The Mechanism and Diagnosis 
of Vertex Presentation. 
BT 
J. CLIFTON EDGAR, M. D., 
Adjunct Professor of Obetetrlcs'Tn’"the Medical Depart- 
ment of the University of the City of New Tork; 
Aseletant Obstetric Surgeon to the New York Ma- 
ternity Hospital; Obstetrician to the Emergency 
Lying-in-Hospital; Attending Physician to the New 
York Lylng-ln-Hospltal. 
REPRINTED PROM THE 
Weto Yotft jf«eUtcal $ountal 
for February 25, 1898. Reprinted from the New York Medical Journal 
for February 25, 1803. 
tiip: mechanism and diagnosis of 
VERTEX PRESENTATION* 
By J. CLIFTON ED£AE, M. D., 
ADJUNCT PROFESSOR OF OBSTETRICS IN THE MEDICAL DEPARTMENT OF 
THE UNIVERSITY OF THE CITY OF NEW YORK ; 
ASSISTANT OBSTETRIC SURGEON TO THE NEW YORK MATERNITY HOSPITAL ; 
OBSTETRICIAN TO THE EMERGENCY LYING-IN HOSPITAL ; 
ATTENDING PHYSICIAN TO THE NEW YORK LYING-IN HOSPITAL. 
If we are familiar with the three factors of labor— 
namely, the passages, the passenger, and the forces—we are 
in a position to appreciate that most interesting part of the 
subject of parturition : the manner or, better, the combina- 
tion of movements by which Nature guides the foetus from 
the uterine cavity through the pelvis into the external 
world. In the whole range of obstetric science and art 
there is perhaps no one subject more worthy of a careful, 
conscientious, and diligent study. There is no one subject 
upon which so much depends as regards the prognosis for 
both mother and child. If perchance one link in the chain 
of these movements going to make up the mechanism of 
labor fails, and we are unable, by reason of our ignorance 
of Nature’s methods, to step in at the right moment and 
* A lecture delivered at the University Medical College, December 
fi and 8, 1892. 
Copyright, 181)3, by D. Appleton and Company. 2 
THE MECHANISM AND DIAGNOSIS OF 
supply tlie deficiency, either mother or child is bound to 
suffer. 
It is quite true that in our first ten or twelve cases of 
labor absolutely no interference may he called for in their 
management, hut it is equally true that in our next series 
of ten or a dozen cases Nature may fail us in some par- 
ticular; we are unable to appreciate the difficulty and to 
correct it, and untold disaster is the result. With equal 
success might we hope to appreciate and treat certain 
cardiac diseases without an understanding of the anatomy 
and physiology of the heart as to attempt the management 
of labor cases without a clear knowledge of the mechanism 
of parturition. 
Before turning our attention to the mechanism of labor 
in vertex presentations, let us recall the statement of Pajot 
that “ all labors, from a mechanical standpoint, are subject 
to the same law, and that there is.really only one mechan- 
ism of labor, no matter what the presentation or position, 
. . . provided only that expulsion occurs spontaneously and 
at term, as abortions do not result in regular expulsion.” 
We may state, then, to-day that there is but one mechan- 
ism of labor, no matter if the presentation is the vertex, 
the brow, the face, or the breech. A recent writer upon 
midwifery would compare the mechanism of labor in ver- 
tex presentation to a tune, the mechanism of labor in all 
other presentations being the same with variations. Fur- 
ther, we may state that, in the mechanism of labor in all 
presentations and positions, six stages may he described : 
1. In the first stage the foetus, pressed upon and influenced 
by the general intra-uterine pressure, and perhaps also to a 
slight extent by the voluntary efforts of the mother, tends 
to accommodate, to mold the shape of its presenting part 
to suit'the canal through which it has to pass. 2. In the 
second stage this molded presentation engages and descends VERTEX PRESENTATION. 
3 
into the pelvis. This stage, then, is the stage of engaging 
and descent. 3. Having molded, having engaged, having 
descended a certain distance—namely, to the pelvic floor— 
the presenting part executes a movement, so as to bring its 
long axis in correspondence with the longest diameter of the 
outlet of the pelvic canal. This is the third stage, or stage of 
internal rotation. 4. Again the presenting part executes a 
further movement by which it sets itself free from the geni- 
tal canal. This is the fourth stage, or, as we may say, the 
stage of expulsion of the first part of the foetus. 5. Again, 
as the result of the internal rotation of that portion of the 
child which is still within the birth canal, we have a rota- 
tion of that part which has already been delivered, and this 
is termed the stage of external rotation. 6. Then the sixth 
and last stage is a second period of expulsion, or the escape 
of that part of the foetus heretofore unexpelled. 
