MANUAL GENERAL, DESCRIPTIVE, AND PATHOLOGICAL ANATOMY, BY w J. F. MECKEL, Professor of Anatomy at Halle, Sec. &c. &c. TRANSLATED PROM THE GERMAN INTO FRENCH, WITH ADDITIONS AND NOTES, BY A. J. L. JOURDAN, Member of the Royal Academy of Medicine at Paris, &c. &c. &c. AND jf G. BRESCHET, Adjunct Professor of Anatomy at the School of Medicine, &c. &c. &c. TRANSLATED FROM THE FRENCH, WITH NOTE SyT BY A. SIDNEY DOANE, A.M., M. D. IN THREE VOLUMES. VOLUME II. PHILADELPHIA CAREY & LEA.—CHESTNUT STREET. 1832. V,2 » Entered ar-cordin* to an act of Confess, in Hie year 1832, by Henry C Sleight, in the officfof the clerk o! "the District Court of the Southern District of New York." Sl.ElGHT AND K0T1INSON, PlilN'i No 111 Nassau St., New York. MANUAL GENERAL, DESCRIPTIVE, AND PATHOLOGICAL ANATOMY. DESCRIPTIVE ANATOMY. BOOK II. OF SYNDESMOLO.GY\ § 818. Under the head of Syndesmology(l) we shall describe only the modes of union between the bones and the cartilages which cover their extremities. The connections between other organs, as the muscles and the viscera, will be mentioned when speaking of those organs. The bones are connected by very different substances, and the degree of motion between the bones which are united varies exceed- ingly. Descriptive syndesmology however treats of the two classes of ligaments, the synovial or capsular (§ 367), and the fibrous or accessory (§299). As these organs are intimately connected with the bones, it will be better to describe them in the same order. Hence we shall mention, first, the ligaments of the trunk, then those of the head, and conclude with those of the extremities. SECTION I. OF THE LIGAMENTS OF THE TRUNK. § 819. The ligaments of the trunk are divided into those of the ver- tebral column, of the ribs, and of the sternum. (1) The principal books of reference are, J. Weitbrecht, Syndesmologia, seu His- toria ligamentorum corporis humani, Petcrsburgl), 1742.—Desmographie, ou De- scription des ligamens du corps humain, Paris, 1752.—M. Alberti, Nutzliche Lehre von der Arliculationen des mcnschlichcn Kbrpcrs, Freybcrgr, 1745. Vol. II. 2 10 DESCRIPTIVE ANATOMY. CHAPTER I. LIGAMENTS OF THE VERTEBRAL COLUMN. § 820. The vertebrae are attached to one another in all parts of their surfaces by fibrous or fibro- cartilaginous ligaments, and in some parts by capsular ligaments also; the former serve to retain these bones in their places and to confine their motions, while the latter faci- litate their motions, but are also covered externally by fibrous liga- ments. The principal ligaments of the vertebral column are, 1st, the inter- vertebral fibro-cartilages, which are of all the modes,the strongest bonds of union; 2d, the synovial capsules, situated between the arti- cular processes and which facilitate their motions. These two kinds of ligaments are strengthened, as in all parts, by fibrous fasciculi, placed directly upon them, or which are attached to the other parts of the vertebral column. These fasciculi are the ante- rior and the posterior vertebral ligaments, the accessory fibres of the capsular ligaments, the yellow ligaments, the interspinal, and the intertransverse ligaments. We had better consider first the fibrous and fibro-cartilaginous liga- ments, and then the synovial capsules. I. FIBROUS AND FIBROCARTILAGINOUS LIGAMENTS. t. BETWEEN THE BODIES OF THE VERTEBRJE. A. ANTEBIOH VEHTEBHAL LIGAMENT. § 821. The anterior vertebral ligament (fascia longitudinalis ante- rior, ligamentum corporibus vertebrarum commune anterius) covers the anterior and convex face of the bodies of the vertebrae. It extends from the centre of the anterior part of the large occipital foramen which Weitbrecht has wrongly disputed, to the last bone of the coccyx. It is composed of longitudinal fibres which do not extend uninter- ruptedly from one extremity of the column to the other, but cover in fact only a single vertebra, and which unite above and below on the surface of the intervertebral ligaments with those of the adjacent vertebrae. The fibres are thicker on the vertebra than in any other part; they grow thinner and shorter as they approach the upper and lower faces of the bone. Hence the anterior surface of the vertebral column is more uniformly convex than it would be without this arrangement, since the bodies of the vertebrae are concave from above downward. Besides the straight fibres, we also find many which are oblique • these cross the former at a very acute angle. SYNDESMOLOGY. 11 This ligament is thicker, and its fibres are much closer in its centre than on the sides'. The fibres separate very much from each other on the two sides of the median line, while on the contrary they unite backward so that they form three bands, the central of which is the strongest while the two lateral bands are weaker. The ligament covers all the anterior face of the bodies of the verte- brae ; it is not confined to the centre and to sending only irregular prolongations to the sides. Its lateral parts are composed of longitu- dinal fibres as regular as those of1 the central portion ; and they differ so little in their essential characters from the periosteum, that the liga- ment may be regarded as a periosteum more developed. We cannot at least refuse it this character in most of the vertebral column, especially in the dorsal, the lumbar, the sacral, and the coccygaeal regions. In the cervical vertebrae, especially the upper two, the anterior ligament assumes still more the appearance of a very thick, rounded, and very projecting band, which covers only the centre of the anterior face, while the fibres on the lateral parts of the bodies are thin and irregular. This differ- ence doubtless exists because the anterior face of the cervical region is covered with muscles, which are not found in the other regions of the vertebral column. The lateral part of the anterior ligament in these last, appears in the neck as the tendons of the anterior muscles of the neck. So too on the second lumbar vertebra, this ligament becomes the tendons of the diaphragm. The narrowness of the anterior ligament on the upper cervical ver- tebrae depends upon the great degree of motion possessed by these bones, and being formed in this manner their motions are not so much obstructed. This ligament is not equally thick on all the vertebrae. Its thickest parts cover the upper cervical and dorsal vertebrae, the thinnest are found on the superior lumbar vertebrae. It not only unites the bodies of the vertebrae forward, but also pre- vents the column from bending too much backward. B. POSTERIOR VERTEBRAL LIGAMENT. § 822. The posterior vertebral ligament (fascia, s. ligamentum commune •poslerius) extends along the posterior face of the bodies of the vertebrae, within the medullary canal. 4f It diminishes in breadth from above downward ; in the cervical ver- tebrae it is as broad as the bodies of the vertebrae; it is -much thinner on the sides in the dorsal vertebrae, and finally disappears entirely in the lumbar regions, becoming a single waving band situated on the median line, being a little broader on a level with the'upper and lower faces of the bodies of the vertebrae. A' the same time, it is attached to the intervertebral substance more firmly than to the posterior face of the bodies of the vertebrae. 12 DESCRIPTIVE ANATOMY. Its relations with the vertebrae and with the dura mater are not ex- actly the same. In most of the vertebral column it is intimately connected with the bodies of the vertebrae, and it is attached to the dura mater only by a loose mucous tissue. But at the third cervical verte- bra its relations with these vertebrae change, since the ligaments ex- tending from the head to the cervical vertebrae form, between it and their posterior faces, a peculiar fibrous mass, the fibrous mass between the head and the cervical vertebral, to which that ligament adheres but very slightly as far as the upper extremity of the vertebral column. In its first portion, it unites as usual to the dura mater ; but at the upper extremity of the vertebral column it is so closely connected with this membrane that some skill is required to separate them ; hence the separation between the fibrous membrane of the central portions of the nervous system and the largely developed periosteum of the vertebrae begins in this place. In the same place the posterior vertebral ligament unites intimately with the fibrous mass between the head and the cervical vertebrae. This ligament limits, to a certain extent, the flexion of the vertebral column forward. C. INTERVERTEBRAL LIGAMENTS. § 823. The intervertebral ligaments (Lig. intervertebralia) are the principal means of uniting the bodies of the vertebrae, and the verte- brae generally ; for the attachments of these bones in other parts, are much looser and much less extensive. These ligaments completely fill the spaces between the bodies of the vertebrae; they form layers, the upper and lower faces of which are attached to the corresponding faces of two superimposed vertebrae. They are formed of a considerable number of perpendicular and almost concentric layers, shaped like the circumference of the upper and lower faces of the vertebrae, and they are consequently annular. Their two edges are attached to the two faces of the vertebrae. Their layers are evidently fibrous ; in the external layers the fibres are oblique, and almost horizontal in the internal. The oblique fibres of the external layers cross at acute angles. The layers adhere very firmly together by the fibres which extend from one to the other; hence they form only a single dense scaly tissue. Between the layers we find a softer, yellowish, gelatinous, and shapeless mass. The nature, the relations, and the proportional quantity of these two substances, differ in all parts of the ligament. In the circumference, and especially in its anterior portion, the layers much exceed the intermediate substance ; they are very compact and are evidently fibrous. Internally, they are much softer; they sepa- rate from each other and finally disappear entirely, so that the nucleus, formed by the gelatinous substance, only remains. In what- SYNDESMOLOGY. 13 ever direction the vertebral ligaments are cut, this nucleus projects from the incision, being pushed out by the elasticity of the fibrous layers. These ligaments are thicker in the centre than on the circumference, because the bodies of the vertebrae are concave in this place. They are very solid, so that the bones of the vertebral column will break before they tear. From their great elasticity, the height of man varies at all periods of life, and diminishes or increases according as the vertebral ligaments have been for a longer or shorter time pressed down by the weight of the head and that of the vertebrae upon each other; hence man is taller in the morning than at night. This difference is not the same at all ages ; it is less evident in old than in young men. In general it amounts to about one inch.(l) The intervertebral ligaments have not the same thickness in all parts. It diminishes from the cervical vertebras to the lower extremity of the vertebral column, whence there is a difference in this respect of several lines. Between the lumbar, these ligaments are only three or four lines thick. § 824. There are no intervertebral ligaments between the first and second cervical vertebrae, nor between the first and the head, between the sacrum and the coccyx, nor between the bones of the coccyx ; these bones are united in a looser manner. § 825. The intervertebral ligaments are strengthened directly by anterior and posterior vertebral ligaments (§ 822, 823), which cover most of their circumference, and pass before them in going from one vertebra to another. II. OF THE FIBROUS AND FIBRO-CARTILAGINOTJS LIGAMENTS BETWEEN THE ARCHES AND THE PROCESSES. A. YELLOW LIGAMENTS. § 826. The arches of the vertebrae are united by the yellow liga- ments (Lig. crurum vel arcuum subfiava, s.flava), as their bodies are connected by the intervertebral ligaments. These two kinds of liga- ments may then be compared to each other. The yellow ligaments are yellowish, lustreless, and smooth; they are formed of several perpendicular and very elastic fibres, of which the external are evidently of a tendinous nature. These external fibres, which have a more oblique direction, fill all the space between the arches of two adjacent vertebrae, from the roots of the transverse processes to the angle of union, which however remains unattached. Their upper edge is always attached to the internal face, and never to the inferior edge of the arch of the vertebra above. The inferior is attached to the upper edge, and slightly to the external face of the (1) Man. de Paris, 1725, 1730. 14 DESCRIPTIVE ANATOMY. arch of the vertebra below. The vertebrae are rough where these liga- ments are inserted. The thickness, solidity, and elasticity of these ligaments are very considerable. They fix the extent of flexion forward and backward in the vertebral column. They are not perfectly similar in all parts of the spinal column. The smallest are in the dorsal region, those in the neck are larger, and the largest in the lumbar region. Those in the lumbar region are the thickest, and the thinnest are those of the cervical region. Their insertions also vary in extent in the different regions ; in the neck they are attached by a thin upper edge to a very narrow portion of the internal face of their arches, above their inferior edge. In the back and loins, this portion is a very broad surface, almost as high as the ligaments, and extends from the centre of the arches to their inferior edge.(l) These differences are worthy of remark, first, because ana- tomists have hitherto neglected the second; secondly, because they serve to increase the power of the lower portions of the vertebral column and the mobility of its upper portions. The yellow ligaments do not exist between the first and the second cervical vertebrae, nor between the first cervical vertebra and the occipital bone, or at least they are developed very feebly in these two parts. B. INTERSPINAL MEMRRANE9 AND SUPRASPINAL LIGAMENTS. § 827. Between the spinous processes we find two kinds of fibrous ligaments, the interspinal membranes (membranes, interspinales), and the supraspinal ligaments (Lig. inter apices processuum spinosorum). a. Interspinal membranes. § 828. The interspinal membranes are thin and broad, and are formed of irregular, and generally of horizontal fibres. They extend from the roots of the spinous processes to near their summits. They limit flexion forward and are destined especially for the insertion of the long mus- cles of the back. b. Supraspinal ligaments. § 829.. The supraspinal ligaments are small rounded bundles of longitudinal fibres, which attach the summits of the spinous processes of the vertebrae to each other, so as to form in fact but one ligament. They also serve to limit flexion forward. (1) Weitbrecht is mistaken in saying of these ligaments (he. cit. pa°-e 107i Mar- ginesprtedwtorum erurum viz scnsibiliter superscandunt, since they are every where attached much higher than the lower edge, and none of their fibres arc inserted in the vertebra; of the neck. SYNDESMOLOGY. 15 C. INTERTRANSVERSE LIGAMENTS- § 830. The intertransverse ligaments (Lig. recta processuum trans- versalium vertebrarum, s. interlransversaria) do not every where exist. They are found only between the transverse processes of the inferior dorsal vertebrae forward. They serve not so much to unite the verte- brae as to multiply the points of attachment for the sacro-lumbalis and the levatores costarum muscles. II. CAPSULAR LIGAMENTS. § 831. We find on each side, between every two vertebrae, a capsu- lar ligament, the ligament of the articular processes (Lig. capsulare processum obliquormn) ; this arises from the circumference of the articu- lar faces of the adjacent oblique processes by irregular bundles of fibres. In the dorsal and lumbar regions this ligament is strengthened ante- riorly by the yellow ligaments. These ligaments have not the same extent in every part. They are much looser and less tense in the neck than in the other parts of the vertebral column. The broadest, the thinnest, and the loosest, is that between the first and second cervical vertebrae. CHAPTER II. OF THE LIGAMENTS OF THE RIBS. § 832. The ligaments of the ribs are divided into three classes : 1st. Those situated between the ribs and the vertebrae. 2d. Those situated between the ribs and the sternum. 3d. Those which exist between the ribs. I. LIGAMENTS BEWEEN THE RIBS AND THE VERTEBRAE. § 833. The ligaments between the ribs and the vertebrae, are some of them synovial capsules, and others supplementary fibres, which unite the posterior parts of the ribs with the bodies and the transverse processes of the vertebrae. A. LIGAMENTS OF THE HEADS OF THE RIBS. § 834. The ligaments of the heads of the ribs (Lig. capitulorum costarum) are short capsules, which extend from the lateral articular facets of the dorsal vertebrae to the heads of the ribs. These capsules are strengthened in front by the oblique fibrous ligaments, which have two different directions; the upper go from within outward, and from above downward, and the inferior in the opposite.direction. 16 DESCRIPTIVE ANATOMT. B. LIGAMENTS OF THE TUBERCLE, AND THE EXTERNAL TRANSVERSE LIGA- MENTS OF THE RIBS. § 835. Short synovial capsules arise from the anterior face of the summits of the transverse processes of the dorsal vertebrae, and go to the circumference of the articular surface of the tubercles. These capsules are looser in the lower than in the upper ribs. The quadrangular ligaments (ligamenta transversaria costarum externa) are situated on them posteriorly, and proceed from the summits of the transverse processes .of the vertebrae: they are formed of very strong, more or less transverse fibres. These ligaments are narrower from above downward than from without inward, and are longer in the inferior than in the superior vertebrae. Their fibres descend to the upper and ascend to the lower ribs, from the transverse processes of the vertebrae. They serve to strengthen the articulations of the ribs with the vertebrae. O. INTERNAL LIGAMENTS OF THE NECKS OF THE RIBS. § 836. The internal ligaments of the necks of the ribs, or the in- ternal transverse ligaments (Lig. cervicis costarum interna s. trans- versaria interna) do not extend, like the former, from the vertebrae to the ribs, which are articulated with them ; but from the inferior edge of the transverse process of the vertebra above, to the neck of the rib below. They are formed of fibres, which proceed obliquely from above downward, and from without inward. Their form is rhomboidal, and they are thinner and more feeble than the former. D. EXTERNAL LIGAMENTS OF THE NECKS OF THE RIBS. § 837. The external ligaments of the necks of the ribs (Lig. costarum cervicis externa) are situated opposite the internal, and are composed of fibres which proceed in an opposite direction, and also extend from the transverse processes of the vertebrae to the necks of the ribs next below. They are scarcely apparent, or in fact do not exist, between the two upper and the two lower ribs. E. ACCESSORY LIAGMENTS OF THE RIBS. § 838. The accessory ligaments of the ribs (Lig. accessoria cos- tarum) are rounded bands situated beyond the articular heads, which, descend from the transverse processes of the vertebrae to the posterior extremities of the bodies of the ribs. II. C0STO-STERNAL LIGAMENTS. §. 839. The ribs unite to the sternum by the costal cartilages, in part directly, in part indirectly. . SYNDESMOLOGY. 17 The cartilage of the first rib is attached to the handle of the sternum, and those of the other six true ribs unite to the articular depressions of this bone by very short capsular ligaments, on which pass strong tendinous fibres united to the periosteum. These ligaments radiate and extend very far, particularly on the anterior face of the body, so that those of one side intercross with those of the side opposite. III. INTERCOSTAL LIGAMENTS. § 840. If we except some tendinous fasciculi of the intercostal muscles which are situated between the bony portions of two adjacent ribs, and which are continuous posteriorly with the intertransverse ligaments of the vertebrae (§ 830), only the costal .cartilages are united by particular and constant ligaments. These ligaments are arranged in two different ways. A. ARTICULAR LIGAMENTS OF THE COSTAL CARTILAGES. § 841. The fifth, sixth, seventh, and eighth costal cartilages are ur.'.'.ed by synovial capsules, on which are strong fibres passing ob- liquely from above downward, and from without inward. Instead of these capsules, we find between the two following ribs only short tendinous fibres ; and between the last ribs only the fibres of the inter- costal muscles, and of th^obliqui abdominis muscles. B. FIBROUS LIGAMENTS OF THE COSTAL CARTILAGES. § 842. Narrower fibrous ligaments (Lig. coruscantia) are situ- ated perpendicularly or obliquely from above downward, and from without inward. They proceed forward, rarely backward, and unite together the costal cartilages, beginning with that of the third rib, except those of the four mentioned in the paragraph above. CHAPTER III. OF THE LIGAMENTS OF THE STERNUM. § 843. Between the three pieces of the sternum is a fibro-cartila- ginous mass formed of horizontal fibres, which go from before back- ward. This mass seldom disappears entirely, and never except at a very advanced age ; but it is effaced between the second and the third pieces more frequently than between the first and second. It may be compared with the intervertebral cartilages (§ 823). On its surface, and also on the anterior and the posterior face of the sternum, are expanded firm tendinous bands, which unite to form membranous expansions termed the anterior and posterior sternal membranes (membrana ossium sterni anterior et posterior). Vol. II. 3 18 DESCRIPTIVE ANATOMY. The posterior sternal membrane is formed almost entirely of perpen- dicular fibres, which are connected with the fibrous bands coming from the membrane of trie costal'cartilages, at the place where the latter unite to the sternum. In the anterior sternal membrane, on the contrary, we see only at its inferior portion and on the median line, a narrow band formed of longitudinal fibres which arise from the fibres of the membrane of the cartilages of the inferior true ribs. Most of its fibres are formed of fan- like expansions, the summits of which correspond to the insertions of the costal cartilages in the sternum, and intercross with those of the posterior face of the sternum, partially covering the longitudinal fibres from the same origin, and partly covered by them. These two sternal membranes evidently correspond to the two ligaments of the vertebral column (§ 821,822). They should then, from analogy, be called the sternal ligaments. SECTION II. OF THE LIGAMENTS OF THE HEAD. § 844. The ligaments of the head are, 1st. The ligaments which unite the head to the vertebral column. 2d. The ligaments of the lower maxillary bone. CHAPTER L OF THE LIGAMENTS BETWEEN THE HEAD AND THE VERTE- BRAL COLUMN.(l) § 845. The head and particularly the occipital bone considered a-s a single bone articulated to the vertebral column, unites with the first and second cervical vertebrae, and with each differently. The pecu- liarities of the articulations between the first and second cervical vertebrae, have determined us to examine them separately and to describe them apart from the general ligaments of the vertebral column. I. LIGAMENTS BETWEEN THE OCCIPITAL BONE AND THE ATLAS. § 846. The connection between the occipital bone and the atlas is less intimate than between the vertebrae. The intervertebral and the yellow ligaments do not exist; they are, like the fibrous ligaments, replaced only by looser fibrous bands, which extend from the anterior and. posterior arches to the large occipital foramen, and are called the occipito-atloidal membranes. (1) Mauchart, resp. Rumelin, Capitis articulatio cum prima et secunda colli ver- tebra, Tubingen, 1747. SYNDESMOLOGY. 19 I. ANTERIOR OCCIPITO-ATLOIDAL MEMBRANE. § 847. The anterior occipilo-atloidal ligament (membrana annuli anterioris atlantis) is, in fact, only the summit of the anterior vertebral ligament, and extends from the anterior arch of the atlas to the anterior edge of the large occipital foramen. It is formed of perpendicular fibres, of which those in the centre are stronger, and form a distinct and projecting fasciculus, which is continuous with the central and pro- minent portion of the anterior vertebral ligament (§ 821), and is attached to the centre of the basilar process of the occipital bone. II. POSTERIOR OCCIPITO-ATLOIDAL MEMBRANE. § 848. The posterior occipito-atloidal membrane (membrana annuli posterioris atlantis) is situated between the posterior extremities of the two articular ligaments, and extends from the upper edge of the posterior arch to the posterior part of the circumference of the occipital foramen, and fills the posterior space between the two bones. It is thinner and weaker than the anterior, and does not form a continuous membrane, as that does. " III. ARTICULAR LIGAMENTS. § 849. The. articular processes of the occipital bone and of the atlas are united, like the articular surfaces of the transverse processes, by a complete capsular ligament (Lig. articulationum capitis cum atlante, Lig. articulare superius), which arises from the circumference of their contiguous surfaces. It differs from the others in being broader and looser, so that it allows more extensive motions. IV. ACCESSORY LIGAMENTS. § 850. The accessory ligaments (Lig. accessoria) are fibrous bands, which proceed obliquely from above downward, and from without inward, from the summit and from the upper edge of the transverse processes of the atlas, and are attached partly to the capsule and partly to the occipito-atloidal membranes, and around the occipital foramen. They strengthen the ligaments already described, and furnish points of attachment to the small deep muscles of the head. II. LIGAMENTS BETWEEN THE BASILAR BONE AND THE AXIS. & 851. The union between the head and the axis by means of the basilar bone is much firmer and stronger than that between the head and the atlas. It is formed by very dense bands of longitudinal fibres, which extend from the edges of the occipital foramen to the centre of the axis. There are no capsular ligaments in this articulation. 20 DESCRIPTIVE ANATOMY. I. SUSPENSORY LIGAMENT OF THE SECOND CERVICAL VERTEBRA. § 852. The middle straight ligament, or the suspensory ligament of the second cervical vertebra(l) (Lig. suspensorium dentis epistrophei, s. rectum medium), is oblong and composed of straight fibres. It extends from the centre of the anterior edge of the occipital foramen to the sum- mit of the odontoid process, to which it is attached directly above the smail anterior articular fossa. It prevents the head from turning too Tar backward. II. LATERAL LIGAMENTS OF THE SECOND CERVICAL VERTEBRA. § 853. The lateral ligaments of the second cervical vertebra (Lig. epistrophei lateralia, s. alaria Maucharti) are one on each side, and arise some lines behind the suspensory ligament, from the anterior part of the lateral region of the occipital foramen, and from the rough fossa situated above the internal edge of the condyles of the occipital bone. Their fibres are oblique and are attached to the lateral edges of the odontoid process. When the head is turned to one side the fibres of the lateral hgament of the opposite side are tense ; so that these ligaments limit the lateral motions of the head. These three ligaments are the most important of those which unite the head with the first cervical vertebra. If one or all three of them be torn, the odontoid process is displaced by the least exertion, slips into the vertebral canal, suddenly compresses the origin of the spinal marrow, and thus occasions death. Hence death from hanging, and hence too, when the head is quickly turned to the side, or when it exe- cutes similar motions, the subject sometimes dies. III. COMMON LIGAMENTS BETWEEN THE BASILAR BONE AND THE CERVICAL VERTEBRjE. § 854. The common ligaments between the basilar bone and the cervical vertebrae are of several kinds, and differ in form, situation, and (1) Scemmerring (Banderlehre, p. 17) has already remarked that Weitbrecht was wrong in denying the existence of this ligament. In fact, we have always found it perfectly distinct from the crucial ligament; so that we cannot ao-ree with Weit- brecht in thinking that anatomists have been induced by this branch to admit its existence, since we have found both of them constantly, and they were separated bv a loose cellular tissue. This remark might seem superfluous, if Bichat had not adopted \\ eitbrecht's opinion. True, he describes a special ligament between the middle of the odontoid process anrl the basilar bone, but he is mistaken in statin^ it to be formed by the upper branch of the crucial ligament and the suspensory liea ment; so that he describes the crucial ligament as formed only of a transverse Dart and of the lower branch, and even mentions a connection between its fibres and those of the posterior ligaments of the vertebra;, although in fact they a re separated bv the capsule of the crucial ligament (§ 85<). ' ; SYNDESMOLOGY. 21 extent. We may divide them into those which are situated ivithin and those which are placed on the outside of the vertebral column. I. COMMON INTERNAL LIGAMENTS. A. CRUCIAL LIGAMENT. § 855. Behind the ligament described we find another, which is weaker, called the crucial ligament (Lig. cruciforme). It is also called the transverse ligament of the atlas(L. atlantis transversale); this term is however improper, as it points out only one of its parts. It unites the basilar bone with the first two cervical vertebrae. Its strongest transverse part, called the transverse ligament of the atlas, is formed of transverse fibres. It is attached by its two extremi- ties to the rough lateral edge of the medullary foramen of the atlas. It is very tense, and is situated behind the odontoid process : it is much broader in the centre than at its two extremities, and it is cartilaginous forward on the side of the posterior face of the odontoid process. Mau- chat has noticed this peculiarity, but he adds, that in this part the liga- ment does not adhere to the process but is only in contact with it. Bichat only has described the connection of this cartilaginous portion with the process; he states that a synovial capsule exists between them. In fact we have constantly observed this capsule, which we have always found also very broad and very loose. This transverse hgament forms the two horizontal branches of the cross. The two perpendicular branches of the cross, the upper and the lower, called also the appendages (appendices), arise from its centre; these are much weaker and are both formed of longitudinal fibres. The upper branch is much longer than the lower, becomes much broader upward, and is not only attached behind the suspensory liga- ment, from which it is evidently distinct at the centre of the occipital foramen, but also extends some fines on the centre of the upper face of the basilar process of the occipital bone. The inferior branch is much shorter than the other, and it is attached directly below the posterior articular facet of the odontoid process, which is smooth and not cartilaginous, to the upper part of the posterior edge of its base, which is considerably rough. The use of this ligament is not merely to strengthen the connections between the three bones to which it is attached, but also to allow the atlas to rotate around the odontoid process as around an axis, in which the synovia] capsule assists, and at the same time to protect the spinal marrow from the action of this process. B. LIGAMENTOUS ENVELOP OF THE HEAD AND CERVICAL VERTEBRA. § 856. Behind the crucial ligament, between it and the posterior hgament of the vertebral column to which it is loosely attached, we 22 DESCRIPTIVE ANATOMY. find a broad layer of longitudinal fibres, which arises from the upper face of the basilar process of the occipital bone and descends to the third or fourth cervical vertebra. This layer unites above with the dura mater and below with the posterior bridge of the vertebrae. It is called the ligamentous envelop of the cervical vertebra (apparatus vertebrarum colli ligamentosus). II. COMMON EXTERNAL LIGAMENT BETWEEN THE HEAD AND THE CERVICAL VERTEBRAE. § 857. The common external ligament between the head and the cervical vertebrae is the cervical ligament (Lig. nucha, s. cervicis), which begins at the spinous process of the seventh cervical vertebra, whence it extends to the posterior occipital spine and to its upper curved line. This ligament is thin and perpendicular, and gradually enlarges as it approaches the head. Its upper edge is thicker, it being formed of the united tendons of the muscles of the neck. It is continuous between the cervical vertebrae with the interspinal ligaments, and its posterior edge represents the supraspinal ligaments. IV. LIGAMENTS BETWEEN THE FIRST AND SECOND CERVICAL VERTEBRJK. § 858. Beside the posterior ligament and the two common capsular ligaments, which are looser here than in the rest of the vertebral column, the anterior face of the odontoid process unites also with the centre of the posterior face of the anterior arch of the atlas by a loose capsular ligament. CHAPTER II. OF THE LIGAMENTS OF THE LOWER MAXILLARY BONE. § 859. The ligaments of the lower maxillary bone are, 1st, those which unite it with the temporal bones ; and, 2d, those between it and the hyoid bones. I. LIGAMENTS OF THE TEMPORO-MAXILLARY ARTICULATION. § 860. The temporo-maxillary articulation is formed by an interar- ticular cartilage, two sijnovial capsules, and by accessory fibrous lio-a- ments. I. INTERARTICULAR CARTILAGE AND SYNOVIAL CAPSULES. A. INTERARTICULAR CARTILAGE. §861. The interarticular cartilage (operculum cartilagineum) be- longs to the class of fibro-cartilages; it is oval, situated horizontally, SYNDESMOLOGY. 