuberosity of the ischium; the great trochanter 
of the femur and its relation to the tuberosity of the ischium 
in inward and outward rotation of the hip. Note also the lower 
border of the gluteus maximus muscle. Before making any in- 
cisions, the student should study carefully the dorsal aspect of 
the whole pelvis, paying special attention to the sacrosciatic 
notch, foramina and ligaments. 
Incisions. As the skin has already been cut along the crest 
of the ilium, it will only be necessary to turn the skin over the 
gluteal region downward and inward as far as the lower border 
of the gluteus maximus muscle. 
Superficial fascia. The fascia is usually very thick over 
this region and contains much fat. The cutaneous vessels are 
small and may be disregarded. The cutaneous nerves are also 
small and difficult to find in the thick fascia. They are: (1) 
branches from the posterior divisions of the last thoracic and 
the lumbar nerves which pass downward over the crest of the 
ilium ; (2) branches from the posterior divisions of the sacral 
nerves near the midline; (3) branches from the sacral plexus 
(anterior divisions) along the lower border of the gluteus max- 
imus muscle. 
Deep fascia. This is part of the fascia lata and over the 
gluteus maximus muscle is finite thin. Above and anterior to 
this muscle, where it covers a part of the gluteus meclius and 
is attached to the crest of the ilium, it is thick and aponeurotic. 
The fascia practically splits and encloses the gluteus maximus 
between its layers and also sends numerous septa in among the 
coarse and loose bundles of the fibers of the muscle. As this 
muscle is the most difficult of all to clean, the dissector can re- 
move both layers of fascia together from the muscle and can 
disregard the cutaneous structures. Curved scissors will be 
found useful in removing the fascia from among the loose mus- 
cle bundles. Turn the fascial layers together in the same direc- 
289 tion as the skin flap. Avoid cutting the small sciatic nerve from 
the sacral plexus which comes up into the fascia at about the 
middle of the lower border of the gluteus maximus. This nerve 
will be studied in the dissection of the thigh. 
Superficial layer of muscles. This layer is composed of 
the gluteus maximus alone. Origin from the ilium, sacrum and 
sacrosciatic ligament. Insertion into the great trochanter of 
the femur and below that point into the fascia lata. Note the 
direction of the fibers and the coarse texture of the muscle. 
There are bursae beneath its insertion and also between it and 
the tuberosity of the ischium which sometimes can be demon- 
strated when the muscle is reflected. A portion of the gluteus 
medius will be exposed at the upper border of the gluteus max- 
imus and the hamstring muscles of the thigh will be seen 
emerging from beneath its lower border. Divide the muscle at 
about its middle and turn the flaps upward and downward. Ob- 
serve the branches from the gluteal and sciatic arteries and 
from the inferior gluteal nerve of the sacral plexus entering the 
deep surface of the muscle. It will probably be necessary to 
cut most of these structures in order to reflect the muscle far 
enough. 
Intermediate layer of muscles. In dissecting this and also 
the third or deep layer, the student should note especially the 
relations of the vessels and nerves to the pyriformis muscle, the 
structures found in each of the sacrosciatic foramina with their 
connections inside and outside of the pelvis, and the relations 
of the muscles and great sciatic nerve to the capsule of the hip 
joint. The vessels are chiefly branches of the internal iliac 
vessels and the nerves are branches from the sacral plexus. 
They arise, therefore, inside the pelvis, and utilize the sacrosci- 
atic foramina to reach the gluteal region. 
1. Gluteus medius; origin from the ilium; insertion into 
outer part of the great trochanter of the femur. 
2. Pyriformis. This muscle lies close to the lower border 
of the gluteus medius and arises from the anterior surface of 
the middle sacral vertebrae. It leaves the pelvis through the 
great sacrosciatic foramen and is inserted into the top of the 
great trochanter of the femur. 
290 3. Obturator internus; arises from the inner surface of 
the obturator membrane and wall of the true pelvis and passes 
through the lesser sacrosciatic foramen to the top of the great 
trochanter. 
4. and 5. Superior and inferior gemellus. These two small 
muscles arise from the margin of the lesser sacrosciatic fora- 
men just above and below the tendon of the obturator internus. 
They fuse with that tendon and form practically a part of the 
obturator internus muscle. 
6. Quadratus femoris. This muscle lies just below the 
inferior gemellus, arises from the tuberosity of the ischium and 
is inserted into the dorsal side of the great trochanter. 
7. Flexor muscles of leg (hamstring muscles). The ori- 
gin of this group from the tuberosity of the ischium will be 
seen close to- that of the quadratus femoris. These muscles will 
be dissected with the dorsal region of the thigh. 
Deep layer of muscles. 1. Gluteus minimus. This mus- 
cle lies underneath the gluteus medius, arises from the ilium, 
and is inserted into the anterior part of the great trochanter. 
2. Obturator externus. This muscle lies under the obturator 
internus and quadratus femoris. Its origin from the external 
surface of the obturator membrane and margins of the obtura- 
tor foramen has been seen in the deep dissection of Scarpa's tri- 
angle. Its tendon passes horizontally outward and backward 
beneath the neck of the femur and then winds around the dor- 
sal surface of the neck to terminate in the digital fossa on the 
medial size of the great trochanter. 
Vessels. 1. The gluteal artery from the internal iliac, 
leaves the pelvis through the great sacrosciatic foramen, emerges 
above the pyriformis muscle, sends superficial branches into 
the deep surface of the gluteus maximus and its deep or main 
branches lie between the gluteus medius and minimus in the 
plane of the deep muscle layer. 2. The sciatic artery from the 
internal iliac leaves the pelvis through the great sacrosciatic 
foramen, emerges at the lower border of the pyriformis muscle 
and passes downward beneath the gluteus maximus to supply 
the muscles on the dorsum of the hip. It anastomoses with the 
termination of the external and internal circumflex branches 
291 from the femoral artery and also with the first perforating 
branch from the deep femoral artery at the lower border of the 
quadratus femoris muscle. These anastomoses can only be 
seen in an especially good injection. 3. The internal pudic 
artery leaves the pelvis through the great sacrosciatic foramen 
and curves inward on the dorsal surface of the lesser sciatic 
ligament and the spine of the ischium, where it can be felt by 
the fingers. It passes out of this region through the lesser sac- 
rosciatic foramen to reach the ischiorectal fossa and the perine- 
um. The veins correspond to the above arteries and are tribu- 
taries of the internal iliac or femoral veins. They may be re- 
moved as the arteries are being cleaned. 
