Reprinted from the New York Medical Record, July 23 and 30, 1887, pp. 93-98, 121-126. NEURO-MYOLOGY: Classification of the Muscles of the Human Body WITH REFERENCE TO THEIR INNERVATION, AND New Nomenclature of the Muscles. BY ELLIOTT COUES, M.D., PROFESSOR OF ANATOMY, NATIONAL MEDICAL COLLEGE ; AND D. K. SHUTE, M.D., PROSECTOR OF ANATOMY, NATIONAL MEDICAL COLLEGE. NEW YORK: TROW'S PRINTING AND BOOKBINDING CO., 201-213 East Twelfth Street. 1887. Reprinted from the New York Medical Record, July 23 and 30, 1887, pp. 93-98, 121-126. NEURO-MYOLOGY: Classification of the Muscles of the Human Body WITH REFERENCE TO THEIR INNERVATION, ' AND New Nomenclature of the Muscles. BY ELLIOTT COUES, M.D., PROFESSOR OF ANATOMY, NATIONAL MEDICAL COLLEGE ; AND D. K. SHUTE, M.D., PROSECTOR OF ANATOMY, NATIONAL MEDICAL COLLEGE. NEW YORK: TROW'S PRINTING AND BOOKBINDING CO., C ' 201-213 East Twelfth Street. 1887. NEURO-MYOLOGY : Classification of the Muscles of the Human Body WITH REFERENCE TO THEIR INNERVATION, AND NEW Nomenclature of the Muscles. Introductory. A nerve may be defined as a line of least resistance to motion in a living organism. A sensory or aesthesodic nerve is one which transmits certain modes of molecular motion from without inward, or froitt the locomotorium to the sensorium of the organism. A motory or kine- sodic nerve is one which transmits a certain mode of molecular motion from within outward, or from the sen- sorium to the locomotorium of the organism. A motory nerve is the means of translating molecular into molar or mechanical motion; a sensory nerve reverses this process. Most nerve-tracts are sensorimotor, acting both ways. A muscle may be defined as a line of least resistance to the motor influence of a nerve. Muscle is next most kinesodic after nerve. This is the tissue in which the cumulative effect of molecular motion in nerve is imme- diately translated and manifested in molar movement. A voluntary muscle is one from which motor influence can be withheld at will. An involuntary muscle is one from which such influence cannot be thus withheld. The simplest case of muscular motion resulting from nervous influence is when one part of a single cell moves mechanically in consequence of a sensation in the other part of the cell. The ciliary vibration of a ciliated epi- thelicell is a case in point : for this implies the transla- 4 tion of sensation, which is a vital mode of motion, into ordinary mechanical movement. All transfer of motion along any line of least resistance, as a nerve, to another line of next least resistance, as a muscle, is no more than the extreme amplification and elaboration of the simple case cited. Motility is the prime characteristic common to nerve and muscle ; it shows their relation to be immediate and their connection to be the closest pos- sible The whole nervimuscular system of an animal main- tains this close connection, which is not less intimate when myriads of cells stand in such inter-relation than when two cells, or two parts of one cell, are thus inter- dependent. Nor is the case altered if, as usually hap- pens, nerves remain slender threads while muscles be- come bulky masses. For muscle is only an aggregate of filaments as fine as nervous fibrils, and both are cells in ultimate analysis. In point of fact, the total motility of a nerve-tract exactly equals that of the correspond- ing muscle-tract; the motor power of nerves being in every case nicely adjusted to the resistance which can be overcome by muscular action. No muscle is developed except in connection with some nerve, and every muscle sustains the character of an instrument of some nerve. From an anatomical as well as a physiological stand-point, upon genetical as well as functional grounds, nerve and muscle are insep- arable. It appears, then, that the whole muscular fabric is built upon the plan of the nervous system. It follows that the clew to the organization of the muscular system, and consequently the rational classification of the mus- cles themselves, is found in the disposition and arrange- ment of the nerves. Neurology is the key to myology; and a neuro-myology is practicable. The coming neuro-myology is forecast in outline in the present article, which offers to classify and name the voluntary muscles of the human body according to the 5 nerves which severally supply them with motor power. We only compromise the matter here and there, in order to disturb the text-book order of things as little as pos- sible. For the present we would rather evade the full consequences of our audacious iconoclasm than lay too violent hands upon the venerated relics of anatomical antiquity. There is too much rubbish to get rid of all at once, and the very cobwebs that cover the bogies in the garret are dear to our hearts. So the new arrangement of the muscles is not quite off with the old love. But we make bold to attack the names of muscles with all our might. There is no reason why a muscle should be called levator labii sttperioris alceque nasi, except that it has been called so ; and it need not be called so any longer, if calling it nasi-labialis will be better. Why must generations of students be compelled to talk of an abductor ossis metacarpi minimi digiti and a musculus accessorius adsacro-lumbalem, because some old anatomist described certain muscles in that way when he wrote in his book about them ? We discard all such cumbersome, meaningless, or otherwise objectionable phrases as names of muscles, and select or invent other words that we con- ceive to be preferable. We are sustained in this raid on the time-honored bugbears by the conviction that the horror with which conservative age views new names for old things is less than the terror with which progressive youth gazes upon our cherished fetiches, and is no greater than our own irreverence for the sleepy old gods of the amphitheatre. But the world moves, and ideas move it, just as nerves move muscles. Half the difficulty of anatomy is inherent; the other half is in wordiness. The trouble with the student is more in the names of things than in the things themselves. He mistakes one for the other, his head swims, and then he founders in a Latin storm at sea. But that need not be. Gray's "Anatomy" takes about 450 words to name the muscles which we here name in 303 words. Gray's 6 names run from one word to five words apiece, aver- aging more than two. Our names are mostly in one word; a few are in two words; none in three or more. This is a positive practical advantage. The old names show scarcely a trace of any system of naming. Some muscles are named from their size or shape or other appearance ; some from their relative position; some from their origin or insertion ; some from their function or office. Some names are historical or complimentary ; others fanciful or whimsical. Some are words, others are phrases; some are nouns, others ad- jectives or participles; some are singular, others plural; some are Greek or Latin, others English or dog-Latin or nondescript. The old classification or arrangement of the muscles in groups for the purposes of description is scarcely less artificial and faulty. Muscles have been mostly divided into "regions," "layers," etc., by a trick caught at the dissecting-table. This presumes upon the ability of the man on the table to describe his own mus- cles scientifically, whereas he can only furnish the in- formation which may enable another to construct a scientific system of myology. We have gone by the old-fashioned landmarks as far as possible, but never hesitated to leave them behind if we must, in threading our way through the muscular labyrinth by the Ariadnean clew which the nervous sys- tem affords. For a favorable sample of the way our plan works, take the muscles of the thigh. It was only necessary to see in the so-called "obturator externus" a muscle of the adductor set, and in the so-called " tensor vaginae femoris" a muscle of the glutaeal region, to see all the femoral muscles leap into their proper places at the will of the lumbar and sacral plexuses. Then we have several clean-cut nervimuscular groups : these we call antecrural, adductorial, glutceal, coxal, and post- femoral. The first two of these are innervated from the lumbiplex; the last three from the sacriplex. The first is anterior, and presided over by the antecrural nerves. 