23 with concave surfaces, and much thinner in its centre than at the edges. There is often in its centre a cavity filled by synovial mem- branes, which are then directly united. Its circumference is attached only to these membranes, and its external edge slightly adheres to the fibrous ligaments. This fibro-cartilage diminishes the friction between the articular sur- faces of the two bones. R. SYNOVIAL CAPSULES. § 862. One of the two synovial capsules (ligamenta cartilaglnig intermedia) is situated above and the other below the interarticular cartilage. The superior synovial capsule arises from the anterior edge of the transverse articular tubercle and from the posterior edge of the articular cavity of the temporal bone, and is attached to the circumference of the interarticular cartilage. It unites above with the cartilaginous covering of the articular surface of the temporal bone, and below with the upper face of the interarticular cartilage. The inferior arises from the circumference of the maxillary condyle, and is attached to the edge of the interarticular cartilage, and unites partly with this cartilage and partly with the cartilage of the maxil- lary condyle. . These two capsules are very loose, and permit very extensive mo- tions, especially upward and downward, since they are not confined forward or backward by fibrous ligaments. II. FIBROUS LIGAMENTS. § 863. The firmness of the temporo-maxillary articulation depends on an external and an internal fibrous Hgament. A. EXTERNAL FIBROUS LIGAMENT. § 864. The external fibrous 'ligament (membrana maxilla inferioris) consists of very firm longitudinal fibres, which arise from the posterior extremity of the zygomatic process of the temporal bone, descend to the neck of the lower maxillary bone, and are attached to the out- side and partly to the posterior part of the circumference of the synovial capsule. It is very tense when the jaw is moved forcibly forward or backward, so that it limits these two motions. B. INTERNAL LATERAL LIGAMENT. § 865. The internal lateral ligament (Lig. maxilla laterale) should not be considered, properly speaking, as belonging to the temporo-max- 24 DESCRIPTIVE ANATOMY. illary articulation; for it is situated at some distance from it and adds nothing to its firmness. It is a thin, oblong, tendinous layer, arises from the spine of the sphe- noid bone, and descends obliquely from above downward, from behind forward, and from within outward, to the lower maxillary bone, where it is attached below the internal orifice of the dental canal. The vessels and the nerves of the lower maxillary bone pass between this ligament and its neck. Its principal use is, to enlarge those sur- faces to which the two pterygoid muscles are attached, the outer part of which arises from them, and it is situated between their outer extre- mities. II. LIGAMENTS BETWEEN THE SKULL, THE LOWER MAXILLARY BONE, AND THE HYOID BONE. § 866. In nearly the same direction as the ligament already de- scribed, but more deeply situated, we find a membrane which is thinner; slightly tense, and formed by condensed cellular tissue : this is strength- ened only by some fibrous bands, which extend from the lower extre- mity of the styloid process of the temporal bone to the posterior edge of the angle of the jaw, and send a cylindrical slip to the small horn of the hyoid bone. This is the stylo-mylo-hyoid hgament (Lig. stylo-mylo hyoideum): it serves partly to unite the temporal, the inferior maxillary and the hyoid bones, and partly to enlarge the surface to which the pterygoideus internus muscle is attached. CHAPTER III. OF THE LIGAMENTS OF THE HYOID BONES. § 867. The body or the central portion of the hyoid bone articulates with the large and small horns by two synovial capsules ; one of them is narrow and tight, and the second is broad and loose. Both, but the first particularly, are strengthened by tendinous fibres. The posterior extremity of the large horn is attached to the superior horn of the thyroid cartilage by a round perpendicular ligament, in the centre of which we often find a round cartilage or bone. SYNDESMOLOGY 25 SECTION III. OF THE LIGAMENTS OF THE EXTREMITIES. CHAPTER I. OF THE LIGAMENTS OF THE UPPER EXTREMITIES. § 868. The ligaments of the upper extremities are, 1st. Those between the trunk and the upper extremities. 2d. Those of the scapula. 3d. Those of the elbow-joint. 4th. Those of the fore-arm. 5th. Those of the wrist-joint. 6th. Those of the fingers. ARTICLE FIRST. LIGAMENTS BETWEEN THE TRUNK AND THE UPPER EXTREMITIES. § 869. The upper extremities are attached to the anterior and superior part of the trunk by the clavicles, to which they are united by synovial and fibrous ligaments. The scapula, trunk, and head, are united only by muscles. The clavicle is articulated, by its anterior extremity, with the clavicle of the opposite side, and also with the first piece of the sternum and the first rib. I. INTERCLAVICULAR LIGAMENT. § 870. The interclavicular ligament (Lig. interclaviculare, trans- versum) is thin and formed of transverse fibres. Its upper edge is loose and concave ; the inferior is straight or slightly convex, and is mostly attached to the upper part of the handle of the sternum. It extends from the upper extremity of the articular surface of the internal edge of one clavicle to the corresponding part of the opposite clavicle; so that it unites these bones with each other and with the sternum, and prevents them from moving too far backward. II. STERNO-CLAVICULAR ARTICULATION. § 871. The clavicle and sternum are connected by an interarticular cartilage, two synovial capsules, and a. fibrous ligament. Vol. II. 4 26 DESCRIPTIVE ANATOMY. A. INTERARTICULAR CARTILAGE. § 872. The interarticular cartilage is* generally very soft, almost membranous, extremely thin in its centre, and, on the contrary, very thick in its circumference, so that its two faces are concave. It is attached downward, backward, and' inward, by a thick and firm fibro- cartilaginous tissue to the facet where the clavicle unites with the ster- num ; downward and forward to the clavicle, and to the inner part of the cartilage of the first rib ; upward, forward, and outward, to the mar- gin of the articular facet of the clavicle. It unites intimately forward and backward, with the fibrous ligaments of the sterno-clavicular articulation. It is firmly attached, and admits of but little motion on account of the thickness and breadth of that part of the cartilage which is external to the synovial capsules. B. SYNOVIAL CAPSULES. § 873. The synovial capsules are two, an upper and external, and a lower and internal. The upper arises from the margin of the anterior part of the anterior articular facet of trie clavicle, which is smooth and covered with carti- lage, and is attached around the upper face of the thin and internal part of the interarticular cartilage. The lower arises from the upper part of the lower face of this cartilage, and is attached to the anterior, inferior, and external portion of the articular facet of the handle of the sternum. Both are small and narrow. C FIBROUS LIGAMENTS. § 874. The synovial capsules are strengthened by fibrous ligaments which are attached princi,-.-rly to the anterior and posterior parts of their circumference, but no cr form a dense layer. The anterior fibrous ligament is the stronger, and* is formed by per- pendicular descending fibres. The posterior is formed jaf radiated fibres which are attached partly to the posterior face of the upper part of the handle of the sternum and partly to the cartilage of the first rib and are united with the anterior and the posterior periosteum of the sternum. III. OF THE COSTO-CLAVICULAR LIGAMENT, OR THE RHOMBOID LIGA- MENT. § 875. The space between the sternal extremity of the clavine the anterior extremity of the rib and most of its cartilage, is fillci bv a hgament formed of oblique intercrossing fibres : this arises from (he posterior edge of the clavicle, goes obliquely from above downward and from behind forward, and is inserted m the upper and posterior SYNDESMOLOGY. 27 edge of the rib and of its cartilage. A band of transverse fibres is often detached from its inner and inferior extremity, which goes to the lower external extremity of the articular facet of the handle to which the clavicle is attached. It is called the rhomboid ligament (Lig. rhom- boideum), from its form. It unites the bones to which it is attached, retains the clavicle and the first rib in their places, and increases the number of points of attachment of the subclavian muscle. ARTICLE SECOND. OF THE LIGAMENTS OF THE SCAPULA. § 876. Some of the ligaments of the scapula unite this bone with the clavicle, and others directly or indirectly with the humerus. I. OF THE LIGAMENTS BETWE.EN THE SCAPULA AND THE CLAVICLE. § 877. The clavicle and scapula are united by a capsular hgament and by several fibrous ligaments. A. ACROMIOCLAVICULAR LIGAMENT. § 878. A capsular ligament (connexio clavicula cum acromio) unites the acromion process of the scapula with the humeral edge of the clavicle. We may then term it the acromio-clavicular ligament (Lig. acromio-claviculare). It is short, very tense, and sometimes double, when an inter-articular cartilage exists between these two bones: this articular cartilage, however, is not constant, and often fuses with them completely. Very solid and transverse fibres go upward and downward, but espe- cially upward, over this ligament, which are attached also to the circumference of the interarticular cartilage. B. CORACO-CLAVICULAR LIGAMENT. § 879. The fibrous ligaments are generally two, which are also known as the common ligaments of the scapula, and both unite the clavicle with the coracoid process of the scapula. We cannot however deny but that it would be more convenient to consider them simply as two bands of the same ligament, the fibres of which have not the same direction; one of them is external, the other internal, and they are uninterruptedly continuous with each other. This ligament is called the coraco-clavicular ligament (Lig. coraco-clavi- culare)'to distinguish it from the preceding, and is formed by strong thjck fibres. It arises from the outer half of the upper face of the coracoid process, and is composed of ascending fibres. It is attached by its upper ex- 28 DESCRIPTIVE ANATOMY. tremity to the inferior face, and to the posterior edge of the scapular extremity of the clavicle, but it does not extend to the outer end of this bone. The internal and posterior fibres are shorter and more perpendicular: the anterior and external are longer and more oblique. The two bands which form this ligament are commonly described, the inner as the common conoid ligament, and the external as the common trapezoid ligament of the scapula (Lig. scapula communia conoides et trapezoides). The conoid ligament arises from the root of the coracoid process, proceeds more from before backward, and is attached to the posterior edge of the clavicle : its blunt summit corresponds to the coracoid process, and its broader base to the clavicle. Its anterior fibres are shorter and more perpendicular than the posterior. The trapezoid ligament arises from about the centre of the upper part of the coracoid process; its direction is more transverse, and it is attached more externally than the preceding, to the inferior face of the scapular extremity of the clavicle. The anterior are longer than the posterior fibres. H. OF THE LIGAMENTS BETWEEN DIFFERENT PARTS OF THE SCAPULA, OR OF ITS PROPER LIGAMENTS. § 880. The proper ligaments of the scapula are simply fibrous, and extend, like a bridge, between the two eminences of this bone. A. ACROMIO-CORACOID LIGAMENT. §881. The acromio-coracoid ligament (Lig. coraco-acromiale s. anterius, majus, triquetrum) is a thin band formed of horizontal fibres which converge from before backward. It sometimes arises by two separate bundles from the whole posterior edge of the coracoid process and is attached to the anterior extremity of the acromion process. It gradually contracts from before backward, and from within outward, and terminates in a very acute summit. The inner and outer edges (the former of which is the longer) are loose. The whole ligament is covered by the scapular extremity of the clavicle, and by the deltoid muscle, rests on the anterior part of the supraspinatus muscle which keeps it in place, and terminates by a thick layer placed under the deltoid muscle; it projects over the scapulo- humeral articulation, and thus prevents the displacement of the humerus upward. B. COSTO-CORACOID LIGAMENT. § 882. The costo-coracoid ligament (Lig. coraco-costoideum) calle also the coracoid (Lig. coracoideum) or the proper small ligament «f (1) Soemmering, loc. cit., p. 42.-Bichat, An. defer., vol. i. p. 273. SYNDESMOLOGY. 29 the scapula (Lig. scapula proprium, posterius, minus, obliquum), is much smaller than the preceding; it has the form of a thin square band, and it extends from the root of the coracoid process to the inner end of the upper edge of the scapula or of the rib above the scapular fissure, which it changes into a canal through which the nerves and vessels of the shoulder pass. It often ossifies. III. HUMERO-SCAPULAR ARTICULATION. § 884. The humero-scapular articulation is formed by a synovial capsule and a fibrous capsule, which covers the former. These two oapulses are called the large capsular hgament of the humerus (Lig. capsulare ossis humeri magnum). A. SYNOVIAL CAPSULES. § 884. The synovial capsule covers the articular surface of the scapula above, and the head of the humerus below. After leaving these two surfaces, it reflects on itself to form a large and loose sac. This sac, like all the synovial capsules,is entirely closed; but it covers also the bicipital groove, and even the upper part of the tendon of the long portion of the biceps muscle, for it is reflected from the groove over the tendon, although no opening exists on this part. B. FIBROUS CAPSULE. § 885. All the surface of this synovial capsule is covered by a com- plete fibrous capsule, which forms a broad and loose sao, open on the two sides. It is attached above to the circumference of the glenoid eavity of the scapula, and below to the neck of the humerus : in both points it is continuous with the periosteum. Its upper edge is continuous with a fibro-cartilaginous ring, which surrounds the glenoid cavity, and' slightly projects above its surface. It is called, the glenoid ligament (Lig. glenoideum). It is formed of closely interlaced fibres, and is thicker at its upper portion than in its other parts, since it is there strengthened by a fibrous band coming from the coracoid process. Its internal face is thinner, and even there we occasionally see spaces filled by the tendon of the subscapularis muscle. It is strengthened above by the tendon of the supra-spinatus muscle, backward by that of the infra-spinatus muscle and of the teres minor muscle. Below and forward its internal edge presents a slight opening, through which the long tendon of the biceps flexor muscle passes. The looseness of this ligament allows great freedom of motion in the ■ upper extremities. 30 DESCRIPTIVE ANATOMY. ARTICLE THIRD. OF THE LIGAMENTS OF THE ELBOW-JOINT. § 886. We find at the articulation of the elbow a synovial capsule and several fibrous ligaments. I. SYNOVIAL CAPSULE. § 887. The synovial capsule (membrana cubiti capsularis) unites the lower extremity of the humerus and the upper extremities of the ulna and radius. Above, after covering the cartilaginous articular surface of the lower extremity of the humerus with which it is blended, it detaches itself forward from the upper part of the two anterior articular cavities; on the sides from the base of the two condyles along the posterior car- tilaginous edges of the pulley and of the lower head ; backward from the upper part of the posterior articular cavity. From these different points it goes toward the radius and ulna, to which its inferior edge is attached. It is much looser and more extensive than on the sides. The portion attached to the radius descends deeply below the head of this bone to the commencement of its neck; so that the head, enve- loped by the reflected portion of the synovial capsule, is loose and in- closed in its cavity. From the inferior part of the neck of the radius it goes on the anterior. side of the upper extremity of the ulna; there it lines the lateral sig- moid cavities, and the upper edge of the condyle and the coronoid pro- cess of the ulna. We find considerable masses of articular fat in many places, but principally in the anterior and posterior articular cavities, especially above the pulley, between the heads of the radius and ulna, and within the large upper sigmoid cavity ^consequently, in all those parts most exposed to compression and friction. From this description it follows that this synovial capsule, between the anterior part of the articular face of the humerus and that of the radius, is much looser than between the posterior and that of the ulna, which is owing to the greater extent of motion of the radius ; for the radius rotates on its axis, while the ulna has only the motions of flexion and extension. II. FIBROUS LIGAMENTS. § 888. The synovial capsule of the elbow-joint is strengthened, on its anterior and posterior faces and on the sides, by fibrous bands, which SYNDESMOLOGY. 31 may be considered so many distinct ligaments, the lateral, the anterior, and the posterior. The two lateral ligaments are oblong and formed of longitudinal fibres. I. INTERNAL LATERAL LIGAMENT. § 889. The internal lateral ligament (Lig. cubiti laterale internium) arises from the inner part of the anterior face of the internal condyle of the humerus, covers the internal part of the synovial capsule, and is attached below to the internal edge of the coronoid process of the ulna. II. EXTERNAL LATERAL LIGAMENT. § 890. The external lateral ligament (Lig. cubiti laterale externum) extends from the anterior face of the external condyle to the inner por- tion of the circumference of the head of the radius. III. ANTERIOR AND POSTERIOR LIGAMENTS. § 891. The anterior and posterior fibrous hgaments (Lig. cubiti anterius et posterius) are formed of less regular fibres, and they are broader but weaker than the lateral hgaments. The anterior is strongest in its centre. It is formed of longitudinal fibres, which are loose at its upper part, oblique in the centre, and more transverse in the lower part. The posterior is not well marked, except on the sides, where it is strongest and composed of bands which converge downward; in other parts it is hardly seen. ARTICLE FOURTH. OF THE LIGAMENTS OF THE BONES OF THE FORE-ARM. § 892. The bones of the fore-arm are united in most of their length, but not in the same manner, nor do the agents of union form a conti- nuous whole. We find at the upper part two fibrous ligaments, in the centre a fibrous ligament, and below a synovial capsule. I. SUPERIOR REGION. I. ANNULAR LIGAMENT. § 893. The annular hgament of the radius (Lig. radii annulare) is very strong, and arises from the anterior and posterior extremities of the lateral sigmoid articular cavity of the ulna. It is formed of horizontal and circular fibres, and loosely surrounds the neck of the radius. Be- 32 DESCRIPTIVE ANATOMY hind the sigmoid cavity it forms a circle, lined by the synovial membrane of the elbow-joint, in which the head and the neck of the radius move. Its fibres interlace above with those of the anterior, posterior, and ex- ternal lateral ligaments; but it terminates downward in a loose edge. This hgament strengthens the synovial capsule ; it confines the motions of the upper part of the radius and keeps it in place. II. ROUND LIGAMENT. § 894. The round or oblique ligament, called also, but very im- properly, the transverse ligament (Lig. antibrachii, s. cubiti teres, s. membrana obliqua, s. transversa), is a thin but strong band, broadest at its upper part, situated on the anterior face of the bones of the fore-arm: it descends obhquely from the tubercle of the ulna to the internal face of the radius, and is attached below its tubercle. Its uses are to limit the motion of supination in the radius. II. MIDDLE REGION. INTEROSSEOUS LIGAMENT. § 895. The interosseous ligament (Lig., s. membrana antibrachii interossea) unites the two bones of the fore-arm in most of their length. It occupies the deepest region of the fore-arm, being situated between the extensor and the flexor muscles. Its upper part commences below the tubercle of the radius. It is attached in its whole extent to the external edge of the ulna, and to the internal edge of the radius, and extends almost to the lower extremity of the bones of the fore-arm • so that its lower part is much broader than its upper. It is formed of parallel fibres ; these descend from the radius to the ulna, and are much stronger at its upper than at its lower part. In several places, particularly above and below, we observe foramina for the passage of the interosseous vessels. III. INFERIOR REGION. SYNOVIAL CAPSULE. § 896. The inferior extremities of the bones of the fore-arm are united by a.very loose and very broad synovial capsule (membrana capsularis sacciformis extremitatum inferiorum cubiti), which is strengthened only by some straight and isolated fibres. This capsule arises on the ulna from the semilunar cavity and on the radius from the corresponding eminence. SYNDESMOLOGY. 33 ARTICLE FIFTH. OF THE LIGAMENTS BETWEEN THE FORE-ARM AND THE WRIST. § 897. The articulation of the bones of the fore-arm with those of the wrist(l) presents a thin and loose synovial capsule and some very strong fibrous bands, Which cover its external surface. 1. SYNOVIAL CAPSULE. § 898. The synovial capsule arises above from the edge of the tri- angular and cartilaginous articular surface at the lower extremity of the radius, and from a fibro-cartilage which terminates this articular surface forward; below, from the cartilaginous circumference of the superior or antibrachial articular facet of the scaphoid, the semilunar, and the pyramidal bones, consequently from the bones of the upper range of the carpus, except the pisiform bone, and also fills the spaces between these bones. Prolongations, called mucous ligaments (liga* menta mucosa), go from several of its parts, among which we disth> guish that which proceeds from the union of the first two bones of the carpus to the projection which arises between the two portions of the articular surface of the radius. These prolongations increase the extent of the surface which secretes synovia. II. INTERARTICULAR CARTILAGE, § 899. The interarticular cartilage (cartilago triangularis interme- dia extremitatum ossium antibrachii) (§ 898) is a small triangular fibro-cartilage; its base looks inward, and its summit outward; it is loose at its external edge, and its internal edge is attached to the ante- rior Age of the lower articular surface of the radius; and it is situated betwi'om the lower edge of the ulna and the semilunar bone. Its upper nee is covered by the synovial capsule, and the inferior by the synovial membrane of the articulation of the fore-arm with the carpus, so that it belongs to neither ; but as it evidently concurs to form the articular surfaces of the bones of the fore-arm, which correspond to the carpus, we must study it* here, instead of describing it when treating of the articulation of the bones of the fore-arm, as is generally done. (1) The carpal ligaments in the back and the palm of the hand, and also the pro- per carpal ligament in the palm of the hand, are not mentioned here, as they serve not to unite the bones, but only to retain the tendons in their places. They will be described in myology. Vol. II. 5 34 DESCRIPTIVE ANATOMY III. FIBROUS LIGAMENTS. § 900. We may describe, as is most usual, four principal fibrous hgaments, which strengthen the synovial capsule of this joint; the palmar, the dorsal, the radial, and the ulnar. The first two are larger and particularly broader than the others. I. FIBROUS PALMAR LIGAMENT. § 901. Thefibrous palmar or the anterior ligament (Lig. accessorium articuli cubito-carpalis, s. lacerti adscitilii palmaris, with the Lig. ac- cessorium obliquum et rectum) is composed of mostly horizontal bands, which leave the lower extremity of the palmar face of the radius and the styloid process of the ulna, go a little outward, meet, and unite, being attached to the palmar face of the pyramidal and the semilunar bones. These bands form particularly the oblique accessory hgament (Lig. accessorium obliquum, Weitbrecht.) Besides, from the posterior part of the palmar face of the inferior edge of the radius arise strong perpendicular fibres, which are attached above the preceding to the upper edge of the palmar face of the pyra- midal and semilunar bones, thus forming the straight accessory hga- ment (Lig. accessorium rectum). These fibres are generally interrupted in parts. II. FIBROUS DORSAL LIGAMENT. § 902. The fibrous dorsal ligament (Lig. fibrosum dorsale articuli cubito-palmaris), or the rhomboid ligament. (Lig. rhomboideum), is, formed of several very strong bands which are also interrupted from place to place ; these arise from the external edge of the articular face of the radius, go obliquely from before backward, and are attached to the dorsal face of the pyramidal bone. Their posterior part is the thickest, and there the fibres are most compactly arranged. III. FIBROUS ANTERIOR OR RADIAL LIGAMENT. § 903. The fibrous anterior or radial hgament (Lig. radiate articuli cubito-carpalis) arises from the summit of the styloid process of the radius, unites at its upper part with the anterior bands of the dorsal hgament, and terminating rather pointedly, is attached to the anterior asperity of the radial face of the scaphoid bone. IV. FIBROUS POSTERIOR OR ULNAR LIGAMENT. §904. The fibrous posterior or ulnar ligament (Lig. cubitale arti- culi cubito-carpalis) is longer and stronger than the preceding, and arises from the summit of the styloid process of the ulna, and, united SYNDESM0L0GY. 35 with the posterior part of the dorsal ligament, is attached to the dorsal face and to the ulnar side of the pyramidal bone. ARTICLE SIXTH. OF THE LIGAMENTS OF THE CARPAL BONES. § 905. The ligaments of the carpal bones comprise those which unite the two ranges and those which unite the separate bones of the same. I. OF THE LIGAMENTS BETWEEN THE TWO RANGES. § 906. The two ranges of carpal bones are connected together by a synovial capsule and by fibrous ligaments. I. SYNOVIAL CAPSULE. § 907. The short and close synovial capsule extends from the first three bones of the upper range to the four bones of the lower, unites with their cartilaginous faces and also sends small culs-de-sac between the adjacent bones, which are covered by the fibrous ligaments; by which the surfaces are kept in continual contact. II. FIBROUS LIGAMENTS. § 908. The fibrous ligaments which exist only externally are very similar to those of the radio-carpal articulation, as respects situation, number, and proportional size. The palmar ligament is short, but broad and triangular. Its central fibres are transverse, its anterior and posterior fibres are oblique; all converge towards the base. They arise from the pyramidal and sca- phoid bones, and are attached below to the trapezoides and the os magnum. The dorsal ligament is weaker than the preceding. It is formed of transverse fibres, and partly of those which are a little oblique. It is attached above to the dorsal face of the three anterior bones of the upper range, and below, to the upper region of the dorsal face of the four bones of the lower range. The anterior lateral ligament is formed of perpendicular fibres which extend from the radial side of the scaphoid bone to the os trapezium. The posterior lateral ligament is situated between the base of the unciform process of the unciform bone and the outer edge of the pyra- midal bone. 36 DESCRIPTIVE ANATOMY. III. LIGAMENTS BETWEEN THE PISIFORM BONE AND THE ANTERIOR RANGE. § 909. Besides these ligaments Ave find two others which are oblique; the upper is smaller, the lower is stronger ; these go from the anterior extremity of the pisiform bone to the unciform bone : the second is attached to the inferior face of the body of this last bone, and the other to the summit of its unciform process. II. OF THE ARTICULATION OF THE DIFFERENT CARPAL BONES. I. SUPERIOR OR ANTEBRACHIAL RANGE. A. ARTICULATION OF THE CORRESPONDING FACES. § 910. The four bones of the upper range of the carpus are arti- culated with each other differently, and do not possess the same degree of motion. The corresponding faces of the three anterior bones are united supe- riorly by short, firm, and solid fibres, which cover the culs-de-sac of the synovial membrane (§ 907) ; these are called transverse or interosseous ligaments (Lig. transversa, s. interossea). The fourth on the contrary is attached to the pyramidal bone by a very loose capsule, the dorsal face of which is covered by transverse fibres. B. ACCESSORY LIGAMENTS. §911. Beside the interosseous Hgament (§ 910) we also see, in several parts of the corresponding faces of the carpal bones, fibres, which go from one of these bones to another; these are called the dorsal and the palmar ligaments of this range. These ligaments are formed of transverse fibres. They unite with each other and also with the supplementary fibres of the synovial capsule, and are stronger in the palm of the hand than on the back. II. INFERIOR OR METACARPAL RANGE. § 912. The corresponding faces of the os magnum and of the unci- form bone, of the os magnum and of the trapezoides, are united by transverse and very tense interosseous ligaments, which are seen at their anterior portion. The strongest are situated between the first two bones. We also observe in this range transverse dorsal and palmar liga- ments, which are formed for the most part of several distinct i...-nds ; these extend from the different small bones of the anterior range to !'.:; bones adjacent, and usually to those of the succeding range: wn generally number three on each side; they are continuous with the fibrous ligaments of the articulation between the two ranges. SYNDESMOLOGY. 37 ARTICLE SEVENTH. OF THE LIGAMENTS OF THE CARPO-METACARPAL ARTICU- LATION. § 913. The five metacarpal bones are united by synovial- mem- branes and external fibrous ligaments with the bones of the anterior or inferior carpal range, and also by bands of fibres with the pisiform bone. I. SYNOVIAL CAPSULE. § 914. The synovial capsule of the first metacarpal bone is loose and broad ; it arises from the edge of the articular surface of the tra- pezium. The others are for the most part only prolongations of the common synovial capsule (§ 907). II. FIBROUS LIGAMENTS. § 915. The synovial capsule of the first metacarpal bone is strength- ened on the radial side by the tendons of the abductor muscles, and also on its edge by longitudinal fibres, which extend from the os trape- zium to the first metacarpal bone. These fibres it is true do not exist every where, but they are strongest on the dorsal face; and as they are almost entirely deficient in some places, we usually number four ligaments in this articulation, the dorsal, the palmar, and two lateral ligaments, the external, and the internal. § 916. The fibrous ligaments of the four other metacarpal bones are divided into dorsal and palmar. The dorsal ligaments are composed of oblique and perpendicular thin fibres, which are general-ly united in bands ; these go from the dorsal faces of the anterior range of the carpal bones to the upper extremity of the dorsal faces of the metacarpal bones. The palmar ligaments on the contrary are composed of more hori- zontal, and in part of more oblique fibres", which are mostly interlaced with the inferior palmar ligaments of the metacarpal bones. They extend from the palmar face of the anterior carpal range to the palmar face of the posterior extremity of the metacarpal bones. The strongest of all these ligaments goes from the anterior extremity of the posterior face of the trapezium to the base of the third meta- carpal bone, and is attached to its anterior edge. We find also some superficial bands which extend from the summit of the unciform process of the unciform bone, from within outward, to the base of the fifth metacarpal bone. § 917. A very strong round ligament arises from the inferior extre- mity of the pisiform bone, and goes directly to the base of the fifth 38 DESCRIPTIVE ANATOMY metacarpal bone, and which, passing under the band extended from the unciform bone to the fifth metacarpal bone, goes obliquely to the base of the third and the fourth, where it unites with the large ligament described above (§ 909). ARTICLE EIGHTH. OF THE ARTICULATION OF THE METACAPAL BONES WITH EACH OTHER. I. SYNOVIAL CAPSULE. § 918. The metacarpal bones of the second, third, fourth, and fifth fingers touch each other at their posterior extremities by smooth and cartilaginous surfaces, over which passes a synovial membrane, which is sometimes only a simple prolongation of the synovial capsule, situ- ated between the posterior and the anterior ranges of the carpal bones (§ 910), but which sometimes also forms several distinct sacs. The metacarpal bone of the thumb is entirely insulated from the others. II. FIBROUS LIGAMENTS, § 919. The fibrous ligaments are situated between the posterior and the anterior extremities of the metacarpal bones. The posterior are of three kinds, the dorsal, the palmar, and the lateralj the anterior are single. I. POSTERIOR FIBROUS LIGAMENTS. § 920. The dorsal ligaments are four ; one between every two metacarpal bones.(l) All are composed of transverse fibres. They increase very much- in breadth and power from the thumb to the fifth finger; the first is however larger than the second. Sometimes they are divided into two bands, an anterior and a posterior ; the latter is broader. The lateral ligaments are the narrowest of all. They are usually formed of several distinct bands, and descend below the former from the upper edge of the ulnar side of the metacarpal bone, to the lower edge of the radial side of the next bone; at the same time they turn a little forward. The inferior or palmar ligaments are the strongest. They are formed of transverse fibres and extend in this direction between the inferior faces of the bases of the adjacent metacarpal bones. The lateral and palmar hgaments are sometimes deficient between the first and second metacarpal bones. (1) Generally, only three are admitted, the ligament between the thumb and finger being considered deficient; but nice dissections convince us that this opinion is erro- neous. SYNDESMOLOGY. 39 II. ANTERIOR FIBROUS LIGAMENTS. § 921. There are three anterior fibrous ligaments formed of trans- verse fibres; they are very tense, and extend between the inferior faces.. of the heads of- the second, third, fourth, and fifth motacarpal bones, where they are continuous with the tendinous fibres. They are much larger and more movable than the precefling. ARTICLE NINTH. OF THE METACARPO-PHALANGEAN AND PHALANGEAN LIGAMENTS. § 922. The anterior extremities of the metacarpal bones, and the posterior extremities of the bones in the first phalanx, and also the three phalanges, are united exactly in the same manner by synovial capsules and accessory hgaments. I. SYNOVIAL CAPSULES. § 923. The synovial capsules are loose and broad, especially on the dorsal face of their circumference. At their upper portion, that which looks towards the fore-arm, they extend much farther on the inferior extremity of the upper of the two bones, between which they are found, so that beside the cartilaginous portion they embrace a considerable part which presents no cartilage. The synovial capsule of the metacarpo-phalangean articulation is much looser and broader than are those of the phalangean articula- tions. II. FIBROUS LIGAMENTS. § 924. Each of these articulations is confined by three strong hga- ments, two lateral and an inferior ligament. I. LATERAL LIGAMENTS. § 925. The two lateral ligaments, the external, and the internal, are rhomboidal, and formed of oblique fibres. They extend from the two rough depressions, at the two extremities of the head of the upper bone to the same depression in the base of the lower. Being attached directly to the lateral faces of the synovial capsule, they prevent it from separating on the sides. II. INFERIOR LIGAMENT. i § 926. The inferior, internal, or anterior hgament is situated on the palmar face of the synovial capsule, and is intimately connected with 40 DESCRIPTIVE ANATOMY. it. It is composed of transverse fibres. Its tissue is fibro-cartilagmous. It forms a very thick square layer, which is more broad than long, and bi-concave, the upper face of which looks towards the articulation, and „the lower to the flexor tendon. The upper part of the synovial capsule has no special fibrous liga- ment, but it is strengthened by the tendon of the extensor muscle of the fingers. # • III. UNGUAL LIGAMENTS. § 927. The ungual ligaments (Lig. unguium, s. lateralia subtensa) are fibrous oblong and rounded bands, situated on both sides of the bones in the third phalanx, and extend from the lateral tubercles of the base to those of the summit. These ligaments are united to the lateral edges of the roots of the nails, and serve to render them firm, and to enlarge the surface on which the nervous tissue of the fingers is expanded. CHAPTER II. OF THE LIGAMENTS OF THE INFERIOR EXTREMITIES. § 928. The ligaments of the lower extremities are, 1st. Those of the pelvis, and those which unite either the lower ex- tremities to the trunk, or the upper parts of the lower extremities with each other. 