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Meckel JF. Handbook of Pathological Anatomy (Handbuch der pathologischen Anatomie) Vol. 2. (1812) Leipzig.

Ligaments: I. Trunk | II. Head | III. Extremities   Muscles: I. Trunk | II. Head | III. Extremities   Angiology: I. Heart | II. Body or Aorta Arteries | III. Body Veins| IV. Pulmonary Artery | V. Pulmonary Veins | VI. Lymphatic System | VII. A Comparison of Vascular System   Nervous System: I. Central Nervous System
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This historic 1812 textbook by J. F. Meckel, Professor of Anatomy at Halle, was translated firstly from German Into French (with additions and notes) by Prof. A. J. L. Jourdan and G. Breschet. Then translated again from French into English (with notes) by A. Sidney Doane.



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Section I. Of The Muscles of the Trunk

§ 997. The muscles of the trunk are divided into those which move the different bones of the trunk and head, and into those which go from the trunk to the first two divisions of the upper limbs: the latter, although they do not act on the bones of the trunk, deserve to be considered in this place, because many of them form the external layers of the muscles situated on the trunk and cover the others. The best method of classing them is to make two series :

  1. The posterior muscles of the trunk , or the muscles of the back and the posterior muscles of the neck.
  2. The anterior muscles of the trunk, or the muscles of the abdomen, of the thorax, and of the anterior part of the neck.


Chapter I. Muscles of the Back

§ 998. The muscles situated on the posterior part of the trunk, or on its dorsal side ( musculi dorsales), form several superimposed layers, which are four in number and which differ in their attachments and also in their modes of action. The external muscles are for the most part larger, but they are fewer. They cover the other muscles of the back and belong to the class of the broad muscles. Those below them are more oblong ; most of them are short, especially those situated most deeply. Some are composed of several short separate bellies.


In regard to the functions and attachments of these muscles, we may say, that most of them belong to the vertebrae, the head, and the ribs ; for but few are attached to the bones of the upper extremities.

The superficial belong to the second section and the deep-seated to the first.

The direction of the fibres is not the same in all. In some for instance, as the trapezius and the latissimus dorsi, it varies in the different regions. But in most of the others it is the same every where. We may remark generally, that no muscle of the back is composed entirely of longitudinal fibres, which are found only in the centre of the trapezius and in the upper part of the latissimus dorsi. The fibres of all the others are more or less longitudinal. The latter may be referred to three classes.

First, those which ascend in a straight line and which move the parts in that direction. These are the sacro-lumbalis and longissimus dorsi muscles, the cervicalis decendens, the interspinales and their corresponding muscles, the rectus capitis posticus major and minor, the intertransversarii, and the lateral muscles of the head, which correspond to them ; these may be called the straight muscles of the back (J\i. dorsales recti).


Second, those which descend obliquely outward ; some arise from the spinous processes, and are attached to the transverse processes of the lower vertebrae, to the ribs, or to the scapula ; others proceed from the transverse processes and go to the scapula or to the ribs ; finally, some proceed from one rib to the following. We may call them the descending oblique muscles ( JW. dorsales obliqui descendenles) from their analogy to abdominal muscles ; these are, considering them from without inward, the levator scapulae, the rhomboidei, the serratus anticus and posticus, the complexus, the digastricus, the spinales colli, the semispinales dorsi, the multifidus spinæ, the obliquus capitis superior, the supracostales, the scaleni, and the intercostales externi.

Third, those which descend obliquely outward, or the ascending oblique muscles (J\I. obliqui dorsales ascendentes). They extend either from the transverse to the spinous processes, or from the internal part of these latter to the bones situated more externally. They are, considering them from the surface internally, the splenii, the serratus posticus inferior, the transversalis, the complexus colli, and the obliquus capitis inferior muscles.


1. Muscles of the First, Superficial, or External Layer

§ 999. The external layer is composed of two muscles, the trapezius and the latissimus dorsi, which are attached not only to the bones of the trunk and which serve principally to move the upper extremities.

I. TRAPEZIUS.

§ 1000. The trapezius muscle, Dorso-siis-acromieri, Ch. ( J\I . cvcullaris, s. trapezius) is so called from its position and its figure when united to that of the opposite side. In fact each of these muscles has an inequilateral triangular form, the base of which looks inward. They unite on the median line, from the centre of the squamous portion of the occipital bone to the last dorsal vertebra, so that they cover the region of the neck, the back, and the shoulder. This muscle at its lower part is still more superficial than the latissimus dorsi, the upper and inner part of which it covers.

This broad, flat, and thin muscle arises, first, from the external occipital protuberance, and from a greater or less portion of the upper curved line of the occipital bone, and rarely also from the mastoid process of the temporal bone ; second, from the cervical ligament, where it blends with that of the opposite side ; third, from the spinous processes of the last cervical, and of the eighth, ninth, tenth, eleventh, and twelfth dorsal vertebrae, also from the interspinal ligaments, where the muscles of the two sides meet. The fibres which come from this last point have in general a very short tendon, except at the centre and at the inferior extremity.

The muscle is attached to the posterior edge, and to the upper face of the external or posterior part of the clavicle, to the acromion process, and to almost all the loose edge of the spine of the scapula.

The upper fibres descend obliquely from behind forward and from within outward, the centre are longitudinal, and the inferior ascend from within outward ; it is much thicker at its upper than at its lower part, and is broadest in the centre. Its fixed point is the vertebral column, so that it acts principally on the scapula and clavicle, which it draws upward by its upper part ; inward, backward, and from the side of the opposite shoulder, by its central part ; below and inward by the lower portion. When all its parts contract simultaneously, it draws these bones, and with them the whole upper extremity, backward. Its upper portion also draws the head backward and bends the neck.

II. LATISSIMUS DORSI.

§ 1001. The latissimus dorsi muscle, Lombo-humeral, Ch. occupies the lower part of the back and the whole lumbar region. Its form is triangular, and it arises from the summit of the spinous processes of from four to eight of the lower dorsal, of all the lumbar and of the sacral vertebrae, from the transverse processes of the sacrum, where it is continuous with the glutaeus maximus muscle, and from the outer lip of the central portion of the crest of the ilium, by a tendon which gradually enlarges from below upward, and finally becomes very large ; and lastly, from the external face of the four lower ribs, near their anterior extremity, by four fleshy digitations, between which the lower digitations of the obliquus abdominis externus muscle are situated. It is attached by a strong tendon to the posterior lip of the bicipital groove of the humerus, directly behind its small tubercle, so that it forms the external wall of the hollow of the axilla. The centre of its upper edge covers the inferior part of the scapula, and it is usually strengthened in this place by a strong fasciculus, which arises from the inferior angle.

The tendon of the latissimus dorsi turns from below upward and from behind forward on the inferior edge of the teres major muscle, with which it is for the most part united. But towards its extremity they most generally separate, and a large bursa mucosa exists between them. At its point of insertion it unites slightly with the tendon of the pectoralis major muscle. Toward its internal extremity, the inferior edge of its tendon sends a tendinous band to the brachial aponeurosis. A second is detached from its posterior face and goes to the small tubercle of the humerus.

The latissimus dorsi is very thin in its inner part, especially at its upper portion, but gradually increases in thickness from within outward and is finally considerably thick. Its upper fibres are longitudinal and the lower ones are oblique ; the latter become straighter as they arise more externally, and are finally almost perpendicular. This muscle acts principally on the upper extremities which it draws downward and backward ; hence the obscene but very significant term anitersor or aniscalptor. When however the upper extremity is fixed, it will draw the ribs to which it is attached upward and outward, so that it acts whenever respiration is very much impeded. Farther, it will under the same circumstances move the trunk upon the upper extremity, and raise or bend it.

§ 1002. A fleshy or tendinous band not unfrequently (about once in thirty times) detaches itself from the upper part of the latissimus dorsi, before the coraco-brachialis muscle, and goes to the posterior face of the tendon of the pectoralis major muscle, to which it is attached. This peculiar arrangement, which is found in the normal state in the mole and in birds, renders the brachial vessels and nerves very liable to com pression.(l) Sometimes also, but more rarely, a similar band goes to the coracoid process of the scapula, where it unites with the upper extremity of the coraco-brachialis muscle. (2)


2. Muscles of the Second Layer

§ 1003. The second layer is formed by the rhomboidei, the levator anguli scapulae, the splenii, and the serrati muscles, which partially or wholly cover each other. All are thin and vary in length and breadth.

RHOMBOIDEI MUSCLES.

§ 1004. The rhomboidei muscles, Dorso-scapulaire, Ch. are the most superficial; they occupy most of the space between the vertebral column and the scapula.

A. RHOMBOÏDE VS MAJOR.

§ 1005. The rhomboideus major or the inferior rhomboid muscle arises by short tendons from the lateral part of the summits of the spinous processes of the four, and sometimes of the five, upper dorsal vertebrae, sometimes even of the last cervical vertebra, and is attached to most of the external lip of the base of the scapula, from its triangular surface to near its inferior angle. Its fibres are parallel, and go obliquely outward and downward.

B. RHOMBOÏDE U9 MINOR.

§ 1006. The rhomboideus minor or superior rhomboid muscle is situated directly above the preceding, and is sometimes blended with it. It is about one fourth the size of it. It arises from the first dorsal, and from the seventh and sometimes the sixth and fifth cervical vertebrae, and is attached, its fibres having the same direction, to that part of the base of the scapula which the preceding does not occupy. At its origin, it is at first blended with the serratus magnus muscle which passes over it.

The uses of these muscles are nearly the same ; they draw the scapula upward and backward, and consequently act in shrugging the shoulders.

(1) Wardrop, in the Edin. Med. Journ. vol. viii. p. 282. — Kelch, Beyträge zur pathologischen Anatomie , 1813, p. 34, Berlin. — We have also seen this anomaly.

(2) Rosenmüller, rar. musc. p. 5. — Kelch, loc. eit. p. 35. We have seen this variety also.


II. LEVATOR ANGULI SCAPULÆ.

§ 1007. The levator anguli scapula muscle, Trachelo-scapulaire Ch. {AI. levator scapula , s. anguli scapula , AI. patientia ) is situated behind and on the side of the neck, over the rhomboidei muscles. It is longer, but thicker and more rounded than these muscles. It arises from the posterior tubercle of four, and more rarely of three or five, of the upper cervical vertebrae, by as many digitations, which are at first tendinous, generally very long, and which, especially the first, remain distinct through the whole length of the muscle. These digitations, the first of which is much the strongest, unite in a common belly, which descends obliquely backward and outward, and is attached by short tendinous fibres to the upper angle of the scapula. It is rare to find only two digitations which are attached to the first two vertebra ; however we have once observed this arrangement which was perfectly symmetrical on both sides ; at the same time, the levator scapulae was completely divided into two muscles, an internal above, an external below ; the latter was inserted in the commencement of the spine.

This formation is similar in more than one respect to what is seen in animals : in fact, in most mammalia, the levator anguli scapulae muscle has but two or three digitations, which are always attached to the upper cervical vertebra, seldom to the occipital bone. On the other hand, in apes this muscle is inserted into the spine of the scapula, and in the dolphin covers the surface of this bone.

Its upper tendons are blended with those of the splenius colli and of the cervicalis descendens. In its course it lies above the splenius muscle and is covered below by the trapezius.

This muscle corresponds in its situation and its action to the rhomboidei muscles, of which we recognize that it is only a repetition when we find it divided into several bellies, each of which is attached to but one vertebra.

It draws the upper angle of the scapula upward, but at the same time turns it round its axis, and depresses the region of the shoulder when it acts alone ; so that it is the antagonist of the trapezius and serratus magnus muscles. When it contracts at the same time with the rhomboidei and trapezius, the shoulder is directly elevated. When the upper extremities are fixed, it draws the neck to its side, if only one muscle acts ; but if both contract, the neck is fixed and kept straight.

§ 1008. Sometimes a long slip is detached from this muscle, which goes between the scapulæ and the vertebral column, an arrangement similar to what is seen in the dolphin.