Nerves. These are branches of the sacral plexus, arise in- 
side the pelvis and pass out through the great sacrosciatic fora- 
men in close relation to the arteries and to the pyriformis mus- 
cle. The origin and formation of the sacral plexus has been 
seen already in the median section of the pelvis, but should be 
studied at this stage. The sacral plexus consists of two main 
parts, an upper or sacral portion and a lower or pudendal por- 
tion which is much the smaller of the two. The following 
nerves arise from the sacral portion of the plexus. 
1. Superior gluteal nerve. This appears with the gluteal 
artery at the upper border of the pyriformis muscle, and passes 
between the gluteus medius and minimus to supply them. 
2. Inferior gluteal nerve. This appears at the lower bor- 
der of the pyriformis muscle and enters the deep surface of the 
gluteus maximus to supply it. It will have to be cut as that 
muscle is reflected. 
3. Great sciatic nerve. This appears at the lower border 
of the pyriformis muscle, passes downward under cover of the 
gluteus maximus muscle and lies on the obturator internus, 
gemelli and the quadratus femoris muscles. It lies between the 
tuberosity of the ischium and the great trochanter of the femur 
behind the hip joint. It then disappears from this dissection by 
passing under the hamstring muscles to enter the thigh. This 
nerve really consists of two nerves in a common sheath, the 
internal and external popliteal nerves, which may in some cases 
be separate at this level. A portion of the pyriformis muscle 
292 sometimes passes between the two divisions of this nerve. The 
branches to the obturator internus, gemelli, and the quadratus 
femoris arise from the internal popliteal. The following nerves 
are from the pudendal portion of the plexus: 
1. The small sciatic nerve. This is the cutaneous nerve 
of the back of the thigh and lies in the fascia at the lower bor- 
der of the gluteus maximus muscle as mentioned above. 
2. The internal pudic nerve. This nerve leaves the pel- 
vis by the great sacrosciatic foramen at the lower border of the 
pyriformis muscle, and follows the course of the internal pudic 
artery. It can be dissected with that vessel as far as the lesser 
sacrosciatic foramen. It has the same distribution as the artery. 
The internal pudic vessels and nerves should here be connected 
with the previous dissection of the ischiorectal fossa. 
The deep layer of muscles and the dorsal aspect of the cap- 
sule of the hip joint must now be dissected. To expose the 
gluteus minimus, cut the gluteus medius near its origin from 
the iliac crest and turn it down. A fairly thick layer of fascia 
will be seen beneath it which covers the gluteus minimus. In 
this fascia will be found the main branches of the gluteal artery 
and superior gluteal nerve. Secure these structures before 
cleaning the muscle. A branch of the nerve may be traced to 
the tensor fasciae latae. To expose the obturator externus, the 
quadratus femoris and obturator internus and gemelli must be 
separated. These muscles can then be divided near their cen- 
ters and turned in and out to display more fully the obturator 
externus and the dorsal side of the hip joint. The upper border 
of the adductor magnus is close to the lower border of the quad- 
ratus femoris and should not be disturbed. In a well injected 
subject the terminal branches of the internal circumflex artery 
may be found at the lower border of and beneath the quadratus 
femoris muscle. 
The hip joint. This is a ball and socket joint between the 
head of the femur and the acetabulum of the innominate bone. 
The adaptation of its joint surfaces is very perfect and adds 
greatly to the strength of the joint. The capsule is reinforced 
by strong ligamentous bands and the joint is deeply placed and 
surrounded by powerful muscles. It is consequently a very 
293 strong joint and well adapted to support the trunk on the thigh 
bones. 
Ligaments. The notch in the acetabulum is filled by the 
transverse ligament and the edges of the fossa are deepened by 
the cotyloid ligament (glenoid labrum). This is a circular band 
of fibrocartilage which is attached to the margins of the acetabu- 
lum. and is about a centimeter deep. The capsule is attached 
to the outer surface of the acetabulum so as to inclose all the 
cotyloid ligament and is prolonged up to the base of the anterior 
inferior spine of the ilium. On the femur it is attached in front 
to the great trochanter and to the intertrochanteric line. It 
passes about a finger's breadth above the lesser trochanter to 
the back of the neck and lies at about the middle of the neck. 
All the anterior part of the neck and about half of the posterior 
part are inside the capsule. The most important band of the 
capsule is the iliofemoral ligament which extends from the an- 
terior inferior spine of the ilium above to the intertrochanteric 
line below and covers the front of the joint. Occasionally there 
is a gap in the ligament ,giving it the form of the letter Y upside 
down. The pubofemoral is a weak collection of fibers on the 
medial aspect of the capsule. Behind is the ischiofemoral liga- 
ment whose fibers run more or less horizontally. The ligamen- 
tum teres is inside the capsule. It is a flat band attached to the 
cotyloid notch of the acetabulum. It is folded up against the 
fatty pad in the depths of the socket and is attached to the dim- 
ple on the head of the femur. It is surrounded by the synovial 
membrane. There is usually a large bursa under the iliopsoas 
muscle on the anterior aspect of the capsule. 
Muscles. The joint is covered in front by the iliopsoas and 
by the pectineus. The deep head of the rectus is on the lateral 
aspect of the capsule. Below is the obturator internus, and be- 
hind the gluteus minimus, pyriformis, obturator internus and 
gemelli, quadratus femoris, and the obturator externus. The 
gluteus medius and maximus lie over all these muscles. 
Movements. The hip is capable of all motions possible in a 
ball and socket joint. The movements are flexion and exten- 
sion, adduction and abduction, rotation and circumduction. Ow- 
ing to the strength of the joint apparatus, these movements arc 
294 not so free as those in the shoulder, but the joint has greater 
strength and stability. 
Dissection of hip joint. The dorsal side of the capsule of 
the hip joint should next be exposed. This can be done by cut- 
ting the gemelli, tendon of the obturator interims, pyriformis, 
obturator externus, and, if necessary, part of the gluteus mini- 
mus. Cut the muscles at the middle and turn the outer half of 
each in and out. so as not to injure the capsule immediately be- 
neath them. The tendon of the obturator externus lies imme- 
diately in contact with the capsule and should be dissected away 
with great care. The vessels and nerves of this region can be 
drawn to one side as the muscles are divided and should not be 
cut. After the posterior surface of the capsule has been 
cleaned, turn the limb over and finish the dissection from the 
front. Remove the iliopsoas and both heads of the rectus. 
Scrape the bones at the periphery of the capsule in order to get 
a good view of its extent and attachments. The capsule can be 
opened from the front and the head of the femur displaced. Be 
sure to leave part of the posterior side of the capsule in place to 
hold the bones together. Study carefully the interior of the 
joint, especially the attachment of the capsule to the femur and 
acetabulum, the ligamentum teres and the socket of the joint. 