7 The second is internal, governed by the obturator nerves. The third is posterior, superior, and superficial, ruled by two special branches of the sacriplex. The fourth is posterior, superior, and deep-seated, im- pressed directly by as many sacriplexal nerves as there are muscles. The fifth is posterior, innervated by branches of the magnisciatic nerve. Next, how shall these muscles be named so as to show to which of these five sets every one of them belongs ? The easiest way is to make the names in each set agree with one another in termination, and differ from those of all the other sets. Acting on this plan, and also compromis- ing with the old lack of system, we name the muscles thus : Antecrural Group : Sarticrurceus, recticruraus, ex- tracrunzus, medicrurceus, intracrurezus, subcrurczus. Adductorial Group : Obturiductor, pectiniductor, breviductor, longidzictor, magniductor, graciliductor. Glutjeal Group : Vaginiglutczus, ectoglutceus, meso- glutceus, entoglutceus. Coxal Group : Pyriformis, obtnriformis, quadrati- formis, gemelliformis, geminiformis. Postfemoral Group : Tendinosus, membranosus, bicipitosus. Here are twenty-four words for twenty-four muscles. Gray has forty for the same. Notwithstanding that this changes almost every name in the text-book, we imagine there are few students who will not recognize them all on sight. Such systematic classification and methodical nomen- clature we have carried out to the best of our ability in the present paper, hoping that we have at any rate got rid of a good deal of dead wood, if we have not also im- proved the order of things in other respects. All the names we use are printed in thick type, and the old ones are bracketed in quotation-marks opposite them for facility of comparison. Our names are all nouns, in due Latin form, nominative case, masculine gender, and 8 mostly singular number. A very few of them are bad Latin, like malledius, complicalis, and trachelalis, but they look well enough, and we found reason for invent- ing them. We sometimes compound words of Greek origin with Latin prepositions, or vice versa, and some- times clip a good deal in compounding; but, as a rule, the words are kept pure in fact as in form. We also incidentally introduce seme new names of nerves, like sacriplex for " sacral plexus," having in view the re- vision of the nerves in like manner on some future oc- casion. We begin by advancing the following : General Propositions. I. Agreeably to the plan of the vertebrate skeleton, which consists of a main axis or trunk, with diverging appendages or limbs, the muscular system is divisible into Axial and Appendicular musculation. Axial muscles are those which belong to the axial skeleton-that is to say, to the trunk, including the head. The muscles of the head, neck, chest, belly, back, and perinaeum, are axial. Appendicular muscles are those which belong to the appendicular skeleton-that is to say, to the limbs. The muscles of the anterior and posterior extremities are ap- pendicular. II. Spinal nerves first divide into "anterior" arid " posterior " trunks. These prime divisions are respec- tively Hypaxial and Epaxial. Hypaxial nerves are those which pass below the ver- tebral axis-that is, in man, in front of the bodies of the vertebrae. Epaxial nerves are those which pass above the ver- tebral axis-that is, in man, behind the bodies of the vertebrae. Cranial nerves do not divide like spinal nerves. Those of them which are motor - that is, those which innervate muscles-correspond to " anterior " 9 divisions only of spinal nerves. They are therefore hypaxial. It is only the "anterior" or hypaxial divisions of spi- nal nerves which form the great knots known as the cer- vical, brachial, lumbar, and sacral plexuses. The " pos- terior " or epaxial divisions are smaller, as a rule, and scarcely or not plexused; their motor function is con- fined almost entirely to the "muscles of the back," and they have nothing to do with the appendicular muscles. III. The muscles of the limbs are innervated entirely from hypaxial nerves-that is to say, from the several plexuses, together with the accessispinal nerve, which is the equivalent of a hypaxial nerve, and only a cranial nerve "by courtesy." Muscles of the limbs are therefore hypaxial as well as appendicular. IV. All the prevertebral muscles-that is, those which are situated in front of the spinal column-are innervated from anterior divisions of spinal nerves, and are there- fore hypaxial. V. All the muscles of the head which are innervated by cranial nerves are innervated as above said-by equivalents of anterior divisions of spinal nerves, and therefore are also hypaxial. VI. It follows from the foregoing that the " muscles of the back " are the only epaxial muscles of the body. VII. Every muscle 1 which is attached to the shoul- der-girdle (scapula, coracoid, or clavicle), or beyond on the fore limb, is also innervated primarily, chiefly, or en- tirely from the brachiplex, or by the accessispinal nerve ; and every such muscle is a Muscle of the Anterior Ex- tremity. VIII. Every muscle which is attached to the femur or beyond on the hind limb is innervated either from the lumbiplex or from the sacriplex ; and every such muscle is a Muscle of the Posterior Extremity. • 1 Save one-the omohyoideus. 10 IX. The muscles of the perinaeum are hypaxial, but they are non-appendicular. For, although they attach to the hip-girdle (ilium, ischium, pubis), such connection with the appendicular skeleton is incidental, like that of various muscles of the back or belly. The perinjeal mus- cles are axial; they develop in relation with the urogeni- tal and digestive systems, and represent muscles of the head at the opposite pole of the body-axis. X. Combining the foregoing considerations respecting (a) Axial and Appendicular skeletal relations of muscles with (b) Epaxial and Hyp axial neural relations of mus- cles, we lay the foundation of a rational classification of muscles as follows : A. EPAXIAL AXIAL MUSCLES. I. The Muscles of the Back : Dorsal Muscles. B. HYPAXIAL AXIAL MUSCLES. II. The Muscles of the Head: Cranial Muscles. III. The Muscles of the Neck. : Cervical Mus- cles. IV. The Muscles of the Chest: Thoracic Mus- cles. V. The Muscles of the Belly : Abdominal Mus- cles. VI. The Muscles of the Perinteum : Perinteal Muscles. VII. The Muscles of the Tail : Coccygeal Mus- cles. 11 C. HYPAXIAL APPENDICULAR MUSCLES. VIII. The Muscles of the Anterior Extremity : Arm Muscles. IX. The Muscles of the Posterior Extremity : Leg Muscles. Innervated by posterior divisions of spinal nerves. A. EPAXIAL AXIAL MUSCLES. The so-called " first layer " and " second layer " of the muscles of the back are not epaxial; are not axial ; and are not innervated by posterior divisions of spinal nerves. They therefore are not muscles of the back. They are hypaxial appendicular muscles of the anterior extremity. There is little foundation in fact for the recognition of the so-called " third layer." In so far as the innerva- tion is concerned, the "third layer''and the "fourth layer " are one, innervated by outer branches of posterior spinal nerves. The so-called "fifth layer" is more distinct, being innervated by inner branches of posterior divisions of spinal nerves. Lengthwise, or axially, the muscles of the back are continuous from occiput to coccyx with such slight modifications that it is needless, if not useless, to di- vide them into "cervical," "dorsal," "lumbar," and " sacral" regions. These muscles require to be renamed and redescribed, as well as reclassified, in order to be intelligible. The most distinct among them, after the splenii and serrati, are those which provide for the move- ments of the head, and of the ribs upon the vertebrae. The " levatores costarum," which Gray puts with the muscles of the chest, are epaxial, and therefore muscles of the back. The most unconformable muscles of the back are the splenii and the serrati. 12 I. THE MUSCLES OF THE BACK. ("Third" and " Fourth" "Layers."] I. SUPERFICIAL GROUP. Innervated by outer branches of posterior divisions of spinal nerves. («) Spleni-serrator Series. 1. Capiti-splenius. [" Splenius capitis."] ra. Colli-splenius. [" Splenius colli."] 2. Supra-serratus. ["Serratus posticus superior."] 3. Infra-serratus. [" Serratus posticus inferior." j This peculiarly unconformable series is oblique: i.e., the muscles arise from spiniprocesses and proceed ob- liquely to mastoid portion of skull, to transprocesses of cervical vertebras, and to ribs. The splenii draw the head back and to either side. The serrati are antago- nistic respiratory muscles. (£) Spinirector Series. (Sacri-lumbar region.) 1. Sacri-Iumbalis. [" Erector spinae."] 2. Dorsi-spinalis. [" Spinalis dorsi."] 3. Lumbi-dorsalis. [" Longissimus dorsi."] 4. Lumbi-costalis. [" Sacro-lumbalis."] 5. Costi-costalis. [" Musculus accessorius ad sacro- lumbalem."] (Lunibi-dorsal region.) (Dorsi-collar region.) 6. Colli-spinaiis. [" Spinalis colli."] 7. Dorsi-cervicalis. ["Transversalis colli."] 8. Costi-cervicalis. [" Cervicalis ascendens."] 13 9. Biventralis. [" Biventer cervicis."] 10. Complicalis. [" Cornplexus."] 11. Trachelalis. [" Trachelo-mastoideus."] (Colli-capital region.) Eleven muscles may be named as more or less dis- tinct in the spinirector series of man; that is to say, there is one muscle, with ten divisions, making eleven. These are all direct; that is, they are longitudinal or vertical, on the whole and in almost every detail. Thus they run from spine to spine of vertebrae, from trans- process to transprocess of vertebra?, from ilium to ribs, from rib to rib, and thence to corresponding positions on the occiput. The muscular masses collectively lie on either side of the middle line of the vertebrae, as far outward as the crest of the ilium, the angles of the ribs, and the mastoid process of the skull. The series is arti- ficially divisible into those sections which run respec- tively along the sacri-lumbar, lumbi-dorsal, dorsi-collar, and colli-capital regions ; that is to say, which lie in the three intervals between these four bounds. In the loin the muscle is indivisible. In passing thence to the thorax it splits into three parts, lying parallel and run- ning abreast. These three parts are : (i) from spine to spine of vertebrae (''spinalis dorsi"); (2) from lateral processes of vertebrae to lateral processes of vertebrae and adjoining parts of ribs ("longissimus dorsi"); (3) from angle of rib to angle of rib (" sacro-lumba- lis "). Then division (3) splits in two, giving (4) the " accessorius ad sacro-lumbalem." This