III. SERRATI MUSCLES.

§ 1009. The posterior serrati muscles {AT. serrati , s. dentati postici superior et inferior) form in fact but a single muscle, since they are united by an aponeurotic expansion. Both arise from the spinous processes of the vertebras, and are attached to the ribs. The inferior is covered by the latissimus dorsi, the upper by the trapezius and the rhomboidei muscles ; both are broad and thin. They are both square, and are attached by several digitations to the ribs.

A. EERRATUS POSTICUS SUPERIOR.

§ 1010. The serratus 'posticus superior muscle, Dorso-costal , Ch., usually arises by a broad tendon from the spinous processes of the last cervical and of the first and second dorsal, rarely also from the sixth cervical and from the third dorsal vertebrae. Its fibres are directed obliquely downward, and divide most frequently into four and more rarely into three digitations, which are attached to the upper edge and to the external face of the second, third, fourth, and fifth ribs, a little beyond their angle.

§ 1011. Sometimes a single head leaves the upper part of this muscle, ascends along the levator anguli scapulae muscle, and goes to the transverse process of the first cervical vertebra.(l)

B. SERRATUS POSTICUS INFERIOR.

§ 1012. The serratus posticus inferior muscle, Lombo-costal , Ch.,is broader but thinner than the superior. It arises by a very broad but thin tendinous expansion from the spinous processes of the last two dorsal and the first three lumbar vertebrae, and adheres to the posterior tendon of the latissimus dorsi muscle so intimately that it may be said in fact to come from it. Its fibres have the same direction as that of the tendon, that is, they descend obliquety from behind and downward, and are attached, usually by four digitations, to the inferior edge of the last four ribs before their angle, from which they separate still mere as they are lower, so that the upper in some measure cover the lower.'

Between these two muscles is an elongated, very thin, aponeurotic expansion (§ 1009), in the tissue of which we evidently perceive transverse fibres in one part and another, but especially at its upper and lower parts : this expansion arises from the spinous processes of the dorsal vertebrae situated between the two muscles, and is attached to the angle of the ribs.

§ 1013. The two muscles form, with the aponeurosis which unites them and the bones placed before them, a kind of canal, in which are situated the subjacent dorsal muscles, which are compressed and kept in place by their simultaneous action. The upper raises the ribs to which it is attached. The lower acts with more power, because the ribs in which it is inserted are less firmly fixed, and it draws them downward and outward. These two muscles assist in inspiration, and are not antagonists.


(1) Rosenmüller, loc.cit., p. 5.


IV. 8PLENII MUSCLES.

§ 1014. The splenii muscles (JVT. splenii ) are considered by many anatomists as forming only one muscle, because their two lower extremities are so intimately connected. But the proportionally small extent of their union makes it more convenient to regard them as two separate muscles, one of which however is a repetition of the other : the lower is the splenius colli , the upper the splenius capitis. Both are situated directly under the trapezius, and go, from below and inward, upward, forward, and outward. They are elongated, flat, and thin. They occupy the space between the spinous processes of the lower and the transverse processes of the upper vertebra or of the corresponding bones.

A. SPLENIU8 COLLI.

§ 1015. The splenius colli muscle, Dorso-trachelien, Ch., arises, by short and tendinous fasciculi which are not very deeply separated, from the spinous processes of the third, fourth, and fifth dorsal vertebrae. It is attached by two, rarely by three, other longer digitations to the extremities of the transverse processes of the two, rarely of the three, upper cervical vertebra.

B. SPLENIUS CAPITIS.

§ 1016. The splenius capitis muscle, Cervico-mastoidien , Ch., is broader and stronger than the preceding, and is situated immediately above it ; hence its lower edge is attached to the upper edge of the other. It arises, by short tendons, from the cervical ligament at the side of the spinous processes of the third, fourth, fifth, and sixth cervical vertebrae, rarely also of the second, from the spinous process of the last cervical vertebra, and more rarely from those of the upper two dorsal vertebrae, and is attached to the posterior part of the mastoid process in its whole extent, where it covers the sterno-cleido-mastoideus muscle, and to the external part of the asperity situated below the upper curved line of the occipital bone, and consequently to a part of the bones of the skull which corresponds to the transverse processes of the vertebra.

§ 1017. The splenius colli muscle turns the neck, and the splenius capitis turns the head, so as to carry the face to the opposite side. At the same time they incline these parts a little backward ; and when they have been turned from the opposite side, they render them straight.

3. Muscles of the Third Layer

§ 1018. The third layer comprises the sacro-spinalis, the cervicalis descendens, the biventer cervicis, the complexus, the trachelo-mastoideus, and the transversales colli muscles which are attached to the ribs and head, and have all an oblong form.

I. SACRO-SPINALIS.

§ 1019. The sacro-spinalis muscle, the largest of all these muscles, extends almost the whole length of the vertebral column. It fills most of the channel between the spinous processes and the transverse processes of the vertebrae and the ribs, and divides into two bellies, which are united below to a considerable extent. The external belly is called the sacro-lumbalis muscle, and the internal the longissimus dorsi muscle.

The common belly, which is considerably thick, arises from the upper, inner, and posterior part of the crest of the ilium, from the upper oblique and spinous processes of the sacrum, from the posterior sacro-iliac ligament, where it unites with the glutæus maximus muscle, from the spinous processes of all, or only from the lower four of the lumbar vertebrae, and besides from each lumbar vertebra by short digitations, the external of which is attached to almost all the transverse process, and the internal to the accessory process ( processus accessorius ) of the latter. Its external part is fleshy. The internal is entirely tendinous at its lower part, but only on the surface at its upper. The tendon is very strong and dense, especially where it comes from the spinous processes of the lumbar vertebrae.

This common belly extends to the twelfth rib, where it divides to form the two muscles above mentioned. These gradually become thinner as they ascend, and divide into a great many slips.

The longissimus dorsi muscle is attached, 1st, by twelve bands, which grow shorter as they ascend, to the extremities of the transverse processes of the dorsal vertebrae ; 2d, farther outward, by seven or eight shorter, weaker, closer, broad slips, to the posterior and smooth face of the necks of the corresponding lower ribs.

The sacro-lumbalis muscle, the outer belly of the sacro-spinalis muscle, receives in its course several accessory fasciculi which may be considered so many origins. These fasciculi arise by tendinous fibres from the angles of the twelve ribs. Their form is oblong, and they become longer and thinner the higher they are ; they go a little upward and outward. Arising from all these points, the muscle is attached by thirteen slips, which gradually diminish in length from above downward, 1st, to the inferior edges of the angles of the ten or eleven lower ribs, and to the upper edge of the angle of the first ör of the two upper ribs, near their tubercles ; 2d, by the thirteenth slip, which is the uppermost, to the transverse process of the last cervical vertebra.

The two bellies extend the trunk, prevent it from bending forward, incline it backward and a little to the side, and draw the ribs downward.

II. CERVICALIS DESCENDERS.

§ 1020. The cervicalis descendons , more properly ascendens muscle, is only, strictly speaking, the upper part of the sacro-lumbalis muscle. It arises from the angle of the third, fourth, fifth, and sixth ribs, by three or four longitudinal slips which correspond to the accessory fasciculi of the sacro-lumbalis muscle, and unite in a short, thin belly. This usually divides into four, sometimes only three or even two digitations, which gradually increase in volume from below upward.

These digitations are attached to the posterior roots of the transverse processes of the third, fourth, fifth and sixth cervical vertebrae.

It draws the neck backward, and inclines it a little to the side. When the neck is fixed, it slightly raises the ribs.

III. BIVENTER CERVICIS.

§ 1021. The biventer cervicis muscle* is situated very near the median line, and is mostly covered by the splenii muscles, which entirely conceal it, except at its upper and lower extremities. It extends from the centre of the pectoral portion of the vertebral column to the occipital bone. It is an elongated and thin muscle composed of two rounded bellies, and of a central tendon nearly as long as the two bellies. The upper part of its external edge blends intimately, especially by the tendon of the upper belly, with the complexus muscle situated at its side.

The lower belly arises by from two to five fasciculi, the inferior of which are the longest and thinnest, from the posterior face of the transverse processes of the second, third, fourth, fifth, sixth, seventh, and eighth dorsal vertebrae.

It usually blends with the longissimus dorsi muscle by one of the inferior fasciculi, or by a distinct muscular band. Its lower extremity is constantly united with the heads of the transversalis colli muscle, and most generally with the lower extremity of the trachelo-mastoideus muscle.

These fasciculi, situated one above another, so that the posterior cover the anterior, unite to the inferior belly, which terminates imperceptibly in a point at its summit, and which almost always sends along the inferior face of the central tendon, a thin muscular slip which extends to the upper belly.

This central tendon, which, from its situation, is much longer, and more apparent on the posterior face of the muscle, the only place, properly speaking, where it is entirely loose ; commences nearly opposite the third dorsal, and extends as high as the fifth cervical vertebra.

  • The long portion of the complexus muscle of m 03 t anatomists.



The upper rounder belly is stronger and longer than the lower, and enlarges at its upper extremity, and is thinner in this part than the rest. It becomes a short tendon upward, by which it is attached to the inner part of the upper curved line of the occipital bone.

Sometimes, and even usually, this muscle has three bellies, because the upper belly at the point of union with the tendon of the complexus muscle, is divided into two portions, an upper larger, a lower smaller, by a tendon which is often an inch long, and which is likewise seen on its posterior face.

Usually also we see one of the three fasciculi coming from the spinous process of the last cervical, or of the first dorsal vertebra, sometimes also from the fifth and the sixth cervical vertebra, to go to the internal edge of the upper belly, a little above its lower extremity.

This muscle extends the neck, keeps it straight, and brings it backward. When it acts with its fellow, it extends it backward.

V. COMPLEXUS,

§ 1022. The complexus muscle is situated at the side of the preceding, and should be regarded as its external portion.(l) It i3 broader and stronger, but shorter than it, and generally extends only from the third cervical vertebra to the occipital bone. Its form is an oblong and irregular quadrilateral.

It arises by from six to nine fleshy heads, which are very tendinous at their lower part, of which an inferior is deficient more frequently than a superior ; these arise from between the third cervical and the fifth dorsal vertebrae. The three or four lower heads arise from the upper and external parts of the transverse processes ; the others more internally, from the articular processes ; so that each of the latter arises from two successive vertebrae. All ascend obliquely, the inferior straighter than the others towards the spinous processes and the biventer cervicis muscle, and unite in a large fleshy belly, in which we can always trace the fasciculi of the heads which form it.

We perceive a little above the centre of this belly an intermediate tendon, more or less perfect, and usually stronger at its internal part j which unites by this part with the second intermediate tendon of the biventer cervicis muscle, and which is also more apparent on its external than on its internal face.

The complexus muscle is attached by very short tendinous fibres which form a broad, single, rounded, and convex edge, to the external part of the upper curved line of the occipital bone.

(1) This muscle and the preceding, are described by Chaussier as the traekelo occipital. F. T,


descriptive anatomy.


Its uses are the same as those of the preceding muscle, but it draws the head more obliquely to its side when it acts alone.

§ 1023. A thin accessory muscle sometimes arises from the transverse process of the second dorsal vertebra, ascends toward the head, and is attached to the occipital bone between the complexus and the rectus posticus muscles. This formation is remarkable as being analogous with the formation of birds.

V. TRACHELO-MASTOIDEUS.

§ 1024. The trachelo-mastoideus muscle, Trachelo-mastoidien, Ch. (M. trachelo-mastoideus, s. mastoideus lateralis, s. complexus parvus), is next on the outside of the complexus muscle, is by no means as powerful, and strictly speaking should not be separated from the transversalis colli muscle, being in fact its internal and upper part.

It arises by from one to seven heads, of which a superior is deficient more frequently than an inferior. It extends from the third cervical to the sixth dorsal vertebra, arising by its lower heads from the upper part of the outer extremities of the transverse processes and from the oblique processes by its -upper heads, and is here intimately united with the origin of the biventer cervicis, the complexus and the transversalis colli, and most generally at its lower part with the longissimus dorsi muscle. These heads unite in a thin muscle, which ascends along the anterior edge of the complexus muscle, and its upper extremity is attached to the posterior edge and to the lower extremity of the mastoid process of the temporal bone.