295 DISSECTION OF THE DORSAL ASPECT OF THE 
THIGH AND POPLITEAL SPACE. 
Superficial anatomy. Bony landmarks. Identify and pal- 
pate the following: the condyles, epicondyles and adductor tu- 
bercle of the femur; the head of the fibula; the condyles of the 
tibia. Compare their positions with the knee flexed and extend- 
ed. Note the insertion of the hamstring muscles, the position of 
the two heads of the gastrocnemius muscle, and the relations of 
these muscles to the popliteal space. 
Incisions. Make an incision transversely across the back of 
the leg a palm's breadth below a line drawn through the con- 
dyles of the femur. This should be approximately on a level with 
the tubercle of the tibia on the front of the limb. In making this 
cut be careful to avoid injuring the superficial nerves and veins 
over the popliteal space. Turn the skin flap from without in- 
wards. 
Superficial fascia. Cutaneous nerves. The chief cutaneous 
nerve is the small sciatic nerve which becomes cutaneous at the 
middle of the lower border of the gluteus maximus muscle and 
passes down the limb in the midline, supplying the skin as far 
as the upper part of the calf of the leg. A few branches from the 
internal and external cutaneous nerves of the front of the thigh 
supply limited areas of skin along the outer and inner parts of 
this region, but they may be disregarded in the dissection. 
Cutaneous veins. A few branches will probably be seen along 
the inner side of the thigh passing to join the internal saphe- 
nous vein. These may be disregarded. Over the popliteal space 
in the midline the short or external saphnous vein will be found 
in the superficial fascia. This vessel should be secured and 
traced through the deep fascia of the popliteal space into the 
popliteal vein. Note the internal or long saphenous vein along 
the inner side of the knee. This vein will be traced further in 
the dissection of the back of the leg. 
Deep fascia. This layer is comparatively thin as compared 
with the same layer on the front and outer part of the thigh. It 
can be removed directly from the surface of the underlying mus- 
296 cles. The dissector should leave a small bit of the iliotibial 
band intact and can begin to remove the fascia from the ham- 
string muscles just posterior to the tensor faciae latae. 
Superficial muscles. These muscles should be cleaned at 
first on their superficial aspect only and disturbed as little as 
possible. 1. Flexor muscles of the leg or the hamstring mus- 
cles. These are three in number and arise more or less together 
from the tuberosity of the ischium. The biceps lies along the 
outer side of the limb and has an additional deep head arising 
from the lower part of the linea aspera of the femur. This mus- 
cle is inserted into the head of the fibula and forms the upper 
and outer boundary of the popliteal space. The semitendinosus 
lies superficial to the semimembranosus along the inner side of 
the thigh. The former is inserted into the tibia in close relation 
to the insertion of the gracilis and sartorius. The latter is in- 
serted into the inner condyle of the tibia and is closely associat- 
ed with the capsule of the knee joint. 2. Gastrocnemius. This 
is the superficial muscle of the leg and will be fully displayed in 
the dissection of that region. It arises by two heads from the 
condyles of the femur and is inserted by the tendo achillis into 
the os calcis. Only the heads of origin will appear in this dis- 
section. Note how they form the lower boundaries of the pop- 
liteal space. 
Popliteal space. Note the boundaries by the muscles men- 
tioned above. Contents. Popliteal nerves. The internal pop- 
liteal (tibial) nerve lies in the midline of the popliteal space just 
beneath the deep fascia. It emerges from under cover of the 
hamstring muscles above and disappears under the heads of the 
gastrocnemius below. Its cutaneous branch will probably be 
found later, but may appear in the fascia near the midline at the 
lower part of the dissection. The external popliteal (peroneal) 
nerve lies along the edge of the tendon of the biceps muscle at 
the outer border of the popliteal space. It can often be felt here 
beneath the skin. The nerve leaves the dissection by passing 
under the biceps tendon to wind around the neck of the fibula 
and reach the front of the leg. Here it divides into the anterior 
tibial and musculocutaneous nerves. The cutaneous branch of 
297 the external popliteal nerve will probably enter the fascia over 
the outer head of the gastrocnemius muscle. 
Popliteal artery and vein. The vein at this stage of the dis- 
section is superficial to the artery and receives the external 
saphenous vein about the middle of the space. The vessels lie 
about in the midline, running somewhat obliquely downward 
from beneath the hamstring muscles and pass under the gastroc- 
nemius muscle below. The internal popliteal nerve is super- 
ficial to the vessels and crosses them from without inward. Nu- 
merous small superficial branches arise from the vessels and go 
to the skin and muscles. 
Deep muscles of the thigh and popliteal space. 1. Deep 
head of biceps. 2. Adductor magnus (posterior surface). 3. 
Popliteus. To expose the deep layers of the thigh cut the super- 
ficial head of the biceps in the middle, turn the ends up and 
down and pull the two inner hamstring muscles to the inner 
side of the limb. Note the position of the deep head of the bi- 
ceps along the outer side of the thigh. The great sciatic nerve 
will be exposed and can be cleaned in its whole extent. It di- 
vides into its two branches somewhere along the back of the 
thigh. After cleaning the nerve, draw it over to the inner side 
of the dissection and clean the posterior aspect of the adductor 
magnus. Observe how this muscle is hung like a large curtain 
along the inner side of the thigh and separates the flexor mus- 
cles behind from the adductors and great vessels on the antero- 
medial aspect of the thigh. Note the difference in the direction 
of the fibers of the adductor magnus and especially its tendon at 
the lower and inner border of the muscle which passes to the 
adductor tubercle. The opening in the muscle for the passage 
of the femoral vessels from the front to the back of the thigh lies 
close to the shaft of the femur under cover of this tendon. This 
opening marks the end of Hunter's (femoral) canal and the be- 
ginning of the popliteal vessels. 
Vessels of thigh and popliteal space. The deep femoral ar- 
tery gives off four perforating branches which pierce the adduc- 
tor longus and magnus to supply the back of the thigh. In a 
well injected subject these form anastomoses all along the thigh 
beneath the hamstring muscles and connect above with the sci- 
298 atic artery and below with branches of the popliteal artery. The 
small veins with them may be removed. These vessels should 
be secured before cleaning the dorsal side of the adductor mag- 
nus. The popliteal artery and vein can now be cleaned as far as 
the point where they pass under the heads of the gastrocnemius 
muscle. The main trunks are held firmly together by a fascial 
sheath and are embedded in a mass of fat which fills the popliteal 
space. Numerous large branches pass around the condyles of 
the femur to form the peri-articular anastomoses. More of these 
branches will be exposed when the gastrocnemius muscle is re- 
flected in a later dissection. The floor of the space is formed 
from above downward by the popliteal surface of the femur, the 
portion, especially the popliteus muscle and the deeper branches 
muscle. Clean up as much of the popliteal vessels and nerves 
as is possible with the gastrocnemius muscle still in situ. Only 
the upper part of the floor can be seen at present and the lower 
portion, especially the popliteus muscle and the deeper branches 
of the vessels and nerves, can be shown when the gastrocnemius 
muscle is reflected in the deep dissection of the leg. 