makes the four partitions, which are best displayed near the middle of the back, say opposite the eighth rib. Thence, in pass- ing from the thorax to the neck, three partitions of the muscle continue on : the " spinalis dorsi " as the " spi- nalis colli; " the " longissimus dorsi " as the " transver- salis colli; " the " accessorius " as the " cervicalis as- cendens." Meanwhile, however, we meet, before leaving the thorax, with the pointed prolongation down upon 14 the thorax of the three muscles which lie parallel with one another and run abreast to the head. These are the " biventer cervicis," the " complexus," and the " trachelo-mastoideus." Their thoracic origin is from transprocesses of vertebrae ; therefore they are the prolon- gations of the " transversalis colli " and " longissimus dorsi " partitions of the whole muscle ; they lie between tne "transversalis colli" and the "spinalis dorsi et colli." Then they rapidly increase in bulk, especially the complexus, and finish the spinirector series by inser- tion in the occipital and mastoid regions of the skull. The series is simplest at its either end ; it is most com- plex at the root of the neck, where good dissection will show no fewer than six bundles of muscle. These are, from the middle line outward, (i) spinalis colli, (2) bi- venter cervicis, (3) complexus, (4) trachelo-mastoideus, (5) transversalis colli, (6) cervicalis ascendens. This means that the three bundles coming down from the head onto the thorax are wedged between the three bundles going up from the thorax onto the neck. The arrangement is really not difficult to learn, but the way it is usually described, with such names as we have used in the foregoing paragraph, makes it almost impossible to remember. Accordingly we have in- vented a system of names which express their own mean- ing ; and which are connected with one another in the same way that the muscles themselves are connected, as will be seen by the following diagram, where the names are printed in somewhat the same relative positions that the muscles themselves occupy : f Dorsi-spinalis .... .. .Colli-spinalis. iuXoiis. |Lumbi'dorsalis-" ... Dorsi-cervicalis... ( Biventralis. ,.. Complicalis. ( Trachelalis. i Lumbi-costalis ... ... .Costi-costalis .. .Costi-cervicalis. It will be observed that these names are each a single word, and that they uniformly end in -alis. This is a mat- ter of such practical convenience that we have changed 15 two very good words, " complexus " and "trachelo- mastoideus," into very dubious forms to make them cor- respond with the rest. Secondly, with the exception of the three occipital muscles of the series, where we retain the old names in a modified form, every name indicates the situation of the muscle it designates. Thirdly, the connections of the names are such that they indicate what divisions of the series are continuous with one another. Thus, dorsi-spinalis + colli-spinalis are the continuous series of slips along the spinous processes of the back and neck. Again, sacri-lumbalis + lumbi- dorsalis + dorsi-cervicalis are the next series, running from the sacrum along the lumbar and dorsal to the cer- vical region, its divisions being lumbi-dorsal and dorsi- cervical. Once more, sacri-lumbalis + lumbi-costalis + costi-costalis + costi-cervicalis are together the outer- most series which run from the sacrum along the ribs to the neck, broken into sets of slips in the lumbi-costal, costal, and costi-cervical portion of its extent. The innervation of this whole series is regular and uniform, from external branches of posterior divisions of the spinal nerves. To this statement the complicalis offers an exception. There being no external branch of the posterior division of the first cervical nerve, the com- plicalis draws upon that nerve direct. But the muscle is chiefly supplied by the "great occipital," the internal branch of the posterior division of the second cervical nerve, and the size of the muscle accounts for that of the nerve. The muscle is, however, in part supplied in the regular way by external branches of cervical nerves. These facts clearly show it to be a compound muscle, quite worthy of its name ; and we suppose that it repre- sents in itself muscles even of different groups. The biventralis, for example, the least distinct part of the mus- cle in man, is very different in birds, resembling a colli- spinalis. 16 2. DEEP GROUP. ["Fifth Layer."] Innervated by inner branches of posterior divisions of spinal nerves. The muscles of this group are more distinct from one another than those of the superficial group, because they lie so deeply between the processes of the vertebrae and the ribs as to be for the most part broken up in passing between successive segments of the trunk, much as the intercostals are. They also differ from the superficial group and resemble intercostals again, in being for the most part oblique; that is, they connect a given process of one vertebra with a different process of another vertebra, or with a rib. Their serial character is quite uniform from sacrum to axis, but is modified, in the thoracic and cervical regions, by the presence of " semispinales" in the thoracic region, by the occurrence of " rotatores " and "levatores," and, especially be- tween the axis, atlas, and occiput, by special provision for the movements of the head. The innervation of the posterior recti and obliqui of the head is also pecu- liar, owing to the special character of the first cervical nerve which supplies these muscles. We may therefore divide the Deep Group into two subgroups, to which a recognizable third may be added for the peculiar coccy- geal condition of man. («) Suboccipital Subgroup. Innervation mainly by suboccipital nerve. 1. Atlanti-rectus. ["Rectus capitis posticus mi- nor."] 2. Axi-rectus. [" Rectus capitis posticus major."] 3. Atlanti-obliquus. [" Obliquus capitis superior."] 4. Axi-obliquus. [" Obliquus capitis inferior."] The first two of these muscles are modified inter- spinales, passing from the spiniprocesses of the atlas and 17 of the axis, respectively, to the supra-occipital bone, which corresponds to the spiniprocess or neural spine of an ordinary vertebra. The last two muscles are semispinales or fidispinales, since they connect a transprocess with a spiniprocess ; the atlanti-obliquus passing from the transprocess of the atlas to the supra- occipital bone, the axi-obliquus from the same point to the spiniprocess of the axis. Besides their regular in- nervation they draw upon the next cervical nerve, the " great occipital," to some extent. Innervation by internal branches of posterior divisions of spinal nerves. (b} Vertebral Subgroup. 5. Semispinales. [" Semispinalis dorsi et colli."] 6. Fidispinalis. [" Multifidus spinae."] 7. Rotispinales. [" Rotatores spinae."] 8. Supraspinales. 9. Interspinales. to. Transpinales. [" Intertransversales."] 11. Costispinales. [" Levatores costaruni."] The arrangement is here very simple and regular. The basis of this system of musculation is the oblique set of fibres called the " multifidus," connecting the transprocess and artiprocess of a vertebra with the lam- ina and spiniprocess of some vertebra higher up. The more superficial the fibres the more vertebrae they pass by, and thus the semispinales, in the thoracic and cervi- cal regions, are seen to be but superficial slips of the ddispinalis, and, similarly, the rotispinales, peculiar to the thoracic region, are but the deepest slips of the fidi- spinalis, passing only from one vertebra to the next. The costispinales (the so-called "levatores costarum"), also peculiar to the thoracic region, are simply the prolonga- tion of the multifid system onto the ribs. The remain- ing muscles are the slips which directly connect spini- processes with one another and transprocesses with one 18 another. The innervation of this whole group is regular, except that the most lateral or superficial slips may at- tract some supply from outer rather than inner branches of the nerves. (/) Caudal Subgroup. 12. Coccygerector. [" Extensor coccygis."] When any muscle is found on the back of the stunted coccyx of man, it is the vestige of epaxial caudal mus- cles which, in some animals, are as numerous, distinct, and even as bulky as those of other parts of the spini- column. The human remnant represents all of these, and therefore can hardly be brought under any of the foregoing categories. It appears most like a prolonga- tion of the spinirector, and to that extent belongs with the spinirector series. B. HYPAXIAL AXIAL MUSCLES. Innervated by anterior divisions of spinal nerves or their equivalents ; and not appendicular. There is little intrinsic difference in the whole series of hypaxial muscles of the trunk, their innervation being continuously derived from anterior divisions of spinal nerves, or, as in the head, by motor cranial nerves which are the equivalents of anterior divisions of spinal nerves. Unlike the disposition of the epaxial muscles of the back, however, the conformation of the parts enables us to group these muscles into the several obvious " regions " of the head, neck, chest, belly, and perinaeum. The first and second (olfactory and optic) nerves, be- ing purely sensory or aesthesodic, have no voluntary muscles attached to them. (The intrinsic involuntary musculation of the eye (iridian and ciliary) is derived from filaments of the nasal branch of the ophthalmic division of the trigeminus, to- gether with filaments from the ophthalmic ganglion of the sympathetic.) 