2d. The ligaments of the ilio-femoral joint. 3d. The ligaments of the knee-joint. 4th. The ligaments of the leg. 5th. The ligaments of the tibio-tarsal joint. 6th. The ligaments of the tarsus. 7th. The ligaments of the tarso-metatarsal joint. 8th. The ligaments of the metatarso-phalangean and phalangean joints. ARTICLE FIRST. OF THE LIGAMENTS OF THE PELVIS. § 929. The bones of the pelvis are connected by fibro-cartilages and by fibrous ligaments; but there are no apparent synovial capsules. The fibro-cartilages are the principal and most extensive modes of union. The fibrous hgaments only strengthen the joint formed by the fibro-cartilages ; some pass upon these articulations, others go to other parts, so that they assist to form the walls of the pelvis, to increase SYNDESMOLOGY. 41 the surfaces for the insertion of the muscles, and to protect the vessels and nerves. I. FIBRO-CARTILAGINOUS LIGAMENTS. §930. The articulations of the first kind are the sacro-iliac sym- physes, and the symphysis pubis. I. SACRO-ILIAC SYMPHYSIS. § 931. The sacro-iliac symphysis (symphysis sacro-iliaca) unites the sacrum with the ihac bones. The mode of articulation is not the same in all parts. The smaller anterior and ear-shaped part of each of these two bones is covered with a smooth cartilage. These two cartilages touch ; but they are rarely united, at least completely. They are very distinct from each other and smooth in youth; but as age advances they become rougher. We even find between them a fluid, which is thicker and less liquid than synovia. ' The two bones are very differently articulated at their larger poste- rior part. The bones there have no cartilage, are very rough, and separated very far from each other, especially upward and backward, and are united by a very dense, strong, felt-like, fibro-cartilaginous, irregular mass,* formed particularly of transverse fibres; this mass is never torn, even when the bones are forcibly separated in this point, but detaches itself from one bone and remains fixed to the other. We may consider this posterior part of the sacro-iliac symphysis as a particular hgament. This has been done by Bichat, who terms it the sacro-iliac ligament (Lig. sacro-iliacum).(l) II. SYMPHYSIS PUBIS. § 932. The symphysis pubis is situated between the upper parts of the descending branches of the pubes. The upper convex portion of the descending branch of the pubis is covered by a thin cartilage, which diminishes from above downward. This cartilage is entirely covered upward, downward, forward, and backward by a very thick layer of ligament, formed of transverse fibres, which are strongly developed at the lower part of the symphy- sis, and which are continuous with the periosteum and with the ten- dons of the adjacent muscles. This mass is generally thin on its inter- nal face, but often also projects longitudinally, a difference not de- pendent on the sex, although sex has no influence upon it. (1) W. Hunter, Remarks on the symphysis of the ossa pubis; in the London Med. Obs. and Enq., vol. ii. p. 321-339.—Tenon, Memoire sur les os du bassin de lafemme, in the Mem. de I'lnstitut, vol. vi. Paris, 1806, p. 149-201. This memoir points out very clearly the varieties in the arrangement of the symphysis. Vol. II. 6 42 DESCRIPTIVE ANATOMY. This fibrous layer always renders the articulation much firmer, and is even the principal agent of it. Its firmness however is less than that of the fibro-cartilaginous layer in the sacro-iliac symphyses, since it is generally ruptured when the bones of the pubis are forcibly sepa- rated. The internal arrangement of the joint is not every where the same. Many anatomists admit that the two articular cartilages of the pubis are always united, others assert that they are always separated ; some think, that in the first case, they form a single cartilage. We have rea- son to think however that the last arrangement never exists, and that when a single cartilage only appears, there are, in fact, two, separated by a layer of fibro-cartilage, which intimately unites with them in their whole length, and is connected forward and backward with the fibrous layer already described ; at least we have, never found a single carti- lage, and this arrangement is always seen when the cartilages are united. The mass of fibro-cartilage is inversely as that of cartilage. The arrangement we have described is not general. At all periods of life, without distinction of age, sex, or any other circumstance, we find the two articular cartilages perfectly separated from each other by a greater or less space, and to a greater or less extent of their height, and united only at their lower extremity by a cartilage, or more properly by a fibro-cartilage, which may be removed without any suspicion of violence. If, sometimes, they are completely united, •they are also often entirely separated at their posterior part. The first mode of articulation is most common in the male, and the second in the female; hence the sexes differ, if not constantly, at least primi- tively and really; for it is not the consequence of pregnancy and par- turition, since it is found also in females before they have attained the age of puberty. II. FIBROUS LIGAMENTS. § 933. Some of the fibrous ligaments of the pelvis are extended over the fibro-cartilages already described, and others attach the bones of the pelvis to its different parts. The former are supplementary, the latter proper hgaments. I. SUPPLEMENTARY FIBROUS LIGAMENTS. § 934. The supplementary fibrous ligaments of the sacro-iliac sym- physis are two, a posterior and an anterior. A. LONG POSTERIOR LIGAMENT OF THE PELVIS. 935. The long posterior ligament of the pelvis (Lig. pelvis posticum, s. ossis ilei longum, s. superficial) extends almost perpendicularly, although a little from without inward, from the posterior extremity of SYNDESMOLOGY. 43 the iliac crest to the summit of the transverse process of the fourth false sacral vertebra. It is very strong, and its form is oblong. B. SHORT POSTERIOR LIGAMENT OF THE PELVIS. § 936. The short posterior ligament of the pelvis (Lig. pelvis, a. ilei posticum breve, s. profundum) arises directly below the preceding; it follows the same direction with it, but is shorter and narrower". It is attached to the summit of the transverse process of the third false sacral vertebra. § 937. Besides these two hgaments, we also see arise from the pos- terior part of the internal face of the iliac crest some irregular fibres, which are for the most part oblique and flat, which intercross and pro- ceed from below upward, from without inward, and from behind for- ward. They unite in several bands, placed one after another from above downward, on the posterior face of the lateral parts of the upper false vertebrae of the sacrum. They concur with the preceding liga- ments to strengthen the sacro-iliac symphyses posteriorly.(l) The latter fibres lead to the anterior pelvic ligaments, which strengthen the sacro-iliac symphysis anteriorly. C. UPPER ANTERIOR PELVIC LIGAMENT. § 938. The upper anterior pelvic ligament (Lig. pelvis anticum su- perius) is composed of oblique fibres, which ascend from the com- mencement of the posterior third of the iliac crest to the transverse processes of the last two lumbar vertebrae. Its form is triangular; it is very thin, and usually perforated for the passage of vessels and nerves, especially when it ascends to the transverse process of the fourth lum- bar vertebra. D. LOWER.ANTERIOR PELVIC LIGAMENT. § 939. The lower anterior pelvic ligament (Lig. pelvis anticum infe- rius) arises from the same point as the preceding, but a little lower and a little farther back. It ascends obliquely from before backward, and is inserted in the transverse process of the fifth lumbar vertebra. It sends fibres downward and forward, which are inserted in the cartilage between the last lumbar and the first sacral vertebra. II. PROPER FIBROUS LIGAMENTS. § 940. The proper fibrous ligaments are three on each side, and serve less to keep the bones in their position than to complete the pari- etes of the pelvis, by a substance, which is solid, but is yielding to a cer- tain extent. Two of them are situated behind, one on each side of the (1) The lateral posterior ligament of the pelvis (Lig. laterale posticum ossis ilei) « will not be described in this place, but in myology. 44 DESCRIPTIVE ANATOMY. pelvis; the third is found forward. The posterior two unite two bones which are separated in the normal state; the anterior is extended between the different parts of one and the same bone. A. SACRO-SCIATIC LIGAMENT. § 941. The sacro sciatic hgament, the large posterior pelvic liga- ment, or the external posterior pelvic ligament (Lig. pelvis posticum magnum, s. tuberoso-sacrum) arises from the posterior and inferior iliac spine, from the posterior part of the external face of the inferior portion of the iliac bones, from the lateral edges, and from the outer part of the posterior face of the inferior portions of the sacrum and coccyx, goes obliquely forward, downward, and outward, contracts and thickens, and is attached to the internal edge of the inferior face of the sciatic tuberosity, where it again enlarges, and gives off a loose, falciform, and thin slip, which goes from the internal face of the ascending branch of the ischium to the descending branch of the same bone. Beside (§ 940) the uses pointed out, it enlarges the surfaces of at- tachment of the glutseus maximus muscle and closes the ischiatic notch, which changes into an oval foramen. B. SMALL SACBO-SCIATIC LIGAMENT. §942. The small sacro-sciatic, or the" sacrospinal hgament (Lig. pelvis posticum parvum, s. spinoso-sacrum) arises before the preceding, from the outer edge of the inferior portion of the sacrum and of the pieces of the coccyx. Its fibres go forward, outward, and upward; the upper fibres descend, the central are straight, and the inferior ascend. It crosses the preceding, and is attached to the sciatic spine. Its form is an equilateral triangle, and its internal face'is usually muscular. This ligament divides the great fissure or the sciatic foramen into two parts, an upper and a lower; the first is much larger, and is sepa- rated from the other by the parts which pass through it. C. OBTURATOR MEMBRANE. *"" § 943. The obturator membrane (Lig. s. membrana obturatoria, s. foraminis thyroidei ossium pubis) is thin, and formed of irregular fibres, which are mostly transverse and a little oblique, and which intercross variously. It arises from the sharp edges of the obturator foramen, further forward at its upper than at its lower portion, and it closes this opening almost entirely. We see at its upper and external part only a constant rounded and oblong hollow, through which the obturator vessels and nerves pass out from the cavity of the pelvis. But this hol- low is partly though imperfectly filled, for one or more bands of very strong transverse fibres go from the anterior edge of the ascending branch of the ischium to the beginning of the external edge of the de°- scending branch of the pubis, several lines behind the membrane ; so SYNDESMOLOGY. 45 that it would seem as if the upper fibres had been separated from each other in this place by the vessels and nerves which pass out from the pelvis. This space deserves notice ; since in thyroidal hernia, which is very rare, the abdominal viscera protrude from it and follow the course of the vessels. We also find other openings in the obturator membrane, particularly at its lower part; but these are less constant. III. CHANGES OF THE PELVIC LIGAMENTS DURING PREGNANCY.(1) § 944. Most usually, the bones of the pelvis have but a slight degree of motion on each other. Hence arises a question, whether this mobility is not increased under certain circumstances, and particularly if this change does not supervene during-pregnancy. Opinions differ in this respect. Some admit that the change occurs normally in every state of pregnancy. Others think it supervenes only under certain circumstances, as when the bones are diseased, or after very difficult labors ; and others, that it never takes place. The first of these opinions, already advanced by Pineau, is undoubt- edly the most correct; since, according to the testimony of the best observers as Sandifort and Hunter, about the period of parturition, the symphyses, especially that of the pubis, always become looser, broader, and yield more easily. Beside, the latter symphysis is always broader in those females who are mothers of several children, than in virgins. This phenomenon deserves to be pointed out, as it demonstrates that all the parts interested in the act of parturition are analogously changed and become looser and more spungy. Finally, this change does not necessarily imply a real separation of the pubic cartilages, but only the softening of the fibro-cartilage,—a state in which the articular cartilages do not seem to participate. Tenon has maintained the contrary, but he is wrong: if the cartilages have sometimes been found really separated, this state must be considered as congenital or morbid ; since this arrangement has been observed even in very young girls, or the loose surfaces of the cartilages were like- wise rough, or pus has been found in the cavity.(2) This softening begins to take place in the eighth month of pregnancy, that is to say, precisely at that time when the lower region of the genital organs begins to enlarge and to secrete a great quantity of mucus. (1) S. Pineau, De distractione ossium pubis inpartu naturali, deque rationibus qui- bus ea probatur ; in libris de virginitatis notis, graviditale etpartu, book ii.—Sandi- fort, Depelvi ejusque inpartu duatatione, Leyden,1763.—Hunter, loc. cit.—Louis, Sur Vecartement des os du bassin, in the Mem de Vac. de chir., vol. iv. Paris. 1769. Hist. p. 63-102.—Tenon, loc. cit. (2) A singular case of the separation of the ossa pubis, in the Med. obs. and inq., vol. ii. no. 28. 46 (£3 DESCRIPTIVE ANATOMY. This phenomenon is important, as by it the pelvis is enlarged and the act of parturition is facilitated. We must not confound it with the separation and the rupture of the cartilages, which may result from disease, either by destroying the fibro-cartilage between the two carti- lages or by detaching the latter from the surfaces of bone, where the fibro-cartilage separates from the two lateral cartilages ; so that then three cartilages are formed, two of which adhere, while the central one is loose.(l) ARTICLE SECOND. OF THE ILIO-FEMORAL ARTICULATION. § 945. The ilio-femoral joint is formed by the fibro-cartilaginous pro- longation of the cotyloid cavity, a synovial capsule, a fibrous capsule, and an internal fibrous ligament. I. FIBRO-CARTILAGINOUS LIGAMENT. § 946. The fibro-cartilaginous ligament of the cotyloid cavity, or the cartilaginous lip (Lig. cotyloideum fibro-cartilagineum, acetabuli labrum cartilagineum), is a complete triangular ring, formed of fibro- cartilage, which is several lines high and thick. It is thickest above and outward, and passes above the cotyloid fissure, so as to complete the edge of this cavity. Its loose edge is sharp and looks a little inward ; hence this ligament serves also to enlarge the cotyloid cavity, but con- tracts its circumference, although but slightly. This ligament is formed entirely of cartilaginous substance only where it passes over the cotyloid fissure. The space below is filled by some bands, situated, one within, the other without,—the external and internal ligaments of the cartilaginous lip (Lig. labri cartilaginei externum et internum), which are continuous, the first with the obturator membrane and both with the fibro-cartilage. II. SYNOVIAL CAPSULE. § 947. The synovial capsule (capsularis synovialis membrana) passes from the bottom of the cotyloid cavity on the cartilaginous lip (§ 945). It is intimately connected with both, completely covers the external face of the lip, then is reflected on itself at an acute angle, and finally descends loosely to go to the femur. There it is attached to the lower extremity of the neck, goes to the anterior oblique line, descending lower forward than backward, reflects at an acute angle from below up- ward, and blends with the cartilage which covers the head. (1) Tenon, loc. cit., Onsiemc obs., p. 174. SYNDESM0L0GY. 47 The posterior, superior, inferior, and external parts of the cotyloid cavityare covered by a semicircular cartilage, which extends, on all sides except the cotyloid notch, even to the loose edge of the cavity and to the cartilaginous lip, from which it is evidently separated. This carti- lage is intimately connected with the synovial capsule. The anterior and middle part of the cotyloid cavity is the deepest, and has an irregular quadrilateral form: it is rough, but is not covered with cartilage. It contains much articular fat. The synovial capsule adheres but slightly in this place, and is separated from the bone by layers of fat. III. ROUND LIGAMENT. § 948. Directly before the portion of the synovial membrane which passes on the space below the bridge formed by the cartilaginous lip, arises a quadrangular ligament about an inch long, called the round ligament of the femur (Lig. ossis femoris teres s. rotundum). The ex- tremities of this ligament enlarge a little, and its outer end is attached to the bottom of the cavity in the head of the femur. It retains this bone more firmly in it's situation. It is formed of longitudinal fibres, which are attached to the upper and lower horns of the cotyloid fissure and unite with the ligaments of the cartilaginous lip and also with the lip itself; but they are covered in all their circumference by a sheath of synovial membrane, which is reflected on itself. This hgament prevents the luxation of the femur upward, outward, and downward, as it prevents the femur from escaping in that direction: it is at least necessarily broken when this dislocation takes place, although the femur can quit the cotyloid cavity forward without its being ruptured. § 949. The round ligament is sometimes deficient, either primitively or from a violent and often repeated compression of the iho-femoral joint. IV. FIBROUS CAPSULE. § 950. The fibrous capsule (capsula fibrosa ossis femoris)* is the strongest and most perfect of all in the body. It arises above from the circumference of the inferior edge of the outer face of the cartilaginous Up, unites very narrowly in its whole extent with the external face of the synovial capsule, and is attached to the lower extremity of the head of the femur exactly in that part where the outer part of the capsule is reflected to cover the neck of the bone. It is very strong at its upper external and anterior portion, is two or three lines thick, and is formed of several superimposed layers of longitudinal fibres. This capsule is protected by the'' adjacent muscles of the thigh; although the tendons of the muscles are not connected with it. 48 DESCRIPTIVE ANATOMY. From its upper, anterior and internal part arise several bands, which ascend obliquely toward the internal part of the anterior face ol the horizontal branch of the pubis and the anterior face of the obturator membrane, with the fibres of which they are blended. ARTICLE THIRD. OF THE ARTICULATION OF THE KNEE. § 951. The knee-joint is the most complex articulation in the body; for the synovial capsule is not only strengthened externally by three fibrous ligaments, but the corresponding surfaces of the femur and tibia are attached within this capsule by strong fibrous ligaments, which are even their principal mode of union. From this arrangement, the knee- joint is also the strongest of all. What renders the joint more complex is, that the two bones are separated from each other by an interarticular cartilage. I. SYNOVIAL MEMBRANE. § 952. The synovial membrane (membrana synovialis articuli genu) arises some fines before the cartilage of the articular surface of the femur, and backward from directly above this same cartilage. It is attached below to all the circumference of the rough edge of the upper articular cartilaginous, surface of the tibia. Its upper and lower faces unite with the cartilages which cover the articular surfaces of the two bones. A part of its anterior face covers also the posterior face and the lateral edges of the patella; so that the patella slightly projects within the cavity. Beside, its upper and anterior portion covers rather closely the lower part of the extensor muscle of the leg, from which however it may be separated more easily than from the bone. The rest is united to the adjacent parts only by a very loose mucous tissue. The lower part of the cavity which it thus forms is divided into a right and a left portion; because a perpendicular fold is formed, which is loose upward and extends from the posterior intercondyloid fossa of the femur to the anterior part of its circumference behind the hgament of the patella, and which is attached in this place below the patella itself. We find considerable accumulations of articular fat in many parts, especially on the anterior wall, around the patella, in the fold we have mentioned, and behind the condyles of the femur. The whole capsule is very broad and loose, especially at its anterior part; less so however on the sides, which must be ascribed to the nature of the motions of the leg, which are only flexion and extension. SYNDESMOLOGY. 49 The outer face of the synovial membrane is strengthened behind by oblique fibres, which descend from the external condyle of the femur to the internal condyle of the tibia. II. EXTERNAL FIBROUS LIGAMENTS. § 953. On the circumference of the synovial membrane we find an internal and two external lateral fibrous hgaments. I. INTERNAL LATERAL LIGAMENT. § 954. The internal lateral hgament (Lig. laterale internum) is the strongest, and is formed of perpendicular fibres. It descends from the anterior part of the internal face of the inner condyle to the upper part of the internal face of the tibia, where it is attached. It is broader above than below and is triangular, the base of the triangle being turned for- ward. It prevents the articular surfaces from being dislocated inward. II. LONG EXTERNAL LATERAL LIGAMENT. § 955. The long, anterior, or external lateral ligament (Lig. genu laterale externum, s. longum, s. anterius) forms an oblong, rounded, firm band. It is situated before the short hgament, between the lower ex- tremity of the external condyle, from the external face of which it arises below, and the anterior part of the external face of the head of the fibula, to which it is attached. III. SHORT EXTERNAL LATERAL LIGAMENT. § 956. The short external or posterior lateral ligament (Lig. genu laterale externum breve s. posterius) is still feebler than the preceding. It arises a little above, and half an inch behind it, from the inferior part of the posterior face of the external condyle of the femur, goes a little obhquely from above downward and from within outward, and is attached to the summit of the head of the tibia, higher than the preceding. The two external lateral ligaments prevent the luxation of the knee- joint outward. The terms anterior and posterior are more convenient than those generally used, as the length of both is the same or nearly the same. III. INTERNAL FIBROUS OR CRUCIAL LIGAMENTS. § 957. The crucial ligaments (Lig. cruciata genu) are the strongest of all the connections between the femur and the tibia. We find two, an anterior and a, posterior. The posterior is longer, broader, and stronger than the other, and its lower part is thicker but narrower than the upper part. It extends Vol. II 7 50 DESCRIPTIVE ANATOMY. from the posterior extremity of the depression between the two condyles of the tibia, toward the anterior extremity of the posterior intcrcondy- loid fossa, at the internal face of the external condyle of the femur, where it is attached by a semicircular edge. Its direction is from below upward, from behind forward, and from within outward. The anterior arises from the anterior extremity of the internal point on the upper articular face of the tibia, goes outward, upward, and backward, crosses the preceding but does not touch it, and is attached a little behind it to the internal face of the outer condyle of the femur. These ligaments unite the tibia to the femur firmly, and also limit the turning of these bones on their axes. The posterior opposes the rotation of the thigh outward and that of the leg inward, while the anterior prevents the rotation of the thigh inward and that of the leg outward. IV. SEMILUNAR CARTILAGES. § 958. The semilunar or falciform cartilages (cartilagines interar- ticulares genu semitunares, s.falcata) derive their name from their form. Both are broader behind than before: the external edge which is con- vex, is much thicker than the internal which is concave and terminates obliquely in a point. The first adheres intimately to the synovial cap- sule, while the second is entirely loose ; but their two extremities are attached by a strong fibrous hgament to the posterior part of the inter- condyloid fossa of the tibia. Another strong transverse ligament unites them at their anterior extremities. Their inferior faces are plain, but their superior are concave to a greater or less extent, and pointed near the two extremities. Each rests on one of the portions of the cartila- ginous face of the tibia, and corresponds to one of the condyles of the femur. They are separated by the eminence on the upper articular face of the tibia, and their concave edges are turned toward each other. The external falciform cartilage is uniformly broader than the inter- nal in its whole extent, and also a little larger; hence it covers more of the upper face of the external condyle of the tibia. Its posterior extre- mity is very firmly attached to the fossa placed behind the spine of the tibia. It is also attached to the femur by a very strong ligament, which arises more posteriorly, ascends obliquely from without inward between the two crucial hgaments, and is inserted directly behind the posterior, on the internal face of the internal condyle of the femur. Its anterior extremity, which is reflected from before backward behind the anterior articular hgament of the two cartilages, is attached to the anterior part of the depression before the spine of the tibia, directly behind the lower extremity of the anterior crucial ligament. The internal falciform cartilage is attached by its posterior extremity farther inward and backward than the external, directly before the posterior crucial hgament, at the posterior extremity of the depression placed behind the spine of the tibia, much farther forward and outward than the external. SYNDESMOLOGY, 51 These two cartilages elevate the edge of the upper articular sur- face of the tibia, and thus impede the ghding of the condyles of the femur; but they prevent particularly the compression of the femur and the tibia in the motions of the leg. § 959. Of all the joints, the articulation of the knee is the most sub- ject to morbid alterations of texture, although it is not often dislocated, since the arrangement and firmness of its fibrous hgaments admit of but slight motions. In this particularly, above all other articulations, abnormal bones and cartilages are developed, which are at first attached to the synovial membrane by thin peduncles, but which in time are detached and isolated. This articulation is also almost the only one exposed to fungus of the joints (fungus articulorum). These conditions depend, partly on its great size, or partly on its position, as it is exposed to mechanical injury and compression more than any other joint. ARTICLE FOURTH. OF THE ARTICULATIONS OF THE BONES OF THE LEG. § 960. The bones of the leg are attached to each other at their upper, middle, and lower portions. I. UPPER ARTICULATION. § 961. The upper articulation of the two bones of the leg is formed by a short synovial membrane, the capsule of the head of the fibula (Lig. capituli fibula), which arises some lines above the head of the cartilaginous lateral articular facet of the tibia, and below the upper articular facet of the fibula, and the anterior face of which especially is strengthened by very strong transverse fibres, which extend from the internal edge of the head of the fibula to the external face of the upper extremity of the tibia. II. MIDDLE ARTICULATION. § 962. The middle articulation is formed by the interosseous hga- ment (Lig. interosseum, s. membrana interossea). This hgament is thin and smooth; it gradually contracts from above downward, and is formed of oblique fibres, which descend from the external edge of the tibia to the crest of the fibula. At its upper part we see a foramen, through which the anterior tibial vessels and nerves pass, and another below for the peroneal artery. We also occasionally see in all its extent similar but smaller openings. 52 DESCRIPTIVE ANATOMY. It is situated between the flexor and the extensor muscles of the leg ; the fibres of which arise in part from its two faces. III. INFERIOR ARTICULATION. § 963. Between the inferior extremities of the tibia and fibula a very narrow slip of the synovial membrane of the articulation of the foot extends in the form of a cul-de-sac, but there is no special articular capsule. This slip is attached by three broad fibrous bands. I. ANTERIOR TIBIO-PERONEAL LIGAMENT. § 964. The anterior tibio-peroneal ligament (Lig. tibio-fibulare ante- rius) arises from the external part of the anterior face of the lower ex- tremity of the tibia, and is attached to the inner part of the anterior face of the external malleolus. It is formed of fibres which descend obliquely from within outward. II. POSTERIOR TIBIO-PERONEAL LIGAMENT. § 965. The posterior tibio-peroneal hgament (Lig. tibio-fibulare posterius) is formed of fibres which follow the same direction as those of the preceding ; they extend from the external part of the posterior face of the inferior extremity of the tibia to the internal part of the posterior face of the external malleolus. III. SUPERIOR TIBIO-PERONEAL LIGAMENT. § 966. The superior tibio-peroneal ligament (Lig. tibio-fibulare supe- rius) is formed of fibres similar to, but much snorter than the two pre- ceding, and extends from the external face of the tibia to the internal face of the fibula, directly above the inferior processes of these two bones. § 967. A division of the anterior (§ 963) and of the posterior (§ 664) ligament into two portions, an upper and a lower, is useless, and does not naturally exist. ARTICLE FIFTH. OF THE ARTICULATION OF THE FOOT. I. SYNOVIAL CAPSULE. § 968. The synovial capsule of the joint of the foot (membrana arti- culi pedis sijnoviulis) arises from the edge of the articular and cartila- ginous face of the articulation of the tibia and fibula, and from the cor- responding face of the astragalus. It blends with all these surfaces and sends a slip between the tibia and the fibula (§ 963). It is .-very where very loose, but loosest at its external part. SYNDESMOLOGY 53 II. FIBROUS LIGAMENTS. § 969. The synovial capsule is covered forward, backward, and on the sides, by several bands, which do not unite in a fibrous capsule, and which extend from the tibia and fibula to the astragalus and cal- caneum. I. ANTERIOR LIGAMENTS. § 970. We may admit two anterior ligaments, an internal and an external. The central part of the anterior wall of the synovial capsule being loose, its two ligaments are much thinner than the others. The internal anterior ligament (Lig. anterius internum) is composed of perpendicular fibres, some of which ascend a little obhquely outward. It is larger than the external, and goes from one part of the anterior edge of the lower articular face of the tibia to the back of the scaphoid bone. The external anterior hgament (Lig. anterius externum) arises from the anterior part of the outer face of the external malleolus, and being formed of oblique fibres, proceeds from without inward and from behind forward, and is attached to the outer part of the anterior face of the body of the astragalus. It is usually formed of two bands, situated one at the side of the other, and separated by an interval. The upper band is much larger than the lower. The whole hgament has an irregular quadrilateral form. II. POSTERIOR LIGAMENTS. § 971. Usually there are two posterior ligaments, one superficial and the other deep. The superficial posterior ligament (Lig. posterius superficiale) has an elongated cylindrical form, and extends from the internal edge of the external malleolus, below the insertion of the pos- terior tibio-peroneal ligament, to the centre of the posterior edge of the body of the astragalus, where it is attached to an eminence of this bone. Usually, a special and smaller band is detached from this point, which unites to the preceding, but goes in a contrary direction down- ward and outward, to be inserted in the upper part of the internal face of the tuberosity of the calcaneum. The deep posterior ligament (Lig. posterius profundum) is much stronger than the preceding, and is separated from it by fat and cellu- lar tissue. It rests directly on the posterior wall of the synovial cap- sule, and is formed of longitudinal and oblique fibres, which arise from the posterior edge of the lower articular face of the tibia, and from the under part of the inner face of the external malleolus. These fibres converge and go downward, and are inserted above the preceding liga- ment in the posterior face of the body of the astragalus. 