Dissection of the leg and deep parts of the popliteal space. 
Surface anatomy. Identify and palpate the following land- 
marks: the os calcis; the internal and external malleoli, noting 
carefully their relations to the os calcis and to the various ten- 
dons passing behind each malleolus. 
Superficial fascia. This fascia is quite thick over the calf 
of the leg and contains the following cutaneous structures. 
Veins. External or short saphenous vein, which arises from the 
outer end of the venous arch on the dorsum of the foot and 
passes behind the external malleolus up the leg in the midline. 
Internal or long saphenous vein, which arises from the inner 
end of the same arch and passes in front of the internal malleo- 
lus up the inner side of the leg. The branches of communica- 
tion between these two sets of veins are numerous but small and 
can be disregarded in the dissection. Nerves. The external or 
short saphenous nerve is formed by branches from the two pop- 
liteal nerves in the lower part of the popliteal space. They may 
join to form a common trunk in the lower part of the leg or may 
stay separate, one lying near the midline, the other along the 
299 outer side. This nerve passes behind the external malleolus and 
supplies the skin along the outer side of the foot. The internal or 
ments. These ligaments bridge over the spaces between the os 
calcis and the malleoli. They hold the peroneal muscles in their 
synovial sheaths firmly in place behind the external malleous, 
and the tibialis posticus and the long flexor muscles of the toes 
in their sheaths firmly in place behind the internal malleolus, 
along the inner side of the foot. The main trunks of these two 
sets of saphenous nerves and veins should be carefully followed 
and preserved. 
Deep fascia. This fascia is relatively thick over the pop- 
liteal space but below becomes reduced to the usual thin layer 
of deep fascia. Behind the two malleoli it becomes thicker and 
forms two fibrous bands, the external and internal annular liga- 
ments. These ligaments bridge over the spaces between the os 
calcis and the malleoli. They hold the peroneal muscles in their 
synovial sheaths firmly in place behind the external malleolus, 
and the tibialis posticus and the long flexor muscles of the toes 
in ther sheaths firmly in place behind the internal malleolus, 
firmly in place behind the internal malleolus. 
Superficial muscles. 1. Gastrocnemius; origin from the 
condyles of the femur. 2. Soleus; origin from the upper part 
of the fibula and the oblique line of the tibia. It lies just under 
the gastrocnemius. The insertion of both these muscles is by a 
common tendon, the tendo achillis, into the os calcis. There is 
a bursa under the insertion of this tendon. 3. Plantaris; arises 
from the external condyle of the femur and its tendon passes 
along the inner side of the tendo achillis to the os calcis. To ex- 
pose the soleus and plantaris, cut the inner head of the gastroc- 
nemius about three inches below its origin and swing the muscle 
outward on its outer head. The short belly and long slender 
tendon of the plantaris will be seen lying between the gastroc- 
nemius and soleus. 
Deep muscles. To expose the deep layers, cut the origin of 
the soleus from the tibia and swing the whole superficial group 
outward, pivoting on the outer head of the gastrocnemius and 
on the origin of the soleus from the fibula. A thick strong layer 
of fascia, continuous with the deep fascia, is thrust like a sep- 
300 turn between the superficial and deep layers of the muscles. This 
fascia is attached to the tibia and fibula and helps to form the 
internal and external annular ligaments behind the ankle. It 
also covers the main vessels and nerves, which therefore are to 
be found with the deep muscles. Cut through this fascia along 
the midline with care as the deep vessels and nerves are just be- 
neath it at this point lying on the deep muscles. 1. Flexor lon- 
gus digitorum arises from the dorsal surface of the tibia. 2. 
Flexor longus hallucis arises from the dorsal surface of the fib- 
ula. 3. Tibialis posticus arises from the interosseous membrane 
and both bones but is partially buried between the first two mus- 
cles, especially at the top of the leg. The long flexors are in- 
serted into the terminal phalanges of the toes and the tibialis 
posticus into most of the tarsal and metatarsal bone. These in- 
sertions will be displayed in the dissection of the sole of the foot. 
4. Popliteus lies in the floor of the popliteal space; it arises 
from the tibia above the oblique line and is inserted into the 
outer condyle of the femur. It sends an expansion from its ten- 
don to the capsule of the knee joint. This muscle is covered up 
by the vessels and nerves in the popliteal space and will not be 
exposed until they have been cleaned and turned out to one side. 
Nerves. Tibial or internal popliteal nerve. This nerve can 
be cleaned after the superficial muscles have been turned aside. It 
sends branches to the superficial muscles of the leg and also to 
the popliteus and at the lower border of the popliteus muscle it 
becomes the posterior tibial nerve. It then passes down the leg 
in the midline between the two layers of muscles, but super- 
ficial to the deep vessels. It supplies the deep muscles and in- 
clining inward passes under the internal annular ligament into 
the space between the os calcis and the internal malleolus where 
it will be followed in the next stage of the dissection. Peroneal 
or external popliteal nerve. This nerve runs along the edge of 
the biceps tendon to the neck of the fibula. At that point it 
passes under the origin of the peroneal muscles, winds around 
the neck of the fibula and divides on the outer and anterior as- 
pect of the leg into the anterior tibial and musculocutaneous 
nerves (superficial and deep peroneal nerves). The dissector 
should trace this nerve around the fibula and connect it up with 
301 the dissection of the front of the leg. This nerve supplies the 
muscles and skin on the front of the leg and on the dorsum of 
the foot. 