19 II. THE MUSCLES OF THE HEAD. I. ORBITAL GROUP. Innervation by the third, fourth, and sixth cranial nerves, (<z) Oculi-motor Subgroup. Third nerve. 1. Palpebralis. [" Levator palpebrae superioris; 2. Supra-rectus. [" Rectus superior."] 3. Infra-rectus. ["Rectus inferior."] 4. Intra-rectus. ["Rectus internus."] 5. Infra-obliquus. [" Obliquus inferior."] (£) Trochlear Subgroup. Fourth nerve. 6. Supra-obliquus. [" Obliquus superior."] (q) Abducent Subgroup. Sixth nerve. 7. Extra-rectus. ['' Rectus externus."] These muscles lift the eyelid and roll the eyeball about. 2. MASSETERIC GROUP. Innervated by the fifth cranial nerve {motor filaments of its infra-maxillary division). 1. Temporalis. 2. Masseter. 3. Ecto-pterygoideus. [" Pterygoideus externus."] 4. Ento-pterygoideus. [" Pterygoideus internus."] These are muscles of mastication ; they move the lower jaw upward and sideways. (For mylohyoideus and predigastricus muscles, also innervated from the fifth nerve, see beyond.) 3, CAPITI-CERVICAL GROUP. Innervated by the seventh cranial nerve {the facial). The panniculus carnosus or platysma myoides and its subdivisions, being the cutaneous muscles, or muscles of expression-innervated by tb* facial nerve-(with cer- tain exceptions noted). 20 1. Occipito-frontalis. [Primary innervation nor- mal, by the facial nerve, to anterior belly of the muscle; secondary innervation, to its posterior belly, by the oc- cipitalis minor, from the cerviciplex\ A. Cranial Region. This muscle moves the scalp to and fro. B. Facial Region, («) Aural Subregion. 2. Attollens. [Innervation irregular, by the occipi- talis minor, like posterior belly of occipito-frontalis.] 3. Attrahens. 4. Retrahens. These muscles move the ear up, to and fro. 5. Orbicularis. ["Orbicularis palpebrarum."] 6. Superciliaris. [" Corrugator supercilii."] 7. Tarsalis. [" Tensor tarsi."] (Z>) Ocular Subregion. These muscles shut the eyelids and wrinkle the skin of the forehead. The orbicularis is the sphincter of the eye.' (c) Nasal Subregion. 8. Pyramidalis. 9. Compressor. [" Compressor nasi," and " Com- pressor narium minor."] 10. Depressor. [" Depressor alee nasi."] 11. Post-dilatator. ["Dilatator naris posterior."] 12. Pre-dilatator. [" Dilatator naris anterior."] These muscles move the nose about, acting especially upon the nostrils. 21 Oral Subregion 13. Oscularis. [" Orbicularis oris."] 14. Buccinator. 15. Nasi-Iabialis. | " Levator labii superioris alreque nasi."] 16. Supra-labialis. [" Levator labii superioris pro- prius."] 17. Canini-labialis. [" Levator angulae oris."] 18. Zygo-labialis. [" Zygomaticus minor."] 19. Malari-labialis. ["Zygomaticus major."] 20. Risi-labialis. [" Risorius."] 21. Anguli-labialis. [" Depressor anguli oris."] 22. Infra-labialis. [" Depressor labii inferioris."] 23. Menti-labialis. ["Levator menti, or labii in- ferioris."] These muscles move the lips, cheek, and chin. The buccinator is the sphincter of the cheek. The oscularis or kissing-muscle puckers the mouth, and is the sphincter of the lips. The labial muscles pull the lips in every di- rection. Those above No. 20 move the upper lip; those below No. 20, the lower lip. This set radiate from the mouth in a half-circle, from the nose around by the ear and thence down to the chin, in the order above given. C. Cervical Region. 24. Platysma. [" Platysma myoides."] This muscle wrinkles the skin of the neck and breast and indirectly lowers the jaw. It blends with all the muscles of the oral subregion. D Tympanic Region. 25. Stapedius. 26. Incudius. [" Laxator tympani."] 27. Malledius. [" Tensor tympani."] These muscles move the bonelets of the ear. No. 26 is improperly called a muscle, and likewise it is 22 called incudius because it is not inserted in the incus. It may seem abrupt to pass from the platysma, a muscle of the skin of the neck, to the stapedius, a muscle of the tympanum. But the facial nerve here proves a safe guide. For the tympanum is primitively an infolding of the skin of the neck, and leads us through the Eustachi- an tube to the next group of muscles. Muscles of the tympanic subregion derive secondary innervation from other sources than the facial, as would be expected from their immediate position and transitional character be- tween cutaneous and palatal regions. (For stylohyoideus and digastricus, innervated from facial in part, see beyond.) [The eighth cranial nerve, auditory, being purely sen- sory, has no muscular connections.] 4. PALATO-PHARVNGEO-LARYNGEAL GROUP. Innervated by the ninth, tenth, and eleventh cranial nerves: sensory, sensori-motor, and motorial (motor influence supposed to be from the eleventli). The innervation in this group is very complex, espe- cially in the palatal subgroup, which is supplied largely by the facial (through branches from the otic and spheno- palatine sympathetic ganglia}, and to that extent the group belongs to the preceding one. At least one mus- cle of the palatal subgroup (the tensor of the palate) may even get some innervation from the infra-maxillary divi- sion of the fifth. But the regional relation of the mus- cles of the soft palate make it most convenient, if it be not also most natural, to bring them under this head. 1. Uvularis. ["Azygos uvulae."] 2. Palati-levator. [" Levator palati."] 3. Palati-tensor. ["Tensor palati," or " Circum- flexus."] 4. Palati-glossus. (a) Palatal Subgroup. 23 5. Palati-pharyngeus. [Nos. 1, 2, 4, 5, < Meckels ganglion, < facial. No. 3, < otic ganglion, < facial; also ? < infra-max- illary nerve. No. 5, also ? < pnettmogastric. ] These muscles move the soft palate, including the pil- lars of the fauces. Pharyngeal Subgroup. 6. Stylo-pharyngeus. 7. Supra-constrictor. ["Constrictor superior."] 8. Medi-constrictor. ["Constrictor medius."] 9. Infra-constrictor. ["Constrictor inferior."] These muscles lift and squeeze the pharynx. The pal- atal and pharyngeal muscles are scarcely "voluntary" or under control of the will. (f) Laryngeal Subgroup. 10. Thyro-glottideus. [" Thyro-epiglottideus."] 11. Supr-aryglottideus. ["Aryteno-epiglottideus superior."] 12. Infr-aryglottideus. [" Aryteno-epiglottideus in- ferior."] 13. Triticeo-glossus. 14. Arytenoideus. 15. Post-arytenoideus. [" Crico-arytenoideus pos- ticus."] 16. Pre-arytenoideus. [" Crico-arytenoideus late- ralis.''] 17. Thyro-arytenoideus. 18. Crico-thyroideus. The laryngeal are involuntary muscles, like the pha- ryngeal, but there is no harm done in naming them here. Nos. io, ii, 12, whose names end in "-glottideus," go to the epiglottis. No. 13, in "-glossus," goes to the tongue. No. 14, the only muscle not paired, is the only one 24 whose name is not compounded of two words. They are innervated by the inferior or recurrilaryngeal nerve from the pneumogastric, excepting No. 18, the crico- thyroideus, which is supplied by the external branch of the superior laryngeal branch of the pneumogastric ; in a word, by the cricolaryngeal nerve. 5. GLOSSO-HVOID GROUP. Innervated by the twelfth cranial nerve. The muscles of the tongue and hyoid bone are well marked by their motor nerve, the hypoglossal, and its descending loop communicating with the cerviciplex, but the motor influence of the facial is here, as nearly everywhere else in the head. The intrinsic muscle of the tongue, the lingualis, is affected by the facial through the tympani-chordal nerve ; and the stylo-hyoideus and post-digastricus are innervated directly by the facial. But the stylo-hyoideus often or usually has a branch from the hypoglossal, showing its proper relation to this group. The mylo-hyoideus and pre-digastricus, forming the floor of the mouth, have attracted their nerve-supply from the infra-maxillary branch of the fifth. (a) Glossal Subgroup. 1. Lingualis. From facial, through tympani-chordal. (7) Mylo-hyoid Subgroup. 2. Mylo-hyoideus. 3. Pre-digastricus. [ 'Anterior belly of the digas- tricus."] These muscles floor the mouth. Innervation from in- fra-maxillary > infra-dental > mylo-hyoid nerve. 25 (c) Temporo-hyoid Subgroup. 4. Post-digastricus. ["Posterior belly of digastri- cus."] 5. Stylo-hyoideus. These muscles lift the hyoid apparatus. Their inner- vation is partly from the hypoglossal, chiefly from the facial. The " digastricus" is a very remarkable muscle, and there is reason to think that it occurs in a highly specialized or even anomalous condition in man. There is no " an- terior belly " in many animals, and the muscle supposed to answer to the posterior belly may go, as in birds, to the angle of the lower jaw, having nothing to do with the hyoid bone. Its innervation in man, from two different sources, and neither of these the hypoglossal, favors our view that it represents two distinct muscles, neither of which, very probably, belong to the glosso-hyoidean group. Though we keep it here for the present, we di- vide it into pre-digaslricus and post-digastricus, asso- ciating the former with the my lo-hyoideus, the latter with the stylo-hyoideus. The "digastricus" is still further anomalous in that its so-called anterior belly perforates another muscle, the stylo-hyoideus. (7) Supra-hyoid Subgroup. 6. Stylo-glossus. 7. Hyo-glossus. 8. Cenio-hyoglossus. 9. Cenio-hyoideus. These four muscles, like the four preceding, lift the hyoid apparatus ; and they lower the jaw. 26 if) Infra hyoid Subgroup. 10. Thyro-hyoideus. 11. Sterno-thyroideus. 12. Sterno-hyoideus. 