While these six stages in the mechanism of labor are 
not always absolutely the same for all presentations and for 
all positions of the foetus ; while we may have flexion in one 
instance, extension in another; while it may be the right 
shoulder that rotates to the front in one and the left in 
another; while the presentation may be face, brow, ver- 
tex, or breech, yet we shall be certain to encounter these 
stages in all labors, no matter what the presentation, no 
matter what the position. 
Having thoroughly grasped these facts, then, let us turn 
injmediately to the consideration of vertex presentation. 
The number of positions of the vertex described vary in 
different countries and according to different authorities. 
The English usually describe four positions ; those American 
writers who follow the teachings of Hodge, on the other 
hand, would have us describe six positions; while the Ger- 
mans, thinking both these classifications too complicated, 
describe usually but two positions. The simplest classifi- 4 
THE MECHANISM AND DIAGNOSIS OF 
cation is to speak of four positions, and we shall therefore 
adopt that; and this is more readily understood if we im- 
agine that the pelvdc inlet is divided into four quadrants by 
the antero posterior and transverse diameters, and that the 
positions vary according as the vertex occupies one or other 
of these four quadrants. And just here let us remember 
that by the right oblique diameter we mean the one passing 
through the right sacro-iliac synchondrosis, and by the left 
the one passing through the left sacro-iliac joint. 
The four positions of the vertex, then, are : 1. The first 
or left occipito-anterior position. 2. The second or right 
occipito-anterior position. 3. The third or right occipito- 
posterior portion. 4. The fourth or left occipito-posterior 
position. And, as regards the relative frequency of these 
several positions, it is to day pretty well agreed by authori- 
ties upon the subject that the first position obtains in from 
sixty-five to eighty per cent, of cases, and that the third, 
second, and fourth positions are the next most frequent in 
the order named. 
We shall first describe the mechanism of labor in the 
first or left occipito-anterior position, and then in the third, 
the next most frequent, or the right occipito-posterior posi- 
tion of the vertex. 
In the first stage, the mechanism that we have to describe 
is one of fiexion and molding, and we can readily compre- 
hend how fiexion is brought about when we hold up a foetal 
cadaver, and we immediately perceive that the forehead, or 
the long end of the lever made by the head upon the spinal 
column, falls, by reason of its own weight, upon the chest of 
the foetus ; consequently, when the force of uterine contrac- 
tion acts upon the head through the spinal column, the short 
end, or the occipital extremity of the head, is more directly 
in the line of action of this force, and consequently tends 
to be driven farther downward in the birth canal, and hence VERTEX PRESENTATION7. 
5 
flexion of the child’s chin upon its sternum is produced. 
We have every reason to believe, however, that flexion is 
in many cases complete before labor actually sets in, for we 
know that the normal attitude or posture of the chi 11 with- 
in the uterus is one of flexion, and we can recall, from our 
observations of labor cases in the New York Lying-in Hos- 
pital, how the child’s posture, immediately after its expul- 
sion from the birth canal, was often one of flexion between 
the thighs of its mother. Even in the absence of uterine 
contraction, flexion may be brought about by this tendency 
on the part of the child to take up this particular attitude, 
and also by a principle of mechanics that is termed a coup- 
let, which latter we will pass over for the present. Mold- 
ing, then, and flexion constitute the first stage in the mech- 
anism. 
Recalling our general principles, the next stage will be 
one of engagement and gradual descent; and, as in all 
mechanisms of labor, one great principle—namely, accom- 
modation or adaptation—plays a prominent part, conse- 
quently the long diameter of the head would tend to enter 
the pelvic inlet in its longest diameter, which is, as we 
know, the transverse; and Spiegelberg has shown that 
the head does in vertex presentation enter the transverse 
diameter of the pelvic inlet in 81-4 per cent, of all cases. 
So far it has been all very simple; there is nothing that 
any one of us can not readily understand and comprehend; 
but we come now to the third stage in the mechanism— 
namely, the internal rotation of the first part, or, in this 
ease, the head. 
Perhaps there is no part of the mechanism of labor that 
has caused the student such difficulty and concerning which 
there has been such difference of opinion as the cause of 
this internal rotation, whether it be the internal rotation of 
the head, or of a shoulder, or of a buttock. There have 6 
THE MECHANISM AND DIAGNOSIS OF 
been various explanations advanced, most of them more or 
less unsatisfactory. For instance, Baudelocque and his fol- 
lowers taught that the anterior and the posterior inclined 
planes of the ischia determined the anterior or the poste- 
rior rotation of the lowest portion of the presenting part. 