Popliteal artery and vein. These vessels lie close to the 
floor of the space, the vein being superficial to the artery. The 
branches of the popliteal vessels are chiefly articular and are di- 
vided into a superior and an inferior set which pass around the 
knee joint above and below the condyles of the femur to form 
the periarticular anastomoses. In cleaning them, the smaller 
veins can be destroyed. At the lower border of the popliteus 
muscle the artery divides into the anterior and posterior tibial 
arteries. The popliteal vein has up to this point been a single 
vein, but beyond this point the veins form the usual venae co- 
mits. The anterior tibial artery passes at once out of this dis- 
section, goes forward between the bones of the leg over the up- 
per border of the interosseous membrane, and runs down under 
the muscles on the anterior aspect of the limb. The vessel should 
be followed so as to connect up with the dissection of the front 
of the leg. The posterior tibial artery passes down the back of 
the leg in the midline and lies on the three deep muscles. The 
nerve is superficial to it but gradually swings across it to reach 
its outer side at the ankle. The artery follows the nerve behind 
the internal malleolus, where both divide into the plantar 
branches which are distributed to the sole of the foot. Besides 
giving off muscular and cutaneous branches, the artery has a 
large peroneal branch which at times is larger than the main 
stem. This branch springs from the very beginning of the pos- 
terior tibial artery and passes down the outer side of the leg 
more or less buried in and under the flexor longus hallucis mus- 
cle. It sends off branches at the ankle which anastomose with 
both tibial arteries and form the periarticular anastomoses about 
the ankle joint. These anastomoses are, however, only seen 
in an unusually well injected subject. The peroneal artery 
should be followed and the fibers of the flexor longus hallucis 
can be cut sufficiently for this purpose. 
It will be necessary to clean the vessels and nerves first and 
then the deep muscles. The vessels and nerves can be pulled to 
one side to expose the muscles. Note the change in relation as 
302 the tendons approach the ankle. The tendon of the tibialis pos- 
ticus passes forward under that of the flexor longus digitorum 
and as the tendons pass behind the internal malleolus the tendon 
of the tibialis posticus lies in front. Clean all the muscles, ves- 
sels and nerves in the deep layer as far as the point where they 
pass under the internal annular ligament, leaving that structure 
intact to hold them in place while being cleaned. The ligament 
can then be cut and the structures studied as they lie between 
the os calcis and the internal malleolus. Note the loose syno- 
vial sheaths which will be removed as the tendons are cleaned 
and pay particular attention to the relations of the tendons and 
the vessels and nerves. From before backward they will lie in 
the following order: tendon of tibialis posticus, tendon of flexor 
longus digitorum, posterior tibial artery, posterior tibial nerve, 
tendon of flexor longus hallucis. Do not carry the dissection 
beyond a line through the os calcis and the malleolus. 
The peroneal muscles, which arise along the whole length 
of the fibula will come partly into this stage of the dissection, 
though they have been partly dissected from the front. These 
muscles should be cleaned and followed behind the external 
malleolus. Leave the external annular ligament in place to stead} 
them while they are being worked out to this point. Then cut 
the ligaments, follow the tendons behind the malleolus as was 
done on the inner side of the ankle. The tendon of the peroneus 
brevis can be followed forward to its insertion into the base of 
the fifth metatarsal on the dorsum of the foot. The peroneus 
longus, and also the tendons behind the internal malleolus, will 
be dissected with the plantar side of the foot. 
The knee joint. This is formed by the femur, tibia, and pa- 
tella, and may be regarded as a compound joint consisting of 
three articulations combined, the joint between the femur and 
the patella and the joints between each condyle of the femur and 
the tibia. The patellar articular surface lies on the anterior as- 
pect of the shaft of the femur and is separated posteriorly by 
two small ridges from the tibial surfaces on the lower and back 
part of the condyles. The articular surface on the outer condyle ex- 
tends straight back, that on the inner condyle runs backward 
in a slight curve. It is longer than the outer surface and there 
303 is a wider range of movement between it and the tibia. The lat- 
eral articular surface on the tibia is smaller and more circular; 
the medial longer and more oval. 
Ligaments. The capsule of the knee joint is large and its 
synovial cavity is the most extensive and complicated of all the 
joints. The capsule is extremely thin and merely forms a sup- 
port for the synovia. It is attached above to the femur to in- 
clude the condyles and the articular surfaces. Below it is at- 
tached to the margins of the condyles of the tibia but does not 
include the head of the fibula. The tibial collateral ligament is 
a flat band passing from the medial epicondyle of the tibia to the 
medial condyle of the tibia. The fibular collateral ligament 
passes from the lateral epicondyle to the head of the fibula. It 
is separated from the capsule by the tendon of the popliteus 
muscle and it splits the tendon of insertion of the biceps at the 
head of the fibula. The posterior aspect of the capsule is rein- 
forced by an expansion from the tendon of the semitendinosus 
muscle, the oblique popliteal ligament. The popliteus tendon 
also gives off bands which strengthen the posterior aspect of 
the capsule. In front, the capsule is attached to the borders of 
the patella. The quadricep extensor muscle gives off two apo- 
neurotic expansions which fuse with the ligamentum patellae 
and are reflected back over the front and sides of the capsule as 
far as the collateral ligaments. A large pad of fat lies between 
the ligamentum patellae and the capsule. Over all this is the 
fascia lata which is attached to the upper ends of the tibia and 
fibula, and forms a reinforcement to the front and sides of the 
joint. 
Inside the joint are the crucial ligaments. The anterior 
arises from the depression in front of the spine of the tibia, the 
posterior from the depression behind the spine. The anterior is 
attached to the medial side of the back part of the lateral con- 
dyle of the femur, the posterior to the medial side of the front 
part of the medial condyle. They cross in the middle of the 
joint, are very powerful ligaments, and prevent anterior and pos- 
terior displacement of the femur on the tibia. They are sur- 
rounded by the synovial membrane. 
The semilunar cartilages are placed on the condyles of the 
304 tibia and deepen to some extent the articular surfaces for the 
condyles of the femur. They are crescent shaped plates, about a 
centimeter deep at the periphery and tapering to a thin edge 
medially. The medial cartilage is semicircular and its extremi- 
ties are attached to the tibia in front and behind the spine. The 
lateral cartilage is circular, and its ends are attached to the tibia 
on either side of the spine between the ends of the lateral carti- 
lage. The origin of the crucial ligaments blend with the at- 
tached parts of the cartilages. At the periphery the cartilages 
are fused to the capsule and are connected in front by a trans- 
verse ligament. 
The synovial membrane surrounds the cartilages and in- 
vests the crucial ligaments. A median band of synovia, the mu- 
cous fold, runs in from the deep side of the capsule below the 
patella to the intercondyloid fossa of the femur and two trans- 
verse bands run laterally below the patella which are known 
as the alar folds. 
Bursae. There is a large bursa above the joint under the 
lower end of the extensor tendon, the suprapatellar bursa, which 
often communicates with the joint. Bursae are found under the 
heads of the gastrocnemius under the tendon of the popliteus. 
Several synovial bursae lie over the patella and the ligamentum 
patella. 
Muscles. Phe joint is covered in' front and at the sides by 
the quadriceps extensor muscle; behind and medially by the 
semitendinosus, semimembranosus and inner head of the gas- 
trocnemius; behind and laterally by the biceps, popliteus and 
outer head of the gastrocnemius. 