13. Omo-hyoideus. These four muscles lower the hyoid apparatus and, with it, the jaw. This subgroup and the last are very fine ones, making up for the difficulty about the others. Down to No. 10, inclusive, the innervation is direct from the hypoglossal; then it comes from the communicat- ing loop of the cerviciplex. With the last of this group, the omo-hyoid, we first find a muscle passing to insertion in a bone of the fore limb, pointing the way to consider the sterno-cleido-mastoid and trapezius as muscles of the anterior extremity. Of these thirteen muscles, throwing out the lingualis, which has no notable bony attachment, leaves twelve, all of which attach to the hyoid bone. These twelve divide into three groups of four each, one of these groups sub- dividing in two. Thus there are four infra-hyoid muscles, four supra-hyoid muscles in one group, and four more in two groups-a regularity of disposition which may help one to remember them. III. THE MUSCLES OF THE NECK. Innervated by deep branches of anterior divisions of cer- vici-spinal nerves. t. Majori-rectus. ["Rectus capitis anticus major."] 2. Minori-rectus. [" Rectus capitis anticus minor."] 3. Lateri-rectus. [" Rectus capitis lateralis."] 4. Colli-longus. [" Longus colli."] 5. Ante-scalenus. [" Scalenus anticus."] 6. Medi-scalenus. [" Scalenus medius."] 7. Post-scalenus. [" Scalenus posticus."] These muscles bend the neck forward, bend the head forward upon the neck, and raise the ribs. No. 4 is 27 strictly vertebral (prevertebral); but its connection with " anterior tubercles " of transverse processes of cervical vertebrae, that is, with pleurapophysial elements, shows its intimate relation with the scalene or costo-vertebral muscles, Nos. 5, 6, and 7. The three upper muscles, Nos. 1, 2, and 3, are cranio-vertebral. These are in- nervated from the upper cervical nerves which form the cerviciplex ; more exactly, by three branches from the first cervical nerve, before it joins the plexus. The four lower muscles are innervated from the lower cervical plexus or brachiplex ; but the scaleni also get some sup- ply from higher up. The lateri-rectus, or "rectus late- ralis," extending from the transprocess of the atlas to a transverse portion of the occipital bone, is by position like an " intertransverse " spinal muscle ; but it is hypax- ial, not epaxial. It may be observed, that those muscles of this group which are supplied from the lower cervical nerves are in- nervated by branches given off before these nerves are plaited into the brachiplex. IV. THE MUSCLES OF THE CHEST. fci) Innervated by the phrenic nerve, etc. i. Diaphragma. The most remarkable and important voluntary muscle of the body, primarily innervated from several cervici- spinal nerves, far from the site of the muscle itself; also from several lower intercostal or thoracispinal nerves, and moreover from the diaphragmatic sympalhetiplex. The physiological activity of the muscle is as extensive and diverse as its innervation, being concerned in respi- ration, circulation, parturition, and defecation. 28 (£) Innervated by upper intercostal (suprathoracic) nerves. 2. Extracostales. [" Intercostales externi."] 3. Intracostales. [" Intercostales interni."] 4. Infracostales. 5. Sterno-costalis. [" Triangularis sterni."] These are among the many muscles of respiration. They are all more or less perfectly intercostal, that is, represent myocommas between and separated by ribs. The " upper intercostal nerves " are a convenient group- ing of the superior set of thoracispinal nerves, being those mainly confined to the thorax. The supracostales or so-called "levatores costarum" are innervated by pos- terior, not anterior divisions of the thoracispinal nerves, and are therefore epaxial. (See muscles of the back.) Innervated by lower intercostal (infrathoracic) and lumbiplexal nerves. V. THE MUSCLES OF THE BELLY. 1. Extrobliquus. ["Obliquus abdominis externus."] 2. Introbliquus. | " Obliquus abdominis interims."] 3. Transversus. | " Transversalis abdominis."] 4. Quadratics. [" Quadratus lumborum."] 5. Intrarectus. [" Rectus abdominis."] 6. Extrarectus. [ ' Pyramidalis."] 7. Cremaster. Muscles of respiration, parturition, and defecation, and likewise flexors of the trunk. They are closely related to intercostals, chiefly differing in not being broken up into myocommas by intervening ribs. Their innervation corresponds to that of the intercostals, being from suc- cessive lower thoracispinal nerves and some of the lumbi- spinal nerves from the Iwnbiplex, as the " ilio-hypogas- tric," " ilio-inguinal," and others. 29 VI.- THE MUSCLES OF THE PERINEUM. Innervated by pudic nerve from sacriplex. 1. Ani-sphincter. [" Sphincter ani externus."] 2. Ani-levator. [" Levator ani."] 3. Transperinaeus. ["Transversus perinaei."] 4. Peni-rector (or Clitoridi-rector). ["Erector penis" (or "Erector clitoridis ").] 5. Urin-accelerator. [" Accelerator urinae."] 6. Urethri-pressor. [" Compressor urethrae."] A very special group of muscles developed in connec- tion with the urogenital and digestive systems, inner- vated by the pudic or perinaeal nerve from the sacriplex. Though attached to the hip-girdle, these muscles are not otherwise related to those of the posterior extremity. VII.-THE MUSCLES OF THE TAIL. Innervated by coccygeal nerves. i. Coccygeus. This is a hypaxial muscle; it is axial in so far as it agrees with other axial muscles, as those of the abdomen, which are, nevertheless, attached to the hip-girdle ; in which latter respect the coccygeus is appendicular. It is also the only vestige in man of various large muscles which in some other animals pass from the coccygispinal or caudal region of the spinicolumn to the pelvis, to the thigh, or even to the leg below the knee. For the present we let it stand by itself. C.-HYPAXIAL APPENDICULAR MUSCLES. Innervated by anterior divisions of spinal nerves (or by the accessispinal nerve') ; and appendicular. These are the muscles of the limbs, obviously divided into those of the Anterior Extremity, fore-limb, or arm, and those of the Posterior Extremity, hind limb, or leg. 30 VIII.-THE MUSCLES OF THE ANTERIOR EX- TREMITY. Innervated by the accessispinal nerve and by the brachiplex. Innervated by the accessispinal nerve. I. CRANIACROMIAL GROUP. 1. Sterno-cleido-mastoideus. 2. Trapezius. Notwithstanding the partial sternal insertion of one of these muscles, they are incontestibly appendicular muscles of the anterior extremity. They are scarcely more than parts of one great craniacromial muscle by which the shoulder-girdle, and so the whole fore limb, is attached to the head. The great extent of the trapezius also attaches the limb to a large part of the spinicolumn. The only other attachment of the fore-limb to the head is slight and incidental, by means of the omo-hyoid, which belongs to the hyoidean group. The prime and main innervation of the craniacromial group is by the accessi- spinal nerve, which, it may be observed, arises from the spinichord, low down in the cervical region, opposite the brachiplex, whence the fore-limb derives most of its nerve-supply. The great length and breadth of these craniacromial muscles attracts additional innervation from some other sources, notably from deep external branches of the cerviciplex. 2. THORACACROMIAL GROUP. Innervated from lower cervical nerves before these form the brachiplex. 1. Clavicu laris. [" Subclavius."] 2. Dorsi-scapularis. [" Rhomboideus major" et " minor."] 3. Cervici-scapularis. ["Levator anguli scapu- lae."] 4. Costo-scapularis. [" Serratus magnus."] 5. Coraco-pectoralis. [" Pectoralis minor."] 31 A group well-marked in several respects. In the first place, all these muscles get their nerve-supply from lower cervical nerves before the brachiplex is fairly formed. Secondly, they are all " short " 1 muscles, connecting the shoulder-girdle with the neck, back, and chest, none of them going on to the humerus. All the nerves to these muscles come off from the forming brachiplex above the clavicle, excepting that to the coraco-pectoralis. The cervici-scapularis attracts additional innervation from deep branches of the cerviciplex, owing to its extension in the neck. The so-called "levator anguli scapulae " and " serratus magnus " really form but a single muscle, extending from pleurapophysial elements of vertebrae, (that is, from anterior tuberices of cervical vertebrae in the neck, and from ribs in the thorax) to the vertebral border of the scapula; in some animals they are obvi- ously one indivisible plan of muscular fibres, forming a musculinteger? The coraco-pectoralis is intermediate be- tween the clavicularis and the pectoralis (" pectoralis major"); it agrees with the former in position and rela- tions (rib to shoulder-girdle), but is innervated by a brachiplexal nerve from a different part of the plexus. The craniacromial and thoracacromial groups of mus- cles together move the shoulder-girdle in every direction, but especially upward and backward. The movements are reducible in ultimate synthesis to circumduction about the sterno-clavicular articulation as a pivotal point. The costo-scapularis is a powerful respiratory muscle. 1 " Short " and " long " muscles.