54 DESCRIPTIVE ANATOMY. Sometimes the two ligaments are blended together. The fibres which come from the fibula are always the strongest. III. LATERAL LIGAMENTS. § 972. The lateral ligaments are much stronger than all the other fibrous ligaments. A. EXTERNAL LATERAL LIGAMENT. § 973. The external lateral ligament (Lig. laterale externum fibula rectum, s. perpendiculare, s. medium, s. triquetrum) is much longer from above downward than from before backward, and gradually enlarges in the first direction. It extends from the summit of the internal mal- leolus to the external face of the calcaneum, to which it is attached, after dividing into an anterior and a posterior fasciculus. B. INTERNAL LATERAL LIGAMENT. § 974. The internal lateral ligament, called generally the triangular ligament, and which might be called the trapezoid (Lig. laterale inter- num deltoides, trapezium), goes from the inferior edge of the internal malleolus to the internal faces of the astragalus and calcaneum. It is more broad than high, is lower than the external, but is broader and as strong. It blends with the inner anterior ligament forward, and with the internal portion of the deep posterior ligament backward. ARTICLE SIXTH. OF THE LIGAMENTS OF THE TARSUS. § 975. All the bones of the tarsus are confined by short and thick synovial capsules, over which in many parts fibrous ligaments are extended. The latter are divided into those of the back, of the sole of the tibial and fibular edges of the foot. I. LIGAMENTS OF THE POSTERIOR RANGE. I. SYNOVIAL CAPSULE. § 976. The two bones of the posterior range are united by two synovial membranes, a proper and a common. The proper synovial capsule (capsula propria aslragalo-calcanea) arises below from the edges of the upper and cartilaginous face of the body of the calcaneum, extends a little backward, over the portion of this same face, which is not cartilaginous, and is attached above to the corresponding circumference of the cartilage on the cartilaginous infe- rior face of the body of the astragalus. SYNDESMOLOGY 55 The common synovial capsule (capsula communis, s. astragalo-calca- neo-scaphoidea) will be described hereafter. It is situated between the upper cartilaginous face of the anterior process of the calcaneum and the lower face of the head of the astragalus. II. FIBROUS LIGAMENTS. § 977. The two synovial capsules are strengthened in several parts by fibrous ligaments, and the proper capsules particularly by the lateral and the posterior hgaments of the articulation of the foot (§ 971). Besides, a broad internal hgament extends from the internal part of the posterior face of the body of the astragalus, to the posterior part of the internal face of the calcaneum, and is called the internal and pos- terior astragalo-calcanean hgament (Lig. astragalo-calcaneum inter- num, s. posterius. The anterior face is confined by an internal. and an external liga- ment. The internal anterior astragalo-calcanean ligament (Lig. astragalo- calcaneum internum anterius) extends from the internal extremity of the cartilaginous surface of the anterior process of the calcaneum to the internal face of the astragalus. The external astragalo-calcanean, or interosseous ligament (Lig. astragalo-calcaneum externum, s. interosseum) is composed of five or six very strong fasciculi, which are situated behind one another, and which diminish in length very much from behind forward and also from with- out inward. These fasciculi go from the external rough part of the upper face of the anterior process of the calcaneum to the external face of the neck and head of the astragalus, and to the channeled and acar- tilaginous part of the inferior face which separates the upper faces of the body and the anterior process. They fill the large space between these two bones. II. OF THE LIGAMENTS BETWEEN THE ANTERIOR AND THE POSTERIOR RANGE. I. SYNOVIAL CAPSULES. § 978. There are two synovial capsules, one for the astragalus, the calcaneum, and the scaphoid bone ; the other for the calcaneum and the cuboid bone. The first, or the astragalo-calcaneo-scaphoid capsule, has already been mentioned (§ 976). It arises from the margin of the anterior articular face of the astragalus, forms a cul-de-sac backward, which is reflected on the upper articular face of the anterior process of the calcaneum, and goes to the circumference of the posterior articular face of the scaphoid bone, and is blended with its posterior cartilaginous face. 56 DESCRIPTIVE ANATOMY. The proper, or the calcaneocuboid capsule (capsula synovialis cal- caneo-cuboidea), extends between the corresponding articular faces of these two bones. II. FIBROUS LIGAMENTS. § 979. The astragalus and the calcaneum are united to the sca- phoid bone, and this latter to the cuboid bone by external fibrous ligaments. A. CALCANEO-SCAPHOID LIGAMENTS. § 980. There are two calcaneo-scaphoid ligaments (Lig. calcaneo- scaphoidea), a superior and an inferior. The superior is much weaker than the other, and arises from the anterior edge of the rough portion of the tuberosity of the calcaneum, and ascends obliquely from behind forward, and from without inward, where it is attached to the external extremity of the back of the scaphoid bone. The inferior, much stronger than the superior, being formed of several distinct bands, is more broad than long. It extends from the anterior edge of the tuberosity of the calcaneum to the external part of the inferior face of the scaphoid bone. It forms, conjointly with the calcaneum and scaphoid bones, a cavity for the head of the astragalus. B. ASTRAGALO-SCAPHOID LIGAMENT. § 981. The astragalo-scaphoid ligament (Lig. astragalo-scaphoi- deum) covers all the upper surface of the synovial capsule of the two bones. It is formed of thin fibres, the direction of which is from before backward. Some of these fibres proceed even to the cuneiform bones. C. CALCANEO-CUBOID LIGAMENTS. § 982. The calcaneum is united to the cuboid bone by superior, external, and inferior ligaments. The superior hgaments (Lig. calcaneocuboidea superiora s. dor- salia) are usually three in number, placed successively from without inward. They form thin and flat bands, which increase progressively in length, from within outward, and are situated between the upper edge of the articular face of the calcaneum and the same edge of the corresponding face of the cuboid bone. The external ligament (Lig.calcaneo-cuboideum externum s.fibidare) extends as high as the cartilaginous faces of the two bones, on the out- sides of which they are attached. It is also thin, but stronger than the superior. The inferior ligament (Lig. cakcuu.o-cuboidcum inferius s. plantar?) may be considered as formed by three superimposed layers, each of SYNDESMOLOGY. 57 which is stronger than the other ligaments of these bones, and which unite to form one of the strongest fibrous ligaments of the tarsus, perhaps the strongest even in the whole body. The superficial layer, the longest and strongest, arises directly from the lower face of the tuberosity of the calcaneum, and is attached to all the tuberosity of the cuboid bone. The central layer is much shorter and narrower, and is not entirely covered on the inside by the preceding. We ought, properly speaking, to consider it as a continuation of the inferior calcaneo-scaphoid ligament (§ 980). It arises from the inner part of the anterior edge of the articular face of the calcaneum, and is attached behind to the internal part of the rough inferior face of the cuboid bone. The deep layer is entirely covered by the superficial; but by the central layer, only at its internal part. It is formed of fibres which go more obliquely from without inward and forward. It arises from the same parts of the two bones, but a little more externally. III. LIGAMENTS BETWEEN THE BONES OF THE ANTERIOR RANGE. I. SCAPHOIDO-CUBOID LIGAMENTS. § 983. The scaphoid and cuboid bones are united, especially pos- teriorly, in their whole extent by the interosseous ligament (Lig. interosseum scaphoido-cuboideum), the fibres of which are oblique, short, and very compact. We usually find a synovial capsule before this ligament. § 984. The external fibrous ligaments are two : 1st. The dorsal scaphoido-cuboid hgament (Lig. scaphoideo-cuboi- deum dorsale) which is square, and arises from fibres which extend obhquely from behind forward, and from within outward. It goes from the external edge of the scaphoid to the centre of the upper face of the cuboid bone. 2. The plantar, Lig. scaphoideo-cuboideum plantare) has the same form and direction as the preceding, but is composed of fibres which are more detached from each other : it extends from the centre of the inferior face of the scaphoid bone to the centre of the internal edge of the cuboid bone. II. LIGAMENTS BETWEEN THE SCAPHOID AND CUNEIFORM BONES. § 985. The ligaments which unite the scaphoid to the three cunei- form bones, are a synovial capsule and fibrous ligaments. A. SYNOVIAL CAPSULE. § 986. The synovial capsule is situated between the commencement of the anterior face of the scaphoid bone, and the posterior face of the three cuneiform bones. It also penetrates between the latter. Vol. II. 8 58 riKsCRlPTIVL ANATOMY. B. FIBROUS LIGAMENTS. § 987. a. The fibrous hgaments are, the dorsal, the internal, and the plantar. We may admit two dorsal ligaments (Lig. scaphoideo-cuboidea dorsalia), an internal and an external. The internal is triangular, and extends from the anterior and ex- ternal part of the upper face of the scaphoid bone to the upper face of the second cuneiform bone. Its fibres go forward and outward. The external is smaller than the other, from which it is entirely separated, is square, and formed of fibres which proceed in the same direction. It arises more externally, immediately at the side of the preceding, and is attached to the upper face of the third cuneiform bone. It is blended with the dorsal scaphoido-cuboid ligament (§ 984). b. A strong internal ligament, (Lig. scaphoideo-cuboideum internum), the fibres of which are straight and almost horizontal, extends from the anterior edge of the internal face of the scaphoid bone to the posterior part of the inner face of the first cuneiform bone, and unites these two bones in their whole extent. c. We may admit three plantar ligaments. The internal, the strongest is the continuation of the preceding, but is thicker than it. It is square, and its fibres which are straight, extend from the tuberosity of the scaphoid bone to that on the inferior face and the posterior edge of the first cuneiform bone. The central is feebler, but longer, and arises at the side of the pre- ceding a little more externally. It goes obliquely from before back- ward, and from without inward, to the posterior part of the inferior edge of the second cuneiform bone. The external, which is feebler and situated more deeply, is composed of detached, oblique, and transverse fascicuh. It extends from the external and anterior part of the inferior face of the scaphoid bone, to the posterior extremity of the inferior edge of the second and third cuneiform bones. III. LIGAMENTS BETWEEN THE CUBOID AND CUNEIFORM BONES. § 988. These ligaments are, a synovial capsule and hvo fibrous lisaments. The synovial capsule is situated between the cartilaginous points of the cuboid and of the third cuneiform bones. There are two fibrous hgaments, a dorsal and a plantar. a. The dorsal ligament, which is not constant, being often entirely replaced by the dorsal scaphoido-cuboid ligament (§ 984), when it exists, is very feeble, and is situated at the external edge of this last ■ it is formed of longitudinal fibres, which extend from the back of the cuboid bone to the posterior extremity of the back of the third cuneiform bone. SYNDESMOLOGY. 59 b. The plantar ligament is much stronger, and is formed of several distinct fasciculi, the anterior of which is the largest, and which all extend transversely from the internal edge of the plantar face, and from the lower part of the inner face of the cuboid bone to the inferior face and to the inferior part of the internal face of the third cuneiform bone. IV. LIGAMENTS O* THE CUNEIFORM BONES. § 989. 1st. The synovial capsules between the three cuneiform bones, arise from the common capsule between the scaphoid and the cuneiform bones (§ 986). 2d. The fibrous ligaments are, a. The dorsal hgaments which form several feeble layers of oblique and transverse fibres, which extend from the first to the second, and from this to the third cuneiform bone. 6. The interosseous hgaments, which are very firm transverse fibres, extend between the internal faces of the first and second, and of the second and third cuneiform bones, where there is no slip from the synovial capsule. c. The plantar ligaments are firm but isolated and usually oblique bands, which go from the posterior part of the internal face of the first cuneiform bone to the posterior extremity of the inferior edge of the second, and from this to the posterior extremity of the inferior edge of the third. They unite with the interosseous and plantar scaphoido- cuboid ligament. ARTICLE SEVENTH. OF THE LIGAMENTS BETWEEN THE TARSUS AND METATARSUS. I. SYNOVIAL CAPSULE. § 990. The synovial membrane between the bones of the metatarsus on one side, the three cuneiform and the cuboid bones on the other, are not arranged in the same manner in all parts nor in all subjects. We however find a special synovial membrane between the anterior extremity of the first cuneiform bone and the posterior extremity of the first metatarsal bone. Usually, the second metatarsal bone is united to the three cuneiform bones by a common synovial capsule. We find a third synovial membrane between the third metatarsal and the third cuneiform bones. Finally, the fourth and fifth metatarsal bones are united to the cu- boid bone by a common capsule. 60 ULSCRIPTIVE ANATOMY II. FIBROUS LIGAMENTS. § 991. The fibrous ligaments which strengthen these synovial mem- branes are divided into dorsal and plantar. a. The dorsal form several square and thin bands, which go from the upper face of the bones of the metatarsus corresponding to the tarsal bones, to the posterior extremity of the latter. The fibres of the external are a little oblique from within outward and from behind for- ward ; those of the internal go directly from before backward. b. The plantar correspond to the dorsal: they are however, except the first, a little weaker. They are strengthened by the tendons of the tibialis anticus and posticus muscles. We see also strong fibrous bands, which go from some of the meta- tarsal to the tarsal bones which do not articulate with them; for instance, from the base of the second and fourth metatarsal bones to the anterior extremity of the third cuneiform bone going directly from before backward, and from the plantar face of the posterior extremity of the fifth metatarsal bone, transversely, to the extremity of the third cuneiform bone. The posterior part of the circumference of the articulation of the first cuneiform bone with the metatarsal bone of the first toe is also furnished with strong ligamentous fibres, which go directly from before backward, ARTICLE EIGHTH. OF THE LIGAMENTS OF THE METATARSAL BONES AND PHALANGES. I. METATARSAL LIGAMENTS. I. POSTERIOR LIGAMENTS. § 992. The metatarsal bones, except the first, have the corresponding faces of their posterior extremities covered by slips of the synovial mem- branes extended between them and the bones of the anterior range of the tarsus (§ 990). The fibrous hgaments resemble those of the metacarpus (§ 919-921). They are divided into dorsal, middle, and plantar. The upper or dorsal (Lig. ossium metacarpi dorsalia) are formed of transverse fibres, which arise from the dorsal side of the corresponding faces of the posterior extremity of the adjacent bones. We find only three of them, because the metatarsal bone of the first toe does not arti- culate in this manner with the second. The upper ligament is how- ever here replaced by an analogous ligament, which extends from the first cuneiform bone to the base of the second metatarsal bone. SYNDESMOLOGY. 61 The middle or interosseous ligaments (Lig. ossium metatarsi media s. interossea) are sometimes only three in number, and proceed obliquely from above and inward to go to the next metatarsal bone: more fre- quently however there are four. Similar fibres exist also between the first and second metatarsal bones. The inferior or plantar ligaments (Lig. ossium metatarsi inferioras. plantaria) are like the dorsal, only three in number, and are the strongest. The hgament between the first and second metatarsal bone becomes a very strong fibrous layer, which extends from the first cunei- form bone to the second and third metatarsal bones. The fibres of this very long ligament proceed in a direction opposite to that of those between the fourth and fifth metatarsal bones ; that is, the former go from behind forward and from within outward, the latter from without inward and from behind forward, so that they converge anteriorly. II. ANTERIOR LIGAMENTS. § 993. On the plantar face between the anterior extremities of all the metatarsal bones, are very strong square ligaments, formed of lon- gitudinal fibres, which are attached to the synovial capsules rather than to the bones. These are called the anterior metatarsal ligaments (Lig. metatarsi anteriora plantaria). II. LIGAMENTS OF THE TOES. § 994. Synovial capsules, with lateral and inferior fibrous ligaments, exist between the posterior phalanx of each toe and the corresponding metatarsal bone, and also between the different phalanges. The final phalanges also have ungual hgaments. These parts being similar to those of the hand (§ 922-927), it is unnecessary to describe them. 62 DESCRIPTIVE ANATOMV BOOK III. OF MYOLOGY. § 995. The general characters of the muscles(l) have been men- tioned in the first volume. We shall here describe only the voluntary muscles, and not all even of these; but shall confine ourselves to those which move the bones; the history of all the others being placed more conveniently after the description of the parts which they move, with which we must first be acquainted if we wish to have an exact idea of the attachments of the muscles and of their modes of action. The sys- tem of the involuntary muscles is distributed in the vascular system and the viscera, in describing which also they will be examined. § 996. We consider as single muscles all those parts of the mus- cular system which can be separated from each other without dividing the fibres. In this manner we count in the normal state two hundred and thirty-eight different muscles, six of which are unmated and com- posed of two parts which unite on the median line, and two hundred and thirty-two are in pairs ; so that the whole number of the muscles is four hundred and seventy. The nomenclature of these muscles is not uniform : for a long time the inconvenient method of numbering them was used. It is, however equally inconvenient to establish 'a uniform principle of nomenclature in myology, by changing the names' of the muscles into descriptions of their situations and attachments, as Dumas and Chaussier have done ; for then the extremely long and very complex names resemble each other too much. The muscles derive their names principally from their modes of action, their attachments, their form, and their volume. (1) Among the descriptions we shall mention: Stenon, Elementorum myologies specimen, Amsterdam, 1669.—Douglas, Myographies comparatce specimen, Leyden, 1729.—Garengeot, Myologie humatne et canine, Paris, 1728.—Albinus, Historia mus- culorum hommis, Leyden, 1734.—Duverney, VArt de dissequer methodiquement les muscles du corps humain, Paris, 1749.—G. F. Petersen, Grundliche Anwiesung zu der Zergliederung der Muskeln des menschlichen Korpers, Hamburg, 1763.—J. Innes, A short account of the human muscles, Edinburgh, 1788.—J. G. Walter, Myologisches Handbuch, Berlin, 1777.—Sandifort, Descriptio musculorum hominis, Leyden, 1781.— Gavard, Traite de myologie suivant la methode de Desav.lt, Paris, an vii.—Fleisch- mann, Anleitung zur Kenntniss der Muskeln des menschlichen Korpers, Erlangen, 1811.—The principal plates are: G. Cowper, Myotomia reformata, London, 1724.— Myologie complete en couleur et de grandeur naturelle, Paris, 1746.—Albinus, Tabu- Ice sceleti et musculorum corporis humani, Leyden, 1747.—Duverney, Tabulce anato- micce, 1748.—G. G. Muller, XII. Kupfertafeln welche die meisten kleinen und zarten Muskeln des menschlichen Korpers vorstellen, Erfort, 1755.—J. Innes, Eight anato- mical tables of the human body, containing the principal parts of the skeleton, muscles, etc., Edinburgh, 1776.—J. Bell, Engravings explaining the anatomy of the bones,mus- cles, and joints, London, 180S.—Lewis, Fines of the muscles of the human body, Lon- don, 1820. MYOLOGY. 63 For the same reason that we commenced in osteology by describing the vertebral column, we shall mention first the muscles of the trunk, then those of the head, and lastly those of the extremities. These three large divisions of the body, from the great number of their muscles and the different layers that they form, are usually sub- divided into a greater or less number of regions (regiones), which mo- dern writers have too extensively multiplied, by insulating the descrip- tions of the different muscles and by disregarding undoubted analogies. When about to describe the muscles, a great difficulty presents itself relative to the order which we should adopt. Must we follow the anatomical order, which regards only the situation and the manner in which the different layers succeed each other ? or the physiological order, which is founded on their action, so that those muscles which should be considered together or immediately after each other, according to the first method, are separated from each other and allied on the con- trary to others, which the anatomical order would separate from them 1 Thus, for instance, many of the muscles which move the upper extre- mities are muscles of the back if we consider their situation; so that they are generally referred to this region. The custom of considering the muscles according to their situation and the order in which they succeed each other is also proper ; since it presents all their relations more exactly and allows us to demonstrate the different layers in the presence of the pupil. This then is the order which we shall adopt, always however with the proviso mentioned above (§ 995). 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 mus- cles 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. 64 DESCRIPTIVE ANATOMY. 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 belhes. In regard to the functions and attachments of these muscles, we may say, that most of them belong to the vertebra?, 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 trape- zius 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 cor- responding muscles, the rectus capitis posticus major and minor, the intertransversarii, and the lateral muscles of the head, which cor- respond to them; these may be called the straight muscles of the back (JVf. 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 descendentes) from their analogy to abdominal muscles ; these are, considering them from without inward, the levator scapulae, the rhomboidei, the serratus ami- cus and posticus, the complexus, the digastricus, the spinales colli, the semispinales dorsi, the multifidus spinae, the obliquus capitis superior, the supracostales, the scaleni, and the intercostales externi. Third, those which descend obliquely outward, or the ascending oblique muscles (M. obliqui dorsales ascendcnles). They extend either from the transverse to the spinous processes, or from the internal MYOLOGY. 65 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. ARTICLE FIRST. 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. THAPEZIUS. § 1000. The trapezius muscle, Dorso-sus-acromien, Ch. (M. cucul- laris, 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 occi- pital protuberance, and from a greater or less portion of the upper curved line of the occipital bone, and rarely also from the mastoid pro- cess of the temporal bone ; second, from the cervical ligament, where it blends with that of the opposite side ; third, from the spinous pro- cesses of the last cervical, and of the eighth, ninth, tenth, eleventh, and twelfth dorsal vertebree, 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 Vol. II. 9 66 DESCRIPTIVE ANATOMY. these bones, and with them the whole upper extremity, backward. Its upper portion also draws the head backward and bends the neck. II. LATISSIMUS DOHSI. § 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 glutesus maximus muscle, and from the outer lip of the central portion of the crest of the ilium, by a tendon which gradu- ally 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 digita- tions 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 strength- ened 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 pectoraks 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 tu- bercle 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 MYOLOGY. 67 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) ARTICLE SECOND. MUSCLES OF THE 8ECOND LAYER. § 1003. The second layer is formed by the rhomboidei, the levator anguh 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. RHOMBOIDEUS MAJOR. § 1005. The rhomboideus major or the inferior rhomboid muscle arises by short tendons from the lateral part of the summits of the spi- nous processes of the four, and sometimes of the five, upper dorsal ver- tebras, sometimes even of the last cervical vertebra, and is attached to most of the external Up of the base of the scapula, from its triangular surface to near its inferior angle. Its fibres are parallel, and go ob- hquely outward and downward. B. BHOMBOIDEUS 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 verte- bras, 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 sca- pula upward and backward, and consequently act in shrugging the shoulders. (1) Wardrop, in the Edin. Med. Journ. vol. viii. p. 282.—-Kelch, Beytrage zur pa- thologischen Anatomic, 1813, p. 34, Berlin.—We have also seen this anomaly. (2) Rosenmullen, var. muse. p. 5.—Kelch, loc. cit. p. 35. We have seen this variety also. 6S DESCRIPTIVE ANATOMY. II. LEVATOR ANGULI SCAPULJE. § 1007. The levator anguli scapula muscle, Trachelo-scapulaire Ch. (M. levator scapula, s. anguli scapula, M. patienlia) 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 vertebra, 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 vertebras; however we have once observed this arrangement which was perfectly symmetrical on both sides ; at the same time, the levator scapulas 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 scapulas 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 mus- cle and is covered below by the trapezius. This muscle corresponds in its situation and its action to the rhom- boidei 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 scapulas and the vertebral column, an arrangement similar to what is seen in the dolphin. III. SERRATI MUSCLES. § 1009. The posterior serrati muscles (M. serrati, s. dentati postici superior et inferior) form in fact but a single muscle, since they are united MYOLOGY. 69 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. SEEHATUS 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 vertebras. 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 anguh scapulas muscle, and goes to the transverse process of the first cervical vertebra.(1) 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 vertebras, 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 obhquely from behind and downward, and are attached, usually by four digitations, to theinferior edge of the last four ribs before their angle, from which they separate still more 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 trans- verse fibres in one part and another, but especially at its upper and lower parts: this expansion arises from the spinous processes of the dorsal vertebras 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) Rosenmuller, loc. cit., p. 5. 70 DESCRIPTIVE ANATOMY. IV. SPLENII MUSCLES. § 1014. The splenii muscles (M. splenii) are considered by many anatomists as forming only one muscle, because their two lower ex- tremities 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 vertebras or of the correspond- ing bones. A. SPLENIUS 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 vertebras. 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 vertebras. 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 cer- vical vertebras, rarely also of the second, from the spinous process of the last cervical vertebra, and more rarely from those of the upper two dorsal vertebras, and is attached to the posterior part of the mastoid process in its whole extent, where it covers the sterno-cleido-mastoi- deus 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 vertebras. § 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. MYOLOGY. 71 ARTICLE THIRD. MUSCLES OF THE THIRD LAYER. § 1018. The third layer comprises the sacro-spinalis, the cervicalis descendens, the biventer cervicis, the complexus, the trachelo-mastoi- deus, and the transversalis 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 pro- cesses of the vertebras 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 glutasus maximus mus- cle, from the spinous processes of all, or only from the lower four of the lumbar vertebras, and besides from each lumbar vertebra by short digita- tions, 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 vertebras. 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 vertebras; 2d, farther outward, by seven or eight shorter, weaker, closer, broad slips, to the posterior and smooth face of the nc^ks of the corresponding lower ribs. The sacro-lumbalis muscle, the outer belly of the sacro-spinalis mus- cle, 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 72 DESCRIPTIVE ANATOMY. eleven lower ribs, and to the upper edge of the angle of the first or 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 VCrtsbfcl. 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 descendens, 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 digitatione, 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 vertebras. It draws the neck backward, and inclines it a little to the side. When the neck is fixed, it slightly raises the ribs. IIL 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 ex- tends 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 vertebras. 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-mas- toideus muscle. These fasciculi, situated one above another, so that the posterior cover the anterior, unite to the inferior belly, which terminates im- perceptibly 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, * The long portion of the complexus muscle of most anatomists. MYOLOGY 73 properly speaking, where it is entirely loose ; commences nearly opposite the third dorsal, and extends as high as the fifth cervical vertebra. 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 com- plexus muscle, is divided into two portions, an upper larger, a lower smaller, by a tendon which is often an inch long, and which is like- wise 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 vertebras, 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 back- ward. When it acts with its fellow, it extends it backward. V. COMPLEXUS, § 1022. The complexus muscle is situated at the side of the pre- ceding, and should be regarded as its external portion.(l) It is 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 vertebras. 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 vertebras. 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; which unites by this part with the second intermediate tendon of the biventer cervicis muscle, and which is also more apparent on its ex- ternal 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 «x- ternal part of the upper curved line of the occipital bone. (1) This muscle and the preceding, are described by Chaussier as the trachelo- occipital, F. T. Vol. II. 10 74 DESCRIPTIVE ANATOMY. Its uses are the same as those of the preceding muscle, but it draws the head more obhquely 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 muscle3. This formation is remarkable as being analogous with the formation of birds. V. TBACHELO-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 pow- erful, and strictly speaking should not be separated from the trans- versahs 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 obhque 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 mas- toid 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. TRANSVEnSALIS 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 vertebras. It arises by five, six, or seven heads from the transverse processes of the upper eight dorsal and the lower three cervical vertebras; 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 at- tached by four or five upper heads to the extremities of the posterior roots of the transverse processes of the first six cervical vertebras, although generally it does not extend to the first. MYOLOGY. 75 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. ARTICLE rOIJRTH. FOURTH LAYER OF MUSCLES. § 1026. The fouith layer comprises numerous muscles, all of which are situated between the vertebras or between these bones and the head. Those between the different vertebras are the semispinalis cervicis, the semispinalis dorsi, the spinalis dorsi, the multifidus spinas, the inter- spinales, the supraspinales, and the intertransversarii; those situated between the upper vertebras and the head are the recti muscles, the obliqui muscles, and the rectus capitus lateralis muscle. I. DORSAL MUSCLES OF THE FOURTH LAYER. A. SEMISPINALIS 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 vertebras. It extends obliquely upward and inward and is attached by four separate heads to the lower edge of the tuber- cles of the spinous processes of the second, third, fourth, and fifth cer- vical vertebras. It extends the neck, and inclines it a little obliquely backward. B. 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 up- ward 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 vertebras. These two muscles should be considered as one, and their separation is purely artificial.(2) When united, they correspond to the complexus and to the biventer cervicis muscle. (1) 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 con- tinuation, 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.) 76 DESCRIPTIVE ANATOMY. 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 spinas situated below, and the semispinalis dorsi muscles. It rests directly on the upper and posterior parts of the arches of the vertebras, 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 vertebras. 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 vertebras. Thi3 muscle represents particularly the digitations of the biventer cervicis muscles, which are usually attached to one or some of the epinous processes of the lower cervical vertebras. It extends the vertebral column and inclines it to its side. D. MULTIFIDUS SPINS. § 1030. The multifidus spina muscle is formed by a great many fleshy bands, which extend obliquely downward from the transverse processes to the spinous processes of the vertebras 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 vertebras 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 semi- spinalis dorsi and colli muscles. Taken as a whole with these three muscles, it represents for the rest of the vertebral column and for the vertebras the biventer cervicis and the complexus. It extends the vertebral column and moves it to one side. E* INTERSPINALES. § 1031. The interspinales muscles are short muscles formed of lon- gitudinal fibres, which are situated between the summits of the spinous processes of two adjacent vertebras. The most apparent are those of the cervical vertebras. Those of the lumbar vertebras are the most feeble. Those of the dorsal vertebree are MYOLOGY. 77 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 supraspinahs muscles (M. interspinales supernumerarii, s. supraspinahs), which are more super- ficial than the preceding and which sometimes pass over several ver- tebras. 