Naegele, however, pointed out the fallacy of this explana- 
tion ; for, contrary to Baudelocque, he demonstrated that 
the occiput rotates anteriorly even when it is originally situ- 
ated on a posterior inclined plane. Cazeaux would have us 
explain the rotation upon mathematical and mechanical 
principles; but, without going into the matter, suffice it to 
say that while they beautifully explain the cause of anterior 
rotation in anterior positions, yet they are absolutely insuf- 
ficient to account for the anterior rotation in originally pos- 
terior positions. Tyler Smith, Leishman, and Playfair, as 
we are aware, teach that the anterior rotation is determined 
by the ischial spines, and while here again the explanation 
fully accounts for the anterior rotation in anterior positions, 
we are unable to understand how they produce anterior 
rotation in the third and fourth positions of the vertex. It 
was not until Paul Dubois performed his experiments upon 
the cadaver that we find anything like a satisfactory ex- 
planation for anterior rotation of the lowest portion of the 
presenting part under all circumstances. Dubois’s experi- 
ments consisted in pushing foetal cadavers of various sizes 
through the birth canal of puerperae recently dead, and he 
found that, no matter in what position he placed the vertex, 
whether to the front or to the rear, anterior rotation of the 
vertex occurred as soon as it reached the pelvic floor; but 
there came a time in his experiments when anterior rotation 
completely failed and the long diameter of the presenting 
part wmuld remain in the same diameter of the pelvis in 
which it entered. 
Recently, through the courtesy of the coroner, I was en- VERTEX PRESENTATION. 
7 
abled to perform similar experiments here at the University 
Medical College. A German girl, twenty years of age, was 
found one morning upon the door of her employer’s store 
dead from post-partum haemorrhage. One twin had been 
born, and when the cadaver was turned over to me the 
second twin and the double placenta I found within the 
uterine cavity. The twin born spontaneously was of such 
a size as to dilate the passages to a very small extent and 
to cause no appreciable laceration whatsoever. Into the 
head of a foetal cadaver at a point half an inch posterior 
to the small fontanelle I fastened this swivel, and, having 
well lubricated it, I attached to the ring of the swivel 
this whipcord. Then opening the abdomen and uterus of 
the unfortunate woman, by means of a uterine dressing- 
forceps I passed the cord attached to the swivel down 
through the cervix, vagina, and out at the vulva. Then I 
commenced my experiments. I placed this foetus in its 
normal attitude within the uterus, first in the L. O. A., then 
in the R. O. A. position, and each time upon making trac- 
tion upon the cord through the vagina, and always in the 
axis of that part of the parturient canal in which the pre- 
senting part rested, I found that as the head approached 
the pelvic floor internal rotation of the head took place 
completely, so that the sagittal suture would appear exactly 
in the antero-posterior diameter of the outlet. In watching 
for the internal rotation of the shoulders, I found that while 
in the first two experiments internal rotation was complete, 
yet in the subsequent ones the rotation became less and less 
marked, until finally there was no attempt at rotation what- 
soever on the part of the shoulders. I placed the foetus in 
the third and in the fourth positions in its normal attitude 
at the pelvic brim; and here again, upon making traction 
from below, anterior rotation occurred in the former in- 
stance about the right side of the pelvis, and in the latter 8 
THE MECHANISM AND DIAGxNOSIS OF 
about the left side, until the sagittal suture once more was 
brought into the antero-posterior diameter of the pelvic 
outlet and the small fontanelle just under the pubic arch. 
Still another test I made : The vertex wTas placed directly 
posterior and just under the promontory of the sacrum, and, 
upon making traction and drawing the occiput to the pelvic 
floor, we found that, instead of remaining permanently at 
the rear, after a few seconds anterior rotation on the part 
of the occiput commenced, and once more we found the 
vertex at the pubes. 
A second time anterior rotation was secured in the 
R. O. P. and in the L. O. P. position, and then the occiput 
was placed once more in the hollow of the sacrum to test 
this position further, and it was found that, in spite of the 
strongest traction we were able to make on the cord through 
the vulva, the vertex remained firmly and permanently in 
the hollow of the sacrum. 
The same result followed experiments in other oblique 
and transverse positions—namely, anterior rotation of the 
occiput failed and the sagittal suture appeared at the out- 
let in almost the same diameter in which it was originally 
placed at the inlet, thus proving that some factor in the 
causation of anterior rotation of our first experiments failed 
us, or performed its duty imperfectly, in the subsequent 
ones. 