-A short muscle is one which lies on only two segments of a limb, i.e., passes over only one joint. A long muscle is one which lies on more than two segments, and passes over two or more joints. Thus, the coraco-brachialis is a short muscle : the biceps-brachialis is a long muscle. Short muscles have as a rule but one function, whether of flexion or extension, long muscles, an additional reciprocal function. Thus the antico-brachialis simply flexes the forearm : the biceps-brachialis flexes the forearm and reciprocally extends the arm. 2 Since this paper was written, we have found in the human subject, and publicly demonstrated, the connection between the " levator anguli scapuli '' and " serra- tus magnus," by means of anomalous additional slips of origin of the former from several lower cervical vertebrae, so that the two supposed muscles constituted an almost continuous single muscle. In some animals, as the opossum, the two mus- cles a»e inseparably one, as pointed out many years ago by Dr. Coues in his trea- tise on the myology of that animal. 32 3. ACROMIAL GROUP. In this group the innervation is from the midst of the brachiplex, that is, after the plexus is fairly formed, and before it is resolved again into the four main nervous chords which are to go along the arm. The muscles agree with one another, moreover, in all going to the upper part of the humerus, at or near the shoulder-joint. But they come from different origins, as far remote, in man, as the sternum and even the sacrum, as opposite as epaxial and hypaxial regions of the body ; while some are " long " muscles, coming from the trunk, past the shoulder-girdle, to the arm, others are " short " muscles, coming directly from the shoulder-girdle to the humerus. This renders it expedient to divide the acromial group into subgroups. On the whole, this group is nearest re- lated to the posterior cord of the plexus. Innervated directly from the brachiplex. («) Pectoral Subgroup. 1. Pectoralis. ["Pectoralis major."] The great sterno-cleido-humeral muscle, innervated from the upper cord of the brachiplex. (II) Dorsal Subgroup. 2. Dorsalis. [" Latissimus dorsi."] The great vertebro-humeral muscle. Notwithstanding its enormous extent on the back, this muscle is closely allied with the subscapularis by its innervation by the long subscapular nerve from the posterior cord of the brachiplex. (<r) Acromial Subgroup. 3. Acromialis. ["Deltoideus."] An acromio-claviculo-humeral muscle, passing farther along the humerus than any other of the acromial group, in position related to the pectoralis, by innervation allied to the infrascapularis; supplied by circumflex branches from the posterior cord of the brachiplex. 33 Scapular Subgroup. 4. Prescapularis. [" Supra-spinatus."] 5. Postscapularis. [" Infra-spinatus."] 6. Infrascapularis. [" Teres minor."'] 7. Subscapularis. ["Subscapularis."] 8. Teretiscapularis. [" Teres major."] These are all scapulo-humeral muscles, and all are " short " muscles, proceeding directly from the scapula to the upper part of the humerus. Those upon the dorsum of the shoulder-blade are innervated by supra-scapular branches from the upper cord of the brachiplex ; the rest by subscapular and circumflex branches from the mid- dle or posterior cord of the brachiplex. The infrascap- ularis is related by origin and insertion to the postscap- ularisy but by innervation it is singularly allied to the acromialis, an apparent anomaly, not easy to explain. The teretiscapularis and subscapularis are clearly related to each other both by position and innervation ; and in the latter respect both agree also with the dorsalis (" la- tissimus dorsi "). The muscles of the acromial group collectively cir- cumduct and rotate the humerus, besides having sundry other effects. All the remaining muscles of the anterior extremity are innervated from the four main cords,1 into which the brachiplex is now resolved-"musculo-cutaneous," "mus- culo-spiral," " median," and " ulnar." 4. BRACHIAL GROUP. Innervated from " musculo spiral" and 1,1 musculo-cuta- neous" nerves. These are the muscles which lie upon the upper arm. 1 These nerves ought to be renamed. " Musculo-cutaneous " is no distinctive name, for it implies what nearly all nerves do-seek the skin after supplying mus- cles. Besides, there is another nerve of the same designation in the leg, in nowise related to that on the arm. 34 (d) Pre-brachial Subgroup. 1. Coraco-brachialis. 2. Biceps-brachialis. [" Biceps."] 3. Antico-brachialis. ["Brachialis anticus."] Innervated by musculo-cutaneous nerve. The extensors of the upper arm and flexors of the fore- arm. Innervation definite, and absorbing all the motor power of the nerve which supplies this group; the antico- brachialis often attracting some additional supply from the "musculo-spiral" nerve. The coraco-brachialis is a " short " muscle, only extending the humerus ; the antico- brachialis is a " short " muscle, only flexing the forearm, constituting its ulnar flexor; the biceps-brachialis is a " long " muscle, scapulo-radial, extending the upper arm, and flexing and also supinating the forearm, of which it is the radial flexor. (/?) Post-brachial Subgroup. Innervated by " musculo-spiral" nerve. 4. Triceps-brachialis. (4a) Extra-triceps. ["Outer head of the Tri- ceps."] Medi-triceps. ["Middle or long head of the Triceps."] Intra-triceps. ["Inner head of the Tri- ceps."] 5. Anconeus. 6. Sub-anconeus. The triple extensor of the forearm. The medi triceps is a "long" muscle, scapulo-ulnar, flexing the upper arm as well as extending the forearm. The extra-triceps and intra-triceps are " short " muscles, humero-ulnar. The anconeus is a prolongation of the extra-triceps. The so- called sztbanconeus is a slight detachment of the triceps inserted in the elbow-joint. 35 5. CUBITAL GROUP. Innervated from musculo-spiral, median, and ulnar nerves. These are the muscles of the forearm, which (a) flex the forearm, (b) pronate and supinate the forearm, (c) flex and extend the hand and fingers. The musculo- cutaneous nerve having been exhausted of motor power higher up the arm, there are left only the continuations of three cords from the brachiplex. These are practically radial, median, and ulnar. (What is meant here by radial is the continuation of the musculo-spiral, giving off its " muscular branches " and dividing into two main branches, the so-called " radial " and the post-cubital.') According to our views, the many muscles of the forearm ought to fall in two primary regions, as in fact they do. (l. POST-CUBITAL REGION.) Innervated from "musculo-spiral" nerve and its continu- ations. This is the " back of the forearm," where are situated all the cubital extensor muscles of the hand and fingers, and with these the supinators. (a) Supinator Subgroup. 1. Longi-supinator. [" Supinator longus."] 2. Brevi-supinator. [" Supinator brevis."] These are " short " muscles, humero-radial. The long supinator arises so high up on the ectocondylar ridge of the humerus that it gets its nerve direct from the musculo-spiral: it is more powerful as a flexor than as a supinator of the forearm. The short supinator has its nerve from the postcubital division of the "musculo- spiral." 36 (£) Extensor Subgroup. (Metacarpal extensors.) 3. Extensor longi-radialis. [" Extensor carpi radi- alis longior."] 4. Extensor brevi-radialis. [" Extensor carpi radi- alis brevior."] 5. Extensor ulnaris. [" Extensor carpi ulnaris."] (Digital extensors.) 6. Extensor digitorum. ["Extensor digitorum communis."] 7. Extensor indicis. 8. Extensor minimi. [" Extensor minimi digiti."] (Pollical extensors.) 9. Extensor meta-poliicis. ["Extensor ossis meta- carpi pollicis."] 10. Extensor primi-pollicis. [" Extensor primi in- ternodii pollicis."] 11. Extensor secundi-pollicis. [" Extensor secundi internodii pollicis."] It will help to recall the nine extensor muscles whose tendons pass over the back of the wrist, to group them by threes-three to the metacarpus, three to the thumb alone (including its metacarpal), and three to the other digits. The extensor longi-radialis arises so high up on the humerus that it gets a nerve direct from the " mus- culo-spiral " ; but all the rest are supplied from the post- cubital division of that nerve after it has given off the radial. All the extensors of the thumb and forefinger arise from the back of the forearm, and are cubiti-digital; all the others from the ectocondyle of the humerus ; and these are either humero-metacarpal or humero-digital. 37 Innervated by median and ulnar nerves. (2. ANTECUB1TAL REGION.) This is the " front of the forearm " where are situated all the cubital flexor muscles of the hand and fingers, and with them the pronators. 1. Tereti-pronator. [" Pronator radii teres."] 2. Quadrati-pronator. ["Pronator radii quadra- tus."] (a) Pronator Stibgroup. These are " short " muscles, humero-radial and ulno- radial; both are innervated from the median, the round pronator directly, the square pronator by a branch from the antecubital nerve. (£) Flexor Subgroup. (Metacarpal flexors.) 3. Flexor radialis. [" Flexor carpi radialis."] 4. Flexor palmaris. [" Palmaris longus."] 5. Flexor ulnaris. [" Flexor carpi ulnaris."] (Digital flexors.) 6. Flexor perforans. ["Flexor profundus digi- torum."] 7. Flexor perforatus. ["Flexor sublimis digi- torum."] 