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 cer- vical 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 vertebras. They extend the vertebral column. P. INTERTEANSVERSARII. § 1033. The intertransversarii muscles are formed of longitudinal fibres and are situated between the transverse processes of two vertebras. 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 per- fectly 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. 78 DESCRIPTIVE ANATOMY A. POSTERIOR RECTI MUSCLES OP THE HEAD. § 1035. The two recti muscles of the head (M. capitis recti) corre- spond 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 supra- spinales 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. epistrophico- occipilalis), 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 bo.ie. § 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., (JVL. posticus capitis minor, s. profundus, s. atlanto-occipitalis), arises from the spinous process of the first cervical vertebra and is at- tached 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 propor- tion 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 corre- sponds to the first; it is not an exception to the rule. B. OBLIQUE MUSCLES OF THE HEAD. a. Obliquus capitis inferior. § 1039. The obliquus capitis inferior muscle, Axoido-atloidien, Ch., is the strongest of the small muscles of the head and has an oblong MYOLOGY. 79 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 colh 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. b. Obliquus capitis superior. § 1040. The obliquus capitis superior muscle, Moido-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 verte- bra. It goes obhquely 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 intertransversarius cer- vicis muscle or as the upper and posterior part of the second interspi- nalis 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 spinas 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, Atloido-sous-occipital, 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 out- ward, 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 httle forward. It evidently wholly or partially represents the posterior intertransver- sarius cervicis muscle, which is here larger and goes a httle farther forward. This muscle is sometimes double, an arrangement normally seen in birds. 80 DESCRIPTIVE ANATOMY. ARTICLE FIFTH. 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 (leva- tores costarum breves) are triangular: they arise from the inferior edge of the summit of the transverse process of the next superior dorsal vertebra, go obhquely 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. LEVATORES COSTARUM LOKGI. § 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 vertebras and pass over one rib to be attached to the following. The long and short levators of the ribs are uninterruptedly con- tinuous 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 vertebras. 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 (1) The levatores breves and longi are sometimes termed collectively the costalea muscles. * MYOLOGY. 81 broad tendon ; 3d, they are attached to the transverse processes of seve- ral cervical vertebras by different tendinous bands; 4th, they flex the neck to the side and raise the ribs. 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. 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 ex- tremity, 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 the third, fourth, fifth, and sixth cervical vertebras. B. SCALENUS MEDIUS. § 1047. The scalenus medius 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 vertebras. 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 posterios extremities of the transverse processes of the fourth, fifth, and sixth cervical vertebras. 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 me- dius, and is sometimes called the Scalenus minimus, Albinus, is some- times formed by the division of the anticus, since it is situated directly behind it and com^ 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 vertebras. Usually, the inferior nerves of the brachial plexus and the axillary vessels pass along its posterior face, between it and the scalenus medius, 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 scalenus anti- cus and medius. Vol. II 11 6>2 DESCRIPTIVE^ ANATOMY 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 exter- nal 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 inter- nal 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 vertebras. The supernumerary scalenus lateralis or posticus muscle is situated between the scalenus medius 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 vertebras. 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 ob- long and rounded muscle, situated at the side of the lumbar vertebras, 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 posterior. The posterior layer is the most extensive. It arises from the inner lip of the iliae crest, a little behind its centre, and from the ilio-lumbar ligament by a broad tendon; becomes larger after aris- ing, 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 vertebras, 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 pre- ceding. (1)Kelch, Bei/tvejre.zurpathologis.rhen anatomic, p. 32, No. xxxh.- MYOLCH.V £3 The quadratus lumborum muscle evidently represents the levatores costarum, the scaleni, the levator anguli scapulas, and the rhomboidei muscles ; and anteriorly, the pyramidal muscles. We must not com- pare this muscle, but the two obliqui abdominis muscles, to the inter- costales muscles. The two layers of which it is composed, fully justify the parallel drawn between it and the preceding muscles. It flexes the lumbar vertebras to its side, and depresses the lower ribs. IV. INTERCOSTALES. § 1052. The intercostales muscles are divided into the proper inter- costales, and the subclavius muscles. I. TEOPER INTERCOSTALES. § 1053. Each intercostal space is filled on each side by two thin muscular layers formed of oblique fibres, which are called the inter- costales 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, obhquely 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 ter- .mination, 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 because their fibres, which follow a contrary direction are straighter. S4 DESCRIPTIVE ANATOMY 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 infracostales muscles. Kelch has described them as the internal serrati muscles.(l) II. SUBCLAVIUS. § 1057. The subclavius muscle, Costo-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) Bcitr. zur Path. Anat., p. 41, No. 32. (2) Rohmer, Obs. Anat, part 1. p. 4.—Rosenmuller, in Isenflamm and Rosenmiil- ler, Beit., vol, i,, p. 375, and De nonnullis muse. corp. humani varietalibns, p, 6. MYOLOGY. >>0 ARTICLE FIRST. 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 hne. I. 03LIQUUS EXTERNUS ABDOMINIS. § 1062. The obliquus abdominis externus or descendens 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, in- ward, 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 latissimus 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 obhque downward and backward, from the first shp to the last; in the rest of its extent, which is less, it follows an inverse direction, and goes obliquely down- ward 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 latissi- Sti DESCRIPTIVE ANATOMV mus dorsi muscle, that all these slips intercross with each other by tendinous edges, directed obhquely 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 ter- minates 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 repre- sents 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 supe- rior 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 ihum 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. MYOLOGY 87 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 de- scribe. It is changed on the inside by the lower part of the obliquus internus and transversahs muscles into a canal, which descends obhquely, 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 hgament of the uterus in the female, leave the abdominal cavity through the superior, posterior, or abdominal opening (aperlura canalis inguinalis superior, posterior, s. abdominalis), and terminates by another inferior, anterior, or external opening (aperlura 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).(1) 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 men- tioned, 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 httle behind it, but in a parallel direction, and extends from the internal part of the upper extremity of the tendon of the tensor fascias- latae 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 hgament 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 .1. Cloqnet, Recherches Anatomiques surlcs hernies de Vabdomen, Paris, 1817-1819. bb DESCRIPTIVE ANATOMY. 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 alteiriate 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 (an- nulus abdominalis). It is an oblong and rounded opening, about an inch and a half long and an inch broad, the direction of which is ob- hque 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 pecu- liar 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 conesponding 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 fas- ciculi 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, et 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 inter- crosses 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 oppo- site 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 semi- canal, 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 obhquus 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. MYOLOGY. 89 The smaller internal portion of the tendon unites very firmly with the tendon of the obliquus internus muscle, and forms with it the ante- rior 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 direc- tion of its fibres, and the slight distance to which its fleshy portion ex- tends 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 ver- tebral 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 ob- liquus 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. ORLIQ.UUS INTERNUS ABDOMINIS. § 1064. The obliquus internus abdominis muscle, Ilio abdominal, Ch. (M. abdominis obliquus internus, s. obliquus ascendens), is situated di- rectly under the preceding, and forms the middle of the three broad mus- cles of the abdomen. It is much smaller than the obliquus externus mus- cle, and occupies the space between the lower edges of the cartilages of the last five ribs, the crest of the ihum, 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 (1) Burn3, in Monro, Morbid anatomy of the human gullet, &c, Edinburgh, 1811, p. 467. Vol. II. 12 90 DESCRIPTIVE ANATOMY. obhque and descending downward and inward. Considered as a whole, it is then formed of fibres which are separated from each other hke a fan. 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 trans- versalis 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 vertebras. It extends forward and downward much farther than the fleshy part of the obliquus externus 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 obhque downward and inward. The inferior edge arises from the central face of the larger anterior part of the crest of the ihum, 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 they 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 semicir- cular edge, concave below, where its fibres separate a httle from each other, and finally disappear. MYOLOGY. 91 The obliquus internus muscle corresponds to the intercostales interni muscles (§ 1045), 1st, by the direction of its fibres; 2d, by its situa- tion 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 direc- tion, so that its effects are the same. III. TRANSVERSALIS. § 1065. The transversalis muscle, Lombo-abdominal, Ch., (M. abdominis transversus s. internus) much resembles the obliquus inter- nus 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 httle obhque from above downward and from behind forward. The external edge is convex outward, and is obhque 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 vertebras. 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 not extend the whole length of the muscle: it does 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. 92 DESCRIPTIVE ANATOMY. 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. c The posterior layer is stronger ; it is composed of transverse fibres, and is attached by separate slips to the summits of the transverse pro- cesses of the upper four lumbar vertebras 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 com- mon 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 vertebras. The transversalis abdominis muscle corresponds to the triangularis sterni muscle in the direction of its fibres, in its situation, in the attach- ments of its external edge to the inner faces of the ribs, 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 albais 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 open- ing, 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 ster- num depends on the general difference of siructure between the tho- racic and abdominal cavities, the former being almost wholly formed of bones, while theparietes of the latter are fleshy and tendinous. MYOLOGY. 93 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 occa- sion 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, Stemo 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 ante- rior 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 ex- tends before it to the sixth rib. The internal slip is attached also to the anterior face of the xyphoid cartilage and its hgaments. 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 ge- neral characters are: 1st. They adhere intimately to the anterior layer of the sheath of this muscle. Generally speaking, they are more apparent forward 94 DESCRIPTIVE ANATOMY. than backward, where they are sometimes invisible; sometimes they are 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 at- tached, 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 peritonasum, to which it unites by very loose cellular tissue. The rectus abdominis muscle contracts the abdominal cavity in the direction of length 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 concert.(l) § 1069. The rectus muscle sometimes presents a fourth slip, which arises from the external or internal part of its upper edge, more usually 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 ex- ternal 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 . fy B5I-tin' M,'™oirc sur I'usage des enervations des muscles droits du bas-ventre, in the Mem. de t'acad. de Paris, 1746, p 585 (2) Kelch. loc. cit. p. 42. MYOLOGY. 95 resembles that of birds, in which the rectus abdominis muscle is very broad. The increase in number of the tendinous intersections of this muscle, and especially their existence below the umbilicus, are two circum- stances important as being analogous with the formation of the ape.(l) VI. PYRAMIDALIS. § 1070. The pyramidalis muscle, Pubio-sous-umbilical, Ch., is situ- ated at the lower part of the sheath formed by the tendons of the three broad abdominal muscles, and is covered forward by the anterior 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 sum- mit upward. It goes obhquely upward and inward and arises from the internal portion of the horizontal branch of the pubis, between the inser- tion 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 muscle 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 pre- senting three or four muscles. VII. DIAPHRAGM. § 1072. The diaphragm (septum transversum, diaphragma(,(5) a thin and broad muscle, is situated between the pectoral and abdomi- nal cavities. It adheres by its upper face to the pleura and pericar- dium, 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 vertebras 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 lumba- ris), a superior or costal portion (pars costalis), and a median tendon (tendo intermedins.) (1)Drelincourt in Blasius, Anat. animal., p. 110.—Vicq. d'Azyr, Encyc.meth., 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) Hallcr, Nova icon, septi transversi, Gottingen, 1741.—Santorini, Tabulce anat. xvii. Parma, 1775, tab. x. fig.—Tissot, Des fonctions du diaphragmc, Montpellier, 96 DESCRIPTIVE ANATOMY. The lumbar part is much thicker and smaller than the other, and arises on each side by four heads from the upper three lumbar verte- brae, 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. Tt goes upward and outward. The fourth arises from the transverse process of the second or first lumbar, or even of the last dorsal, vertebras. The heads of the left side generally arise half or even a whole ver- tebra 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 pillars of the diaphragm. MYOLOGY. 97 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 uninter- ruptedly 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 por- tion 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 situ- ated deeper than the upper. The posterior wall of this canal is consi- derably 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 fascicuh are reflected, the anterior and posterior of which go obhquely 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 termi- nates 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 obhque, 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, (1) Hubci, in Sazmmerring, Muskcllehre, p. 162. Vol. II 13 98 DESCRIPTIVE ANATOMY. 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. 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 abdomi- nal 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 down- ward, 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 inspira- tion 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 cavit}' of- the thorax. Simulta- neous 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 con- sequently takes place in all cases where fascal matter or urine is retained from any cause whatever, as dysentery, inflammation of the neck of the bladder, parturition, &c. § 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 diaphragm- atic hernia (hernia diaphraghmatica) which generally has no herniary sac. (1) Bourdon (Reehcrchcs sur le mecanisme 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 that in respect to these efforts, it only pre- pares 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. MYOLOGY, 99 \RTICLE SECOND. OF THE MUSCLES OF THE CHEST. I § 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-humtral, Ch., an ex- tensive 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 clavicularis), 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 cen- tral are transverse, and the lower go more and more obliquely upward. They all converge towards a very strong tendon, composed of trans- verse 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 apo- neurosis, 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. 100 DESCRIPTIVE ANATOMY § 1076. The clavicular portion of this muscle is very 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 pec- toralis 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 dorsi 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 tho- racic, the straight sternal or the sternal muscle of animals (M. tho- racicus, rectus sternalis, sternalis brutorum). This muscle is a more or less perfect repetition of the rectus abdo- minis 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 an unusually long slip of the latter. The accessory muscle varies in thickness, breadth, and even in num- ber, 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 influ- ence the existence of this muscle.(l) 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. ch. vi. p. 82-88.—Meckel De monstr. duplieitate, Halle, 1815, p. 35-40.—Kelch., Beytrwge, p. 33, No. 25. MYOLOGY 101 II. PECTORALIS MINOR. § 1078. Directly below the pectoralis major we find the pectoralis minor muscle, Costo-coracoidien, Ch., (JVT. 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 turned upward and backward. Its anterior edge is generally attached by three, more rarely by two or four slips, 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 liga- ment otohe scapulohumeral articulation.(2) III. SERRATUS MAJOR ANTICUS. § 1080. The serratus major anticus muscle, Costo-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 poste- rior 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 (1) Rosenmuller, p. 6. (2) Gantzer, p. 11. 102 DESCRIPTIVE ANATOMY. obliquus externus abdominis muscle. The lower edge is loosr. The posterior is attached to all the internal lip of the inner edge of the scapula. 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 the serratus major muscle is deficient, so that it is completely divided into two unconnected parts. IV. TRIANGULARIS STERNI. § 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 shps 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-abdo- minal muscle (J\t. slemo-abdominalis).(l) It at least always represents in the thorax the transversalis abdo- minis muscle. This comparison terminates the analogy betwen the muscles of the abdominal and thoracic parietes. ARTICLE THIRD. OF THE ANTERIOR MUSCLES OF THE NECK. § 1083. The anterior muscles of the neck form a superficial and a deep layer. (1) Rosenmuller, De nonnullis musculorum corp. hum. varictatibus, Leipsic, 1814. MYOLOGY. 103 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 pha- rynx, 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 attach- ment have not yet been described ; 2d, because it is more convenient to refer the history of those which are inserted in parts already de- scribed, 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., (M. latissimus colli, s. platysma myoides, s. quadratus, s. tetragonus gena), has an oblong square form. It is very thin and composed of muscular bands, which are generally very loosely united and often have consi- derable 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 obhquely 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 by the direction of its fibres. The looseness of its lower edge, which is wholly unattached, corresponds very well with the arrangement of the anterior part of the lower edge of the broad abdominal muscles, as like- wise 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. 104 BESCRIPTIVE ANATOMY. 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. § 1086. 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 masseter 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 musclej 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. STERNO-CLEIDO-MASTOIDEUS. § 1087. The sterno-cleido-mastoideus muscle, Sierno-mastoidien, Ch., must be regarded not as a single muscle but. as the union of two mus- cles, since its two bellies are more distinct from each other than some other muscles, especially those of the dorsal region, which are consi- dered as separate. The anterior belly, the sterno-mastoideus muscle (JVL. sterno-masloideus, 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 ster- num. 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-masioideus muscle (JVE. cleido mastoi- deus, s. nutator capitis posterior), is shorter and weaker than the pre- ceding. 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 be- comes 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. (1) Gantzer, loc. cit., p. 111. (2) Fleischmann, in Erlangcr Abhandl., vol. i. p. 28.—Gantzer, lot. cit., p. 6. (3) Zagorsky, Mem. de I'acad. de Petersburgh, vol. j. p. 357. MYOLOGY, 105 These two muscles correspond from above downward, the first 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 obhquely for- ward, 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 num- ber, arising from the detachment of some fasciculi from the rest of the mass.(l) Thus for instance we not unfrequently find 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 ante- rior 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 sterno-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 fre- quently doubled. Besides, this always increases in volume and num- ber 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 situ- ated directly on the anterior face of the upper part of the vertebral column. It comprises the rectus capitis anticus major, the rectus capi- (1) G. Meckel, De duplicitate monstrosd, p. 40, 41.—Kelch, Beytrcege zur path. anat., p. 31. (2) Brugnone, p. 160. Vol. II. , 14 106 DESCRIFTIVB ANATOMY. tie minor, aad the hngut colli muscles, all of which serve to bend the head and neck. I. RECTUS CAPITIS ANTICUS MAJOR. § 1090. The rectus capitis anticus major muscle, Grand trachelo- sous occipital, Ch. (M. 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 tendinous slips, which increase in size from below upward, from the transverse processes of the third, fourth, fifth, and sixth cervical vertebras, and from one slip of the longus colli mus- cle, which is attached to the sixth cervical vertebra. It goes from below upward and from without inward, gradually approaching its congeni- tal. 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 shps which come from the first and second cervical vertebras, an arrange- ment resembling the formation of the carnivorous animals. II. RECTUS CAPITIS ANTICUS MINOR. § 1092. The rectus capitis anticus minor muscle, Petit trachelo-sous occipital, Ch. (JVf. 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, as- cends, 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. HI. LONGUS COLLI. § 1093. The Longus colli muscle, Predorso-atloidien, Ch., descends from the first cervical to the third or fourth dorsal vertebra. Its struc- ture 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 verte- bras, and also from the body and the anterior roots of the transverse pro- cesses of the lower four cervical vertebrae, ascends in a straight fine, and is attached externally, by two or three short tendons, to the ante- MYOLOGY, 107 rior 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 shps from the anterior roots of the transverse processes of the third, fourth, and fifth cervical vertebras. It ascends obhquely 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. ARTICLE FOURTH. OF THE SACRO-COCCYGCEAL MUSCLES. § 1094. The sacro-coccygaal muscles (JW. sacro-coccygai, s. curva- tores 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 coccygceal 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 conespond to the three muscles of the upper half of the body, which we have just described. SECTION II. OF THE MUSCLES OP THE HEAD. § 1095. The muscles of the head comprise those of the skull and those of the face. The muscles of the skull are the occipito-frontalis, the auricular muscles, and one muscle of the lower jaw. The muscles of the face are those of the eyes, the nose, the lips, the other muscles of the lower jaw, and the hyoid muscles. Of these muscles we shall here examine only the occipito-frontalis, and those of the lower jaw, both because the parts which must neces- sarily be known to understand the descriptions of the others are not yet mentioned, and also because it is more convenient to examine them 108 DESCRIPTIVE ANATOMY. in connection with the other constituent parts of the organs which they assist to form. I. OCCIPITO-FRONTALIS. § 1096. The occipito-frontalis or epicranial muscle (M. epicranivs, s. cranii cutaneus, s. occipito-frontalis) is a flat, digastric muscle, situ- ated directly under the skin, to which it is intimately attached, and covers the anterior, upper, and posterior parts of the skull, and also the central and upper part of the face. Its posterior belly, which is also described as a separate muscle, termed the occipitalis, has an oblong square, or triangular form. It arises by tendinous fibres from the root of the mastoid process, and from the upper occipital ridge of the.basilar bone, where it unites with the sterno-cleido-mastoideus and trapezius muscles, soon becomes fleshy, ascends on the squamous portion of the occipital bone, and terminates by a concave edge which unites with the median tendon. This tendon is called the skull-cap (galea capitis), and is formed of very distinct longitudinal fibres. It extends all along the skull to the frontal bone, where it is attached to the anterior belly or the frontalis muscle. The anterior belly or the frontalis muscle is much more exten- sive than the posterior. It begins by an upper convex edge, then descends along the squamous portion of the temporal bone, goes straight to its inner part, which is the thickest, and obliquely forward to the outer, which is thinner, and terminates as follows : at its inner part, it is continuous by several slightly tendinous slips with the pyra- midalis nasi and the levator labii superioris akeque nasi muscles; in the region of the inner angle of the eye, it is attached to the nasal pro- cess of the upper maxillary bone and to the lower portion of the frontal bone; finally, at its outer part, it blends with the corrugator supercilii and the orbicularis palpebrarum muscles. Tb»s occipito-frontalis muscle corresponds in situation and attach- ment to the interspinales muscles of the vertebras. It resembles one of these muscles which is enlarged, rounded, and divided in its centre, from before backward, into two parts, united hyan intermediate tendon Considered as a whole, this muscle moves the skin of the top of the head. Its two bellies wrinkle in a transverse direction the skin above them, and extends that near them when they contract from the side of their tendon. Thus the frontal muscle raises that of the upper part of the neck. II. MUSCLES OF THE LOWER MAXILLARY BONE. § 1097. The muscles of the lower maxillary bone comprise those which raise it, those which move it to the side, and those which depress it. MYOLOGY. 109 I. LEVATORS OF THE LOWER JAW. § 1098. The lower jaw is moved by three levators, the action of which is to bring it towards the upper jaw, which is fixed. These are the temporalis, the masseter, and the pterygoideus internus muscles. A. TEMPORALIS. § 1099. The temporalis muscle, Temporo-maxillaire, Ch., the largest and strongest of all the muscles of the lower jaw, is broad and trian- gular. It occupies all the lower region of the central part of the lateral face of the skull, for it fills the temporal fossa, and covers the plain semicircular surface. It arises by very short tendinous fibres and by a convex edge from the semicircular line which bounds the lower part of the outer face of the frontal bone, from the large wing of the sphenoid bone, from the parietal bone, and the squamous portion of the temporal bone, and by fleshy fibres from the parts of these same bones situated below this fine. Its posterior fibres go from above downward and from behind forward, the central are almost perpendicular, the upper go from above downward and from before backward; all converge to unite in the temporal fossa. As they leave the circumference the muscle becomes narrower and thicker, and terminates in a short but very strong tendon, which is attached to the coronoid process of the lower maxillary bone. The entire muscle is covered externally by a tendinous expansion, formed of descending fibres which arise immediately over it, serves for the attachment of its fibres above, is separated below, on its outer face, by a greater or less quantity of fat, and is very loosely united to it in this place by cellular tissue and vessels, and is attached to the poste- rior edge of the malar bone and also to the upper edge of the zygo- matic arch. This muscle draws the lower jaw forward and upward. B. MASSETER. § 1100. The masseter muscle, Zygomato-maxillaire, Ch. (M. masse ter, s. mandibularis externus), has an oblong square form. Its length exceeds its breadth, and it is formed of fibres which go upward. It covers the outer face of the ascending branch of the lower maxillary bone, and fills the space between the posterior part of the lower edge of this bone and the zygomatic arch. It is very evidently formed of two layers entirely separate from each other, which differ also in the direction of their fibres, and which may be regarded as two distinct muscles. The anterior external layer is the longest and strongest, and covers most of the lower. It is formed of fibres which are oblique from above 110 DESCRIPTIVE ANATOMY. downward and from before backward, and become a little narrower from below upward. It arises by short tendinous fibres from the lower edge of the malar bone, and is attached to the lower half of the ascend- ing branch of the lower maxillary bone, as far as its inferior edge and its angle. The inferior or posterior layer is much smaller and feebler than the preceding; its form is also square, and it is composed of fibres which go backward. It becomes thicker from below upward, is loose poste- riorly, and is covered anteriorly by the preceding layer. It arises by fleshy fibres from the lower edge of the posterior part of the zygomatic arch, and is attached by short tendinous fibres above the upper end of the insertion of the external layer in the centre of the outer face of the ascending branch of the lower maxillary bone. The two layers unite and draw the lower jaw upward, the ex- ternal brings it forward, and the internal backward. C. PTEBTGOIDKUe INTERNUS. § 1101. The pterygoideus internus muscle, Grand ptereygo-maxil- laire, Ch., an oblong quadrangular muscle, arises by its upper thick edge from all the pterygoid fossa of the pterygoid process of the sphenoid bone, goes obliquely downward and outward and is attached, opposite the preceding, but to a much less extent than it, to the lower part of the inner face of the ascending branch of the lower maxillary bone, as far as the angle. It draws the jaw upward and inward; but if the muscles of both sides act, the jaw is moved directly upward. II. PTERYGOIDEUS EXTERNVS. § 1102. The lower jaw is moved laterally by a single muscle, the pterygoideus externus muscle, Petit pterygo-maxillaire, Ch., situated between the lower maxillary bone and the pterygoid process. This is the smallest muscle of the lower jaw, and differs from the others in the transverse direction of its fibres. It arises by short tendinous fibres from all the outer face of the outer layer of the middle sphenoid or pterygoid process, then goes directly backward and outward, and is inserted by short tendinous fibres in the inner face of the neck, and of the condyle of the lower maxillary bone. It draws the lower jaw from the opposite side, that is inward and forward, when it acts alone; but forward only when it contracts with its synonymous muscle of the other side. MYOLOGY. Ill III. DIGASTRICUS. § 1103. Although several muscles contribute more or less directly to depress the lower jaw,(l) there is however but one appropriated specially to this function; this is the digastricus muscle, JWastoido- genien, Ch., (JVf. biventer maxilla inferioris), so named because formed of two oblong bellies united by a central tendon. The posterior longer and stronger belly is more rounded than the other and arises from the mastoid fissure of the temporal bone, and is covered in this part by the upper end of the sterno-cleido-mastoideus muscle. Leaving this point, it goes downward, forward, and inward, and gradually becomes a thinner oblong median tendon, which is at- tached by a small tendinous expansion on its anterior extremity to the lateral end of the central piece of the hyoid bone; so that it is situated between the temporal and hyoid bones. The anterior belly is shorter and flatter than the posterior, and arises behind the median tendon; goes forward and inward, and is attached directly at the side of the synonymous belly of the opposite side to the centre of the inner lip of the lower edge of the jaw. This muscle draws the lower jaw downward and backward. If the posterior acts alone, it raises the hyoid bone and draws it backward. If the anterior acts singly, this bone is also raised but carried forward. When the posterior belly contracts behind and the anterior before, it draws the skull and the face, except the lower jaw, backward, and thus by its action on the skull raises the upper jaw, separates it from the lower, and opens the mouth. § 1104. A very common anomaly of this muscle consists in the union of the anterior bellies of the two sides with each other and with the pterygoideus externus muscle, by the formation of a larger or smaller fleshy portion.