We may draw our own conclusions as regards these ex- 
periments. If anterior rotation in any position is caused 
by the ischial planes or spines, then why was it, in the ex- 
periments that I have just cited, rotation of the presenting 
part failed after the foetus had been drawn a certain num- 
ber of times through the pelvis ? If the rotation is due to 
the inclination of the pelvis, as was maintained by Tarnier, 
or to the shape of the foetal head, as was taught by Pajot, or 
to the ischial planes or spines, why should the rotation fail VERTEX PRESENTATION. 
9 
wlien no evident change took place in the shape of the 
child’s head in the inclination of the mother’s pelvis, or in 
the ischial planes or spines ? We are pretty safe in stating, 
then, that the main and determining cause of the rotation 
of the lowest portion of the presenting part is the resist- 
ance of the posterior portion of the pelvic door, and more 
particularly of the two levator ani muscles which have been 
so beautifully dissected out and illustrated by Dr. Dickin- 
son, of Brooklyn. When they lost their resistance and be- 
came relaxed in the cadaver, as the result of repeated trials 
with the foetus and swiveled string, anterior rotation failed 
to occur. It is undoubtedly the fact that it is not one 
factor alone, but several that determine this internal rota- 
tion. Accommodation ; adaptation ; the great principle that 
runs through all the mechanism of labor, whereby the long 
diameter of the presenting part adapts itself to the long di- 
ameter of that part of the pelvis in which it may bnd itself ; 
this corkscrew-like arrangement of the pelvis; the lessened 
resistance caused by the urethral and vaginal orifices in front; 
the greater resistance of the thicker and heavier tissues in the 
posterior half of the pelvis ; the inclination of the pelvis ; the 
shape of the child’s head ; the inclination of the uterus 
causing the anterior portioyi of the presenting part to reach 
the pelvic door drst—all play their part in the causation of 
anterior rotation. 
Having understood this, then, the remaining stages are 
readily comprehended. Rotation being complete, there 
comes a time when the occiput, having passed under the 
subpubic ligament and being partially born, the shoulders 
attempt to enter the pelvis with the head; and as under 
ordinary circumstances there is not sufficient room for both, 
the head escapes from the vulva by a movement of exten- 
sion, thereby leaving the pelvis free for the shoulders to 
enter. We say the head escapes by a movement of exten- 10 
THE MECHANISM AND DIAGNOSIS OF 
sion. This is not strictly true, for repeated observations 
have convinced me that the bulk of the head, including the 
occiput, is born before the chin leaves the sternum—a fact 
we must always remember in our attempts at perineal pro- 
tection and forceps delivery. This escape of the head is 
caused by the force of uterine contraction acting through 
the spinal column and by the contraction of the muscles 
that go to make up the pelvic floor, and we see the beauti- 
ful provision of Nature that has caused only the smallest 
diameter—namely, the suboccipito-bregmatic, three and a 
half inches in length—to be passed through the birth canal. 
And even at the vulva, as we can readily appreciate from 
the manikin, the occiput having been born first, all the 
diameters of the foetal head that pass in succession through 
the vulvar opening are measured, not from the occipital 
protuberance, but from a point midway between it and the 
foramen magnum, and are consequently the smallest or the 
suboccipital diameters. 
The first part now is born and it only remains to follow 
the mechanism of the second part, and we have completed 
the mechanism of labor in the first position. The shoulders, 
we have every reason to believe, enter the pelvic inlet in 
the opposite oblique to the one in which the head entered; 
or, if the head entered in a transverse diameter, it is possible 
in a roomy pelvis, and with a child that is not too large, for 
the shoulders to enter in the opposite diameter or in the 
antero-posterior diameter of the inlet. At all events, we 
usually dind the shoulders first in an oblique diameter, 
and, as we have learned, the anterior portion of the pre 
senting part, because of the direction of the axis of the 
superior strait, is lower than is the posterior ; consequently 
it is this part that first reaches and is first influenced by 
the resistance at the floor of the pelvis and is deflected an- 
teriorly to the pubic arch. If both shoulders came to the VERTEX PRESENTATION. 