8. Flexor pollicis. [" Flexor longus pollicis."] The bulk of the flexor system is much greater than that of the extensor, but the muscles are fewer by three, and in onlj'' two sets instead of three sets. Thus there is but one radial carpal flexor, whereas there are two radial carpal extensors. There is but one pollical flexor, to offset three pollical extensors. There is no individual flexor of the index or little finger to offset the respective extensors of these digits; but all the digits except the thumb have two sets of flexors collectively, "sublime" and " profound," or perforatus and perforans. There is 38 also a gain of a palmar flexor, to which there is no cor- responding extensor. The innervation of this whole region is mainly from the median, either direct, or through its antecubital branch. This nearly exhausts the motor power of the median, leaving very little to supply to the hand. The flexor ulnaris, as would be expected, is innervated from the ulnar nerve. The case of the flexor perforans is inter- esting, its supply being from both median and ulnar nerves, indicating that it is a compound muscle. The real division of the deep flexor system would appear to be radial and ulnar; that is, the deep flexors of the thumb and of the index and middle finger would form one division, innervated from the median ; and the ring and little finger flexors would form the other division, innervated by the ulnar nerve. Such a view is borne out by the innervation of the four accessory muscles of these tendons, the lumbricales, whereof the two outer, or first and second lumbricales, belonging to index and middle fingers, are supplied by the median ; whereas the other two lumbricales are supplied by the ulnar. To sum the motor power of the four main nerve- trunks of the fore limb it may be said : (a) that the " musculo-spiral " presides over the whole extensor sys- tem of the limb ; (b) the " musculo-cutaneous," over the flexor system of the upper arm ; (c) the median, over the flexor system of the forearm, with some assistance from the ulnar; (d) and the ulnar, over the flexor system of the hand, with some assistance from the median. 6. MANUAL GROUP. Innervated by ulnar and median nerves. These are the muscles which lie wholly in the hand, and subserve the movements of the fingers. They are all palmar, though certain interossei are sunk so far be- tween the metacarpals as to be best seen from the back of the hand. They constitute adductors and abductors of all the digits; short flexors and extensors of all the 39 digits (except that the thumb has no such extensor), with certain additional short flexors of the thumb and little finger. The extensor function is confined to the dorsal interossei; it is only incidental to their adducting and abducting office, and its exhibition is only partial. (a) Thenar Subgroup. 1. Opponens pollicis. ["Flexor ossis metacarpi pollicis."] 2. Abductor pollicis. 3. Adductor pollicis. 4. Breviflexor pollicis. [" Flexor brevis pollicis."] Muscles of the ball of the thumb. Nos. 1, 2, and outer head of No. 4, from median nerve; rest from ulnar nerve. The breviflexor may be two muscles, of which the outer head is related to the abductor, the inner head to the adductor. 5. Accessiflexor indicis. 'j 6. Accessiflexor medii. I r,.T , • , . . „ . . M Lumbncales. 7. Accessiflexor annularis. { L J 8. Accessiflexor minimi. J (fl) Lumbrical Subgroup. These are the four lumbricales, ancillary to the ten- dons of the flexor perforans. They lie all on the radial sides of the tendons they respectively subserve, and their innervation is the same as that of these tendons. 9. Breviflexor minimi. ["Flexor brevis minimi digiti."] 10. Abductor minimi. [" Abductor minimi digiti."] 11. Opponens minimi. ["Flexor ossis metacarpi minimi digiti."] 12. Transpaimaris. ["Palmaris brevis."] (r) Hypothenar Subgroup. Muscles of the ball of the little finger: innervation entirely from ulnar nerve. The transpaimaris is an uncertain as well as inconstant muscle, agreeing with this subgroup in innervation and position, but differing from 40 it in the direction of its fibres, in which it resembles the outer head of the breviflexor pollicis to some extent. These superficial muscles of the manual group are seen to fall in three subgroups, of four muscles apiece. (d) Interosseous Subgroup. 13. Dorsosseus primus. 14. Dorsosseus secundus. r.ITA , • , - _ X..- > "Dorsal interossei. I 15. Dorsosseus tertius. L J 16. Dorsosseus quartus. 17. Palmosseus primus. 1 18. Palmosseus quartus. > ["Palmar interossei."] 19. Palmosseus quintus, 1 These are the four dorsal and three palmar interossei; all innervated from ulnar nerve. They are enumerated from the radial side: the numeral names show what fingers they serve. Thus, the index has a dorsal and a palmar ; the middle finger, two dorsals; the ring finger, a dorsal and a palmar; the little finger, only a palmar. The dorsals have their tendons all directed toward the axis of the middle finger: the palmars, all away from this axis. There is no second or third palmar ; and there is no fifth dorsal. IX.-THE MUSCLES OF THE POSTERIOR EXTREMITY. The musculation of the hind limb is very definite and easy to classify, if we regard its innervation, yielding some of the most perfectly neural groups of muscles to be found in the body. Thus the muscles of the front of the thigh are all supplied from one part of the lumbiplex, those of the inner aspect of the thigh from another part of the lumbiplex, and all the rest of the hind limb from the sacriplex. Innervated from the lumbiplex and sacriplex. Innervated from upper portions of the lumbiplex. I. PSOATIC GROUP. 1. Parvipsoas. [" Psoas parvus."] 2. Magnipsoas. [" Psoas magnus."] 41 This is the least satisfactory group. The parvipsoas, an irregular and inconstant muscle in man, is particu- larly unconformable. It is, moreover, vertebro-pubic, stopping short of the hip-joint, and thus not falling in with any muscles of the thigh. The magnipsoas is verte- bro-femoral, but very closely related to the iliacus in all other respects, as of innervation, function, and insertion. Its nerve-supply is primarily from high in the lumbiplex, but it also attracts some from the antecrural part of the plexus, like the iliacus. 2. ILIAC GROUP. 1. Iliacus. An ilio-femoral muscle, thus a " short " one, proceed- ing from the venter of the ilium to the enfotrochanter; in- nervation from antecrural nerve. This antecrural nerve is mainly derived from the fourth nerve of the lumbiplex (that is to say, from the old " third" nerve *) but has con- nections both with the nerve above it and the nerve be- low it. It supplies the magnipsoas in part, as well as the iliacus, showing the connection of these muscles with the antecrural group. 3. ANTECRURAL GROUP. Innervation by the antecrural nerve. 1. Sarti-cruraeus. ["Sartorius."] 2. Recti-cru raeus. ["Rectus femoris."] 3. Medi-cruraeus. ["Cruraeus."] 4. Extra-cruraeus. [" Vastus externus."] 5. Intra-cruraeus. [" Vastus internus."] 6. Sub-cruraeus. The muscles of the front of the thigh, or anterior fe- moral region ; a well-defined group, exhausting the motor power of the antecrural set of nerves. The "sartorius" 1 It should be here noted that Dr. Coues' renumeration of the spinal nerves counts seven instead of the alleged "eight" cervical nerves. Consequently, the so-called "eighth cervical" is with him the first dorsal, and each succeeding nerve changes its number by one, the so-called "first dorsal" being his second dorsal, etc. See his article in the American Naturalist, xviii., 1884, p. 379. 42 and "rectus" are ilio-tibial, and therefore "long" mus- cles, flexing the thigh as well as extending the leg. Ex- tension of the leg upon the thigh is the primary and proper function of the sartorius, its flexion of the leg in the human subject being an acquired peculiarity. The crurceus and its subdivisions, inner and outer, are fe- moro-tibial, and therefore " short " muscles, simply ex- tending the leg upon the thigh. The so-called " tensor vaginas femoris " has nothing to do with this group. 4. ADDUCTORIAL GROUP. Innervation by the obturator nerve. 1. Obturiductor. [" Obturator externus."] 2. Pectiniductor. [" Pectinaeus."] 3. Breviductor. [" Adductor brevis."] 4. Longiductor. [" Adductor longus."] 5. Magniductor. [" Adductor magnus."] 6. Graciliductor. [" Gracilis."] Rightly regarded, this is one of the most perfect mus- cular groups in the body. The innervation of all these masses of muscle is almost exclusively by the obturator nerve, including of course its accessory, and thus pri- marily from the fifth and last-the old " fourth "-nerve of the lumbiplex. The pectiniductor seems to attract a little supply from an antecrural source, and the magni- ductor, owing to its great size, steals a little from the sciatic. The trouble has been, that this group has never before been properly put together, the obturiductor, the so-called " obturator externus," having always been grouped with the "obturator internus," with which it has nothing to do, instead of being recognized as one of the adductors. Excepting the graciliductor, these adductors are all pubo-femoral or ischio-femoral, and therefore " short" muscles. They extend down the thigh-bone to an increasing extent from the insertion of the obturiduc- tor in the ectotrochanter to that of the magniductor in the entocondyle. The graciliductor is pubo-tibial, a " long " muscle, and therefore flexes the leg on the thigh as well as adducts the limb. 43 Innervation from upper part of the sacriplex. 5. GLUTZEAL GROUP. 1. Vaginiglutseus. ["Tensor vaginae femoris."] 2. Ectoglutseus. [" Glutaeus maximus."] 3. Mesoglutseus. [" Glutaeus medius."] 