This is the usual arrangement : but sometimes this muscle is divided into two bellies by a long intermediate tendon. Sometimes its upper part is separated into two and even three slips, the lower of which are attached to the transverse processes of the first and even of the second cervical vertebra.

It flexes the neck, which it inclines obliquely to its side, making the head lean a little in the same direction.


VI. TRANSVERSALIS COLLI.

§ 1025. The transversalis colli muscle is situated on the outside of the preceding, and is sometimes closely united with it and sometimes separated from it in a very inconstant manner. It extends between the first cervical and the middle and even the inferior dorsal vertebræ.

It arises by five, six, or seven heads from the transverse processes of the upper eight dorsal and the lower three cervical vertebræ ; so that the upper heads are deficient more frequently than the lower.

Usually it is not situated so high, does not arise so low, and is attached by four or five upper heads to the extremities of the posterior rootsof the transverse processes of thefirst six cervical vertebræ, although generally it does not extend to the first.

Its size, the number of slips of its origin and insertion, are opposite to those of the trachelo-mastoideus muscle in all these respects, if we would consider it a muscle distinct from the last.

It extends the neck and inclines it a little backward.


4. Fourth Layer of Muscles

§ 1026. The fourth layer comprises numerous muscles, all of which are situated between the vertebrae or between these bones and the head. Those between the different vertebra; are the semispinalis cervicis, the semispinalis dorsi, the spinalis dorsi, the multifidus spinae, the interspinales, the supraspinales, and the intertransversarii ; those situated between the upper vertebrae and the head are the recti muscles, the obliqui muscles, and the rectus capitus lateralis muscle.

I. DORSAL MUSCLES OF THE FOURTH LAYER.

A. SEMISPISTALIS COLLI.

§ 1027. The semispinalis colli muscle(l) arises by five or six heads, the inferior of which are the longest, feeblest, and straightest, from the posterior face of the extremities of the transverse processes of the five or six upper dorsal vertebrae. It extends obliquely upward and inward and is attached by four separate heads to the lower edge of the tubercles of the spinous processes of the second, third, fourth, and fifth cervical vertebrae.

It extends the neck, and inclines it a little obliquely backward.

D. SEMISPINALIS DORSI.

§ 1028. The semispinalis dorsi muscle resembles the preceding in form and situation. It arises by six or seven inferior heads from the posterior faces of the transverse processes of the fifth, sixth, seventh, eighth, ninth, tenth, and eleventh dorsal vertebrae, goes obliquely upward and inward, and is attached by five or six separate slips to the lower edge of the summit of the spinous processes of the lower two cervical and the three or four superior dorsal vertebrae.

These two muscles should be considered as one, and their separation is purely artificial. (2) When united, they correspond to the complex us and to the biventer cervicis muscle.

(It This muscle is generally termed the spinalis colli muscle ; but this term should be rejected, because then its analogy with the following muscle, of which it is the continuation, is neglected. Albinus noticed this fact. (Hist. muse. p. 381.)

(2) Albinus' remark upon these muscles is generally correct ; “With which (the spinalis) it is sometimes so blended, that it is doubtful to which the proximate heads and extremities belong.” (Hist. muse. p. 382.)


The semispinalis dorsi resembles the preceding in its action on the back and lower part of the neck.

C. SPINALIS DORSI.

§ 1029. The spinalis muscle, usually called the spinalis dorsi muscle, can never be presented as a distinct muscle, being always blended with the longissimus dorsi, the multifidus spinæ situated below, and the semispinalis dorsi muscles. It rests directly on the upper and posterior parts of the arches of the vertebræ, and arises by four or five separate heads from the lateral faces of the spinous processes of the upper two lumbar and lower two or three dorsal vertebræ. These heads remain for a long time tendinous. The middle belly soon divides into from four to eight upper heads, which are attached to the lateral faces of the spinous processes of the upper dorsal vertebræ.

This muscle represents particularly the digitations of the biventer cervicis muscles, which are usually attached to one or some of the spinous processes of the lower cervical vertebræ.

It extends the vertebral column and inclines it to its side.

P. MULTIFIDU9 SPINÆ.

§ 1030. The multifidus spinæ muscle is formed by a great many fleshy bands, which extend obliquely downward from the transverse processes to the spinous processes of the vertebræ above, and which interlace so differently that they thus give rise to a muscle. This muscle forms the last layer of the muscles of the back and neck, and fills the inner and deepest part of the hollow between the transverse and spinous processes.

The highest slip is attached by its upper extremity to the spinous process of the second cervical vertebra, and the lowest slip is inserted in the transverse processes of the fourth and fifth vertebræ of the sacrum.

The muscle becomes considerably thinner as it ascends, and in the same proportion less fleshy but more tendinous. The lower its fibres the more perpendicular its direction.

It is united more or less intimately with the spinalis and the semispinalis dorsi and colli muscles. Taken as a whole with these three muscles, it represents for the rest of the vertebral column and for the vertebræ the biventer cervicis and the complexus.

It extends the vertebral column and moves it to one side.

E. INTEBSPINALE8.

§ 1031. The interspinales muscles are short muscles formed of longitudinal fibres, which are situated between the summits of the spinous processes of two adjacent vertebræ.

The most apparent are those of the cervical vertebræ. Those of the lumbar vertebræ are the most feeble. Those of the dorsal vertebræ are the least distinct and often partially deficient. The cervical, as their spinous processes enlarge, become doubled more frequently than in the other regions, and thus divide into two separate muscles, a right and a left.

§ 1032. We sometimes find in the neck supraspinales muscles (M. interspinales supemumerarii , s. supraspinales), which are more superficial than the preceding and which sometimes pass over several vertebras. Thus we sometimes find in the same subject thin and small muscles, which pass from the summits of the transverse processes of the sixth or seventh to the corresponding parts of the second cervical vertebra, and below them other feebler muscles, which go from the seventh to the third cervical vertebra : both exist either on one or on both sides. These supraspinales muscles are sometimes shorter.

According to our dissections, the supraspinales muscles exist more frequently than they are absent. They evidently correspond to the spinalis dorsi muscle (§ 1029) ; so that they would be more properly termed the spinales cervicis muscles. They are generally situated on the summits of the spinous processes and not on their sides. Their presence in the neck is remarkable as an analogy with the rectus capitis posticus major muscle, which normally passes over the first cervical vertebra.

They are always looser and more detached than the fleshy slips which compose the spinalis colli muscle, in which they resemble the type of the other muscles of the neck and of the cervical vertebræ.

They extend the vertebral column.

F. INTERTRAN6VESSARII.

§ 1033. The intertransversarii muscles are formed of longitudinal fibres and are situated between the transverse processes of two vertebræ. In the cervical region they are double, like the interspinales muscles, and are called the anterior and posterior : the former extend between the anterior roots and the latter between the posterior roots of two transverse processes.

They incline the vertebral column to the side.

II. MUSCLES OF THE FOURTH LAYER BELONGING TO THE HEAD.

§ 1034. The muscles of the fourth layer belonging to the head perfectly resemble in their essential characters those muscles of the same layer which belong to the back or those of the layers over them, and are more largely developed only from the weight which they are obliged to move. They are imbedded in loose cellular tissue, which separates them from each other and from the muscles below.

They are the two straight, two oblique, and one lateral muscle.


A. POSTERIOR RECTI MUSCLES OF THE HEAD.

§ 1035. The two recti muscles of the head (JVT. capitis recti ) correspond to the interspinales muscles, and are in fact the two superior. The transition from them to the latter is marked by the interspinales colli muscles, which are strongest and in pairs, and also by the supraspinales muscles, (§ 1032), which are often seen.

a. Rectus capitis posticus major.

§ 1036. The rectus capitis posticus major muscle, Jlxoido-occipital, Ch., (M. capitis posterior rectus major, s. superficialis, s. epistrophicooccipitalis), is triangular and arises from the upper face of the spinous process of the second cervical vertebra. It begins below in a point, enlarges very much at its upper part, passes above the arch of the atlas and over the rectus capitis posticus minor muscle, and is attached by a thin and rounded edge to the lower curved line of the occipital bone.

§ 1037. This muscle not unfrequently occurs double, and this excess is analogous to the normal formation in the ruminating animals and in birds.

It extends the head directly backward.

b. Rectus capitis posticus minor.

§ 1038. The rectus capitis posticus minor muscle, Atloido-occipital, Ch., (JW. posticus capitis minor, s. profundus, s. atlanto-occipitalis), arises from the spinous process of the first cervical vertebra and is attached to the internal part of the lower curved line and also to the rough surface below, between it and the posterior edge of the large occipital foramen. It is triangular like the former, but much broader in proportion to its length. Its summit is likewise turned downward.

This muscle acts like the preceding, but is less powerful, from its smallness and its' unfavorable insertion.

These two muscles represent the upper two spinales colli muscles. The rectus major muscle corresponds to the second, which from the great weight it moves passes by the first vertebra and is attached to the corresponding part of the occipital bone. The rectus minor corresponds to the first ; it is not an exception to the rule.

8. OBLIQUE MUSCLES OF THE HEAD.

a. Obliquus capitis inferior.

§ 1039. The obliquus capitis inferior muscle, Jlxoido-atloidien, Ch., is the strongest of the small muscles of the head and has an oblong quadrilateral form. It arises below and on the outside of the rectus capitis major muscle (§ 1035), from the lateral face of the spinous process of the second cervical vertebra, goes obliquely upward, outward, and forward, and is attached to the posterior face of the extremity of the transverse process of the first cervical vertebra.

It moves the neck and at the same time the head, which it rotates on their axes ; so that the face is turned toward the side of the muscle which contracts.

This muscle seems to be the external part of the second spinalis colli muscle largely developed, the upper extremity of which would proceed to the next vertebra, as do all the other spinales muscles, but it goes more externally on account of the turning of the head. Farther, we may compare it to the splenii muscles of the preceding layer, for it resembles them perfectly in its insertions, direction, and uses.

6. Obliquus capitis superior.

§ 1040. The obliquas capitis superior muscle, Jltloido-sous-mastoi dien , Ch., is triangular. It arises above the preceding, from the upper face of the summit of the transverse process of the first cervical vertebra. It goes obliquely upward and inward, enlarges, and is attached to the occipital bone on the external part of the rough surface in the space between the two ridges.

It draws the head backward and a little to the side, so as to bring it near the occiput and turn the face from the opposite side ; hence it is the antagonist of the preceding muscle.

We may consider it as a part of the upper interfransversarius cervicis muscle or as the upper and posterior part of the second interspinalis muscle, and consequently as the upper part of the preceding. This similarity however is still greater if we compare it to the upper slip of the multifidus spinee muscle, the deficiency of which as stated by most anatomists will be compensated for in this manner.

C. RECTUS CAPITIS LATERALIS.

§ 1041. The rectus capitis lateralis muscle, Æloido-sovs-occipiial, Ch., is the smallest in this region, and arises from the upper part of the transverse process of the first cervical vertebra, goes forward and outward, and is atttached to an impression in the occipital bone behind the posterior edge of the foramen lacerum.

It draws the head to the side and a little forward.

It evidently wholly or partially represents the posterior intertransversarius cervicis muscle, which is here larger and goes a little farther forward.

This muscle is sometimes double, an arrangement normally seen in birds.


5. Accessory Muscles of the Fourth Layer

§ 1042. We may also for the convenience of study refer to this fourth layer of the dorsal muscles the levatores costarum, the scaleni, the quadratus lumborum, and the intercostales muscles, and oppose them to the preceding as being accessory muscles, from the analogy of the bones of the trunk.

I. LEVATORES COSTARUM. (1)

A. LEVATORES COSTARUM BREVES.

§ 1643. Each rib has a short levator muscle. These muscles (levatores costarum breves ) are triangular : they arise from the inferior edge of the summit of the transverse process of the next superior dorsal vertebra, go obliquely downward and outward, gradually enlarge in their course, and are attached to the posterior and superior edge of the portion of the ribs comprised between the tubercle and the angle, but they do not extend to the latter.