11 
pelvic floor at one and the same time, we have every rea- 
son to believe that they would both be equally influenced by 
the factors causing anterior rotation, and consequently the 
bisacromion diameter would remain in the same diameter in 
which it entered the pelvic inlet. Investigation has taught 
me that while complete anterior rotation of the head is the 
rule, yet complete rotation of the shoulders is not by any 
means so constant as is that of the head. Even before the 
shoulders begin to rotate internally we see an unwinding, as 
it were, of the muscles of the neck that have been twisted in 
the internal rotation of the fcetal head, and, as a consequence, 
the head makes a partial movement of external rotation, 
and this first partial movement of rotation is termed resti- 
tution. Now, a glance only at the manikin will show us 
that when the shoulders rotate within the pelvis there must 
in consequence be a decided rotation on the part of the 
head which is already delivered, and this further and more 
marked rotation of the head is termed the external rotation 
of the head that you are familiar with, whereby the face of 
the child looks almost directly to the inner surface of the 
right thigh of its mother. 
We have now followed the bisacromion diameter into 
the antero-posterior diameter of the pelvic outlet, and if 
we have observed our cases of labor in the tenement 
houses carefully, we shall remember that in most instances 
the anterior shoulder was the one that first appeared at the 
vulva ; and if we are close observers, we shall further re- 
member that sometimes it was this anterior or right shoul- 
der that first was fully born, and in other instances it was 
the posterior or left shoulder and arm that were born first, 
and circumstances seem to determine whether it shall be the 
anterior or the posterior arm that is first expelled. In a mul- 
tipara, particularly if her parts are roomy, if her perinseum 
has been partially destroyed at a previous confinement, the 12 
THE MECHANISM AND DIAGNOSIS OF 
posterior shoulder and arm are very apt to be the first born ; 
whereas, on the other hand—and we are speaking, you un- 
derstand, of spontaneous delivery where we do not inter- 
fere with the birth of the shoulders—if the case is one of 
a primipara with perinseum intact and with somewhat rigid 
soft parts, it may be the anterior shoulder and arm that are 
first brought into the world. So the shoulders are born ; 
the body usually follows immediately afterward. Some 
obstetricians would speak of a stage of rotation of the but- 
tocks, but we have every reason to believe that when the 
shoulders rotate the buttocks rotate with them, and conse- 
quently there is little or no torsion of the body, but the 
buttocks come down and are expelled in the antero-pos- 
terior diameter of the outlet in practically the same way as 
are the shoulders. 
Let us now describe the mechanism of the third or 
R. 0. P. position, and this will be sufficient to illustrate the 
mechanism in all posterior positions of the vertex. The 
suboccipito-bregmatic diameter in this instance, as you see 
in this pelvis, enters the inlet in the right oblique or per- 
haps in the transverse diameter; of course we presuppose 
that flexion and molding have taken place. Following 
engagement we have descent—descent in some cases until 
the pelvic floor is reached—before any rotation in either 
direction takes place ; and yet we will observe cases where 
anterior rotation of this vertex occurs before the pelvic 
floor is reached, and in these instances we have every rea- 
son to believe that it is the resistance of the posterior wall 
of the uterus or of the rectovaginal sfeptum that determines 
this rotation. When once the vertex has reached the pelvic 
floor the case may terminate in one of four ways, and, stat- 
ing them in the order of their frequency, they are as fol- 
lows : First, complete anterior rotation of the occiput about 
the right half of the pelvis until the pubes is reached ; VERTEX PRESENTATION. 
13 
second, posterior rotation of the vertex into the hollow of 
the sacrum and birth of the head with the occiput to the 
rear by extension over the perinaeum; third, posterior rota- 
tion and impaction; and fourth, the conversion of the ver- 
tex presentation into one of face presentation ; and al- 
though this latter termination is extremely rare, yet, as 
there are some half a dozen cases on record, we are com- 
pelled to recognize its possibility. 
1. It is needless for us to spend any time in a descrip- 
tion of the first method of termination ; the same princi- 
ples apply here as apply in the first and second positions. 
The increased resistance of the posterior inclined plane of 
the pelvis causes the occiput to be deflected in the direc- 
tion of least resistance—namely, to the vulvar orifice. 