Movements. The chief movements are flexion and extension. 
When the joint is flexed the femur revolves around the tibia on a 
transverse axis like any hinge joint, but at the same time the con- 
dyles roll and slide on the tibia. There is also a slight rota- 
tion in the joint as the inner condyle has farther to travel than 
the outer. As a result of this there is a slight rotation outward 
of the tibia on the femur at the end of extension, which tends 
to throw the foot outward; at the end of flexion there is a slight 
rotation inward of the tibia on the femur. The movement of 
the patella on the femur is one of gliding. The patella is fixed 
305 to the tibia by the ligamentum patellae and does not change 
its position to that bone. In extension the patella is drawn up 
on the front of the femur and only its lower part is in contact 
with the articular surface of the femur. In semi flexion the 
middle parts of its articular surfaces are in contact with the 
proximal margin of the patella surface of the femur, and in full 
flexion the upper part of the patella is opposite the notch be- 
tween the condyles, and most of the bone is directly in front cf 
the joint. 
The superior tibiofibular joint has a joint cavity and a cap- 
sule strengthened in front and behind by bands. The inter- 
osseous membrane is composed of fibers which run chiefly down- 
wards from the tibia to the fibula. The inferior tibiofibular 
joint has no real cavity and no articular surfaces. The bones 
are held directly together by ligaments. Only passive move- 
ments are permitted in these joints. The upper joint allows of 
simple gliding, the lower of slight displacement to preserve 
close adaptation between the bones of the ankle joint. 
The dissection of the knee joint had better be done after 
the dissection of the back of the leg has been completed. The 
posterior aspect of the capsule in the floor of the popliteal space 
should be cleaned and the relations of the semitendinosus, bi- 
ceps and popliteus muscles noted. The gastrocnemius may be 
cut. Turn the limb over and define the collateral ligaments and 
the expansion of the quadriceps muscle over the front and sides 
of the capsule. Do not separate the expansion from the cap- 
sule. Cut into the capsule above the patella and turn the lower 
part of the capsule with the patella in it downwards. Note the 
prolongations of synovia running into the joint, and the deep 
side of the patella. Flex the knee and clean the synovia away 
from the crucial ligaments. The anterior crucial ligament may 
be cut to expose the posterior. Then cut the posterior, open 
the joint widely to see the upper surface of the tibia and the in- 
terarticular cartilages. Leave the posterior part of the capsule 
intact to hold the bones together. 
306 DISSECTION OF THE PLANTAR ASPECT OF THE 
FOOT 
Surface anatomy. Palpate and identify the following: the 
inferior tubercles of the os calcis; the tuberosity of the sca- 
phoid ; the heads of metatarsal bones. 
Skin and superficial fascia. The skin over the sole of the 
foot is unusually thick and is closely united with the underly- 
ing superficial fascia which is also extremely thick and dense. 
The skin and the greater part of the superficial fascia can be re- 
moved together but great care must be taken to avoid injuring 
the deep fascia. The skin and fascia can be dissected off the 
os calcis, turned forward to the base of the toes and cut off at 
that point. The cutaneous nerves may be disregarded over the 
sole of the foot as far as the bases of the toes. Here the fascia 
is thinner and the nerves to the toes can be followed without 
much difficulty. 
Nerves. The posterior tibial nerve sends an internal cal- 
canean branch to the inner side of the heel. The main branches 
of the internal and external saphenous nerves will be found along 
the sides of the foot. At the toes the internal plantar nerve 
supplies the sides of the three inner and half of the fourth toe, 
and the external plantar nerve supplies the rest of the fourth 
and the fifth toe. They are accompanied by branches from 
the plantar arteries. 
Deep or plantar fascia. Dissect the remains of the super- 
ficial fascia from the deep fascia along the midline from behind 
forward. Here the deep fascia forms a very thick aponeurotic 
band which, attached behind to the tubercles of the os calcis. 
spreads out as it passes forward and is inserted by slip into the 
sides of the toes. The digital vessels and nerves pass to the 
toes between the slips, while the flexor tendons pass beneath 
them. This central part of the deep fascia is of importance in 
supporting the longitudinal arch of the foot and under it will 
be found the long flexor tendons of the toes and the main ves- 
sels and nerves. On either side, the fascia becomes very much 
thinner and covers two elevations which are formed by the 
307 short muscles of the first and fifth toes respectively. The fatty 
superficial fascia should then be dissected off the lateral parts 
of the deep fascia but great care must be taken, as the under- 
lying deep fascia is thin. Prolongations from the sides of the 
strong central part of the deep fascia extend into the depths of 
the foot and divide the foot into three compartments. The 
short muscles of the first and fifth toes are in the lateral com- 
partments and the longer tendons and the vessels and nerves 
are in the central compartment. These partitions can only be 
demonstrated in sections or special preparations. 
First layer of muscles. To demonstrate this layer, detach 
the central part of the plantar fascia from the os calcis and 
turn it forward to the toes. This must be done carefully as the 
flexor brevis digitorum lies just beneath it in the midline and 
some of its fibers arise from the deep surface of the fascia. 1. 
Flexor brevis digitorum takes origin from the os calcis and the 
plantar fascia and is inserted into the middle phalanges of the 
four outer toes. It corresponds to the flexor sublimis in the 
hand. 2. Abductor hallucis lies along the inner border of the 
above muscle, arises from the os calcis and plantar fascia and 
is inserted into the proximal phalanx of the great toe. 3. Ab- 
ductor digiti quinti lies along the outer margin of the flexor 
brevis digitorum, arises from the os calcis and plantar fascia and 
is inserted into the proximal phalanx of the little toe. The thin 
lateral parts of the plantar fascia may be simply dissected off 
the last two muscles to expose them. 
Second layer of muscle. To expose this layer cut the ori- 
gin of the flexor brevis digitorum from the os calcis and turn 
it toward the toes, but do not cut its insertion. 1. Flexor lon- 
gus digitorum. This tendon passes rather obliquely forward 
(in close relation with that of the flexor longus hallucis) from 
the internal malleolus to the four inner toes and like the flexor 
profundus of the hand is inserted into the terminal phalanges. 
2. Lumbrical muscles. There are four of these muscles ar- 
ranged practically on the same plan as those in the hand. They 
are inserted into the dorsal expansion of the extensor tendons 
on the dorsal aspect of the first phalanges. The fibrous and syn- 
ovial sheaths along the plantar surface of the phalanges are 
308 similar to those in the hand. 3. Accessorius (quadratus plan- 
tae). This muscle arises from the os calcis, runs forward in 
the midline and is inserted into the tendon of the flexor longus 
difitorum. It is really a part of the long flexor and tends to 
correct the oblique action of that muscle. 4. Flexor longus 
hallucis. This tendon lies on the deep surface of that of the 
flexor longus digitorum close against the sustentaculum tali 
of the os calcis. These tendons are often connected by a ten- 
dinous band. The flexor longus hallucis runs forward to the 
base of the terminal phalanx of the great toe. 