They are mostly tendinous on their posterior face.

B. LEVAT0RE3 COSTARUM LONGI.

§ 1044. Besides, the three to five inferior ribs have long levators ( levatores costarum longi ), which are also triangular, but broader, situated more externally, and more superficially than the short. They arise near the summit of the transverse processes of the inferior dorsal vertebræ and pass over one rib to be attached to the following.

The long and short levators of the ribs are uninterruptedly continuous with the external intercostal muscles.

The action of these muscles is indicated by their name.

II. SCALENI.

§ 1045. The scaleni should be called the long levators of the upper ribs, for they resemble the preceding in situation and form, although they act less on the ribs than upon the cervical vertebræ.

Their general characters are:- 1st, they are oblong, triangular, and pointed at their two extremities ; 2d, they arise from the upper edge and from the external face of one or both of the two upper sides by a single broad tendon ; 3d, they are attached to the transverse processes of several cervical vertebrae by different tendinous bands; 4 th, they flex the neck to the side and raise the rib3. Their number is not always the same, and varies from three to six. The most constant and the largest are three in number ; the anterior , the lateral or middle , and the posterior..


(1) The levatores breves and longi are sometimes termed collectively the supracostaleo musclee.


A. SCALENUS ANTICUS,

§ 1046. The scalenus anticus muscle, Costo-trachelien , Ch., is situ* ated behind and below the sterno-cleido-mastoideus muscle. It arises from the upper face of the first rib, some distance behind its anterior extremity, goes upward and backward, and terminates in two, three, or four bellies, which are usually separated only at their upper part, and are attached to the anterior tubercles of the transverse processes of tjcie third, fourth, fifth, and sixth cervical vertebrae.

B. SCALENUS MEDIUS.

§ 1047. The scalenus médius muscle, the longest of all, arises from the first and second ribs, about an inch farther backward and outward than the preceding, goes directly from below upward, and is attached most generally by seven slips to the posterior tubercles of the transverse processes of the seven cervical vertebrae.

C. SCALENUS POSTICUS.

§ 1048. The scalenus posticus muscle, the shortest of all, arises much farther back than the others, from the posterior part of the external face of the second rib, goes obliquely upward and forward, and is attached, behind the two preceding by two and rarely by three long and tendinous slips, to the posterior extremities of the transverse processes of the fourth, fifth, and sixth cervical vertebrae. It is sometimes deficient.

D. SUPERNUMERARY SCALENI MUSCLES.

§ 1049. The unusual or supernumerary scaleni muscles are usually developed between those already described and are smaller than them. An anterior, which is situated between the scalenus anticus and médius, and is sometimes called the Scalenus minimus , Albinus, is sometimes formed by the division of the anticus, since it is situated directly behind it and comes from the first rib. It is attached by one, two, or three heads to the anterior extremity of the transverse processes of the fifth, sixth, and seventh cervical vertebrae. Usually, the inferior nerves of the brachial plexus and the axillary vessels pass along its posterior face, between it and the scalenus médius, and the upper nerves along its anterior face, between it and the scalenus anticus muscle, although when this muscle is deficient they all pass between the sc.alenus amicus and médius.


This supernumerary scalenus anticus muscle often forms a more distinct muscle, being still more remote from the anticus and arising farther behind the upper face of the first rib. It is then always shorter, and is attached only to the summit of the transverse process of the sixth cervical vertebra, or of this and the fifth.

We have sometimes found it double. In this case there is an external and an internal , the former situated behind and the second before the last two nerves of the brachial plexus. The external or posterior is attached by a double upper slip to the anterior and posterior tubercle of the transverse process of the sixth cervical vertebra ; and the internal or anterior is inserted by four slips placed above each other only in the anterior tubercles of the transverse processes of the fifth and sixth cervical vertebra.

The supernumerary scalenus lateralis or posticus muscle is situated between the scalenus médius and the scalenus posticus. It arises from the posterior part of the first rib and is attached between the slips of these muscles to the summits of the transverse processes of the fourth, fifth, and sixth cervical vertebra.

We have sometimes found these three supernumerary scaleni at once in the same subject.

§ 1050. It is more unusual to find an analogous muscle coming from the transverse process of the sixth cervical vertebra and inserting itself into the inferior face of the humeral extremity of the clavicle.(l)

III. QUADRATUS LUMBORUM.

§ 1051. The quadratics lumborum muscle, Ilio-costal , Ch., is an oblong and rounded muscle, situated at the side of the lumbar vertebra, between the posterior portion of the crest of the ilium and the twelfth rib, so that it forms- in part the posterior wall of the abdomen.

It is composed of two more or less evident layers, an anterior and a â– posterior. The posterior layer is the most extensive. It arises from the inner lip of the iliac crest, a little behind its centre, and from the ilio-lumbar ligament by a broad tendon ; becomes larger after arising, inclines inward toward the vertebral column, divides into five or six heads which are attached to the inferior portion of the extremities of the transverse processes of the three or four upper lumbar vertebras and to the lateral portion of the bodies of the two inferior dorsal vertebra, and is finally inserted by a broad slip in the inner part of the inferior edge of the twelfth rib.

The anterior layer is thinner, and arises by some tendinous slips from the upper part of the extremities of the transverse processes of the three or four inferior lumbar vertebras,, and blends with the preceding.

(I ) Kelch, Beylrtçge zur pathologischen anatomie , p. 32, No. xxxi>-'

The quadratus lumborum muscle evidently represents the leratores costarum, the scaleni, the levator anguli scapulae, and the rhomboidei muscles ; and anteriorly, the pyramidal muscles. We must not compare this muscle, but the two obliqui abdominis muscles, to the intercostales muscles. The two layers of which it is composed, fully justify the parallel drawn between it and the preceding muscles.

It flexes the lumbar vertebrae to its side, and depresses the lower ribs.


IV. INTERCOSTALES.

§ 1052. The intercostales muscles are divided into the proper intercostales, and the subclavius muscles.

L PROPER INTERCOSTALES.

§ 1053. Each intercostal space is filled on each side by two thin muscular layers formed of oblique fibres, which are called the intercostales muscles. The whole number of these muscles is consequently forty-four, of which eleven on each side are external, and eleven internal.

a. Intercostales Externi.

§ 1054. The intercostales externi muscles, go from the lower part of the external face of the ribs, obliquely from behind forward, to the upper part of the outer face of the next rib below, so that their posterior fibres are more oblique than their anterior. They commence near the tubercle of the ribs, and extend to the costal cartilages. At their termination, they are replaced by an aponeurosis formed of fibres which have the same direction. Many tendinous fibres leave their upper and lower edges, and are expanded on their external face, which extend almost to the opposite edge.

b. Intercostales Interni.

§ 1055. The intercostales interni muscles occupy all the space between the costal cartilages and the bony parts of the ribs to their angle. Their fibres are oblique from within outward, and from before backward, and extend from the internal margin of the inferior edge of each rib to the internal lip of the upper edge of the rib directly below.

The inferior, at their posterior part, occasionally give off slips which pass to the next rib, and even to the one below.

The central are divided by slips, situated between each pair of costal cartilages, into two portions ; an anterior , which is smaller, and a

posterior , which is larger.

They differ from the intercostales externi muscles because they extend farther forward, and not so far backward ; because they are not so broad, and beeause their fibres, which follow a contrary direction, are straighter.


The two layers of intercostal muscles approximate the ribs to each other, and usually raise the lower ribs which are more movable, to the superior, which are less so.

§ 1056. We also remark on the internal face of the cavity of the thorax, muscular fasciculi, which are not constant, have no fixed place, vary much in size, sometimes lean to one side, and may be called the ùifracostales muscles. Kelch has described them as the internal serrati muscles.(l)

II. SUBCLAVIUS.

§ 1057. The subclavius muscle, Cosfo-claviculaire, Ch., resembles the intercostales, especially the externi, in situation and uses.

It arises by fleshy fibres, which descend obliquely downward and outward from the greater external part of the inferior face of the clavicle, and from the outer part of the anterior face of the rhomboid ligament ; and it is attached by a strong tendon, which extends along its inferior edge to the anterior face of the cartilage of the first rib, not far from its anterior extremity.

It brings the clavicle towards the first rib, which it most generally draws downward ; but it can also act in an opposite direction, and approximate the rib to the clavicle.

§ 1058. The analogy between the subclavius and the intercostales muscles, is sometimes rendered more evident by the presence of a second subclavius muscle, which arises from the coracoid or the acromion process, and is attached to the first rib. (2) This anomaly indicates the relation between the subclavius and the pectoralis minor muscles, and connects the normal state with that in which we find a third accessory muscle,

Chapter II. Anterior Muscles of the Trunk

§ 1059. The anterior muscles of the trunk comprise the muscles of the abdomen and chest, the anterior muscles of the neck, and the muscles of the sacrum and coccyx, when they exist.


(1) Beitr. zur Path. Anat., p. 41, No. 32.

(2) Rohmer, Ohs. Anat. part 1. p. 4.— Rosenmüller, in Isenflamm and Rosenmiiltfr, Beit., vol, i., p. 375, and Dc nonnullis muse. corp. huyiani varietatibus, p, 6.


1. Of the Abdominal Muscles

§ 1060. We find in the abdominal region seven pairs of muscles which form its parietes; four are broad, two are long, and one is short.

§ 1061. The four broad muscles are the obliquus externus, the obliquus internus, the transversalis, and the diaphragm. The two long muscles are the rectus abdominis and the pyramidalis. The short muscle is the quadratus lumborum (§ 1051). This latter has already been described.

Among the broad muscles, the first three are situated before and on the sides of the abdominal cavity, while the diaphragm occupies the upper and posterior part : the two long muscles belong to the anterior wall, and are situated on the median line.

I. OÏLIQUUS EXTERNUS ABDOMINIS.

§ 1062. The obliquus abdominis externus or descendais muscle. Costo-abdominal , Ch., is situated directly under the skin. It covers not only the other two broad abdominal muscles, but also the anterior part of the inferior intercostales and the last eight ribs, on the anterior face of which it is placed.

Its posterior part is fleshy, and its fibres go obliquely downward, inward, and forward. It arises from the last eight ribs by eight slips, the extremities of which are tendinous, and which are blended with the pectoralis major, the serratus major, and the latissimns dorsi muscles.

Of the eight slips which form the external edge of this muscle the upper is the thinnest, but the longest. It is united by the lower part of its anterior edge with the inferior part of the pectoralis major muscle, while the upper part of this same edge proceeds directly at the side of the lower part of the posterior edge of this muscle, and is attached to the external face of the fifth rib, about two inches behind its anterior extremity.

The second and third slips are the broadest. The fourth, fifth, and sixth gradually become narrower ; the seventh and eighth are much narrower than the others, with the exception of the first.

The eighth is attached not only to the cartilage of the last false rib, but also, by its lower part, to the common tendon of the two succeeding abdominal muscles. The whole posterior edge is oblique downward and backward, from the first slip to the last ; in the rest of its extent, which is less, it follows an inverse direction, and goes obliquely downward and forward.

The four upper slips are so blended with the four lower slips of the serratus magnus muscle, and the four lower with those of the latissiraus dorsi muscle, that all these slips intercross with each other by tendinous edges, directed obliquely upward and inward.

The substance of the muscle becomes much thicker from above downward.

The inferior edge of the fleshy portion is attached by short tendinous fibres to the anterior half of the internal lip of the iliac crest. It terminates at the anterior and superior iliac spine. The anterior edge describes, inward and forward, two convexities, a superior which is shorter, and a posterior which is much larger, which are separated by an intermediate depression. It is continuous with the broad anterior tendon.

The fleshy part of the obliquus externus abdominis muscle represents an oblong rhomboid, the centre of which is the broadest portion and the upper part the narrowest.

The tendon of this muscle is as broad, but much higher than its fleshy portion, since it extends from the inferior edge of the pectoralis major muscle and the cartilage of the sixth rib to the symphysis pubis.