2. We see instances, however, where from some cause— 
it may be the roominess of the pelvis ; the smallness of the 
child; want of rigidity of the pelvic floor from numerous 
labors or from other causes ; rupture of the floor ; distention 
of the floor by the passage of the first twin; incomplete 
flexion of the head, permitting the sinciput to be as low or 
lower than the occiput—this anterior rotation fails. Ac- 
cording to authorities it is a rare condition, yet according 
to Naegele’s statistics it occurred once in seventy-three 
cases of labor. Should, then, anterior rotation fail and the 
occiput remain in the posterior half of the pelvis, it is pos- 
sible, under certain conditions, for the occiput to follow 
the posterior wall of the parturient canal and be born by 
extension over the edge of the perinaeum. Labor then is al- 
most always prolonged and in some instances impossible as 
the result of impaction. The cause of the prolongation of 
the labor under such circumstances was first pointed out by 
P. Dubois, and by reference to this diagram that hangs be- 
fore us and to this foetal cadaver which I hold up in my hand, 
we can readily see how it is that the labor is either exceed- 14 
TIIE MECHANISM AND DIAGNOSIS OF 
jngly tedious and prolonged or absolutely impossible. 
Glance at the back of a child’s neck, and we see that it is 
not much over two inches in length ; observe the posterior 
wall of the parturient canal from the promontory of the 
sacrum to the edge of the perinaeum, and we readily see 
that the distance is in the neighborhood of ten inches, count- 
ing five inches from the promontory to the tip of the coccyx 
and five more from the tip of the coccyx to the edge of the 
distended pelvic floor. If an anterior position of the vertex 
obtains, hirtli of the head is readily and easily accomplished, 
for the two inches of the back of the neck without any 
difficulty pass over the inch and a half of the anterior 
pelvic wall measured at the symphysis, and the head is born 
before the shoulders necessarily enter the pelvic inlet. 
IIow different when the reverse obtains! For the head to 
be born in an occipito-posterior position we may hope for 
no break in the straight or rigid branch that the foetus 
represents until the head, together with the neck, has trav- 
ersed the ten inches of the posterior pelvic and perineal 
wall, and the head is finally permitted to be born by exten- 
sion over the perinaeum. 
Delivery under such circumstances is certainly possible 
by the natural forces, and some of you, to my certain knowl- 
edge, have seen such instances in your service in the New 
York Lying-in Hospital, and you will recall how, after an 
exceedingly tedious labor and extreme flexion of the head 
on the sternum and with the occiput distending the pelvic 
floor for perhaps several hours, finally, with tremendous bear- 
ing-down efforts on the part of the parturient, the occiput 
was enabled to climb up, as it were, over the perinaeum, the 
forehead and face appeared under the pubes, the perimeum 
slipped by the occiput and along the neck of the child, and 
extension completed the birth of the head. 
3. But, unfortunately, we occasionally meet with in- VERTEX PRESENTATIONS 
15 
stances in our practice where either anterior rotation of the 
occiput or spontaneous delivery with the occiput to the rear 
absolutely fails to occur. And then, if we have added to 
this an impaction and swelling of the shoulders that have 
partially entered the pelvic cavity, we have one of those 
tragedies of midwifery practice which I trust you may never 
be called upon to face. Given a normal-sized foetus, a pelvis 
of ordinary dimensions in perhaps a priinipara with rigid 
soft parts, and the cause of the impaction of those cases of 
occipito-posterior position that have been improperly treated 
early in the second stage of labor is easily understood. 
Once more 1 must ask your attention to this diagram and 
to the foetal cadaver which I hold up before you. The oc- 
ciput passes into the hollow of the sacrum, reaches the coc- 
cyx perchance, but still is several inches from the edge of 
the perinaeum—what must, what only can happen under the 
given circumstances ? Why, the body of the child must 
enter the pelvic cavity together with the head in order to 
allow of the occiput’s reaching its ultimate goal. Then why 
do we have impaction ? We have impaction because the 
dorso-sternal diameter (four inches) is added, as you see, to 
the fronto mental diameter (three inches and a half), giving 
us an antero-posterior diameter of the foetal mass of seven 
inches and a half that the uterine forces are attempting to 
drive through a pelvis the average diameter of which is 
usually considered to be not more than four inches and three 
quarters. And this is not all ; as has been pointed out, the 
length of the foetal ellipse when the child is in its normal 
attitude is half the length of the entire feetus—namely, about 
eleven inches; consequently, when the occiput has come up 
to the edge of the perinaeum the breech of the child has 
practically entered the inlet of the pelvis, and the uterus 
under such circumstances can not but act at a disadvantage. 
We can readily see, then, what either spontaneous or arti- 16 
THE MECHANISM AND DIAGNOSIS OF 
ficial birth of the foetus means to the mother—almost in- 
variably a partial or complete loss of her perineal structures. 
I have only recently been requested to see a puerperal woman 
suffering from sepsis, where the forceps had been applied 
under the conditions that we have just named, and the for- 
ceps delivery had resulted in an entire loss of the wom- 
an’s perinaeum and an inch and a half of the recto vaginal 
soeptum. 