Plantar arteries. These vessels arise from the posterior 
tibial artery behind the internal malleolus and pass forward 
between the flexor brevis and accessorius muscles. The internal 
plantar artery is the smaller of the two and runs with the nerve 
of the same name toward the base of the great toe. It gives 
off digital branches to the inner toes, passes to a deeper plane 
and anastomoses with the terminations of the external plantar 
artery and the dorsal artery of the foot. The external plantar 
artery follows the course of the external plantar nerve as men- 
tioned above, and when it has passed under the long flexor mus- 
cle it sweeps inward forming the plantar arterial arch in the 
plane of the fourth layer of muscles. Digital branches pass from 
the arch to the toes. 
Plantar nerves. The posterior tibial nerve divides behind 
the internal malleolus into the internal and external plantar 
nerves. These and the corresponding arteries run between 
the flexor brevis digitorum and the accessorius. The internal 
plantar is the chief sensory nerve of the toes and supplies only 
four muscles, the abductor hallucis, flexor brevis digitorum, 
flexor brevis hallucis, and the inner lumbrical. The external 
plantar nerve has only, a limited skin distribution, as stated 
above, and supplies all the other muscles of the foot. It passes 
outward with the corresponding artery to the base of the fifth 
metatarsal bone and then leaves this stage of the dissection by 
running under the flexor longus digitorum to reach the deeper 
parts of the foot. 
Third layer of muscles. 1. Flexor brevis hallucis arises 
from the tarsus and is inserted by two tendons on either side 
309 of the base of the proximal phalanx of the great toe. Two good 
sized sesamoid bones are found usually in these tendons. 2. 
Flexor brevis minimi digiti arises from the base of the fifth 
metatarsal and is inserted into the base of the proximal phalanx 
of the little toe. 3. Adductor obliquus and transverse hallucis 
arise from the metacarpal bones and are inserted into the base 
of the proximal phalanx of the big toe. The first two muscles 
lie in the lateral compartments, the third muscle in the central 
compartment of the foot. 
Fourth layer of muscles. 1. Interosseous muscles. The 
four dorsal muscles should be dissected on the dorsum of the 
foot. They occupy the spaces between the metatarsal bones and 
are inserted into the bases of the proximal phalanges of the sec- 
ond, third and fourth toes. They are so arranged that they 
abduct those toes from a line drawn through the second toe. 
The plantar interosseous muscles are three in number, arise 
from the plantar surface of the third, fourth and fifth metatar- 
sals, and arc inserted on the medial aspect of the base of the 
proximal phalanges of these toes. They adduct them towards 
the second toe. 2. Peroneus longus. The tendon of the pero- 
neus longus passes forward to the groove on the outer and in- 
ferior surface of the cuboid bone and turns abruptly under the 
foot, its tendon usually containing a sesamoid bone or a piece 
of cartilage to reduce friction at this point. The tendon ex- 
tends obliquely across the foot lying under all the other muscles 
already mentioned, and is inserted into the internal cuneiform 
and base of the first metatarsal bones. 3. Tibialis posticus 
passes from behind the internal malleolus to the tubercle of the 
scaphoid bone which is its primary insertion. From this point 
slips are given off to all the tarsal bones except the astragulus, 
and to the second, third, and fourth, metatarsal bones. These 
slips blend with the ligaments on the plantar side of the foot 
nad are not easy to demonstrate. 
After the dissection of all the structures in the second layer 
has been completed, the accessorius, flexor longus digitorum and 
flexor longus hallucis can be cut and turned downward to the 
toes. The plantar vessels and nerves should not be cut and 
can be drawn to one side. The muscles in the third layer may 
310 be disregarded and the adductor and flexor brevis hallucis can 
be divided to expose the fourth layer. Here the plantar arch 
and deep branch of the nerve should be dissected and lastly the 
tendon of the peroneus longus should be fully exposed in its 
course across the foot. The tibialis posticus should be followed 
to its primary attachment into the scaphoid, but its terminal 
slips need not be dissected as they blend so closely with the 
plantar ligaments. The student should appreciate the impor- 
tance of the various tendons about the ankle joint and the foot, 
both in the support of the ankle and especially in the support 
and maintenance of the arch of the foot. The two peroneal 
muscles on the outside and the tibialis anticus and posticus on 
the inside are of special importance in the support of the arch 
and can be regarded as forming a sort of sling or stirrup which 
holds the bones of the foot firmly in place. 
Ankle joint. This is a hinge joint and is formed by the 
lower ends of the tibia and the upper surface of the astragulus. 
The lower ends of the bones of the leg, with the malleoli, form 
a socket in which the convex trochlear surface of the astragulus 
fits. The socket is not solid, as the half joint between the tibia 
and fibula permits of a little yielding. The anterior end of the 
trochlea articular surface is broader than the posterior end and 
can be accommodated in the socket in full extension by the 
yielding of the inferior tibiofibula .joint. 
Ligaments. The capsule is thin and is attached above to 
the tips and margins of the malleoli and to the anterior and 
posterior borders of the lower extremity of the tibia. Below it 
is attached to the groove about the periphery of the trochlear 
surface of the astragulus. The tibial collateral or deltoid liga- 
ment supports the capsule on the inner side and is attached to 
the tip of the internal malleolus. The anterior fibers are at- 
tached to the navicular, the middle to the sustentaculum tali of 
the os calcis, and the posterior to the medial surface of the as- 
tragulus. The fibular collateral ligament is attached to the tip 
of the external malleolus and consists of three separate bands; 
the anterior passes to the front part of the body of the astragu- 
us, the middle to the lateral surface of the os calcis and the 
posterior runs backward behind the joint to the back of the 
311 body of the astragulus. The joint is supported on all sides by 
the long flexor and extensor tendons and their sheaths. Move- 
ments are those of flexion (dorsi flexion) and extension (plan- 
tar flexion) only, with a certain yielding or spring to the joint 
provided by the inferior tibiofibular joint. This joint does not 
communicate with the ankle joint. 