Its upper part is the weakest and thinnest, and it terminates upward in a straight edge, which corresponds to the median line ; backward by another edge which is channeled in two places, a superior and an inferior. The anterior edge of its fleshy portion is attached to the latter. Its inferior edge is oblique from above downward. The superior is much shorter than the others and is attached to the anterior face of the cartilage of the sixth rib, and blends with the tendinous fibres of the pectoralis major muscle.

The internal is so intimately united with the same muscle of the other side that the fibres of both muscles extend in their whole extent a little beyond the median line.

The inferior is loose, and extends from the upper and anterior spine of the ilium to the symphysis pubis ; its direction is consequently oblique from above downward and forward. It forms a kind of bridge, which is extended over the space which exists in this place between the crest of the ilium and the horizontal portion of the pubis. This inferior edge is very improperly called the ligament of Fallopius ( Lig . Fallopii , s. Pouparti) ; it is more properly termed the crural arch ( arcus cruralis).

Although the lower edge of the tendon of the obliquus externus abdominis muscle leaves the bones when it reaches the anterior and superior spine of the ilium, still it unites intimately an inch and a half farther, below and inward, with the outer part of the anterior face of the crural aponeurosis, and of the tendon of the fascia-lata muscle, which fixes it so firmly that the origin of the crural aponeurosis cannot be displaced except at the place where this union ceases. From its point of union with the aponeurosis of the thigh, fibres ascend, of which the internal particularly are very strong, and go to the anterior face of the tendon.


The crural arch is the thickest and strongest part of the tendon of the obliquus externus muscle. In its course, it turns slightly upward and inward, thus forming a channel or semicanal, in the anterior part of which the spermatic cord descends.

This semi-canal commences about an inch on the outside of the external angle of the inguinal ring which we are about to describe. It is changed on the inside by the lower part of the obliquus internus and transversalis muscles into a canal, which descends obliquely, and may be called the inguinal canal (canalis inguinalis) , This canal commences at the place where the spermatic cord in the male, and the round ligament of the uterus in the female, leave the abdominal cavity through the superior , posterior, or abdominal opening ( apertura canalis inguinalis superior, posterior , s. abdominalis), and terminates by another inferior, anterior, or external opening ( apertura canalis inguinalis inferior, anterior, externa), called also the inguinal or abdominal ring ( annulus abdominalis).

From the posterior wall of the crural arch a thin layer arises, which is often formed by tendinous fibres, and is frequently simply cellular, called the transverse band ( fascia transversalis) .(] ) This band extends between the external face of the transversalis muscle and the external face of the peritoneum. It strengthens, sustains, and limits the upper opening of the inguinal canal.

The connection between the aponeurosis of the thigh and the crural arch can be observed in no other place except the point above mentioned, and we may always demonstrate the loose and smooth edge which terminates it. Still a tendinous band, some lines broad, not unfrequently separates from the inferior edge of the tendon, being attached to it only by a condensed cellular tissue, and proceeds below and a little behind it, but in a parallel direction, and extends from the internal part of the upper extremity of the tendon of the tensor fascitelatæ muscle to the pubis, where it is attached to the internal part of the posterior face of its horizontal branch.

This band causes, to a certain extent, the crural arch to appear double, or it may be regarded as a special ligament which contracts the opening over it.

Below the crural arch the crural nerves and vessels pass out of the cavity of the abdomen to go upon the thigh, and are attached to it only by a very loose cellular tissue. The abdominal viscera follow the same route in crural hernia.

The tendon of the obliquus abdominis externus muscle is formed principally of fibres which descend obliquely inward. We however see on the whole of its anterior face other more feeble and less adherent fibres, which go in a contrary direction upward and inward, cross the preceding, and serve to increase the solidity of the tendon.

(1) Cooper in Munro, Morbid Anatomy of the human gullet, &c., p. 422. — See also J. Cloquet, Recherches Anatomiques sur les hernies del’ abdomen, Paris, 1817-1819


This tendon presents at its internal part a dozen rounded foramina, situated one above another, and forming two series which are not arranged in pairs, but on the contrary alternate regularly. These openings are for the passage of the cutaneous vessels and nerves.

The lower part of this tendon presents a broader and more important foramen. This foramen is called the inguinal or abdominal ring (annulus abdominalis). It is an oblong and rounded opening, about an inch and a half long and an inch broad, the direction of which is oblique downward and inward, which is formed by the separation of the fibres of the tendon.

The opening in this place is only a greater development of the peculiar arrangement of the tendon of the obliquus externus muscle. In fact, when we examine this last attentively, we perceive that from the external and concave edge of the inguinal ring to the posterior edge of the tendon, and in a direction corresponding to that of the ring, thin fibres unite in fasciculi separated from each other, so that here and there the tendon is formed of weak external fibres, through which the color of the subjacent muscles may be seen. The two fibrous fasciculi are called pillars ; they immediately surround the inguinal ring, and the upper is generally in part separated from the rest of the tendon by two very considerable foramina, through which nerves and vessels pass. They are distinguished into the upper or internal and the lower or external pillar ( crura annuli abdominalis superius, s. internum , ct inferius , s. externum). These are the thickest and strongest parts of the tendon. The lower pillar is stronger than the upper.

The upper pillar is broader and flatter than the lower and intercrosses with that of the opposite side, so that, the left usually covering most of the right, each is attached to the spine of the pubis of the opposite side, and is blended more or less intimately in this place with the fibres of the lower pillar of the other side.

The lower pillar is shorter and more rounded than the upper, and forms the true termination of the lower edge of the fallopian tendon or ligament. It is slightly concave at its upper part, and forms a semicanal, which receives the lower part of the spermatic cord. It is attached for nine or ten lines by an edge, which is oblique from without inward and from behind forward, to the inner part of the horizontal branch of the pubis, as faras its spine.

The spermatic cord passes through the inguinal ring, following the direction of the greatest diameter of this foramen, and fills its lower portion. Many ascending fibres of the external layer, which are weaker and adhere less firmly to each other, go upon its anterior part.

The external portion of the tendon of the obliquus externus muscle is loose and united with that of the obliquus internus muscle, which lies below it, only by a looser mucous tissue. The outer half of this part corresponds to the anterior region of the fleshy portion, and the inner part to the posterior edge of the tendinous portion of the obliquus internus muscle.


The smaller internal portion of the tendon unites very firmly with the tendon of the obliquus internus muscle, and forms with it the anterior layer of the sheath of the rectus abdominis muscle. This muscle is the most superficial and the largest of all the abdominal muscles which it covers almost entirely, except- a small posterior and inferior part of the obliquus internus and transversalis muscles. It corresponds so much to the intercostales externi muscles in its position, in the direction of its fibres, and the slight distance to which its fleshy portion extends forward, that we are authorized to say that it represents them in the abdomen.

It draws the ribs downward, contracts the abdominal cavity in every direction, and in this manner it assists the other muscles in expelling the foreign bodies contained in it. At the same time, as the abdominal viscera acted upon by it tend to escape in every direction, it contributes immediately to compress the chest from below upward, and hence is a muscle of expiration. It assists a little to flex the vertebral column forward.

§ 1062. This muscle presents sexual differences in the form of the inguinal ring. In fact, in the male, where the large spermatic cord passes through it, the ring is broader and rounder than in the female, where it gives passage only to the thin round ligament of the uterus.

§ 1063. Besides the absence of a greater or less portion of its middle and anterior part, a defect of formation which is common to it with the other muscles of the abdomen in the fissure of the abdomen, the obliquus externus muscle is subject also to another anomaly, viz. the lower part of its anterior tendon is very imperfectly developed, is feeble, and presents numerous foramina. This anomaly depends on the absence of the external fibres which tie down and retain those of the deep layer. It results in a variety of external inguinal hernia, which resembles crural hernia because the viscera do not escape through the ring, but much more outward.(l)

II. onuauus INTERNUS ABDOMINIS.

§ 1064. The obliquus internus abdominis muscle, Itio abdominal, Ch. (JVÎ. abdominis obliquus internus, s. obliquus ascendens ), is situated directly under the preceding, and forms the middle of the three broad muscles of the abdomen. It is muchsmaller than the obliquus externus muscle, and occupies the space between the lower edges of the cartilages of the last five ribs, the cres . of the ilium, the pubis, and the median line.

The direction of its fibres is directly opposite to that of the fibres of the obliquus externus muscle, for they proceed inward, forward, and upward. The posterior however are straight, the central very oblique, the internal, anterior, and inferior longitudinal, and the lowest of all oblique and descending downward and inward. Considered as a whole, it is then formed of fibres which are separated from each other like a fan.

(1) Burns, in Monro, Morbid anatomy of the human gullet, &c., Edinburgh, 1811, p. 467.


The fleshy part of this muscle arises, by its upper edge, by short tendinous fibres from the whole inferior edge of the cartilage of the tenth and from the anterior part of those of the eleventh and twelfth ribs.

Its posterior edge unites with the posterior aponeurosis of the transversalis abdominis muscle, and with the common aponeurosis of the latissimus dorsi and of the serratus inferior posticus muscles, which aponeurosis arises from the spinous processes of the lumbar and sacral vertebrae.

It extends forward and downward much farther than the fleshy part of the obliquus extemus muscle, and passes as far below it as the latter rises above it.

Its anterior edge is convex above, concave below ; it extends from the summit of the cartilage of the tenth rib to near the symphysis pubis, terminates about half an inch above this articulation, and its direction is generally oblique downward and inward.

The inferior edge arises from the central face of the larger anterior part of the crest of the ilium, and below its anterior and superior spine, from the larger external part of the internal face of the crural arch. Its inferior fasciculi go very obliquely downward, pass out through the inguinal ring with the spermatic cord, which thpy surround externally, and descend with it into the scrotum : they form the cremaster muscle.

The tendon of the obliquus internus muscle is less extensive than that of the obliquus externus muscle ; but from its origin it divides in the centre into two layers, an anterior and external, and a posterior and internal. The anterior layer is intimately blended with the tendon of the obliquus externus muscle (§ 1061), and forms the anterior wall of the sheath of the rectus abdominis muscle. The posterior layer unites in the same manner with the tendon of the transversalis muscle, and forms the posterior wall of the same sheath.

At its two extremities, on the contrary, the tendon is single, and formed only by the anterior layer which passes before the rectus muscle, and unites less intimately with the tendon of the obliquus externus muscle, especially below.

The upper edge of the tendon begins at the cartilage of the ninth rib ; but the posterior layer disappears in the space between the seventh and eighth ribs. After leaving this point, the rectus muscle is situated directly on the tendon of the transversalis muscle, and higher on the costal cartilages.

The posterior layer of this tendon terminates downward, in the centre of the space between the umbilicus and symphysis pubis, by a semicircular edge, concave below, where its fibres separate a little from each other, and finally disappear.

The obliquus internus muscle corresponds to the intercostales interni muscles (§ 1045), 1st, by the direction of its fibres ; 2d, by its situation below the obliquus abdominis externus muscle ; and 3d, because its fleshy fibres extend farther forward than those of the latter.

Like the preceding, it contracts the abdominal cavity in every direction, so that its effects are the same.

III. TRANSVERSALIS.

§ 1065. The transversulis muscle, Lombo-abdominal , Ch., (JVT. abdominis transversus s. internus ) much resembles the obliquus internus muscle in its extent and direction. Its fleshy part is however longer and narrower. The fibres which form it have a transverse direction ; the direction of the lower fibres however is a little oblique from above downward and from behind forward.

The external edge is convex outward, and is oblique from above downward and from within outward. Most of it arises, by seven broad fasciculi which generally are not very distinct, from the internal face of the cartilages of the seven lower ribs, and is here blended with the anterior edge of the costal portion of the diaphragm.

The smaller and the inferior part of the posterior edge goes directly downward, and is attached to the anterior edge of the posterior tendon to be described directly, which comes from the lumbar vertebræ.