4. The fourth manner in which this posterior position 
may terminate is for the occiput in some way to become ar- 
rested in its course, and then, the chin leaving the sternum, 
rotation on a biparietal diameter takes place, the head, as 
it were, turns a somersault, becomes extended within the 
pelvic cavity, and we have resulting a face presentation of 
the mento anterior variety. This is all that we shall say 
concerning the mechanism of vertex presentation until we 
speak of the management of the same. 
Diagnosis of Vertex Presentation.—We are now in a po- 
sition to consider the diagnosis of vertex presentation, and 
we are here called upon to make the diagnosis, first, during 
pregnancy; secondly, during labor; and thirdly, after labor 
has been completed. The diagnosis of vertex presentation 
during pregnancy or before the os is sufficiently dilated to 
permit of our distinguishing sutures or fontanelles or the 
character of the presenting part is made almost entirely by 
what is known as external or abdominal palpation. Let me 
say here that the subject of abdominal palpation is one that 
we can not become too familiar with and one that we can 
not practice too often. There are those who maintain that 
if we could do away with all personal contact (by that we 
mean all internal examination or the use of instruments or 
catheters) we could absolutely do away with that scourge 
of former years—namely, puerperal septicaemia, in fact, 
Leopold, of Dresden, professes to have demonstrated by sta- VERTEX PRESENTATION. 
17 
tistics—and statistics do occasionally prove something— 
that in proportion as the number of vaginal examinations 
diminishes, the percentage of fever-free convalescences in- 
creases. Such an assertion of necessity implies that there 
is no such thing as self-infection in the puerperal woman, 
that the cause of the infection resides not in the patient 
herself but in her attendants. And while we are not ready 
as yet to do away entirely with vaginal examinations dur- 
ing labor, still our aim should be to make these examina- 
tions as infrequently as an intelligent management of the 
case will permit. 
1. [In the lecture as delivered the author proceeded as 
follows] : “ In order to illustrate more clearly how abdomi- 
nal palpation should be conducted, I have had one of my 
patients brought over from the Emergency Lying-in Hos- 
pital who is a primipara and within two weeks of full term. 
The patient, as you see, is placed upon a hard examining table, 
with her clothes so loosened and arranged that we may 
readily examine the abdomen from the hips to the free bor- 
der of the ribs ; and then, to render the anterior abdominal 
walls as lax as possible, we have the woman flex her thighs 
somewhat. As you see, I take my stand at the woman’s 
right and facing her. I place the palms of my hands over 
the lower part of the uterus so that the finger-tips meet in 
the median line, and then, by passing them gently upward, 
all the time carefully manipulating the uterine contents, we 
determine whether the long axis of the child lies vertically 
or obliquely in the uterus, whether the head or breech occu- 
pies the fundus, and something regarding the size of the 
foetus. Having determined that the child lies vertically, 
that the breech and not the head occupies the fundus, and 
that the fundus reaches nearly to the ensiform cartilage, we 
next seek by another manipulation the position of the small 
parts and the dorsal plane of the foetus. To do this the 18 
THE MECHANISM AND DIAGNOSIS OF 
hands are separated and are placed flat, one on each side of 
the fundus of the uterus. Then, by passing the contained 
foetus gently from hand to hand, we determine to which 
side lies the smooth hard plane of the back, and in which 
side lie the irregular, movable small parts. We may great- 
ly aid our endeavors by pushing the foetus with one hand 
firmly up against the palm of the other, thus dislodging 
the liquor amnii, which may interfere with our palpat- 
ing. So far we have learned that the head presents, that 
the back of the child looks to the left of its mother, and 
that the small parts—namely, the feet—lie to the right in 
the fundus uteri. The next question to be decided is, Is the 
head, which we can now feel in the lower part of the uterus, 
engaged ? To determine this we separate the thumb and 
fingers of either hand as widely as possible, and with the 
tips of the thumb and middle finger we attempt to seize 
the presenting part just above the pubes in this manner. 
Were this woman a multi para, in all probability we could 
move the head readily from side to side by this means ; 
but we find when we grasp what appears to be the head 
just at the pelvic inlet that we are unable to move it from 
side to side, or, in other words, the head, as is usually the 
case in a primipara, is engaged in the entrance of the pel- 
vis. Now, to determine the amount of this engagement, 
we take another position—namely, with our back to the 
face of the patient. Then, with the tips of the fingers of 
both hands, we slowly and gradually follow the lower part 
of the foetus as deeply along the sides of the pelvis as we 
are able; and you see, by exerting no sudden or jerking 
movements, after we have partially overcome the resistance 
of the muscles, that we may pass our fingers to a consid- 
erable extent into the pelvis of this gravid woman, and we 
determine that the head, which we can now distinctly feel, 
has descended somewhat in the pelvic cavity. Now, what VERTEX PRESENTATION1-. 