4. Entoglutaeus. ["Glutaeus minimus."] Nothing has tended to obscure the true character of the glutaeal group so much as the location of the vagini- glutceus among the muscles of the anterior femoral region. In man this muscle is inseparable from the ectoglutceus without arbitrary use of the knife, it being clearly contin- uous with that part of the great glutaeus which is inserted into the latifascia of the thigh. Its innervation, hitherto regarded as "exceptional," is now seen to be regular and conformable with that of the other glutaei. The enor- mous development of the ectoglutceus in man makes it attract from the sacriplex a nerve of notable size, which has received the special name of " small sciatic." But this nerve comes from the u'pper part of the sacriplex near the origin of the " superior glutaeal " nerves which go to the other glutaeal muscles. The name " small sciatic " has no special meaning, and makes the upper glutaeal part of the sacriplex liable to be confounded with the main continuation of the plexus. It would be better to say supraglutceal for the nerve which goes to the vaginiglutceus, mesoglutceus and entoglutceus, and confor- mably therewith to say infraglutceal for the nerve to the ectoglutceus muscle, which, after exhausting its motor power on that muscle, become cutaneous in the glutaeal, pudendal, and postfemoral regions. Innervation by muscular branches direct from the sacri- plex. 5. COXAL GROUP. 1. Pyriformis. 2. Obturiformis. [" Obturator interims."] 3. Cemelliformis. ["Gemellus superior."] 4. Ceminiformis. [" Gemellus inferior."] 5. Quadratiformis. [" Quadratus femoris."] 44 A neat group, each member of which has its own nerve direct from the sacriplex. Of the six muscles collectively called "rotatores femoris," proceeding from the pelvis to or near the ectotrochanter, one, the so-called " obturator externus," belongs elsewhere (see above), and two others, the " gemelli," are simply ancillary to the obturi- for mis. Innervation by muscular branches direct from the sciatic nerve. 6. POST-FEMORAL GROUP. 1. Bicipitosus. [" Biceps femoris."] 2.. Membranosus. ["Semimembranosus."] 3. Tendinosus. [" Semitendinosus."] Another good group, being the muscles which lie along the back of the thigh, tapping the sciatic nerve as it passes by. The bicipitosus is as to its long head a " long " muscle, ischio-fibular ; as to its short head a " short" muscle, femoro-fibular. The other two are " long " ischio-tibial muscles. The group extends the thigh and flexes the leg. J. PRETIBIAL GROUP. Innervation from the pretibial branch of the ectopop- litceal nerve. 1. Flexor tarsi. [" Tibialis anticus."] 2. Extensor hailucis. [" Extensor proprius pollicis pedis."] 3. Extensor digitorum. ["Extensor longus digi- torum."] 4. Flexor metatarsi. [" Peroneus tertius."] The muscles of the front of the leg, a group all sup- plied by the pretibial, one of two main branches of the ectopoplitceal. They are the long flexor system of the foot and the long extensor system of the toes. All their tendons pass over the instep in front of the malleoli- one to the tarsus on the tibial side, one to the great toe, one to the other toes, one to the metatarsus on the fibular 45 side. The latter has been very badly named " peroneus tertius." Innervation from the peroneal branch of the ectopoplitceal nerve. 8. PERONEAL GROUP. 1. Longiperoneus. [" Peroneus longus."] 2. Breviperoneus. [" Peroneus brevis."] These are the only two peroneal muscles proper, lying in the fibular region, their tendons passing behind the ex- tramalleolus to sole of foot. They are long extensors of the tarso-metatarsus. The peroneal nerve which pre- sides over this group is badly named " musculo-cutane- ous." 9. POST-TIBIAL GROUP. Innervation from post-tibial continuation of the entopop- litceal nerve. 1. Poplicaeus. 2. Ecto-gastrocnemius. [" Gastrocnemius exter- nus."] 3. Ento-gastrocnemius. [" Gastrocnemius inter- nus."] 4. Soleus. 5. Plantaris. 6. Extensor tarsi. [" Tibialis posticus."] 7. Flexor digitorum. " Flexor longus digitorum."] 8. Flexor hallucis. [" Flexor longus pollicis."] This is an extensive group, which might, perhaps, be advantageously subdivided, according to its innervation from the entopoplitaeus itself-that is to say, from the main poplitaeal trunk above the lower border of the poplitaeus, and from its continuation below that line as the post-tibial. This would practically give us a super- ficial subgroup and a deep subgroup. The former would consist (a) of the very peculiar poplitceus, a " short " femoro-tibial muscle whose oblique direction recalls a pronator or supinator of the forearm ; and (b) of the very 46 compound gastrocnemius, the outer and inner portions of which are perfectly distinct to the heel in some animals, but in man are blended and further complicated by the development of a soleus to an extent unknown in other animals; and (c) of a plantaris, vestigial in man, in comparison with its great size in some species. All these excepting the poplitseus have a common insertion by an Achillean tendon in the heel-bone; they extend the whole foot and (excepting the soleus) reciprocally flex the leg on the thigh. The remaining three muscles com- plete the extensor system of the foot, and constitute the long flexor system of the toes. IO. PEDAL GROUP. Innervation by an extratarsal branch of the pretibial nerve. i. Brevextensor digitorum. ["Extensor brevis digitorum."] The only muscle on the instep, representing the short extensor system of the toes. Innervation by intraplantar and extraplantar branches of the post-tibial nerve. IT. PLANTAR GROUP. The muscles of the sole are numerous and do not agree well with their innervation by the inner and outer plantar nerves, if we are to treat them in any similar way to that in which the palmar muscles have been grouped : that is, according to their position and relation to the digits. (a) Digital Subgroup, i. Breviflexor digitorum. ["Flexor brevis digi- torum. "] To the toes collectively, excepting the great toe. In- nervation intraplantar. Though confined to the sole this muscle is a flexor perforatus, corresponding to that so named in the forearm. 47 (7) Accessidigital Subgroup. 2. Accessiflexor digitorum. ["Flexor digitorum accessorius."] 3. Accessiflexor secundi. ] 4. Accessiflexor tertil. I p. Lmnbricales... . 5. Accessiflexor quarti. [ L J 6. Accessiflexor quinti. J This is the accessory flexor set, ancillary to the ten- don of the long flexor digitorum. The nerve-supply is nearly conformable, being mainly extraplantar, only the lumbricales of the second and middle toes being supplied by the intraplantar nerve. But this separation of the lumbricales into two sets, inner and outer, by their nerve- supply, agrees with the case of the palmar lumbricales. We have named the plantar lumbricales to agree with the name accessiflexor, in the first place, and secondly, to distinguish them as going to the second toe, middle toe, fourth toe, and little toe. Each goes to the inner side of the toe and tendon to which it is related. 7. Abductor hallucis. ["Abductorpollicispedis."] 8. Breviflexor hallucis. ["Flexor brevis pollicis pedis."] 9. Adductor hallucis. ["Adductorpollicispedis."] 10. Transductor hallucis. [" Transversus pedis."] (r) Hallucal Subgroup. The muscles peculiar to the great toe; named in their order from the inner to the outer side of the sole : the inner two supplied from the intraplantar nerve, the outer two from the extraplantar. It is very convenient to speak of the great toe as the hallux, to distinguish it from pollex, the thumb, so as to be able to say hallucis simply instead of " pollicis pedis." (/7) Minimal Subgroup. 11. Abductor minimi. [" Abductor minimi digiti."] 12. Breviflexor minimi. ["Flexor brevis minimi digiti."] The muscles peculiar to the little toe ; innervation extraplantar. 48 (<?) Interosseous Subgroup. 13. Dorsosseus primus. 14. Dorsosseus secundus. . ,,, ,5. Dorsosseus tertius. H"Dorsalinterossei. ] 16. Dorsosseus quartus. 17. Plantosseus tertius. ) 18. Plantosseus quartus. > [" Plantar interossei."] 19. Plantosseus quintus. ) There are four dorsal and three plantar interossei, all with extraplantar innervation. They are enumerated from the inner side of the foot; and the numerals show what toes they serve, since the great toe, like the thumb, has none. Thus the second toe has two dorsossei, the primus and the secundus. The third toe has both the tertii, one dorsal, the other plantar. The fourth toe has the two quarti, one dorsal, the other plantar. The little or fifth toe has the only quintus, a plantar one. The dorsals have their tendons all directed to the axis of the second toe ; the plantars, all away from this axis. There is no second or third plantar ; and no fifth dorsal. The arrangement is thus exactly as in the hand, excepting that the axial digit is the second toe instead of the third finger. The total number of plantar and palmar muscles is the same, viz., nineteen. There is the same number of dor- sal and plantar interossei of hand and foot, seven ; and the same number of lumbricales, four. The peculiar mus- cles of the thumb and great toe are the same in number, four. There are only two muscles of the little toe, to correspond to four of the little finger (if we count the transpalmaris as one of these); to balance which dis- crepancy the sole has a brevifi'exor digitorum, wanting in the palm (the corresponding perforated flexor being carried up to the forearm), and also an accessiflexor di- gitorum, with nothing to correspond in the palm; thus bringing about the same number, nineteen. But the foot has a brevextensor digitorum on the in- step, to correspond with which there is no muscle on the back of the hand.