The inferior edge is attached to the internal lip of the large anterior part of the crest of the ilium, and gradually unites, from the anterior and upper spine of the iliac bone to near the inguinal ring, with the inferior edge of the obliquus internus muscle ; so that it also gives fibres to the cremaster muscle.

The anterior edge is very concave, especially directly below its centre. Its upper part is attached by short fibres to the lateral.edge of the xiphoid cartilage, but in almost all its length it is attached to the anterior tendon. This latter is a little broader at its centre than that of the obliquus internus muscle ; but it is much narrower above, because of the greater breadth of its fleshy portion.

It is composed almost wholly of transverse fibres, and forms the posterior layer of the sheath of the rectus muscle. This sheath does notextend the whole length of the muscle: itdoes not ascend to the same height, and is deficient on the costal cartilages which the recti muscles cover ; it frequently terminates also downward, a little above the centre of the space between the umbilicus and the pubis ; but we generally find in this place a very thin tendinous expansion, to which the lower part of the anterior edge of the transversalis abdominis muscle is attached, and which sometimes passes behind the rectus muscle, to unite beyond its internal edge to the anterior layer of the sheath, and sometimes, especially at its inferior part, unites at its external edge principally with that of its lower tendon.


Besides this anterior tendon, the transversalis muscle has a posterior.

This is attached by a straight edge to the posterior edge of the fleshy portion of the muscle, and divides into two layers, an anterior and a posterior.

The posterior layer is stronger ; it is composed of transverse fibres, and is attached by separate slips to the summits of the transverse processes of the upper four lumbar vertebrae and to the lower edge of the twelfth rib. Near its insertion, the fibres converge from above and below, and unite in a point. This layer is situated between the common belly of the longissimus dorsi and quadratus lumborum muscles.

The anterior layer is much thinner, passes before the quadratus lumborum muscle, and is attached by its posterior edge to the roots of the transverse processes of the lumbar vertebrae.

The transversalis abdominis muscle corresponds to the triangularis sterni muscle in the direction of its fibres, in its situation, in the attachments of its external edge to the inner faces of the libs, and by the insertion of its inner edge in the sternum and linea alba.

It acts like the preceding, but serves especially to contract the cavity of the abdomen in a transverse direction.

IV. LINEA ALBA.

§ 1066. The linea alba is a very firm tendinous band, which extends along the median line of the anterior wall of the abdomen. It is formed, by the union and crossing of the anterior tendons of the three broad abdominal muscles, within the sheath of the rectus abdominis muscle. Its greatest breadth, which is nearly half an inch, corresponds to the region of the umbilicus. From the umbilicus to the pubis, it narrows very rapidly ; but it is there much thicker than at its upper part, where it is, on the contrary, much broader. Above, for nearly two thirds of the space between the umbilicus and xyphoid cartilage, it is from two to four lines broad ; but below the umbilicus it is a line or two less.

In place of the umbilicus, in the early periods of life, we find an opening, called the umbilical ring ( annulus umbilicalis ), through which the umbilical vessels and cord pass ; but shortly after birth the opening closely unites with the remains of these same, so that here the linea alba has the most firmness.

The tendinous part of the anterior wall of the abdomen is here the firmest and strongest.

The linea alba is to the abdomen what the sternum is to the chest, except that it is not formed of bones. The anterior tendons of the broad muscles are attached to it, as the cartilages of the ribs articulate with the sternum ; and the difference of tissue between it and the sternum depends on the general difference of structure between the thoracic and abdominal cavities, the former being almost wholly formed of bones, while the parietes of the latter are fleshy and tendinous.


Finally, we find in the crocodile a real abdominal sternum and abdominal ribs, a more perfect development of what is only indicated in man and most other animals.

§ 1067. The linea alba is sometimes deficient in a greater or less portion of its extent, from a primitive deformity, or at least from an imperfect development. It often happens that it is torn or accidentally distended.

These original deformities and these consecutive alterations occasion an abnormal prolapsus of the abdominal viscera, which is called umbilical hernia ( hernia umbilicalis) when it takes place through or near the umbilicus, and is most frequently the cause of ventral hernia (hernia ventralis ) when it exists in any other place.

V. RECTUS ABDOMINIS.

§ 1068. The rectus abdominis muscle, Sterno pubien, Ch., is situated on the inner part of the anterior face of the abdomen. It is very long, and narrow in proportion to its length, but still more thin than narrow. Its thickness gradually diminishes from below upward, while its breadth in this direction increases.

It is attached to the anterior edge and to the lower part of the anterior face of the cartilages of the fifth, sixth, and seventh ribs by three broad slips, of which the internal is the deepest and the external the highest. The two internal are the broadest and are generally equal in breadth. The external is sometimes much thinner, simply tendinous, and adheres to the first slip of the obliquus externus abdominis muscle, or is replaced by it entirely ; so that the rectus abdominis muscle extends before it to the sixth rib.

The internal slip is attached also to the anterior face of the xyphoid cartilage and its ligaments.

Below, the rectus muscle terminates by a broad and short tendon, which is attached behind the pyramidalis muscle to the upper face of the horizontal branch of the pubis. Sometimes this tendon divides into two pillars, an external and an internal, the latter of which is broader ; although this division is not generally very perceptible.

The tendons of the two recti muscles are blended with each other at their lower part, even partly intercross, and descend from the symphysis pubis to the suspensory ligament of the penis.

The rectus abdominis muscle belongs to the class of poly-gastric muscles, and exhibits this arrangement more evidently than any other muscle. In fact it is always divided into several bellies by undulating tendinous intersections, formed of longitudinal fibres. Usually there are three of these intersections and hence there are four bellies.

All these intersections have not exactly the same type. Their general characters are :

1st. They adhere intimately to the anterior layer of the sheath of this muscle. Generally speaking, they are more apparent forward than backward, where they are sometimes invisible ; sometimes they arc seen in one part only. They adhere slightly and usually not at all to the posterior layer of the sheath.

2d. They are not generally found except above the umbilicus. The first is situated about as high as this region, the upper an inch below the upper extremity of the muscle, and the central about the centre of the space between the other two, although usually a little nearer the upper than the lower end.

Generally the lower two extend completely across the muscle, while the upper exists only in its inner part.

Sometimes however we find a fourth which is imperfect, below the umbilicus. Sometimes also one of the superior is deficient or is at least imperfect, as is always the case with the third.

These tendinous intersections are doubtless imperfect representations of the ribs in the parietes of the abdomen.

The rectus muscle is enclosed in a sheath formed by the three broad abdominal muscles, with which it is united by mucous tissue. Its fleshy portion is but feebly attached to it, but the tendinous intersections are very firm.

The posterior layer of this sheath is deficient at the upper part of this muscle, that which covers the costal cartilages to which it is attached, and at its lower part, from about the centre of the space between the umbilicus and the symphysis pubis. In these two parts the muscle rests directly on the anterior face of the costal cartilages above, and below on the anterior wall of the peritonæum, to which it unites by very loose cellular tissue.

The rectus abdominis muscle contracts the abdominal cavity in the direction of lenglh and assists to flex the vertebral column.

As it unites by its tendinous intersections with the external and internal oblique muscles, the effects of its contractions extend to these muscles, which in their turn affect the recti muscles. Consequently all these muscles act in concertai )

§ 1069. The rectus muscle sometimes presents a fourth slip, which arises from the external or internal part of its upper edge, more usualty from the internal, and goes to the fourth rib. This formation resembles that of most mammalia, where it usually reaches to the second rib. It leads also by an insensible gradation to the formation of a special external abnormal sternal muscle.

This muscle divides in the direction of breadth more rarely than in that of length. We have however found on each side external to the proper rectus abdominis muscle, between the two obliqui muscles, a muscle which extended from the lower edge of the tenth rib to the centre of the external edge of the crest of the ilium.(2) This formation resembles that of birds, in which the rectus abdominis muscle is very broad.


(1) Bertin, Mémoire sur l'usage des énervations des muscles droits du bas-ventre, in the Mém. de l’acad. de Paris, 1746, p. 585.

(2) Kelch, loc. cit. p. 42.


The increase in number of the tendinous intersections of this muscle, and especially their existence below the umbilicus, are two circumstances important as being analogous with the formation of the ape.(l)

VI. PYBAMIDALIS.

§ 1070. The pyramidalis muscle, Pubio-sous-umbilical, Ch., is situated at the lower part of the sheath formed by the tendons of the three broad abdominal muscles, and is covered forward by the anteiior layer of this sheath and backward by the lower part of the rectus muscle. It is triangular and oblong ; its base is turned downward and its summit upward. It goes obliquely upward and inward and arises from the internal portion of the horizontal branch of the pubis, between the insertion of the external pillar of the descending oblique muscle and the symphysis pubis, and its summit is attached to the lower part of the linea alba.

It strengthens the linea alba, and contracts the abdominal cavity from above downward.

§ 1071. The pyramidalis muscle is rarely abnormal. It is most usually deficient on one or both sides, and then the lower part of the rectus muâcle is thicker and broader. (2) The absence of this muscle is a remarkable analogy with the formation of most animals.

More rarely it is multiplied on one(3) or on both sides, (4) thus presenting three or four muscles.

VII. DIAPHBAGM.

§ 1072. The diaphragm ( septum transversum , diaphragma ( , ( 5 ) a thin and broad muscle, is situated between the pectoral andi abdominal cavities. It adheres by its upper face to the pleura and pericardium, and by its inferior face to the peritoneum. Its form resembles an inverted figure oo, for it is broader from one side to the other than from before backward, contracts in the centre, and is circumscribed by rounded and convex edges. It arises from the upper lumbar vertebræ and is attached to the lower six ribs, and generally also to the unciform cartilage.

We may distinguish in it an inferior or lumbar portion ( pars himbaris ), a superior or costal portion ( pars costalis ), and a median tendon ( tendo intermedius.)


(1) Drelincourt in Blasius, Anat. animal., p. 110. — Vicq. d’Axyr, Encyc.mêth., Syst. anat. quadrup., vol. ii. p. 22.

(2) Santorini, Obs. anat. ch. ix. p. 160.

(3) Winslow, Exp. anat. p. 36.

(4) Sabatier, Tr. complet d’anat., vol. i. p. 263.

(5) Haller, Nora icon, septi transversi, Gottingen, 1741. — Santorini, Tabulce anat. xvii. Parma, 1775, tab. x. fig. — Tissot, Des fonctions du diaphagme, Montpellier,


The lumbar part is much thicker and smaller than the other, and arises on each side by four heads from the upper three lumbar vertebrae, and terminates in the posterior edge of the central tendon. The two halves of this portion represent an X ; in fact they unite in their centre and again separate from each other above.

The four heads (crura), by which each portion of the lumbar part arises, follow from within outward and from below upward, so that they gradually shorten and go still farther outward and backward. Besides, the heads of the two sides are not perfectly similar ; those of the left are generally smaller than those of the right.

The first, the internal or most inferior right head is stronger than the left, and arises below it, by a broad tendon, from its half of the anterior face of the third lumbar vertebra, sometimes also from the intervertebral ligament situated between the third and fourth. It is the largest of all.

The second strait head is situated behind the first, arises usually by a single tendon, sometimes by two, from the anterior face of the body of the second lumbar vertebra. Its muscular fibres are attached behind those of the first.

The third, which is sometimes larger and broader than the preceding, comes from the anterior face of the intervertebral ligament of the first and second lumbar vertebrae, and from the lateral part of the body of the first. It goes upward and outward.

The fourth arises from the transverse process of the second or first lumbar, or even of the last dorsal, vertebrae.

The heads of the left side generally arise half or even a whole vertebra higher than those of the right side.

Between the internal heads we find an oblong rounded transverse opening, tendinous at its lower part, which is the most extensive, and called the hiatus aorticus, through which the aorta descends, from the cavity of the thorax to that of the abdomen.

When the fleshy fasciculi of the several heads of the same side are united(l) those of the right and left side are blended, and partly cross, before the upper extremity of the first lumbar vertebra.

A small part of the internal fasciculus of the left side usually passes before the right ; but a much larger portion of the right passes to the left, beneath this fasciculus, and forms the most internal portion of the left half of the lumbar part of the diaphragm.