19 
have we determined so far ? We have a cephalic presenta- 
tion, with the back of the child pointing to the left of the 
mother; and if, moreover, we make use of the stethoscope 
and find that the foetal heart sounds are most distinct at a 
point midway between the left anterior superior spine of the 
ilium and the umbilicus, and if by this last manipulation of 
forcing the finger-tips alongside of the head into the pelvic 
cavity we feel certain there is no extension of the head, we 
have every reason to believe, without any internal examina- 
tion whatsoever, that we have a vertex presentation to deal 
with, and that the position is or will be the left occipito- 
anterior.” 
2. Such abdominal palpation may be carried out, as you 
have seen me perform it upon this gravid woman, just as 
well during labor, in the intervals between the pains, as in 
pregnancy, and while I would not advise you to do away 
entirely with internal examination during parturition, yet in 
most instances one examination at the beginning of the first 
stage, to corroborate our external examination and to deter- 
mine the condition of the cervix, membranes, and pelvis, 
and one when the membranes rupture, to satisfy ourselves 
that there is no prolapse of the cord or an arm, and that 
the presentation and position are normal, will be, in most 
instances, quite sufficient. When labor has far enough ad- 
vanced for us to palpate the vault of the skull, the diagnosis 
of vertex positions is made from the position and character 
of the fontanelles and sutures which we are enabled to pal- 
pate, and which we become sufficiently familiar with in our 
biweekly practice with the manikins and in the tenement- 
house service. 
3. After labor is completed we are sometimes called 
upon, for medico-legal purposes, to express an opinion re- 
garding the presentation in which the child was born. To 
illustrate this point I have had sent over to-day from the 20 
THE MECHANISM AND DIAGNOSIS OF 
morgue the cadavers of three still-born children, and we 
notice several points of interest about the conformation of 
their heads. We usually rely upon two points in making 
the diagnosis of the presentation after delivery. The first 
of these is the shape of the child’s head, and the second is 
the position of the caput succedaneum. Where labor has 
been rapid, where there has been no caput formed, and 
where there has been little or no molding of the child’s 
head, as was undoubtedly the case in this cadaver which I 
hold up, there is absolutely nothing by which we may be 
enabled to express a positive opinion; and we may say just 
here that there is nothing in any case in the genital canal of 
the woman to aid us in making our diagnosis. But when 
we select this second cadaver we find that the shape of the 
child’s head is distinctly different from the first. On ex- 
amining it closely, we find that the diameters of the foetal 
head have been extensively changed from the normal as the 
result of the resistance and pressure within the parturient 
canal. You see as we measure them that there is a distinct 
diminution of the suboccipito-bregmatie, of the occipito- 
frontal, and the bitemporal diameters, and that there is a 
compensatory increase in the diameter running from the 
chin to a point in the vertex situated between the apex of 
the occipital bone and the large fontanelle. This molding 
of the head, of course, is rendered possible by the approxi- 
mating and overlapping of the bones at the sutures and 
fontanelles, and this particular shape of the head that we 
have in this foetus is always characteristic of a vertex presen- 
tation and an anterior position, and we still further strength- 
en our opinion by finding that the caput succedaneum is 
situated along the inner posterior border of the right parie- 
tal bone. And, moreover, in this instance we may distinctly 
see the ecchymotic spots left by the blades of the forceps 
that were evidently applied over the occipito-mental cir- VERTEX PRESENTATION. 
21 
cumference of the head. We take up another foetal cada- 
ver, and while there is in this instance a somewhat charac- 
teristic molding of the head, still it is much less marked 
than in the second case, and upon a superficial examination 
we are unable to find anything that resembles a caput suc- 
cedaneum. But, by incising the scalp from the root of the 
nose to the posterior extremity of the sagittal suture and 
pulling back the scalp from the cranium, we find that the 
tissues that cover the inner and posterior portion of the 
right parietal bone appear somewhat more tumefied and 
certainly contain more serum than the corresponding re- 
gion on the left parietal bone, and hence the diagnosis of 
vertex presentation is, to say the least, probable. REASONS WHY 
Physiolans sMa Sntaile 
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