Joints of the foot. It is convenient to regard the tarsal and 
tarsometatarsal joints as a complex joint inclosed in a common 
capsule. The fibers of the capsule begin above by blending 
with those of the ankle joint proper and pass down to the heads 
of the metatarsal bones, being attached to each bone of the 
tarsus on the way. This common capsule is reinforced by sev- 
eral definite ligaments which are found chiefly on the plantar 
surface. The long plantar ligament runs from the plantar sur- 
face of the os calcis to the cuboid and base of the metatarsal 
bones. The short plantar or calcaneo cuboid ligament lies be- 
neath it, and extends from the os calcs to the ridge on the cu- 
boid. These are very strong ligaments. The plantar calcaneo 
navicular ligament passes from the sustentaculum tali to the 
navicular bone. It has a disk of cartilage on its dorsal aspect 
which completes the inner part of the joint between the head 
of the astragulus and the navicular bone. The interosseous as- 
tragulocalcanean ligament passes between the astragulus and 
the os calcis. Interosseous ligaments pass between the os calcis 
and the cuboid and navicular; between the cuboid and lateral 
cuneiform; between the cuneiforms; between the medial cunei- 
form, and first and second metatarsals, and between the bases 
of the metatarsal bones. There are many other small ligaments 
with special names, but they can be conveniently omitted and 
included in the common capsule. 
Synovial cavities. There are several separate synovial cav- 
ities. 1. The ankle joint proper is separate from the joint cavi- 
ties of the foot, but it is closely allied with them in the move- 
ments of the foot and ankle. 2. Posterior calcaneo-astraguloid 
joint. 3. Anterior calcaneo-astragulo-navicular joint. 4. Cal- 
caneo-ocuboid. 5. Cuboid and 4th and 5th metatarsals. 6. In- 
ternal cuneiform and 1st metatarsal. 7. Navicular cuboid cu- 
312 neiform joints between these bones and the bases of the 2nd 
and 3rd metatarsal bones. 
Movements. It is convenient to study the movements of 
the tarsal joints with those of the ankle. At the ankle, above 
the astragalus, there are movements of dorsi Hexion and plantar 
flexion only. In the tarsus, below the astragalus, are found the 
lateral movements of the foot. These movements are known 
as inversion and eversion, adduction and abduction. Inversion 
is combined with adduction, and in this movement the medial 
border of the foot is raised and carried inwards and the lateral 
border depressed. Eversion is combined with adduction and in 
this movement the lateral border is raised and carried outwards 
and the medial border depressed. There is some degree of plan- 
tar flexion with inversion and of dorsi flexion with eversion. 
The range of inversion is greatest in the extended and that of 
eversion greatest in the flexed position of the ankle joint. These 
movments occur simultaneously in the calcaneo-astragulo- 
navicular and in the calcaneo-cuboid joints. The tarsal bones 
in front of the astragulus and the os calcis move practically as 
one piece. The 4th and 5th metatarsals follow the cuboid, the 
1st, 2nd, and 3rd the cuneiform and navicular bones. 
Only slight gliding movements are possible between the 
distal tarsal joints, at the tarsometatarsal joints, and between 
the metatarsal bones. These joints'adapt the foot to the ground 
and absorb shock. The movements at the metatarsophalangeal 
and at the interphalangeal joints are the same as those in the 
hand, but are more restricted. The ligamentous arrangement 
is also essentially the same as in the hand. 
Dissection of the ankle joint. The tendons behind the 
malleoli can be drawn out of place and the posterior part of the 
capsule cleaned. Then clean the anterior part and the collat- 
eral ligaments. The joint can be opened in front and the bones 
displaced to show their articular surfaces. The tibiofibular 
joints need not be opened. 
Dissection of the joints of the foot. The plantar ligaments 
should be cleaned and identified. The other plantar and the dor- 
sal ligaments, which form the common capsule, ' can be dis- 
played by freeing the long flexor and extensor tendons and their 
313 sheaths from both sides of the tarsus. The joints between the 
astragalus, os calcis and navicular should be opened in front, 
the interosseous ligament between the astragalus and os calcis 
cut, and the astragulus turned up. Leave the posterior part of 
the capsule intact to maintain some connection with the os cal- 
cis. The joints between the os calcis and cuboid, navicular and 
cuneiform, and the tarsometatarsal joints can be opened from 
the front to expose their articular surfaces. The plantar liga- 
ments should be left to hold the bones together. 
314 ACTION OF MUSCLES: LOWER EXTREMITY 
Hip joint. The following list of muscles acting on the hip 
is not complete. Only the more important muscles concerned 
in each movement are given. 
Flexion: Iliopsoas, sartorius, pectineus, rectus, tensor fas- 
cia latae, adductor longus and brevis, gracilis, gluteus min- 
imus. 
Extension: Gluteus maximus, gluteus medius, hamstrings, 
adductor magnus (posterior part). 
Abduction: Gluteus medius and minimus, tensor fascia 
latae. 
Adduction: Adductors, gracilis, pectineus, quadratus femo- 
ris, obturator interims and externus, gluteus maximus (lower 
fibers). 
Rotation inward: Gluteus medius and minimus (anterior 
fibers), semi-membranous, semitendinosus, tensor fascia 
latae, iliopsoas, adductor longus and brevis. 
Rotation outward: Gluteus maximus and medius, quadratus 
femoris, obturators and gemelli, pyriformis, adductor mag- 
nus (lower part) biceps, sartorius, gracilis. 
Knee joint. 
Flexion: Biceps, semitendinosus, semimembranosus, gas- 
trocnemius, popliteus, sartorius, gracili. 
Extenion: Quadriceps extensor. 
Ankle joint. 
Flexion (dorsi flexion): Tibialis anterior, extensor longus 
digitorum, peroneus tertius, extensor longus hallucis. 
Extension (plantar flexion): Gastrocnemius, soleus, plan- 
taris, peronei, flexor longus digitorum, flexor longus hal- 
lucis. 
Inversion of the foot: Tibialis anticus and posticus. 
Eversion of the foot: Peroneus longus, brevis, tertius. 
315 Toes 
Flexion: Flexor longus digitorum (quadratus plantar), 
(3rd phalanx). Flexor brevis digitorum (2nd phalanx), in- 
terossei and lumbricals (1st phalanx), flexor brevis and ab- 
ductor digiti quinti (little toe). Fexor longus hallucis (big 
toe, terminal phalanx). Flexor brevis and abductor hallu- 
cis (big toe, proximal phalanx). 
Extension: Extensor longus digitorum (acting on all pha- 
langes), extensor brevis digitorum (acting on 1st phalanx, 
big toe; all phalanges 2nd, 3rd, 4th toes), extensor longus 
hallucis (terminal phalanx, big toe), interossei and lumbri- 
cals probably do not act as extensors. 
Abduction: Dorsal interosii (2nd, 3rd, 4th toes), abductors 
of 1st and 5th toes. 
Adduction: Plantar interossei (3rd, 4th, 5th toes), adductor 
of big toe. 
316