This union is about an inch long. Above its upper extremity the lumbar portions of the muscle again separate, and form a longitudinal, rounded, and very oblong fissure, called the hiatus or foramen of the esophagus. This opening is from an inch and a half to two inches long, and is a little on the left of the median line, and gives passage to the esophagus. This opening is formed upward and inward by some thin fasciculi of the lumbar portions of the two sides, which incline towards each other and are blended together.

(1) The four heads on each side unite to form the â– pillars of the diaphragm.


The upper anterior edge of the two lumbar portions which proceeds on each side obliquely downward, outward, and backward, is attached to the posterior edge of the median tendon. The external is uninterruptedly continuous with the costal portion of the muscle.

The fibres of this part go from below upward. They separate like the sticks of a fan. The median tendon is triangular. Its form is similar to that of a trefoil leaf, and is broadest in the centre ; its anterior edge is convex, and the posterior is concave. It extends from within outward, and from before backward, and its anterior and median portion is nearer the anterior edge of the muscle than the lateral parts are.

It is formed of tendinous fibres which extend in different directions. The strongest and most numerous follow the direction of the fleshy fibres, that is, the internal and anterior go forward, those next more obliquely outward, the posterior backward, outward, and downward. But on the lower face of the tendon we also see others which cross them, and are very apparent on the sides, especially toward their posterior edge. The latter tend very much to strengthen the tendon.

We rarely find on a part of the inferior face of this tendon muscular fibres separate from the others.(l)

The right lateral portion of this tendon is perforated at its origin, near its central part, towards its posterior edge, and directly before the insertion of the lumbar portion ; this opening is of an oblong square form, and is called the foramen quadratum , or the foramen of the vena cava, and the vena cava inferior passes through it. This foramen forms a short canal rather than a simple hole, for its lower edge is situated deeper than the upper. The posterior wall of this canal is considerably higher than the anterior, and is formed by the upper part of the right lumbar portion, which is covered with tendinous fibres. Around these edges considerable fibrous fasciculi are reflected, the anterior and posterior of which go obliquely inward, forward, and upward, while the internal and external go downward.

From the anterior edge, and the external part of the posterior edge of this median tendon, the costal portion of the diaphragm arises by a very concave edge, and goes outward and backward, where it terminates by a convex edge.

The two halves of this portion are blended 'with each other forward and on the median line, but they are separated backward by the lumbar portion.

The anterior fibres are the shortest and the central fibres the longest . The anterior go directly forward ; the next in succession became more oblique, and finally go transversely outward ; the posterior go from before backward, and from within outward.

The external edge of this part is always attached by rounded slips, which are separated more or less distinctly and are sometimes cleft, to the internal face of the cartilages of the seventh, eighth, ninth, tenth, and eleventh ribs, and also to the inner face of all the twelfth, and usually blends with the posterior edge of the transversalis abdominis muscle, which goes forward to meet it.


(l) Huber, in SÅ“mmerring , Muskellehre, p. 162.



The central part of the anterior edge is also most generally fixed to the posterior face, and to the lower extremity of the xiphoid cartilage, by two thin slips, which go downward and outward.

Sometimes however these slips do not exist. Their absence must be considered as a slight indication of the imperfect union of the right and left halves of the body.

When the diaphragm contracts it acts on the thoracic and abdominal cavities ; but its action on them is opposite. In contracting, it rises and falls ; its fleshy portion, which is attached backward to the lumbar vertebrae, and forward to the ribs, draws the central tendon downward. Hence the pectoral cavity is considerably enlarged from above downward, while the abdominal cavity is proportionally diminished in the same direction. The former places the diaphragm among the agents of inspiration ; in fact, when the respiration is calm and tranquil, its contraction and relaxation produce the alternate motions of inspiration and expiration. Again, it constantly contributes, by the changes it causes in the cavity of the abdomen, to the progress and in general the motion of the substances in the alimentary canal, and consequently it assists directly in digestion. In this last relation it is an auxiliary to the other broad and straight muscles of the abdomen, while it is an antagonist to them in relation to the cavity of the thorax. Simultaneous and powerful contractions of the diaphragm and of the other abdominal muscles, produce efforts (nixus)(l) which contract the abdominal cavity as much as possible, in order to expel the foreign matters actually within or which we believe to be within it, and the expulsion of which is unusually difficult. This combined action consequently takes place in all cases where fÅ“cal matter or urine is retained from any cause whatever, as dysentery, inflammation of the neck of the bladder, parturition, &e.

§ 1073. The diaphragm is sometimes wholly or partially deficient from a primitive deviation of formation, or it may be torn by some mechanical cause acting with violence on it. In both cases, as also when the muscle is ruptured, a part of the viscera usually passes into the chest through the abdominal opening ; hence results a diaphragmatic hernia ( hernia diaphraghmatica ) which generally has no herniary sac.

(1) Bourdon ( Recherches sur le mécanisme de la respiration et sur la circulation du sang , Paris 1820) has determined by some interesting inquiries that the functions of the diaphragm are confined to inspiration and analogous acts, and that it thus affects digestion and the abdominal secretions ; but t hat in respect to these efforts, it only prepares for them by filling the lungs with air, and that it does not take an active part in this phenomenon, since the suspension of respiration, which is the principal source of them, and which depends upon the closing of the glottis, occurs, not during' respiration, but during the tendency to expiration, which is caused solely by the contraction of the abdominal muscles. F. T.

2. Of The Muscles of the Chest

§ 1074. In the pectoral region of the anterior and lateral faces of the body we count three superficial muscles, which go from the first two sections of the upper extremities to the accessory bones of the trunk, and are usually attached to the latter. These muscles are the pectoralis major, the pectoralis minor, and the serratus major anticus muscles.


I. PECTORALIS MAJOR.

§ 1075. The pectoralis major muscle, Sterno-lmmeral , Ch., an extensive muscle, the largest and most superficial of those found on the anterior part of the chest,, is triangular, or, to speak more precisely, is irregularly quadrilateral, and is much thicker but much narrower at its outer than its inner part. Its smaller upper edge arises by short tendinous fibres from the greater inner half of the anterior edge of the clavicle. The inner edge, which is larger and concave, also arises by very short tendinous fibres, from the anterior face of the handle of the sternum, from that of almost all the upper part of the body of this bone, and also from the upper edge of the anterior face of the cartilage of the fifth rib. A smaller slip is also detached from the rest of the muscle in all its extent, which sometimes descends very low, and unites to the second slip of the obliquus externus abdominis muscle, as the lower outer part of this edge blends with the upper edge of the tendon of this muscle and of its upper slip.

The upper part of the pectoralis major muscle is called the clavicular portion (pars clavicular is), the central part the sternal portion (pars sternalis), and the lower the costal portion (pars costalis). The last however is not separated from the others as the first is.

The upper fibres of this muscle descend obliquely outward, the central are transverse, and the lower go more and more obliquely upward. They all converge towards a very strong tendon, composed of transverse fibres, which, passing above that of the long head of the biceps flexor muscle, goes to attach itself to the lower part of the outer rough line of the humerus, and blends in the bicipital groove with the tendon of the latissimus dorsi and teres major muscles, unites in this place with the lower part of the deltoid muscle, and becomes an aponeurosis, which envelops the muscles of the shoulder.

This muscle draws the arm, and also all the upper extremity, inward and forward, which at the same time is turned on its axis inward and depressed if it be raised. Its central and transverse portion goes directly inward and forward ; the upper portion raises the arm, the lower depresses it.


§ 1076. The clavicular portion of this muscle is veiy often entirely separated from the. sternal portion, so that a considerable space exists between them, and on the anterior edge of the latter we see several fissures of different depths. This formation is very analogous with that of the mammalia, in most of which the pectoralis major muscle is divided into several distinct muscles.

A considerable muscular band is sometimes detached from the pectoralis major muscle, which goes to the arm, where it is attached either to the aponeurosis, or to the short head of the biceps flexor, or finally to the latissimus clorsi muscle, which arrangement resembles the common muscle of the arm, shoulder, and head, found in animals destitute of a clavicle.

§ 1077. On the anterior face of the pectoralis major muscle, more or less distant from its inner edge, directly between it and the cellular coat, we often find a supernumerary muscle, called from its situation the thoracic , the straight sternal ox the sternal muscle of animals (JVf. thoracicus , reclus s /emails, st emails brutorum).

This muscle is a more or less perfect repetition of the rectus abdominis and of the sterno-cleido-mastoideus. It often unites these two muscles, or at least, extends from one to the other ; sometimes also it is unconnected with either, and is attached by its upper extremity to the handle of the sternum and by the lower to the costal cartilage or to the lower part of the sternum : its two .extremities are often blended with the pectoralis major muscle. In certain cases it is indicated only by a tendon, which extends from the sterno-cleido-mastoideus to the rectus abdominis muscle, or by a.n unusually long slip of the latter.

The accessory muscle varies in thickness, breadth, and even in number, no less than in its length. In fact its thickness is sometimes only a few lines and is sometimes several inches ; sometimes it exists only on one side, sometimes also it is double either on one or on both sides ; sometimes we number four of these muscles.

In certain subjects there are transverse tendinous intersections, which render it still more analogous to the rectus muscle : these intersections are not common.

The side of the body and the sex of the individual seem not to influence the existence of this muscle. (1)

It is curious inasmuch as it establishes a relation between man and animals, renders the analogy between the anterior and posterior halves of the body more sensible than it is generally, and particularly renders the whole anterior face more uniform.

It is not peculiar in blacks.

^1) For farther details on this interesting- muscle, see Sandifort, De muse, nonnullis qui rarius occurrunt , in the Exerc. acad. Book i. eh. vi. p. 82-88. — Meckel, Dc monstr. cluplicitate, Halle, 1815, p. 35-40.— Kelch., Beytrœge, p. 33, No. 25.


II. PECT OE ALIS MINOR.

§ 1078. Directly below the pectoralis major we find the peciorulis minor muscle, Costo-coracoidien , Ch., (M. pectoralis minor, s. serratus anticus minor), which is much smaller. The form of this muscle is an elongated triangle, the base of which looks downward and forward, and the summit is tamed upward and backward.

Its anterior edge is generally attached by three, more rarely by two or four s’ips, all of which proceed equally far forward but at unequal distances from each other, to the anterior face and upper edge of the third, fourth, and fifth, rarely also the sixth rib.

A fourth slip is sometimes found behind the second, and more or less covered by it and also by the third, which is inserted in the outer face of the fourth rib.

The upper and the posterior or lower edge, which are much longer than the anterior and which are nearly equal in length, are loose and unite above in a tendon, which is attached to the anterior edge of the summit of the coracoid process of the scapula.

The pectoralis minor muscle is much narrower but also much thicker at its upper than at its lower part.

It draws the coracoid process and consequently the scapula forward, downward, and inward. When the scapula is fixed, this muscle raises the ribs to which it is attached.

§ 1079. Sometimes we find a curious analogy with the formation of birds in the existence of a third pectoral muscle below these : this arises from the first and second ribs by separate digitations, and is attached to the coracoid process of the scapula.(l) A similar anomaly consists in a band, which sometimes comes from the upper rib, and which, covered by the pectoralis minor muscle, ascends to the capsular ligament of the scapulo-humeral articulation. (2)

III. SERRATUS MAJOR ANTICUS.

§ 1080. The serratus major anticus muscle, Costa -scapulaire, Ch., is a broad, thin, and triangular muscle, the base of which is downward and the summit upward. It covers in great part the lateral region of the upper eight ribs.

Its anterior concave edge arises by nine triangular slips, of which the lower four are situated farther forward than the others, from the bony parts of the first eight ribs, nearer their anterior than their posterior extremity.

The number of slips then exceeds that of the ribs, because the second and third, one of which is often deficient, are attached together to the second rib. The four lower slips intercross with the upper four of the obliqiius externus abdominis muscle. The lower edge is loose The posterior is attached to all the internal lip of the inner edge of the scapula.


(1) Rosenmüller, p. 6.