(2) Sometimes too we find, between it and the skin a special transverse fasciculus, which is extended between the branches of the lower maxillary bone.(3) These anomalies are evidently imitations of what is seen in several mammalia, where the anterior bellies even blend with each other. More rarely the anterior belly does not extend to the chin, but is attached to the centre of the horizontal branch of the lower maxillary bone, as is also the case in many mammalia, where the single muscle. with which it is provided is also inserted more posteriorly than in man (1) A Monro, Remarks on the articulation, muscles, and luxation of the lower jaw, in the Edinburgh medical Essays,vo\. i. p. 103-129.—J. C. Platner, De musculo digas- trieo maxilla inferioris, Leipsic, 1737.—Winslow, Observ. par Panatomie eomparee sur Vusage des muscles digastriques de la machoire inferieure dans I'homme, in the Mem. de JParist anno 174% p. 236. (2) G. Meckel, Deduplie. monttr.,p. 42. (3) FUischmann, in the Erlanger Abhandl., vol, i. 112 DBSCRIPTIVE ANATOMY. SECTION II. OF THE MUSCLES OF THE EXTREMITIES. § 1105. The muscles of the extremities form the greater part of these sections of the body. Most of them have a more or less elongated form and assume a longitudinal direction, although this is not the direc- tion of their fibres, which go obhquely from one or more edges to the tendons. Very few of them have a transverse direction or one inter- mediate between it and the preceding: the latter are shorter. The muscles which follow the longitudinal direction flex and extend the different parts of the limbs; the transverse and the obhque separate them from each other or turn them on their axes. The muscles of both extremities are surrounded with general tendi- nous sheaths (fascia aponeurotica) and the tendons of the inferior, which are the longest in proportion, and are firmly attached in several places by strong fibrous ligaments to the bones over which they pass. In regard to situation, arrangement, and number, they correspond perfectly in their essential particulars, and differ only in modifications dependent on the different functions of the two limbs. CHAPTER I. MUSCLES OF THE UPPER EXTREMITIES. § 1106. The muscles which move the first section of the bones of the upper extremity, or the bones of the shoulder, all come from the bones of the trunk, from which arise also some of those which move the bone of the second section—the humerus. The former are the trapezius, the rhomboidei, and the levator anguli scapulae; the others the pectoralis major and the latissimus dorsi muscles, which have already been described (§ 1001). It is convenient to commence the description of these muscles by that of their common aponeurotic sheath. ARTICLE FIRST. OF THE APONEUROTIC SHEATH OF THE UPPER LIMBS. § 1107. The muscles of the upper extremities are surrounded by a tendinous envelop called the brachial aponeurosis (fascia brachialis). M-SOLOGY. 113 This arises in very muscular subjects from the deltoid muscle, but sometimes we do not see it except below this muscle. It is always stronger on the fore-arm than on the arm. However, at the posterior part of the anterior and posterior faces it is always much thicker than on the other faces and strengthened by transverse and oblique fibres, which cover the longitudinal fibres externally. In most of its extent it envelopes the muscles externally only. How- ever, at the lower end of the arm, in the inner angle, there is a triangu- lar slip, the internal and external intermuscular ligament (L. intermuscu- tare internum et externum), which leaves the aponeurosis and goes for- ward. The external extends from the outer condyle to the upper ex- tremity of the projecting part of the anterior angle; the internal from the inner condjle to the corresponding point of the inner angle. They extend between the extensors and flexors of the fore-arm and increase their surfaces of attachment. Two similar but much weaker ligaments are also found in the fore- arm in a similar situation. They separate the flexors and the extensors, both on the ulnar and radial side; because they proceed from the inner face of the aponeurosis to the posterior edge of the ulna and of the radius to which they are attached. Near the lower end of the fore-arm, the transverse fibres disappear, or at least become evidently thinner; but they again accumulate on the end of its posterior face and on the back of the thumb, become much more thick than high, and give rise in this place to the dorsal ligament of the carpus (Lig. carpi dorsale, s. armillare). This ligament extends from the transverse process of the radiul to the small head of the ulna, the pisiform, and the tuberosity of the fifth metacarpal bones. It is formed at its upper part, which is the weakest, of transverse fibres, which descend from the ulna to the radius, and at the lower part of fibres, which go backward and downward from the ra- dius, and consequently partially cross the preceding. Under it pass the tendons of the abductor magnus and extensor pol- licis, the radiales externi, the extensor digitorum communis, the ex- tensor indicis proprius, the extensor minimi digiti proprius, and the ulnaris externus muscles. Their passage is facilitated by the partitions which descend from the inner face of the hgament to the asperities on the ends of the bones of the fore-arm and divide it into six parts. ^ The first, the anterior, extends from the anterior edge of the lower end of the radius to the first asperity on the back of this bone, and con- tains the tendons of the abductor pollicis longus and of the extensor pollicis brevis muscles. Through the second, which is larger and which extends from the first dorsal asperity to the second, pass the tendons of the two radialei externi muscles. The third, a little oblique forward and downward, extends from the second to the third dorsal asperity of the radius, to the posterior edge Vol. II. 15 114 DESCRIPTIVE ANATOMY. of its lower extremity, and lodges the tendon of the extensor pollicis longus muscle. The fourth, the largest, extends from the third dorsal eminence to the posterior edge of the radius, and receives the tendons of the exten- sor digitorum communis and extensor proprius indicis muscles. The fifth, the smallest, is comprised between the radius and the anterior edge of the small head of the ulna; it receives the tendon of the extensor minimi digiti proprius muscle. Finally, the sixth, which extends from the posterior edge of the small head of the ulna to its styloid process, embraces the tendon of the ulnaris externus muscle. The lower edge of this ligament, which should be regarded not as a separate hgament but only as the development of the brachial apo- neurosis, is uninterruptedly continuous with the aponeurosis of the back of the hand, which gives a loose common envelop to the tendons of the extensor muscles, blends with the oblique tendinous fibres by which the tendons of the extensors of the fingers are retained in place, and concurs to form them. The brachial fascia is also strengthened at the lower part of the an- terior face of the fore-arm and on the palmar side of the carpus. The upper part of this portion, which is the feeblest and which extends from the anterior edge of the radius to the pisiform bone, forms the common palmar ligament of the carpus (Lig. carpi volare commune). It unites at its ends with the dorsal ligament. Under it pass the tendons of the flexors of the fingers, and in a special sheath that of the radialis internus. The lower part, which is much stronger, forms the proper palmar ligament of the carpus (Lig. carpi volare proprium). This ligament is formed by transverse and oblique fibres. Above, it blends in great part with the preceding. Below, it strengthens the palmar aponeu- rosis. Its two edges arise from the palmar eminences of the carpus, which are formed on the radial side by the trapezium and the pyramidal bones and on the ulnar side by the pisiform and unciform bones. ARTICLE SECOND. MUSCLES OF THE SHOULDER. § 1108. The muscles of the shoulder, Avbich surround the scapula and which extend from this bone and also from the clavicle to the hu- merus, are the deltoides, the supraspinatus, the infraspinatus, the teres major, the subscapularis, the teres minor, and the coraco-brachialis muscles. I. DELTOIDES, OR THE EXTENSOR OF THE ARM. §1109. The deltoides muscle, Sus-acromio-humeral, Ch. (M. del- toides, levator, attollens humeri), is a very strong muscle, which occupies MYOLOGY. 115 the upper and anterior part of the region of the shoulder. It arises by its upper longest and concave edge from the anterior edge of the sca- pular end of the clavicle, from the anterior edge of the acromion process, and from the lower edge of all the spine of the scapula at its anterior part, by fibres almost entirely fleshy or which at least have very short tendons, and by very long tendinous fibres at its posterior. After leaving this point, the muscle gradually becomes thicker, goes downward, and terminates by a fleshy summit externally, but possessing within a very long tendon, which is attached directly below the tendon of the pectoralis major muscle, at the posterior end of the external linea aspera, which arises from the outer tubercle of the humerus and at the central part of the outer face of this bone, which presents in this place a triangular impression. These fibres converge from above downward; so that the central are straight, the anterior oblique from before backward, and the poste- rior from behind forward. In examining this muscle more attentively, we recognize that it is composed of two orders of triangular fasciculi. The first order con- tains four fasciculi, which are larger than the others and the bases of which are turned upward and their summits downward. Between are the three smaller fascicuh of the second order, which are broader below than above but the two ends of which are a httle narrower than the central part. Below the upper edge of this muscle, between it and the capsular ligament, we find a considerable mucous bursa, which corresponds usually to the acromion, extends between this last process and the proper anterior hgament of the shoulder, and sometimes divides into two bursas, one of which is situated near the coracoid process. The deltoid muscle raises the arm and separates it from the side of the body. § 1110. A remarkable analogy with the structure of the mammalia is the existence of a posterior shp, entirely distinct from the rest of the muscle, which we have found several times. This slip arises from the tendinous expansion of the infraspinatus muscle (§ 1112), and from the centre of the inner edge of the scapula, by a broad and thin tendon, and is attached to the tendon of the deltoides. In most mammalia, in fact, the deltoides divides into a clavicular and a scapular portion and the latter is subdivided into an acromial and a spinous portion. We more frequently find the posterior part of the muscle simply separated from the anterior. We ought also to place among these anomalies the existence of a head, which goes from the anterior edge of the scapula to the deltoides,(l) and which is still more analogous with a part of the deltoides in birds. (1) Albinus, p. 422. 116 DESCRIPTIVE ANATOMY II. ROTATORS OUTWARDLY. I. SUPRASPINATUS. § 1111. The supraspinatus muscle, Petit sus-scapulo-trochiterien, Ch., is a triangular muscle which fills the supraspinal fossa, and is formed of fibres which converge from behind forward, from below upward, and from within outward. At first it is rather thick, but gra- dually becomes thinner. It arises from all the supraspinal fossa, from that part of the posterior edge of the scapula situated above the spine, and from the posterior part of the upper edge and also from the up- per face of this spine. It changes under the acromion process, directly below the large proper ligaments of the scapula, into a short and strong tendon, which, passing below the capsular ligament of the scapulohu- meral articulation, which it contributes to strengthen, goes to attach itself to the upper and inner part of the outer tubercle of the humerus. This muscle turns the arm outward and raises it. II. IKFRASPIKATUS. § 1112. The infraspinatus muscle, Grand sus-scapulo-trochiterien, Ch., arises from all the infraspinal fossa of the scapula, except its lower part. It goes outward and forward, so that its upper fibres are transverse, and the lower become more obhque forward and upward the lower they are. Its thickness gradually increases as it proceeds outwardly and it terminates in a strong tendon, which extends farther on the posterior than on the anterior face. This tendon adheres to the capsular ligament of the shoulder which it strengthens, blends above with that of the preceding muscle, and is attached to the central part of the outer tubercle of the humerus. We find a large mucous bursa between the scapula and this tendon. This muscle draws the humerus backward and downward, and rotates it from within outward. III. TERES MIITOR. § 1113. The teres minor muscle, Plus petit sus-scapulo-trochiterien, Ch. is quadrangular, and is scarcely distinguished from the preceding. It arises from the central part of the posterior lip of the anterior edge of the scapula, and goes directly before the lower and anterior edge of the infraspinatus muscle forward, outward, and downward, where, gradually becoming narrower but thicker, it terminates by a short and strong tendon at the lower part of the outer tubercle of the humerus, and at the outer ridge of the humerus which descends from this tu- bercle. It acts like the preceding, but it draws the humerus more outward- MYOLOGY. 117 III. ROTATORS INWARD. SUB-SCAPULARIS. § 1114. T^e subscapularis muscle, sous-scapulo-trochinien, Ch., the strongest of the two muscles which turns the humerus on its axis inward, occupies all the lower face of the scapula. Its upper fibres descend obliquely outward and forward, the central are transverse, and the inferior are very obhque from behind forward and from within outward. It gradually contracts to a considerable degree, passes behind the upper end of the coraco-brachialis, and the short head of the biceps muscle, and terminates in a short, flat, and thick tendon, which is attached to all the circumference of the inner tubercle of the humerus. Its structure is very complex, and we may reduce it to two orders of fascicuh which are more or less evidently distinct. The first, com- monly five in number, arise by a tendinous summit along the inner lip of the posterior edge, and the asperities which are found on the ante- rior face of the scapula. The lower, which is also the strongest, forms the lower and outer part of the muscle. All progressively enlarge, and are attached to the upper tendon. We find the second layer between them; this also is formed of five fasciculi, of which the upper likev/ise forms the upper part of the mus- cle. These fasciculi are generally stronger and broader externally, and pointed inwardly. They come from the spaces between the emi- nences, whence the former arise. These two layers however interlace more than once, and we cannot insulate them without cutting their fibres. The third layer, which is described in most works on anatomy, does not in fact exist. This muscle has two mucous bursas. The larger is sometimes united with the capsular ligament of the scapulo-humeral articulation, and is situated on the neck, and at the base of the coracoid process of the scapula. The smaller, which does not always exist, is situated much lower and further forward, between the capsular ligament and the tendon of the muscle. The subscapularis muscle draws the arm towards the trunk, turns it on its axis from without inward, and depresses it when it is raised. If the arm is fixed it can carry the scapula outward. II. TERES MAJOR. § 1115. The teres major muscle, Scapulo-humeral, Ch. (JVf. teres, s. rotundus major, s. deprimcns humerum rotundus) arises from the lower and triangular part of the outer face of the scapula, and from the pos- terior lip of the anterior edge, where it usually adheres to the subscapu- laris and teres minor muscles ; but it soon leaves these two muscles and ascends, always much less obliquely than the teres minor, from which 118 DESCRIPTIVE ANVTOMY. it is separated by the long portion of the biceps, between the latter and the coraco-brachialis, approximates the humerus, and is attached by rather a short, broad, but thin tendon, to the inner rough hne, directly behind and a little below the latissimus dorsi. Its form is the same as that of the teres minor, but it is at least twice as large as that muscle. We find below and forward, between its tendon, the latissimus dorsi muscle, and the humerus, a small mucous bursa, and beside these, we also find one or more in its anterior tendon where it. divides. This muscle draws the humerus backward, downward, and inward; when the arm is turned outward, it brings it a little inward. § 1116. It is often united with the posterior part of the latissimus dorsi muscle by a large fasciculus which leaves its posterior extremity. IV. CORACO BRACHIALIS. § 1117. The coraco-brachialis muscle, Coraco-humeral, Ch. (M. coraco-brachialis, s. coracoideus, s. perforatus Casserii) is formed like an oblong triangle. United above, rather intimately, and to some extent, to the origin of the short portion of the biceps flexor muscle (§ 1120), it arises from the coracoid process farther forward than the latter. It is tendinous before, in most of its length, and fleshy behind. In quitting the short portion of the biceps muscle it goes inward, becomes thicker at its central part, but contracts much at its lower end, and is attached, partly fleshy, partly tendinous, to the middto region of the inner face of the humerus. The musculo-cutaneous nerve generally perforates it in its centre. Its lower part often blends with the upper end of the brachialis internus muscle, a curious fact, as it adds a new feature to the analogy between the flexors of the fore-arm and those of the leg. We find one imper- fect bursa, and sometimes two, between its upper tendon, that of the short portion of the biceps muscle, and the capsular ligament of the scapulo-humeral articulation. This muscle approximates the humerus and the scapula to each other, carries the arm to the side of the body, and rolls it a little out- ward, when it is turned inward. Sometimes, instead of a simple perforation, it presents a real fissure, which is often confined to its lower part, and sometimes exists its whole length, so that the tendons are separated although the musculo- cutaneous nerve passes constantly between the two portions. This arrangement establishes a striking similarity with the structure of the apes. MYOLOGY, 119 ARTICLE THIRD. MUSCLES OF THE ARM. § 1118. The muscles found on the humerus arise partly from this bpne, others from the scapula, and are attached to the bones of the fore-arm. They are the triceps extensor, the biceps flexor, and the brachi- ahs internus ; the first is situated at the posterior and outer part of the arm; the other two are placed on its anterior and inner face. I. TRICEPS EXTENSOR, § 1119. The triceps extensor muscle, Scapulo-olecranien, Ch. (JVf. triceps brachii, cubiti, s. brachieus externus, s. posterior) occupies most of the posterior face of the humerus, and extends from the scapula to the olecranon process. The long or the posterior head (caput longum, anconaus longus) arises by a short, flat, and thick tendon, directly before the anterior insertion of the teres minor muscle, from the upper end of the anterior edge of the scapula, and goes from above downward, gradually increas- ing in thickness. The tendon descends very low on its inner face. Its lower tendon extends in all its lower half along the inner part of its inner face, and the fleshy fibres are inserted in it obliquely. Its form is elongated. The large head, or the outer head, (caput externum, s. magnum, an- conaus magnus, s. externus) arises above by a thin extremity which terminates by a convex edge, and presents very short ^tendinous fibres. This end is attached, directly below the insertion of the teres minor muscle, at the upper part of the posterior face of the humerus. The fleshy fibres come also from all the anterior edge of the bone. This head descends as far as the outer condyle, by a short tendon, which is oblique from above downward, from before backward, and from with- out inward, unites backward and inward to the lower tendon of the long head. In all its lower portion its inner and posterior part is covered by the common lower tendon of the brachialis internus muscle. Its form is that of an elongated rhomboid, its breadth exceeds its thick- ness. The short or internal head arises, directly below the upper extremity of the preceding, from most of the posterior face of the humerus, and descends along the inner edge of the bone to near the inner condyle, rests, by its posterior and inner edge, upon the tendons of the teres major and coraco-brachialis muscles, and also the inner edge of the brachialis internus. Its fibres go obliquely downward and outward; they are attached to the lower tendon of the long head in all the lower part of the short head. 120 DESCRIPTIVE ANATOMY. The common lower tendon of these three heads, which covers them outwardly at their lower part, is not destitute of fleshy fibres except in a very small portion of its extent below, and is inserted in the upper broad edge of the posterior face of the olecranon process of the ulna. We find a considerable mucous bursa between this tendon and the olecranon process, besides which we sometimes find two smaller ones on each side. We less commonly see another, also smaller, above. This muscle extends the articulation of the elbow and usually moves the fore-arm; but it can also move the arm when the/ore-arm is fixed. The long head brings the scapula towards the humerus, and draws the latter inward and backward. II. BICEPS FLEXOR. § 1120. The biceps flexor muscle, Scapulo-radial, Ch. (flexor antibrachii biceps, s. radialis, s. biceps internus), is a very long muscle, situated on the anterior and the outside of the am, and extends its whole length. Its two heads are separated above in almost all the muscle, and extend from the scapula, whence they arise, to the upper extremity of the radius. The internal, posterior, or short head (caput breve), called also the coraco-brachialis muscle, from one of its attachments, is not only shorter but also thinner than the long head. It arises from the coracoid pro- cess by a short, flat, and narrow tendon, which it has in common with the coraco-brachialis muscle, more forward and outward than the latter, proceeds on its outside a little obliquely from within outward, covers below the inner and upper part of the brachialis internus muscle, and lower down becomes a tendon, which is first seen on its external face, on the side corresponding to the long head. This tendon, which unites to that of the last, is attached to the tuberosity of the radius. The long head (caput longum, s. JVL. glcno-radialis) arises by a long, thin, and flat tendon from the centre of the upper part of the edge of the glenoid cavity of the scapula. This tendon is inclosed in a special fold of the capsule of the scapulo-humeral articulation, which answers as a mucous sheath, passes upon the head of the humerus, and is situ- ated in the groove between the two tuberosities of this bone, where it is retained by the fibres of the fibrous ligament of the shoulder-joint, and on the anterior extremity of which the mucous sheath ceases. It thus comes to the anterior and outer side of the arm, where it soon con- tinues with its fleshy belly but deeper than the tendon of the short head. This latter descends above, along the anterior and external edge of the triceps extensor muscle ; below, before the central part of .the bra- chialis internus muscle: at its lower extremity it is attached" on one side, that is by its internal face, to the tendon of the short head; on the other to a peculiar tendon contained within it, and which when en- tirely destitute of fleshy fibres is united with that of the first head, be- ing inserted at the same place with it. MYOLOGY. 121 We find a large mucous bursa between the lower tendon, that of the supinator brevis and the tuberosity of the radius, to which sometimes a smaller is added, situated on the outer face of the tendon. The principal use of this muscle is to flex the articulation of the elbow. It also turns the fore-arm backward, contributes to draw it inward when it is extended, and depresses the scapula toward the humerus. § 1121. The biceps flexor muscle is one of those muscles most subject to variation, and presents the most singular anomalies. The least considerable anomaly is where the two heads arise much lower than usual, so that they are only united by the inferior tendon.(l) A greater anomaly, which is not rare, is when a third head exists, which is usually smaller than the other two and which arises near the centre of the internal face of the humerus,(2) more rarely from only the brachialis internus muscle,(3) although it is often blended with it. Sometimes also it is united with the coraco-brachiahs muscle. This ano- maly is very remarkable, as it is a repetition of the small head, which properly belongs to the biceps femoris muscle, and because its union with the coraco-brachialis muscle makes the number of the long flexors of the fore-arm equal to those of the long flexors of the leg. At the same time it approximates man to animals; since in birds the long flexor of the fore-arm presents a second smaller head, which arises from the lower tuberosity of the humerus; while in apes the brachialis internus muscle extends much higher. The number of heads of this muscle sometimes increases still more, so that we number five; but these are not inserted in one common inferior tendon.(4) At the side of the third which is most usually met with we sometimes find a fourth, and along the tendon of the short head a fifth, which unite and are attached to the radius below the usual tendon; in this case, consequently, there were in fact three flexors, as is always found in birds. III. BRACHIALIS INTERNUS. § 1122. The brachialis internus muscle, Humero-cubital, Ch. (M. flexor cubitalis ulnaris, s. brachieus internus), a broader and thicker muscle, especially at its posterior part, which entirely covers the infe- rior portion of the internal and anterior faces of the humerus, arises by an external and an internal slip, the former being higher, from the ex- ternal and internal faces of the humerus above its centre. These two slips surround the lower extremity of the deltoides muscle; the internal extends to the coraco-brachialis and the external to the upper (1) Weitbrecht, Comment. Pctrop., 1731.—Albinus, loc. cit.—Rudolphi, in Gantzer, 6,—We have seen it several times but always on one side. (2) Albinus, loc. cit., p. 438, 439.—Mayer, loc. cit. (3) Kelch, loc. cit., p. 35. (4) Pietsch, in Roux Journal de Med., vol. xxxi. p. 245. Vol. II. 16 122 DESCRIPTIVE ANATOMY. extremity of the large head of the triceps extensor muscle. Its ante- rior edge descends along the external edge of the humerus, and the posterior along the internal edge of this bone to the part where it sud- denly enlarges. Its fibres are attached to a strong rounded inferior tendon, which re- ascends on the anterior face of the muscle almost to its centre. This tendon is inserted in the tuberosity of the ulna. Between the tendon of the brachialis internus, that of the biceps flexor cubiti, the supinator brevis muscle, and the capsular ligament, we find a mucous bursa, which is not however constant. This muscle flexes the articulation of the elbow. § 1123. We sometimes find at the side of it, but more forward and outward, a second brachialis internus muscle, which is smaller and which is an exact repetition of it as respects its attachments, the inferior tendon of which is inserted deeper than that of the other, and which even presents a rudiment of the preceding muscle, which we said be- longed to birds. The first degree of this anomaly is the separation of the posterior from the anterior part of the muscle, which not unfre- quently occurs. This division of the brachialis internus muscle into two parts is also worthy of remark, as it assimilates this muscle to the flexors of the leg. Its abnormal union with the biceps flexor by a mus- cular slip (§ 1121) is on the contrary the first index of the formation of a third head to the latter (§ 1121). The anomalies of the brachialis internus, the.biceps flexor, and the coraco-brachialis muscles (§ 1116), considered collectively, seem to be so many efforts by which nature endeavors to establish a perfect resem- blance between the upper and lower extremities. They are generally found singly; but if we suppose them united, we have an arrangement perfectly similar to that of the lower extremities. The coraco-brachialis and brachialis internus muscles, divided into two portions and often united with each other, evidently represent the semimembranosus and the semitendinosus muscles. The muscular band which goes from the brachialis internus to the lower part of the biceps flexor muscle, united with the unusually deep division of the latter, may be considered as tending to insulate the two heads and to form a second flexor of the ulna, even as the tibia is flexed by two distinct muscles. ARTICLE FOURTH. MUSCLES OF THE FORE-ARM. § 1124. The muscular mass of the fore-arm is formed of those mus- cles which move the bones upon each other or on the humerus, by the muscles which act on the carpus, and by the long muscles of the fingers. The motions of the bones of the fore-arm on each other, or pronation and supination, are performed by four muscles, the supinator longus MYOLOGY. 123 and the supinator brevis, the pronator teres and the pronator quadratus, all of which except the first are situated deeper than the other muscles of the fore-arm. The two bones of the fore-arm are moved on the humerus by one muscle, the anconeus. Five muscles move the carpus ; the extensor carpi radialis longus and the extensor carpi radialis brevis extend it; it is flexed by the flexor carpi ulnaris and the flexor carpi radialis muscles; the extensor carpi ulnaris draws it backward. The fingers are extended by the extensor digitorum communis, the extensor pollicis longus and brevis, the extensor indicis proprius, and the extensor minimi digiti proprius ; they are flexed by the flexor sublimis, the flexor profundus, and the flexor pollicis longus. These different muscles succeed each other in the following order, when we commence their description at the radial edge and follow the external face of the fore-arm to the ulnar edge and return from this to the radial edge along the internal face of the arm. I. MUSCLES OF THE INTERNAL FACE OF THE FORE-ARM. I. SUPINATOR LONGUS. § 1125. The supinator longus muscle, Humero-sus-radial, Ch.,isa long muscle, which arises by short tendinous fibres from the inferior part of the anterior edge of the humerus, where it unites with the large head of the triceps extensor muscle. It goes downward and passes on the inferior and external part of the brachialis internus, which it covers, and reaches the fore-arm along and before the inferior extremity of this muscle ; it goes on the radial edge of the fore-arm and is changed high up into a long and thin tendon, which covers above only the internal face, and is finally attached to the anterior face of the internal edge of the radius, a short distance above its inferior face. It turns the radius backward and inward, consequently carries the hand to the state of supination, and flexes the fore-arm. II. EXTENSOR CARPI RADIALIS LONGUS. § 1126. The extensor carpi radialis longus muscle, Humero-sus- metacarpien, Ch., resembles the preceding and appears at first view to be a part of it. It arises from the lowest part of the outer edge of the humerus, descends to the outer condyle, passes on the outer part of the articular edge of the humerus, and on the head of the radius; in its course it becomes first thicker, afterward narrower, and terminates at the same place as the preceding in a tendon, at first rather broad, flat- tened, and loose to a much greater distance, which descends in the same direction along the radius and enters below into the anterior groove of the outer face of the lower extremity of the radius under the posterior ligament of the carpus, thus arrives at the carpus and is attached to 124 DESCRIPTIVE ANATOMY the anterior part of the posterior face of the base of the second metacar- pal bone. The lower tendon is surrounded with a mucous sheath where it passes over the lower extremity of the radius. We also find a small bursa at its insertion in the root of the second metacarpal bone. This muscle extends the hand and draws it a httle toward the radial side of the fore-arm; it also serves to execute the motion of pronation to a certain extent and flexes the articulation of the elbow. § 1127. Sometimes a smaller and feebler muscle is detached from its lower edge, which succeeds the extensor carpi radialis brevis mus- cle and is attached a httle above it to the root of the third metacarpal bone.(l) III. EXTENSOR CARPI RADIALIS BREVIS. § 1128. The extensor carpi radialis brevis muscle, Epicondyla-sus- metacarpien, Ch., is very similar to the preceding, but is smaller. Its upper tendon, which is very strong, exists nearly the whole length of its posterior face. It arises from the anterior face of the outer condyle of the humerus, and is attached, below the middle of the fore-arm, by an elongated, flat, but narrow tendon, the upper part of which covers the lower part of the outside of the muscle. This tendon is inserted in the outer face of the base of the third metacarpal bone, and slightly also in that of the second. There is a small bursa between it and the third metacarpal bone. This muscle acts in the same manner as the preceding. § 1129. It is sometimes entirely deficient,(2) as in several mammalia, where we never find but one extensor radialis muscle : the first degree of this formation is the complete union of the second radiahs muscle, of which several instances are known. Sometimes its tendon divides into two slips, which are attached to the third metacarpal bone only, or one is inserted into this bone, and the other into the next; even as in the mammalia, which have only one radialis muscle, the tendon divides into two slips. Besides the bursas already mentioned, the tendons of the two muscles are surrounded by two common sheaths, the upper of which is situated above the lower end of the radius, while the lower is placed at a short distance from it on this extremity, and on the upper range of the carpal bones. IV. EXTENSOR DIG1TORUM COMMUNIS. § 1130. The extensor digitorum communis muscle, Epicondylo-sus- phalangettien commun, Ch., commences by a strong tendon, which (1) Albinus, loc. cit., p. 448. (2) J. G. Salzmann, Diss. sist. plurium pedis musculorum defectum, Strasburg, 17o4, p. 11. MYOLOGY. 