(2) Gantzer, p. 11.



The upper fibres descend obliquely forward and inward : the central are transverse; the lower fibres have the same direction as the upper, but are less perpendicular than they.

This muscle generally draws the scapula and with it all the upper extremity forward and inward. When this bone is fixed it carries the ribs to which it is attached outward and backward.

§ 1081. Sometimes but very rarely the central portion of theserratus major muscle is deficient, so that it is completely divided into two unconnected parts.

IV. TRIANGULARIS STERNE

§ 1082. The triangularis sterni muscle, Sterno-costal , Ch., is thin ; it is situated upon the inner face of the sternum and costal cartilages, and is formed of several successive slips placed over each other. It arises by a thin and broad tendon from the edge of the under part of the body of the sternum, from the ensiform cartilage, and from the inner face of the costal cartilages from the third to the sixth or seventh. Its fibres are oblique and go to the cartilages of the second, third, fourth, and fifth ribs, to which they are attached by long digitations.

Of all the muscles this is one of the most variable. Sometimes one or more slips are deficient, and the internal edge is not attached to the costal cartilages but only to the inner face of the sternum ; and again several slips are formed which are entirely isolated, or at least some of them are not connected with the others.

It is always continuous at its lower extremity by tendinous fibres and often by its fleshy portion with the upper end of the transversalis abdominis muscle ; so that in many cases, but not however in all, we may consider it as forming but one with it and call it the sterno-abdominal muscle (JVf. sterno-abdominalis).(l)

It at least always represents in the thorax the transversalis abdominis muscle. This comparison terminates the analogy betwen the muscles of the abdominal and thoracic parietes.


3. Of the Anterior Muscles of the Neck

§ 1083. The anterior muscles of the neck form a superficial and a deep layer.

(1) Rosenrmitler, De nonnullis musculorum corp. hum. varietatibus, Leipsic, 1814.


I. SUPERFICIAL LAYER.

§ 1084. The superficial layer of the anterior muscles of the neck is situated in front and on the sides of the larynx, the trachea, the pharynx, and the hyoid bones. It comprises the platysma myoides, the sterno-cleido-mastoideus, the sterno-hyoideus, the omo-hyoideus, the sterno- thyroideus, and the muscles which extend from the larynx to the hyoid bones, from the thyroid to the cricoid cartilages, and from the skull to the hyoid bones and to the pharynx. We shall mention in this place only the first two. The others will be described with the organs of digestion and of voice, — 1st, because their points of attachment have not yet been described ; 2d, because it is more convenient to refer the history of those which are inserted in parts already described, as for instance the muscles of the hyoid bones, to that of the muscles near them, which are intimately connected and always act with them.


I. PLATYSMA MYOIDES.

§ 1085. The platysma myoides muscle, Thoraco-facial, Ch., (JVC, latissimus colli , s. platysma myoides , s. quadratics , s. tetragonus genæ ), has an oblong square form. It is very thin and composed of muscular bands, which are generally very loosely united and often have considerable spaces between them. It is situated directly below the cellular tissue, to which it adheres, and arises in the thoracic and scapular region by separate bands, which extend a little below the clavicle, so that it covers part of the upper edge of the deltoides and pectoralis major muscles. It gradually contracts, becomes thicker, and going obliquely upward, inward, and forward, on the side of the neck, attains the lower part of the face, where it is attached partly to the under edge of the lower maxillary bone, and partly blends with the levator anguli oris muscle and ascends to the corner of the mouth, and partly loses itself below the adipose covering of the face.

It wrinkles the skin which covers it and draws the mouth downward and outward. The latter motion is executed particularly by the last fasciculus, hence called the risorius Santorini muscle.

This muscle is evidently only a rudiment of the intercostales and of the broad abdominal muscles in the neck, as is proved by its situation, its relations with the other muscles and the common integuments, and bj’ the direction of its fibres. The looseness of its lower edge, winch is wholly unattached, corresponds very well with the arrangement of the anterior part of the lower edge of the broad abdominal muscles, as likewise its insertion in the lower maxillary bone resembles that of the upper edge of these muscles in the ribs, to which the lower maxillary bone is analogous.


Its less degree of development depends partly on the smallness of the region in which it is found and partly also because there is no special cavity in it.


§ i086. A special fasciculus frequently but not always arises from its upper part and goes toward the face. This fasciculus is sometimes loose under the cellular tunic and sometimes arises from the tendon of the masse ter muscle. It goes from behind forward and is attached with the platysma to the angle of the lip; it is sometimes replaced by the upper part of the latter which is broader.

It is more rare to find an inferior slip arising from the clavicle, which extends under the skin to near the deltoid muscle, where it disappears in the cellular tissue ; it resembles the fleshy coat of animals.(l)

We also rarely find a small transverse muscular slip between the platysma and the skin, below the chin. (2).

We more rarely see the platysma not thin and superficial as usual but rounded and thick, not proceeding forward but going backward and attached to the occipital bone.(3)


II. S1ERNO-CLEIDO-MASTOIDEUS.

§ 1087. The stemo-cleido-mastoideus muscle, Sterno-mastoidien , Ch., must be regarded not as a single muscle but as the union of two muscles, since its two bellies are more distinct from each other than some other muscles, especially those of the dorsal region, which are considered as separate.

The anterior belly, the slerno-masloideus muscle (JVf. sterno-mastöideus, s. nutator capitis anterior ), arises by a short but strong tendon from the most upper and outer part of the anterior face of the handle of the sternum. It is elongated and rounded and becomes insensibly broader and thinner at its summit, goes obliquely upward and backward, and is attached to the outer face of the mastoid process of the temporal bone and to a small part of the outer face of the upper curved line of the occipital bone.

The posterior belly, the cleido-masloideus muscle (JVf. clcido masloideus , s. nutator capitis posterior ), is shorter and weaker than the preceding. It arises an inch more outwardly, from the upper edge and the upper part of the anterior face of the sternal part of the clavicle (but it does not come from its inner edge) by a thin and broad tendon ; it descends obliquely but straighter than the preceding, gradually becomes round, and terminates in a point, where it is attached below the preceding, to the lower part of the outer face of the mastoid portion of the temporal bone by a rounded tendon, which covers its upper portion and with which it is united by some separate fibres.

(11 Gantzer, loc. eil., p. 111.

(2) Fleiscbmann, in Erlanger Abhandl., vol. i. p. 28.— Gantzer, loc. cit., p. 6.

(3) Zagorsky, Mém. de l’acad. dc Putcrsburgh, vol. i. p. 357.


These two muscles correspond from above downward, the fust to the rectus abdominis and the second to the pyramidalis muscle, in this respect, that they are more similar than the latter in regard to size. They represent also from before backward the splenii muscles, to which they are antagonists.

The sterno-cleido-mastoideus muscle inclines the head obliquely forward, so as to bring the face from the opposite side. When the two act in concert the head is flexed. The external belly draws it more directly forward and downward, and the inner belly more obliquely from the opposite side.

§ 1088. The greatest anomaly of this muscle is an increase in number, arising from the detachment of some fasciculi from the rest of the mass.(l)

Thus for instance we not unfrequently lind between the two bellies a special and smaller fasciculus, which sometimes continues separated as far as its upper extremity, or which before arriving there blends with one of the other two ; this generally arises directly at the side of the anterior belly, either on the outside of it from the sternum or from the most internal part of the sternal end of the clavicle.

We less frequently find a thinner and usually very broad accessory muscle, which arises from the clavicle behind the second belly, ascends behind it from before backward, and attaches itself on the outer side of it to the occipital bone.

The numerous divisions and multiplications of this muscle remind us of the analogy between it and the rectus abdominis and pyramidalis muscles.

Nor is it rare to see a fleshy or tendinous slip which extends from the lower edge of the stemo-mastoid portion to the angle of the lower maxillary bone. (2)

All these varieties form so many analogies with animals ; for in most mammalia the sterno-mastoid and cleido-mastoid portions are almost entirely separated from each other, and the latter is most frequently doubled. Besides, this always increases in volume and number outwardly ; this circumstance establishes a manifest relation with the formation in most mammalia, in which the cleido-mastoideus muscle is generally blended with the clavicular portion of the deltoides muscle ; even in the solipedes, the sternal portion extends only to the lower maxillary bone.

II. DEEP LAYER.

§ 1089. The deep layer of the anterior muscles of the neck is situated directly on the anterior face of the upper part of the vertebral column. It comprises the rectus cupitis anticus major , the rectus capitis minor , and the longus colli muscles, all of which serve to bend the head and neck.

(1) G. Meckel, De duplicitale monstrosâ, p. 40, 41. — Kelch, Beytrœge zur path, anat., p. 31.

(2) Brugnone, p. 160.



I. RECTUS CAPITIS ANTICUS MAJOR.

§ 1090 . The reclus capitis anlicus major muscle, Grand trachelosous- occipital, Ch. (JVf. rectus capitis anterior , s. internus, s. major), is oblong and thicker at its upper than at its lower part. It generally arises by five thin and tqpdinous slips, which increase in size from below upward, from the transverse processes of the third, fourth, fifth, and sixth cervical vertebrae, and from one slip of the longus colli muscle, which is attached to the sixth cervical vertebra. It goes from below upward and from without inward, gradually approaching its congenital. It is mostly strongly tendinous. Its upper edge is attached directly before the large occipital foramen to the basilar process of the occipital bone.

It bends the head directly forward.

§ 1091 . We sometimes find two additional upper tendinous slips which come from the first and second cervical vertebræ, an arrangement resembling the formation of the carnivorous animals.

II. RECTUS CAPITIS ANTICUS MINOR.

§ 1092 . The rectus capitis anlicus minor muscle, Petit trachelo-sous occipitcd, Ch. (JVJ. rectus capitis anterior, s. internus, s. minor), is a smaller, thinner, and triangular muscle, which gradually enlarges from below upward. It arises above and forward from the anterior arch and from the root of the transverse process of the first cervical vertebra, ascends, covered by the preceding, before the articular ligament between the occipital bone and the first cervical vertebra, goes obliquely inward, and is attached before the occipital foramen to the basilar process, and more outwardly to {the fibro-cartilaginous mass which fills the space between the body of the occipital bone and the petrous portion of the temporal bone.

It bends the head forward and a little to the side.


III. LONGUS COLLI.

§ 1093 . The Longus colli muscle, Predorso-atloidicn, Ch., descends from the first cervical to the third or fourth dorsal vertebra. Its structure is very complicated, and we may consider it to a certain extent as formed of two muscles, an upper and lower, which are united.

The internal is smaller, and goes directly downward and a little outward. It arises by separate tendinous slips from the side of the body, and the intervertebral cartilages of the upper three dorsal vertebræ, and also from the body and the anterior roots of the transverse processes of the lower four cervical vertebræ, ascends in a straight line, and is attached externally, by two or three short tendons, to the anterior tubercle of the transverse processes of the fourth and fifth cervical vertebrae ; and inward, by a strong tendon, to the anterior face of the bodies of the second and third cervical vertebrae.

The upper muscle is stronger than the preceding, and is directly continuous with it ; it arises by small tendinous slips from the anterior roots of the transverse processes of the third, fourth, and fifth cervical vertebrae. It ascends obliquely inward, gradually becomes straighter, and is attached to the anterior tubercle of the first cervical vertebra, seldom to the basilar portion of the occipital bone.

The longus colli muscle bends the neck forward, and a little to the side.

4. Of the Sacro-coccygeal Muscles

§ 1094, The sacro-coccygeal muscles (JVf. sacro-coccygœi, s. curvaiores coccygis) are not constant. When they exist they appear as small, elongated, thin, and mostly tendinous fasciculi, situated on the two sides, which arise from the anterior face of the last sacral and first coccygœal vertebra, and are attached by several slips to the anterior face of the lower pieces of the coccyx, where that of the right and left are usually blended.

They draw the lower pieces of the coccyx forward and upward, so as to curve the whole range of these bones.

These muscles are the rudiments of the caudal flexors in animals. They evidently correspond to the three muscles of the upper half of the body, which we have just described.