125 extends on the upper part of the external face of its belly. It arises from the lower and back part of the outer condyle of the humerus, directly under and behind the radialis externus brevis muscle, with which it is intimately connected for several inches. Near the centre of the fore-arm it separates into three bellies, the posterior of which also divides a little farther in two others, so that the whole number of these bellies is four; these are inserted into as many elongated and flat tendons, of which the second is usually the strongest, the third smaller than the first, and the fourth is the weakest. All these tendons pass under the posterior hgament of the carpus, between it and the outer face of the lower end of the radius. They become broader and thinner on the back of the hand, partially separate, especially near the anterior end of the metacarpus, and are again united by strong obhque intermediate tendons of various breadths. They go to the second, third, fourth and fifth fingers, and contract on the articu- lation of the metacarpus with the phalanges; but in this place they give off on each side fibres, which go downward; farther on they again enlarge, and are blended on each side with the tendons of the interosseous muscles. On the first joint of the phalanges they divide into a central and two lateral portions, which are much longer ; the central tendon, having strengthened the dorsal face of the capsular ligament, is attached to the upper edge of the base of the second pha- lanx ; the other two are united forward, and are inserted in the upper part of the back of the third phalanx. At the lower end of the fore-arm, of the carpus and metacarpus, the tendons of this muscle have a mucous sheath, which is single above, but divides on the carpus into three branches, each of which goes with its tendon to the base of the first phalanx. This muscle extends the second, third, fourth, and usually the fifth finger also. § 1131. Sometimes its three bellies are separated high up, and even at their origin.( 1) Sometimes it divides into four tendons; the fourth goes to the little finger, and unites to its proper extensor. This fourth tendon sometimes divides on the back of the hand into two parts ; the outer joins the tendon of the extensor minimi digiti proprius muscle, and the inner again divides into two portions, one of which unites to the tendon of the fourth finger, and the other to that of the fifth.(2) In some sub- jects the third and fourth tendons go to the third finger. In this case the muscle itself often divides into two bellies, each of which has two tendons.(3) These divisions of the fleshy part of the muscle are curious, being similar in one respect to the extensors of the toes and also to the flexors of the fingers, which are both double. (1) Albinus, loc. cit., p. 452.—Brugnone, loc. cit., p. 167. (2) Albinus, loc. cit. (3) Brugnone, loc. cit. 126 DESCRIPTIVE ANATOMY. V. EXTENSOR MINIMI DIGITI PROPRIUS. § 1132. The extensor minimi digiti proprius muscle, Epicondylo- sus-phalangettien du petit doigt, Ch., is slender, elongated, and thin. It arises by two tendinous heads from the outer part of the head of the radius, from the part of the capsular ligament surrounding this head, and from the upper end of the anterior edge of the ulna. It descends behind the preceding, with which it is closely united for some distance, and near the lower end of the fore-arm becomes a thin tendon, which passes below the posterior ligament of the carpus in a special groove, enlarges along the metacarpal bone of the fifth finger, unites inward with the fourth tendon of the preceding muscle, and is attached to the upper face of the head of the third phalanx of the little finger. Its tendon is surrounded from the lower part of the fore-arm to the centre of the fifth metacarpal bone by a sheath, which is single above, but below divides hke the tendon into two parts. This muscle extends the little finger. § 1133. It is sometimes deficient,(l) and then it is generally replaced by a tendon of the extensor digitorum communis muscle. In other cases, on the contrary, its tendon divides into two slips, one of which goes to the fourth finger, an arrangement worthy of remark because of its analogy with several mammaha. VI. EXTENSOR CARPI ULNARIS. § 1134. The extensor carpi ulnaris muscle, Cubito-sus-metacarpien, Ch. (J\I. ulnaris externus, s. extensor manus ulnaris), arises by two ten- dinous slips, of which the smaller and shorter is situated at the side of the extensor digitorum communis, and comes from the posterior and lower part of the external condyle of the humerus, and the longer arises from the upper part of the anterior face of the tubercle of the ulna. These two slips soon unite in a considerable belly. The latter is tendinous at its inner and outer faces, and adheres in a considerable extent to the extensor proprius minimi digiti muscle, descends along the outer face of the ulna, from which it receives some fibres, and be- comes, near the lower third of the fore-arm, a strong tendon, which, passing across a particular portion of the dorsal ligament of the carpus, comes on the back of the hand, where it is attached to the tubercle of the metacarpal bone of the fifth finger. There is but one mucous bursa between its upper extremity and the head of the radius. This muscle extends the hand and draws it backward toward the posterior edge of the fore-arm. § 1135. A tendon of greater or less extent, is often detached to go to the fifth finger, and at the base of the first phalanx unites with that of its proper extensor. (1) Brugnone, p. 167.—We have known two instances where it was deficient. MYOLOGY. 127 VII. ANCONEUS. § 1L36. The anconazus muscle, Epicondylo-cubilal, Ch. (M. anco- neus, s. anconaus quartus), is a triangular muscle and mostly covered by the upper extremity of the preceding ; it arises by a short and strong tendon from the inner part of the outer condyle of the humerus, descends toward the ulna, and is attached by a broad fleshy surface to the upper part of the anterior face of this bone. Its upper straight edge usually blends with the outer belly of the triceps extensor muscle. This muscle extends the fore-arm, also turns the radius backward, so that it assists in supination. VIII. SUPINATOR BEEVIS. § 1137. The supinator brevis muscle, Epicondylo-radial, Ch., is tri- angular ; its base looks upward, and its apex downward. It arises from the upper part of the anterior face of the ulna, and is tendinous outwardly and fleshy inwardly. Its upper fibres are transverse and the lower obhque. It goes downward and forward, turns on the upper part of the radius, and is attached by a broad fleshy edge to the ante- rior part of the capsule of the.ulna, and also to the upper part of the anterior and inner faces of the radius as far as its posterior edge. It turns the hand and the radius on their axes backward and outward. § 1138. The upper part of this muscle often separates from the lower sooner than usual, and differs from it in the direction of its fibres, is sejJarated from it by the radial nerve, and is attached to the radius without being connected with it. This anomaly leads to that in which two small supinator muscles exist; the upper extending from the outer condyle of the humerus to the anterior edge of the upper end of the radius, while the internal goes from the head of the radius to its centre.(1) Probably the second variety may be considered as an index of the formation peculiar to apes, in which three supinators exist.(2) IX. ABDUCTOR POLLICIS LONGUS. § 1139. The abductor pollicis longus muscle, Cubilo-sus-me'ta- carpien du pouce, Ch., is a considerable muscle inserted, by very short tendinous fibres, directly below the anconeus and the supinator brevis, to the second fifth of the anterior edge of the ulna, to the outer face of the interosseous ligament, and to the central part of the outer face of the radius. It descends along the last, passes below on the anterior face of the radius, and there becomes a strong tendon, which passes through a particular division of the dorsal ligament of the carpus. This tendon (1) Sandifort, Hist. muse. p. 93.—Brugnone, loc. cit. p. 163. (2) We have found at least in the Simia apclla two long supinators, situated at the side of each other. 128 DESCRIPTIVE ANATOMY. generally divides into two or three slips: the strongest, which is also the most anterior, is attached to the radial edge of the base of the first metacarpal bone ; the other two blend with the posterior extremity of the antagonist muscle of the thumb. The tendon near its upper extremity is surrounded by a large, oblong, and rounded mucous sheath. This muscle separates the thumb from the fingers, and moves it toward the radius. § 1140. It is often more or less divided into two bellies, each of which terminates by a tendon, and the lower is usually larger than the upper. The tendons of these two bellies are often divided, and some- times unite ; sometimes they are attached to the first bone of the meta- carpus and to the trapezium:(l) We more rarely find a digastric abductor of the thumb, which arises from the outer condyle of the humerus, and is inserted into the base of the first phalanx of the thumb. X. EXTENSOR »OLLICIS BREVIS. § 1141. The extensor pollicis brevis muscle, Cubito-sus-phalangien du pouce, Ch., is a very small muscle, situated below the preceding, and adheres intimately to its inferior edge. It arises from the outer face of the interosseous ligament and from the radius, and becomes a very thin tendon, which passes through the dorsal ligament of the carpus in the same groove with the abductor pollicis longus, then goes on the back of its metacarpal bone, becomes broader, and is attached to the centre of the upper edge of the base of its first phalanx. This muscle extends the thumb, and at the same time removes it from the other fingers. § 1142. A small tendon sometimes arises from the anterior extremity of its tendon, which blends with that of the next muscle. Sometimes this muscle does not exist as a distinct muscle, and forms only the lower part of the abductor pollicis longus muscle. XI. EXTENSOR POLLICIS LONGUS. § 1143. The extensor pollicis longus muscle, Cubito-sus-phalanget- tien du pouce, Ch. (M. extensor pollicis major s. longus), is much stronger than the preceding, and covers its upper part; it arises, a httle below the abductor magnus, and directly below its upper extremity, above from the outer face and below from the anterior edge of the ulna, and from the adjacent part of the external face of the interosseous ligament. It soon becomes a long tendon, which passes through the second groove of the dorsal hgament of the carpus, goes forward at the side of the preceding, but much more inwardly, partially covers it, and (1) Fleischmann, in the Erlangcr Abhand., vol. i. p. 28. MYOLOGY. 129 is attached to the base of the second phalanx of the thumb, in the same manner as the tendon of the extensor digitorum communis is; but it does not divide. Its tendon has two mucous sheaths: the upper and larger is situ- ated at the lower part of the fore-arm, and extends to the carpus ; the inferior is smaller, and is placed on the carpus and on the base of the first metacarpal bone. It extends the thumb, and brings it a little towards the other fingers. § 1144. Sometimes it is completely double. XII. EXTENSOR INDICIS PROPRIUS. § 1145. The extensor proprius indicis muscle, Cubito-sus-phalanget- tien de Vindex, Ch. (M. indicator, s. indicatorius, s. indicis extensor, s. abductor), is nearly as large as the preceding. It arises directly below it by two slips from the third quarter of the anterior face of the ulna, and near the lower part of the fore-arm becomes a strong tendon, which, covered by that of the extensor digitorum communis, passes with it through the third division of the dorsal ligament of the carpus, below the tendinous band which goes from the latter muscle to the indicator finger; it proceeds more inwardly than this band, and is attached to the base of the first phalanx of the finger, blending with it. It extends the indicator finger, and approximates it a little towards the third. § 1146. Sometimes it is digastric, and interrupted in its course by a long tendon.(l) This muscle presents several anomalies which are exceedingly interesting: they consist in its more or less perfect multiplication and in the formation of the extensor pollicis tertii proprius. The lowest degree of this anomaly is the division of its portion into two slips both of which go to the second finger,(2) or the division of its belly into two parts, the tendons of which unite before arriving at this finger,(3) or finally the existence of two bellies of the usual size, which are entirely distinct, and of which one arises from the radius.(4) The most complete anomaly is when one of the shps of the tendon does not go to the indicator, but to the middle finger.(5) Sometimes a small and perfectly distinct muscle arises from the lower part of the outer face of the radius and from the dorsal-ligament of the carpus, and is attached to the first phalanx of the indicator.(6) This variety is only a more perfect development of the case in which the muscle arises by two heads. Next comes the anomaly where we find a proper extensor of the middle finger; this muscle is always smaller than the extensor indicis (1) Rosenmuller, loc. cit., p. 6. (2) We have seen it several times. (3) Albinus, p. 458.—Heymann, p. 13. (4) Gantzer, p. 14. (5) Albinus, p. 468.—Peitsch, Sylloge obs. anat. (6) Albinus, Ann. acad., vol. iv. ch. vi.—Heymann, p. 12. Vol. II 17 130 DESCRIPTIVE ANATOMY. proprius, and arises more or less below and under it. This formation varies the least possible from the normal state when th«>. new muscle comes from the ulna;(l) but sometimes it arises from the radms(2) or from the dorsal ligament of the carpus.(3) The greatest anomaly is where we find, beside the extensor indicia proprius%n extensor for the middle finger, which divides into two ten- dons, one of which is attached to the metacarpal bone of the index finger, and the other to that of the middle finger. Finally, we have seen in one case a small tendon, which extended from this proper extensor of the middle finger to the base of the first phalanx of the index finger. All these anomalies are curious in two respects: 1st, as a repetition of the normal formation of the lower extremities, since they represent the extensor communis digitorum brevis, and that more perfectly as the supernumerary muscles arise lower ; 2d, as analogous with animals ; for in many apes the tendon of the extensor indicis proprius furnishes a slip to the middle finger, and in others, for instance in the simia apella, we find a proper extensor of the index finger. (4) II. MUSCLES OF THE INTERNAL FACE OF THE FORE-ARM. I. PALMARIS LONGUS AND BREVIS AND THE PALMAH APONEUROSIS. § 1147. The palmaris longus muscle, Epilrochlo-palmaire, Ch., is a thin oblong muscle, which arises, directly below the preceding and farther back than it, from the upper part of the anterior face of the inner condyle of the humerus. It goes directly forward and downward, and becomes in the middle of the fore-arm a broad and thin tendon, which is very near the skin. This tendon however is covered by the anti-brachial aponeurosis in most of its length, and passes over this aponeurosis only at its lower part. At its lower end, it divides into two fasciculi: the anterior, which is shorter, and which is attached to the posterior end of the abductor pollicis ; and the posterior, which is much larger, and is called the palmar aponeurosis (aponeurosis pal- maris). This aponeurosis is thinner than the tendon, but much broader and triangular. It gradually enlarges from behind forward, so that it corresponds by its anterior edge to the four fingers. It how- ever becomes thin, and its fibres occasionally have intervals between them. It is composed essentially of longitudinal fibres, hke the tendon of which it is the expansion. Its anterior edge is however formed of transverse fibres, which are arranged over the preceding. It covers most of the muscles of the palm of the hand, except those of the thumb and the little finger. (1) We have seen it several times. (2) We have seen it once. (3) Brugnone, loc. cit., p. 168. (4) Meckel, Beytragc zur verglcichcndcn anatomic, vol. ii. p. 11. MYOLOGY. 131 The palmaris brevis muscle, which is composed of transverse fibres, is attached to its internal edge at its upper part. This muscle, the internal edge of which comes from the skin, serves to tense the apo- neurosis outwardly. § 1148. The palmaris longus muscle is often deficient; sometimes it is replaced by a tendon of the flexor digitorum sublimis.(l) In other cases, on the contrary, it is unusually developed in fact thinner, but very broad, and descends almost into the palm of the hand.(2) This rudi- ment of a peculiar muscle, which sometimes extends from the coronoid process of the ulna to the palmar hgament of the carpus, is worthy of remark, especially as it forms an analogy with apes.(3) II. RADIALIS INTERNUS. § 1149. The radialis internus muscle, Epitrochlo-metacarpien, Ch. (M. radialis internus, s. flexor manus radialis), is much larger than the preceding, and is blended above with it, and on both sides with the pronator-teres and the flexor communis digitorum sublimis ; it comes from the anterior face of the inner condyle of the humerus, and some- times also by a small head from the radius. It is partly covered by the preceding and goes downward and a httle forward, and near the middle of the fore-arm becomes a broad tendon. This tendon passes under the palmar ligament of the carpus in a special canal, formed by the palmar hgament, and by the os trapezium ; it is harder and thicker in this place than in other parts. After leaving this canal it becomes thinner but broader, and is attached partly to the os trapezium, but more particularly to the inner face of the second metacarpal bone. We find a mucous bursa between the lower end of the tendon, the 03 trapezium, and the proper palmar ligament. This muscle flexes the hand and carries it a little forward. III. PRONATOR TERES. § 1150. The pronator teres muscle, Epitrochlo-radial, Ch., a shorter but stronger muscle, arises by very short tendinous fibres from the upper edge and the upper part of the anterior face of the inner condyle of the humerus. It swells a little below its origin, goes obliquely downward and forward, and is covered at its lower part and at its upper edge by a strong tendinous expansion, and is attached by means of this, below the supinator brevis, and before the abductor pollicis longus, to the anterior face and outer edge of the radius, a little above its centre. It turns the radius and also the hand inward, forward, and down- ward. (1) Rosenmiiller p. 6. (2) Albinus, p. 474. (3) Perrault, Mem. in Valentini Tkeatr. toot. p. 151. —Vicq. tl'Azyr, Encyal. mcth., seel.anat., vol. ii. p. 25, 'IZ1. 132 DESCRIPTIVE ANATOMY. § 1151. It is sometimes double. In this case the supernumerary muscle extends from the posterior edge of the ulna to the posterior edge of the normal muscle, which is an analogy with apes. IV. FLEXOR ULNARIS. § 1152. The flexor ulnaris muscle, Cubito-carpien, Ch. (M. ulnaris internus, s. flexor ulnaris), arises by two rather short heads, of which the upper comes from the lower part of the inner face of the inner con- dyle of the humerus, and the posterior or the inferior from the inner face of the olecranon process of the ulna. It descends along the ulna, from which it is always separated by the flexor digitorum communis, and be- comes a strong tendon at the lower end of the fore-arm which is attach- ed to the pisiform bone ; we find a very loose mucous bursa between it and this bone. It flexes the hand and inclines it toward the ulna. V. FLEXOR DIGITORUM COMMUNIS SUBLIM1S. § 1153. The flexor digitorum communis sublimis muscle, Epitrochlo- phalanginien commun, Ch. (JVf. flexor digitorum communis sublimis, s. perforatus), arises below the four preceding, by a much larger head, from the lower part of the anterior face of the inner condyle of the humerus, from the inner part of the capsular ligament of the elbow joint, and from the inner face of the coronoid process of the ulna; it also arises by a small shp from the inner face of the radius at the lower end of the supinator brevis muscle. Long before this slip has joined the upper head, it divides into three bellies, of which the internal and posterior divide still lower into two others. Each of these bellies becomes a tendon, which all pass under the special palmar ligament of the carpus to arrive at the palm of the hand. Nearly opposite the centre of the first phalanx each tendon divides into two shps which unite farther on the second phalanx, so that their inner fibres interlace and again separate below this point to attach themselves behind the middle of the second phalanx to its radial and ulnar edges. These tendons are surrounded by a common sheath, near the lower extremity of the fore-arm, which, when arrived at the carpus, divides into several sacs, each of which goes with one of them to the base of the first phalanx. This muscle flexes the second phalanx of the fingers. § 1154. One of the tendons, particularly that of the little finger, is sometimes deficient; it is then replaced by one of the tendons of the flexor profundus muscle ; sometimes a belly of this muscle, especially that which belongs to the index finger, is entirely separated from the others, and divided besides into two fleshy portions by a long central tendon. As the anomaly is seen more commonly in the belly of the indicator finger, it is worthy of remark, from its analogy with the outer DESCRIPTIVE ANATOMY. 133 face of the fore-arm, since it represents the proper extensor of the index finger, and more, as the latter is also digastric in some subjects. VI. FLEXOR DIGITORUM PROFUNDUS. § 1155. The flexor digitorum profundus muscle, Cubito-phalanget- tien commun, Ch. (JW. flexor digitorum communis profundus, s. suadus perforans), is stronger than the preceding, which covers it anteriorly,and arises from the upper two-thirds of the inner and posterior faces of the ulna, so as to envelop this bone almost entirely, and divides, but much deeper than the flexor sublimis, into four bellies, which become as many tendons. These tendons are retained together by numerous interme- diate filaments and by folds of the mucous sheaths, and pass under the palmar ligament of the carpus, with those of the preceding, and go to the same fingers. In this place we see a fissure along the upper and lower faces. They pass through the sheath of the flexor sublimis, afterwards become broader and thinner, and are attached to the base of the third phalanx. This muscle flexes the third phalanx of the fingers. §1156. Sometimes a muscle proceeds between the flexor sublimis and the flexor profundus, and extends from the inner condyle of the humerus to the latter ;(1) and again, a muscular fasciculus arises from the flexor pollicis longus as high as the wrist, which is attached by a tendinous expansion to that tendon of the flexor profundus which goes to the index finger.(2) VII. LIGAMENTS OF THE FLEXORS OF THE FINGERS. § 1157. The tendons of the flexor profundus and sublimis are sur- rounded in two places by fibrous hgaments and mucous sheaths.^ § 1158. The upper fibrous ligaments are the common palmar liga- ment and proper palmar hgament of the carpus. Below them we find the upper mucous sheath, an elongated sac, which surrounds all the tendons of the two flexors, commences about an inch and a half above the radio-carpal articulation, and extends to the centre of the carpus. Its outer layer is attached to the palmar ligaments of the bones of the carpus, and to the interossei muscles. Numerous folds arise from all the internal face of this outer layer which go inward, surround the tendons of the two flexors, and unite them but very loosely. § 1159. The second place, where the common flexors are surrounded with similar ligaments, is that portion which corresponds to the lower face of the fingers. § 1160. The lower fibrous ligaments are situated outwardly, and form for the mucous sheath an envelop, which is divided on account of the motion of the fingers. (1) Gantzer, p. 13. (2) Gantzer, ibid. 134 DESCRIPTIVE AM ATOMY. The strongest portion is termed the ligamentous sheaths (Lig. vagi- nalia). These sheaths are formed almost entirely of transverse fibres ; in part, however, especially on the surface, of obhque fibres which cross the preceding. They are etrongly extended, like a bndge, from the radial to the ulnar edge of the first and second phalanges. That of the indicator finger is much stronger than the others in every respect. The feeblest which stand more distinct, extend in the same manner over the metacarpo-phalangcean and the second phalangcean articula- tions. Their size diminishes much from the first to the third articula- tion. They are called the ligamentous rings of the articulations (annuli juncturarum ligamentosi). Analogous fascicuh are found between the preceding and the liga- mentous sheaths ; these are the oblique or crucial rings of the first and second phalanges (annuli obliqui, s. cruciati phalangis prima ei secunda). § 1161. The inner faces of these fibrous ligaments are covered with elongated mucous sheaths, which begin some lines behind the meta- carpo-phalangcean articulation, are attached in this place to the flexor sublimis and profundus of each finger, and extend to the centre of the terminating phalanx. Their upper part is inserted in the upper part of the palmar face of the phalanges. The tendons of the two flexors are mostly loose in these mucous sheaths, of which each finger possesses a separate one; however, from the dorsal face of the sheaths, that which covers the palmar face of the fingers, arise several broader and narrower irregular folds, the largest of which contains more or less fat; these proceed from before backward, are very thin from one side to the other, and are attached to the tendons of the flexor sublimis and profundus. The upper are usually very thin and rounded, and are attached to the radial slip of the flexor sublimis. They are generally deficient in one or several fingers. The succeeding which are larger are also more constant; they arise near the second phalangcean articulation, and are usually attached to the tendon of the flexor sublimis, where its two slips unite. Usually we find also within or on their sides other prolongations, which go to the tendons of the flexor profundus. A third prolongation generally arises from the base of the third pha- lanx which is attached directly to the two anterior slips of the flexor sublimis, unites them, goes from this point to the anterior extremity of the flexor profundus which covers the third articulation, and is there attached in all its extent. Other single or divided prolongations extend also in many parts between the tendons of the two flexors in their course along the fingers. These are the short and long accessory or vascular ligaments of the flexors (vincula tendinum sublimis el profundi accessoria, s. vasculosa brevia et longa). MYOLOGY. 135 VIII. FLEXOR POLLICIS LONGUS. § 1162. The flexor proprius pollicis longus muscle, Radio-phalan- gettien du pouce, Ch., is much feebler and shorter than the preceding, with the second belly of which its central part usually adheres more or less intimately. It arises by a small distinct slip from the tubercle of the ulna, but in most of its length it arises by fleshy fibres from the lower two-thirds of the inner face, and the anterior edge of the radius. The strong tendon which terminates it passes under the palmar hga- ment with those of the two preceding muscles, and goes between the abductor and flexor pollicis brevis on the internal face of this finger, and is attached not far from its inferior edge to the second phalanx. This tendon is surrounded by a special mucous sheath from the lower extremity of the fore-arm to the centre of the first phalanx. It flexes the second phalanx of the thumb. We sometimes find a second head which comes from the inner condyle of the humerus, and which is only a greater development of its upper slip. IX. PRONATOR QUADRATUS. § 1163. Thepronator quadratus muscle, Cubito-radial, Ch. (JVf.pro- nator quadratus, s. inferior), is an almost equilateral quadrilateral mus- cle, being rather more long than broad, which occupies the lowest part of the inner face of the fore-arm, where it is covered by the tendons of all the long muscles. Its fibres are oblique and extend from the posterior edge and from the inner face of the ulna to the inner face and anterior edge of the radius. This muscle rotates the radius, and the hand with it, on its axis from behind forward and from without inward. § 1164. It is sometimes deficient,(l) as in several mammalia. Again, it is sometimes divided into two bellies which are entirely separated, the fibres of which proceed in opposite directions and cross.(2) ARTICLE FIFTH. MUSCLES OF THE HAND. § 1165. Themusclesofthehand(3)arisefromthetendonsofthe flexor profundus, from the carpus, and from the metacarpus, and are attached to the metacarpal bones and also to the phalanges. They are princi- pally designed to approximate and separate the fingers and serve less (1) We know of one instance. (2) We have once seen this. (3) Albinus, Icones musculorum manus iv., ad calcem hist, muscul., Leyden, 1734. 136 DESCRIPTIVE ANATOMY to flex them. Hence they are divided into abductors, adductors, and flexors. The adductors and abductors which are attached to the two external fingers, the thumb, and the little finger, fulfill only the one or the other of these two functions, while those which move the other three fingers are both adductors and abductors; because, in approxi- ting a finger toward that on one side, they necessarily separate it from that of the other side. The abductor and adductor muscles of the fingers, except the thumb, are] called the interossei muscles, from their situation; the flexors of the second and third and also one of the little finger are called the km- bricales, from their form. I. LUMBRICALES. § 1166. The four lumbricales muscles, Palmi-phalangien, Ch., are long, rounded muscles, which arise fleshy from the lower face and the radial edge of the tendons of the flexor digitorum profundus toward the upper end of the metacarpus. They proceed at the side above and below these tendons and arrive at the fingers, where they become thin tendons, which are reflected on the radial face of the first phalanx, enlarge, and blend with the anterior edge of the tendon of the extensor muscle. They flex the first phalanx. § 1167. We often find one or more of these muscles more or less completely double, and then the supernumerary head or the whole muscle is inserted in the ulnar side of the adjacent finger. II. INTEROSSEI. § 1168. The interossei muscles, Metacarpo-phalangiens lateraux sus-palmaire and the metacarpophalangiens lateraux, Ch., are situated between the metacarpal bones. Their anterior tendons are attached partly to the lateral faces of the posterior heads of the first phalanges, partly also to the extensors of the fingers. They are divided into two classes, the external (M. interossei externi, s. bicipites), and the internal (JW. interossei interni, s. simplices.) I. INTEROSSEI EXTERNI. § 1169. The common characters of the external interossei mus- cles are. 1st. They appear on the dorsal and palmar faces of the hand. 2d. They arise from the corresponding faces of two metacarpal bones by two heads, which is inserted in a common tendon. We number four, which are attached to the index, middle, and little fingers. The first, which is the strongest, is situated between the thumb and the index finger It differs from the others, not only in volume but also in the complete separation of its two heads. MYOLOGY. 187 The anterior and stronger head arisesfrom the upper larger partof the ulnar face of the metacarpal bone of the thumb. The posterior, which is smaller, arises from almost all the radial face of the second metacarpal bone. These two heads unite below in a common tendon, which is attached partly to the radial face of the base of the first phalanx of the index finger, and partly blends with the tendon sent by the common extensor of the same finger. The great distance between the two heads has led some anatomists to consider them as two distinct muscles: they have termed the ante- rior head the adductor indicis and the posterior the first internal inter- osseous muscle. It draws the second finger toward the thumb. The other external interosseous muscles are much smaller; then- heads unite much higher even in the centre of their course. The second arises by a smaller anterior and deeper head from the ulnar side of the second, and by a larger posterior looser head from the radial side of the third metacarpal bone. It is also attached to the radial side of the middle finger. This muscle brings the middle finger toward the index finger. The third, situated in the space between the third and fourth meta- carpal bones, is inserted in the ulnar side of the middle finger. It brings the middle finger toward the fourth. The fourth is placed between the fourth and fifth metacarpal bones, and is inserted in the ulnar side of the fourth finger. It brings the ring finger to the fifth. II. INTEROSSEI INTERNI. § 1170. The interossei interni muscles are three in number, when we do not consider the posterior head of the first external interosseous muscle as the first internal interosseous muscle. They are attached to the second, fourth, and fifth fingers. They arise by a single head from the lateral face of the metacarpal bone of the finger to which they are attached, and are very distinct in the palm of the hand. The first arises from the ulnar face of the second metacarpal bone, is inserted in the ulnar side of the base of the first phalanx of the indi- cator finger, and blends in the same place with the tendon sent by the common extensor to this finger. It separates the index finger from the thumb and draws it toward the middle finger. The second comes from the radial side of the fourth metacarpal bone. The third arises from the radial side of the fifth metacarpal bone. The second is attached to the first phalanx of the fourth finger, and the third to the first phalanx of the fifth finger. Both draw the fingers to which they are attached from the side of the thumb or from the radial edge of the hand, and consequently in- ward. Vol. II. 18 138 DESCRIPTIVE ANATOMY. The index finger has then an external and an internal interosseous muscle ; the middle finger has two external interosseous muscles; the fourth finger an external and ah internal, and finally the fifth finger an internal interosseous muscle. §1171. The interosseous muscles rarely present anomalies. We have however found the second external interosseous muscle attached to the ulnar side of the index finger, and the first internal interosseous muscle attached not to this finger but to the radial side of the third—a variety the more interesting in the history of the inversion of the organs because it presents an exact repetition of the normal formation of the foot, and because the hand in which we found it presented also an ad- ductor of the thumb, formed likewise in the same manner as that of the great toe. m. muscles of the thumb. § 1172. The metacarpal bone of the thumb is surrounded by a con- siderable muscular mass, called the ball of the thumb (thenar), formed of four muscles, the abductor pollicis brevis, the opponens pollicis, the flexor pollicis brevis, and the adductor pollicis. I. ABDUCTOR POLLICIS BREVIS. § 1173. The abductor pollicis brevis muscle, Carpo-sus-phalangien du pouce, Ch., the most superficial of the four muscles, arises from the anterior part of the inner face of the ligament of the carpus and of the Os trapezium. It is generally blended by a short intermediate tendon with the tendon of the abductor longus (§1139), and extending forward along the radial edge of the metacarpal bone of the thumb, it is at- tached by a short tendon to the outer face of the posterior head of its first phalanx. It also usually blends more anteriorly with the tendon of the flexor pollicis brevis muscle. It separates the thumb from the index finger and extends it a little. II. OPPONENS POLLICIS. § 1174. The opponens pollicis muscle, Carpo-metacarpien du ponce, Ch., is smaller than the preceding, which it partly covers, and its form is rhomboidal. It arises below it by a broad edge and by very broad tendinous fibres from the anterior part of the inner face of the palmar hgament and from the os trapezium, then descends to the metacarpal bone of the thumb, and is attached by a short tendon to all the anterior part of its radial edge. It draws the thumb inward and turns it on its axis; so that it op- poses its palmar face to that of the other fingers. myology, 139 III. FLEXOR POLLICIS BREVIS. § 1175. The flexor pollicis brevis muscle, Carpo-phalangien du pouce, Ch. (J\I. flexor pollicis brevis, s. mesothenar, s. antithenar), is stronger than the two preceding. Its upper extremity, which is very much divided, arises first below and inward from the palmar hgament and the os trapezium, on the other side from the palmar face of the os trape- zoides, from the os magnum, and the os pyramidale. It partly covers the preceding and is attached to the outer sesamoid bone of the thumb. It flexes the first phalanx of the thumb. § 1176. The largest head, which comes from the palmar ligament, is sometimes entirely separated from the other, which is smaller and situated lower; so that this muscle is in fact double. On the other hand, it often happens that the small head is entirely blended with the adductor pollicis muscle. IV. ADDUCTOR POLLICIS. § 1177. The adductor pollicis muscle, Metacarpo-phalangien du pouce, Ch. (M. mesothenar, s. hypothenar), is the strongest and the deepest of the four muscles of this finger. Its form is triangular, the base looking toward the ulnar edge and the summit toward the radial edo-e. It arises by fleshy and tendinous fibres from the palmar face of the os magnum, and in a greater or less extent from the palmar edge of the third metacarpal bone, goes forward and outward, and is attached by a short tendon to the inner sesamoid bone. This muscle draws the thumb toward the index finger and slightly rotates it on its axis, so that it turns its palmar face toward that of the other fingers. § 1178. Sometimes it divides into a posterior and an an tenor belly, which are completely distinct, the posterior being the larger. In this case the first arises only from the os magnum or at the same time from this bone and a small upper portion of the third metacarpal bone : as to the second, it comes from the lower part of the anterior head of the third and fourth metacarpal bones; sometimes also from the fifth as well as from the capsular ligament of the first phalangean articulation, and goes across or a little obliquely from before backward, to the first phalanx of the thumb, where it unites with the posterior head. This anomaly is worthy of remark, as it coincides perfectly with the normal arrangement of the adductor of the large toe. IV. MUSCLES OF THE LITTLE FINGER. § 1179. The little finger is moved by three muscles, an abductor, a flexor, and an adductor. 140 DESCRIPTIVE ANATOMY. I. ABDUCTOR MINIMI DIGITI. § 1180. The abductor minimi digiti muscle, Carpo-phalangien du petit doigt, Ch., the shortest of these three muscles, extends along the ulnar edge of the metacarpus. It arises by short tendinous fibres from the pisiform bone, and near the first phalanx of the finger becomes a small flat tendon, which blends with the ulnar edge of the tendon of its extensor. It separates the little finger from the others. II. FLEXOR MINIMI DIGITI. § 1181. The flexor minimi digiti muscle (J\l. flexor proprius digili quinti) is covered by the preceding. It arises below and before it from the pisiform bone and from the unciform process of the unciform bone: it forms a short tendon forward, which is attached to the radial side of the first phalanx of the httle finger. It flexes the little finger and separates it from the others. It is often deficient and then the preceding is more developed. III. ADDUCTOR MINIMI DIGITI QUINTI. § 1182. The adductor minimi digiti muscle, Carpo-metacarpien du petit doigt, Ch. (M. adductor digiti quinti), is thickest and shortest, and arises from the lower anterior edge and the outer face of the unciform process of the unciform bone, goes upward, and is attached to all the ulnar face of the metacarpal bone of the fifth finger. It carries the little finger forward and draws it toward the others, causing it to rotate around its axis on the metacarpal bone. When it acts in concert with the opponens pollicis muscle, which very much resembles it, the cavity of the palm of the hand enlarges. § 1183. The proper muscles of the thumb and little finger are only the lumbricales or interossei muscles largely developed and divided into several fascicuh. We must consider the flexor pollicis brevis muscle as the first lumbricalis. The abductor pollicis brevis and the opponens pollicis correspond to an external; the adductor repre- sents an internal interosseous muscle. The abductor and the flexor minimi digiti muscles form only one muscle, which represents the last external interosseous muscle. The adductor minimi digiti muscle is only an enlarged internal inter- osseous muscle. MYOLOGY. 141 CHAPTER II. MUSCLES OF THE LOWER EXTREMITIES. § 1184. The muscles which have with the upper section of the abdominal members relations similar to those which exist between the superficial muscles of the back and of the region of the shoulder, or the broad muscles of the abdomen, have already been examined. We may then pass immediately to those which go from the first section of the bones of the lower extremities to the femur; but we must here also commence by describing the general aponeurotic envelop. ARTICLE FIRST. APONEUROTIC SHEATH OF THE LOWER EXTREMITIES. § 1185. Most of the muscles of the lower extremities, especially those of the thigh, leg, and sole of the foot, are enveloped by an apo- neurotic expansion, which is not arranged every where in the same manner. This expansion is called on the thigh th e fascia lata, on the leg the crural aponeurosis, in the sole of the foot the plantar aponeurosis. The first two form a whole more continuous with each other than with the plantar aponeurosis, and are also still more similar in their form, as they surround the thigh and the leg. The fascia lata commences behind on the gluteaeus maximus muscle, where it is very thin, and gradually loses itself at its upper portion. It arises forward from the iliac crest and from the Fallopian hgament. It extends as far as the knee. It adheres very intimately by the upper and external part of its anterior edge to the lower edge of the tendon of the obliquus externus abdominis muscle, to which it is much more loosely attached on its inner side. It is thickest at the outer part and thinnest at the inner part of the thigh. It is half a line thick in every part and above even a line in the first region, while it hardly equals the twelfth of a line in the second. In general it is evidently formed of two layers of fibres: the internal is stronger and its fibres are longitudinal; the external is weaker and its fibres are oblique downward, inward, and backward, and are more insu- lated, and gradually approach each other from below upward. From the inner face of this aponeurosis arise septa which extend between most of the muscles of the thigh which they separate from each other; we readily distinguish in most of these septa transverse and obhque fibres. 142 DESCRIPTIVE ANfcTOMY. The fascia lata presents oblique fibres in every part, m many places, especially at the inner portion of its circumference, these fibres are extended over a layer which is not evidently fibrous, especially forward, but at the outer part this layer is manifestly formed of longi- tudinal fibres, and at the same time its inner face presents in different parts more insulated oblique fibres, so that here the aponeurosis evi- dently consists of three layers. The outer part of the crural aponeurosis is also much thicker, and formed in this part of two layers ; the fibres of the internal are longi- tudinal, those of the external, which is weaker, are oblique. At the upper part of the aponeurosis the direction of the oblique fibres is inversely that of the oblique fibres of the fascia lata, that is, they pro- ceed forward, downward, and inward. At the lower part of the crural aponeurosis they have an opposite direction, and at the same time other fibres are developed on the inner side of the aponeurosis, which are oblique from behind forward and from above downward. These outer and inner fibres cross on the anterior face of the articu- lation of the foot, and as they increase in strength in this part they there form the crucial ligament (Lig. cruciatum), composed of two fascicuh, which cross each other in the centre. One of these fasciculi descends from the outer malleolus, goes downward and inward, and is attached to the tibial side of the first metatarsal bone. The second arises from the internal malleolus, and goes to the tuberosity of the fifth metatarsal bone. Below, they are both continuous with the thin aponeurosis of the back of the foot, which covers the tendon of the extensor digitorum longus and the belly of the extensor communis digitorum pedis, and is lost near the anterior extremity of the metatarsus. This aponeurosis at the back of the foot is often much stronger toward the posterior end of the first metatarsal bone in this place, where it passes over the tendon of the extensor proprius pollicis pedis, than in the rest of its extent, and it is formed of very evident transverse fibres which are attached internally to the inner side of the metatarsus, and outside to a special fasciculus of the extensor brevis digitorum pedis. In this case, this portion of the aponeurosis of the foot is pro- vided with a proper tensor muscle. II. TENSOR VAGIN2E FEMORIS. § 1186. The aponeurosis of the fascia lata, like most of the aponeu- rotic expansions which surround the muscles, has a proper muscle called the tensor vagina femoris muscle, llio-aponeurosi-femoral, Ch. (M. tensor fascia lata). This muscle is situated at the anterior edge of the upper part of the lateral face of the thigh. It arises by a short but very strong tendon from the outer face of the anterior and superior spine of the ilium. MYOLOGY, 143 Thence it goes downward and outward, gradually enlarges, and is continuous by very short tendinous fibres, towards the summit of the middle third of the thigh, with the fascia lata, which is united with its outer face more firmly than with any other muscle. ARTICLE SECOND. MUSCLES OF THE PELVIS. § 1187. The muscles of the pelvis arise partly from its outer face, partly from its inner face, and partly from the lumbar portion of the vertebral column; they are attached to the upper part of the femur which they extend, flex, and turn around its axis. I. EXTENSORS OF THE THIGH. § 1188. The thigh is extended by three muscles called the glutai, situated over each other; and they cover the outer face of the iliac bones, and descend outward, downward, and forward toward the femur. I. GLUTJEUS MAXIMUS. § 1189. The glutaus maximus muscle, Sacro-femoral, Ch., is the largest of all the muscles of the body, and is nearly a regular rhomboid. It arises by its posterior and inner edge from the posterior part of the outer lip of the crest of the ilium, from the lower part of the posterior face of the sacrum, from the sacro-sciatic ligament, and from the sciatic tuberosity. It arises by these different points by short tendinous fibres, goes from within outward and from above downward, forming a very strong and thick muscle, composed of distinct and large fasciculi which are loosely connected with each other. It is attached by a broad and very strong tendon which is continuous below with the lateral part of the fascia lata to the lower part of the large trochanter, and to the linea aspera which descend from this tubercle. Several mucous bursa? are found on the inner face of the lower tendon of this muscle. The largest and at the same time the uppermost is situated between it and the outer face of the large trochanter. Farther backward and downward we find another which is also large but a little smaller, between it the upper extremity of the vastus externus muscle and the lower end of the tensor vaginae femoris muscle. Fi- nally, between this muscle and the femur, farther backward and down- ward, are two which are smaller. The glutaeus maximus extends the thigh, brings it toward the ver- tebral column, rotates it a httle outward, and approximates it to that of the side opposite. When it acts from below upward it draws the iliac bones downward, inward, and forward. 144 DESCRIPTIVE ANATOMY. II. GLUTEUS MEDIUS. § 1190. The glutaus medius muscle, Grand ilio-trochanterien, Ch., is a large muscle, but smaller and closer than the preceding, and has a triangular form. It is covered at its posterior and lower part by the gluteus maximus, and forward by the fascia lata only, with which it is intimately connected. It arises from the outer lip of the crest of the ilium, and from the upper and anterior part of the outer face of the iliac bones which is situated between the iliac crest and the curved line. Its posterior fibres are oblique from behind forward and from without inward ; the anterior go from above downward. It proceeds towards the large trochanter, and is attached to its outer face by a broad, short, and very strong tendon, which blends with that of the gluteus maximus muscle. A small mucous bursa exists between the upper face of this muscle, the pyrifarmis, the gemellus superior, and the inner face of the large trochanter. The glutseus medius muscle raises the femur, separates it from that of the opposite side, and inclines the pelvis as much as possible towards its side. Its posterior part turns the thigh outward, and its anterior turns it inward. III. GLUTAUS MINIMUS. § 1191. The glutaus minimus muscle, Petit ilio-trochanterien, Ch., has the same form as the preceding, while it is much smaller and is entirely covered by it. It arises directly below it by its upper face and anterior edge from the curved line, and from the anterior and lower part of the outer face of the iliac bones. It is attached by a short and strong tendon to the upper edge of the upper part of the inner face of the large trochanter. A small synovial capsule exists forward between it and the large trochanter. Its action is the same as that of the preceding. II. MUSCLES WHICH ROTATE THE THIGH OUTWARDLY. § 1192. The thigh is turned outward by six muscles, the pyriformis, the obturator internus, the obturator externus, the two gemelli, and the quadratus femoris. I. PVRIFORMIS. § 1193. The pyriformis muscle, Sacro-lrochanterien, Ch. (M. pyri- formis, pyrimidalis, iliacus externus), is a small muscle of an oblong MYOLOGY, 145 triangular form coming from the cavity of the abdomen, where it arises by three or four digitations from the sacrum. It arises from the anterior face of this bone, between the third and fourth, the second and third, and the first and second pairs of the anterior foramina of the sacrum, and from the inner face of the posterior and lower spine of the ilium, and from the upper part of the posterior edge of the iliac fossa. It descends through this last behind the upper part of the descending branch of the ischium, goes outward and forward, and is attached by a rounded, strong, and proportionally broad tendon to the summit and upper part of the inner face of the large trochanter. There is a small mucous bursa between its tendon and the gemellus superior muscle. It rotates the thigh outward, separates it from that of the side opposite, and raises it a little. § 1194. It sometimes divides into an upper and a lower portion, between which the glutseal nerve passes.(1) II. OBTURATOR INTERNUS. § 1195. The obturator internus muscle, Sous-pubio-trochanterien interne, Ch. (JVf. obturator internus, s. marsupialis, marsupialis inter- nus), arises from the inner face of the obturator foramen by radiating fibres, which suddenly change their direction on leaving the pelvis and turn at a right angle on the posterior face of the descending branch of the ischium, covered before by this part of the bone, and behind by the sacro-sciatic ligament. It then proceeds outward and forward; and is attached by a strong tendon to the central part of the inner face of the great trochanter, far below the tendon of the pyriformis muscle. The arrangement of this tendon is then very peculiar. It begins within the pelvis, a short distance from the descending branch of the ischium, but extends to about the centre of the space between the ischium and the trochanter. It does not appear except on the anterior and inner face of the muscle, where it consists of five very regular and very distinct fasciculi, two of which form the upper and lower edge of the muscle. The outer extremity of the middle belly extends between them by four triangular fasciculi, and then immediately unite in a strong tendon near the centre of the space between the ischium and the great trochanter. We find an oblong synovial capsule backward and outward between the tendon of this muscle, the gemelli, and the great trochanter. A second, external and rounded, situated between the ischiatic spine and the great trochanter, surrounds the inner part of the tendon. . The obturator internus muscle turns the thigh directly outward and draws it from that of the opposite side. (1) Winslow, Expos, anat., vol. ii. p. 125. Vol. II. 19 146 DESCRIPTIVE ANATOMY. III. GEMELLI. § 1196. The gemelli muscles, Ischio-trochantericn, Ch. (M. gcmini femoris, marsupiales externi, marsupium), are two small oblong mus- cles, which are very similar and placed one over the other: they are separated backward and outward by the tendon of the obturator inter- nus muscle, also by that portion of this muscle which is situated out of the pelvis. Their thin edges touch forward. The upper arises by a pointed extremity from the lower part of the posterior face of the ischiatic spine. The lower arises by a broad and semilunar edge from the upper face of the sciatic tuberosity and from the outer face of the desc ending branch of the ischium. It gradually becomes thicker from within out- ward. These two muscles are intimately connected with the obturator internus, especially in their outer portions, entirely cover it, and are attached with it to the inner face of the great trochanter. They act in the same manner as the preceding. § 1197. The upper gemellus is frequently deficient(l)—a remarka- ble analogy with what is seen in the ape.(2) We know of one case where both these muscles were deficient, as in bats. IV. QUADRATUS FEMORIS. § 1198. The quadratus femoris muscle, Ischio-sous-trochanterienf'h., is oblong and composed of transverse fibres. It is broader from with- out inward than in any other direction, and its height much exceeds its thickness. It arises from the anterior edge of the sciatic tuberosity and from a small part of the .ascending branch of the ischium, passes directly below the gemellus inferior to the posterior face of the femur, where it is attached to a*square impression situated between the roots of the large and small trochanters above the posterior intertrochanterian hne. We find a synovial capsule between it and the small trochanter. It acts hke the preceding. §1199. Sometimes it does not exist.(3) More rarely it is divided into several fasciculi, three of which have been known to exist.(4) V. OBTURATOR EXTERNUS. § 1200. The obturator externus muscle, Sous-pubio-lrochanterien externe, Ch., is a rounded and triangular muscle, at first thin, but after- (1) Gantzer, p. 4. (2) Vicq. d'Azyr, Enc. mcth. syst. anat. des quadrup., p. 29. (3) Albinus, loc. cit., p. 530.—We know of one case where the gemelli were very large. (4) Jancke, De caps. tend, articul., Leipsic, 1753. MYOLOGY. 147 Wards it becomes thicker and again grows thinner. It arises by a rounded edge from the outer face of the ascending branch of the ischium and by short tendinous fibres from the two branches of the pubis and from the anterior face of the obturator membrane, After contracting considerably in its outer portion and being covered by a broad tendon on its anterior and posterior faces, it is reflected from the anterior to the posterior face of the body, goes obliquely upward and outward directly behind the neck of the femur, and is attached by a short but very strong tendon to the fossa and to the inner face of the great trochanter, a little distance below the tendons of the obturator internus and the gemelli muscles. It turns the thigh outward, draws it backward toward that of the opposite side, and brings the anterior face of the pelvis to its side. III. FLEXORS OF THE THIGH. § 1201. There are two flexors of the thigh, the psoas magnus and the iliacus internus muscles : to these a third is usually attached, the psoas parvus muscle; but this does not always descend to the thigh. I. PSOAS MAGNUS. § 1202. The psoas magnus muscle, Prelombo-trochanterien, Ch. (JVT. psoas magnus, s. lumbaris, s. lumbaris internus), is a considerable elon- gated and rounded muscle, occupying the inner and anterior part of the lumbar region directly on the side of the bodies of the lumbar ver- tebra. It extends from the upper extremity of this region downward and outward to the inner face of the femur. It arises by an external and posterior and an internal and anterior range of short, flat, and triangular slips from the five lumbar vertebras and the last dorsal. The anterior slips come from the lateral faces of the short ligaments and the intervertebral hgaments ; the posterior arise from the lower and anterior parts of the transverse processes of the lumbar vertebrae. The belly of this muscle descends outward, covers the inner part of the iliacus internus, becomes rounded as it descends, and forms before the sacro-iliac articulation, rather outward than inward, a strong tendon which emerges from the abdomen below the crural arch behind the femoral vessels, and is attached to the anterior face of the small tro- chanter. The psoas magnus muscle bends the thigh and turns it a little inward, bends the trunk and turns it a little toward its side. § 1203. Between this muscle and the iliacus internus we sometimes find another smaller, which arises from one or more transveise pro- cesses of the upper lumbar vertebras, proceeds on the outside of the psoas magnus muscle, and is attached to the small trochanter and 148 DE8CRIPTIVE ANATOMY. sometimes to the tendon of the last. Tho crural nerve usually passes between it and the psoas magnus muscle.(l) This anomaly reminds us of the multiplication of the psoas magnus muscle in several apes.(2) This and not the next muscle, as some anatomists assert, is the muscle which sometimes exists abnormally.(3) II. PSOAS PARVUS. § 1204. The psoas parvus muscle, Prelombo-pubien, Ch., has an oblong square form, and arises from the lateral face of the first lumbar vertebra, and from the intervertebral ligament between it and the last dorsal vertebra, and sometimes from the twelfth dorsal vertebra. It arises generally by one but sometimes by two slips, which come either from the two vertebra? or only from the first lumbar. It soon after becomes a flat and very long tendon, situated on the outside of the psoas magnus muscle, crosses it to go inward, and is attached in that part where the body of the pubis and ilium unite. Below, the tendon becomes an aponeurosis, which covers the lower part of the psoas magnus and of the iliacus, is attached to the crural arch, and blends with the fascia lata. This muscle bends the vertebral column forward and increases the force of the two muscles situated above it, furnishing them with a point of support. § 1205. It is sometimes deficient, but this is rare. III. ILIACUS INTERNUS. § 1206. The iliacus internus muscle, Biaco-lrochanterien, Ch. (M. iliacus, s. iliacus internus), is a broad and considerable muscle, which fills all the upper part of the inner face of the iliac bones, whence it descends to the inner part of the thigh. It arises by a semicircular and convex edge and by short tendinous fibres from the inner lip of the iliac bone, and also by fleshy fibres from the inner face of this bone to near the anterior and inferior iliac spine, goes inward and forward, becomes in its course considerably narrower and thicker, and is attached a little above the crural arch to the outside of the tendon of the psoas magnus muscle, by which it is fixed to the anterior face of the small trochanter. We find a considerable mucous bursa between the common tendon of the psoas magnus and the iliacus internus muscle and the capsular hgament of the coxo-femoral articulation. There is another, which is smaller, between it and the small trochanter. This muscle bends the thigh and carries it inward. It draws the pelvis and with it the trunk downward and forward. (1) We have seen it several times.—Albinus, p. 315. (2) Valentine, Amph. zoot., p. 151. (3) Kelch, Beytrage zur path, anat., p. 22. MYOLOGY. 149 ARTICLE THIRD. MUSCLES OF THE THIGH. § 1207. Among the muscles which form the mass of the thigh some serve to move it and others act on the ieg. Not only the first but also some of the second arise from the bones of the pelvis. The muscles of the first class are the adductors of the thigh; those of the second are the adductors, the flexors, and the extensors of the leg. I. ADDUCTORS OF THE THIGH. § 1208. The two lower limbs are drawn toward each other by the adductors (adductores), which form almost all the internal and posterior part of the muscular mass of the thigh. Three of these muscles in particular have been termed the adductors. They have been considered as forming only a single muscle, called the triceps muscle (J\t. femoris triceps), but wrongly, as they are not united by a common tendon. The fourth has been described as a separate muscle, called the pecti- naus, although it might be considered as a fourth head of the common adductor, as well as the other three. I. PECTIN.EUS. § 1209. The pectinaus muscle, Sous-pubio-femoral, Ch. (M.pecti- naus, s.pectinalis), a flat, long, quadrangular muscle, arises by its upper thin and horizontal edge from the crest of the horizontal branch of the pubis, on which its upper and anterior face passes. It goes from above downward, from within outward, and is attached by a perpendicular edge to the upper end of the inner lip of the rough line of the femur. We find a small synovial capsule below the small trochanter, between this muscle and the femur. It draws the thigh toward that of the opposite side, raises it and car- ries it forward, turns it a little inward, and shghtly inchnes the pelvis outward and downward. § 1210. We sometimes find a second pectinaeus, which is smaller, which blends below with the tendon of the other, and is attached above to the inner part of the upper edge of the obturator foramen.(1) § 1211. The three adductors, properly so called, are distinguished into the long, the short, and the great adductor. II. ADDUCTOR LONGUS. § 1212. The adductor longus muscle, Pubio-femoral, Ch. (M. ad- ductor femoris longus, caput primum tricipitis), has the form of an ob- (1) Winslow, Expos, anat., vol. i. p. 117. 150 DESCRIPTIVE ANATOMY. long triangle. It is the second of the three adductors in size and the longest of°all. It arises by a short, narrow, but very strong tendon from the inner part of the anterior face of the horizontal branch of the pubis, from the spine of the pubis, and from the anterior part of the symphysis pubis. Thence it goes outward and downward, in a direc- tion more obhque than the preceding, becomes broader and at the same time thinner, and is attached by a tendinous and interrupted edge to the third quarter of the posterior lip of the rough line of the femur. Its lower end usually unites to the vastus internus muscle. Its action is nearly the same as that of the pectinaeus. § 1213. It is sometimes divided into two. And again, it descends much lower, by a thin tendon united to that of the adductor magnus: so too in some mammalia and in birds the pectinaeus or the other por- tions of the adductor muscle descend very low. III. ADDUCTOR BREVIS. § 1214. The adductor brevis muscle, Sous-pubio-femoral, Ch., (M. adductor femoris brevis, s. adductor secundus, s. caput alterum tricipitis), is rather abroad triangular muscle. It arises at the side of the tendon of the gracilis muscle, but much higher and more externally than it, and is closely united with its upper extremity. Its upper end, situated directly below the adductor longus and formed of very short tendinous fibres, arises from the inner part of the outer face of the horizontal branch of the pubis. It is much broader and much shorter than the preceding, goes less obliquely outward than it, and is attached to the posterior face of the small trochanter and also to the upper third of the inner lip of the rough line of the femur, by several strong tendinous slips, which succeed each other from above downward. At its. lower extremity it is connected more or less intimately with the pectinaeus and the adductor magnus muscles. It acts like the preceding. § 1215. It is often partially or wholly divided into two slips, which forms a remarkable analogy between man and the ape. IV. ADDUCTOR MAGNUS. § 1216. The adductor magnus muscle, Ischiofemoral, Ch. (M. adductor femoris magnus, s. caput tricipitis tertium), is the largest of the three proper adductor muscles ; it also has a triangular form, the base of which rests in the thigh, and the apex looks toward the pelvis. It arises from the anterior face of the descending branch of the pubis, and is intimately connected in this part with the outer face of the lower part of the tendon of the gracilis muscle. It arises also from the ascending branch of the ischium and from the lower edge of the sciatic tuberosity. Its upper and anterior fasciculi go directly 'downward and outward. The posterior and inferior on the contrary, which are attached to the MYOLOGY. 151 sciatic tuberosity, go from below upward, around and behind the latter, so that the muscle seems at its upper part to have been twisted on itself, and is much thicker there than in the rest of its course. Before the extremity of the portion inserted in the sciatic tuberosity, the upper edge, which is loose and fissured in a semilunar form, goes toward the femur, where it is attached to the posterior lip of the linea aspera, behind the pectinaeus and the other two adductors, always descending deeper than they. The lower tendon is very strong, parti- cularly at its lower part, and extends to the posterior face of the inner condyle of the femur. About the latter fourth of the thigh this tendon is perforated by the superficial vessels of the leg, which pass from its anterior to its posterior face. It unites below to the vastus internus muscle. This muscle draws the thigh inward, carries it forward, turns its anterior face a httle outward, flexes the pelvis forward, and directs its anterior face to the side. § 1217. We sometimes find it divided into two portions, as in apes. II. MUSCLES OF THE THIGH WHICH MOVE THE LEG. § 1218. The muscles situated on the thigh forming its mass, and which move the leg, are distinguished into adductors, extensors, and flexors. I. ADDUCTORS OF THE LEG. § 1219. Those nearest the surface are the adductors, of these there are two, the sartorius and the gracilis. A. SARTORIUS. § 1220. The sartorius muscle, Mo-pretibial, Ch., the longest of all the muscles of the body, is very thin, and has an elongated square form. The short tendon by which it arises descends lower on its ex- ternal than on its internal edge. It is inserted directly at the side of the tensor vaginae femoris muscle, more inward and forward, on the anterior and upper spine of the iliac bone. Thence it passes onward and inward, above the lower part of the adductor longus and adductor magnus muscles. In this manner it attains the anterior face of the thigh, where its lower portion goes to the inner face of the same part. Thence it proceeds directly forward and at the side of the gracilis, and soon becomes rounder and narrower, and forms a short rounded tendon which, passing behind and below the inner condyle of the femur, comes to the inner face of the leg. In this place it rests directly on the upper part of the inner face of the tibia, it becomes broader, and is attached by its anterior edge to the inner face of this bone, near its spine, and is contiguous below with the aponeurotic expansion of the leg. 152 DESCRIPTIVE ANATOMY. This muscle flexes the knee, and when this articulation is bent it turns the tibia inward, so that the end of the foot approaches the other. When it acts in an opposite direction it draws the haunch a httle for- ward and turns it inward. § 1221. We have met with one subject in which the sartorius muscle did not exist. Sometimes, on the contrary, there are two which may happen in several different ways.(l) The normal muscle usually appears curved inward, and the additional muscle terminates sooner below, where it is attached either to the tendon of the first or to the femur. Sometimes the fibres of the sartorius muscle are interrupted by a considerable intermediate tendon which is firmly united to the fascia lata.(2) B. GRACILIS. § 1222. The gracilis muscle, Sous-pubio-pretibial, Ch. (M. gracilis, s. rectus internus), is a thin muscle of an oblong triangular form which arises by abroad base which forms its upper edge, from the anterior face of the lower portion of the descending branch of the pubis, and from the upper part of the ascending branch of the ischium. Thence one of its edges turns forward and the other backward, one of its faces out- ward and the other inward; it goes to the inside of the thigh, and above its latter sixth, becomes a thin and rounded tendon, which pro- ceeds directly behind the lower part and the tendon of the sartorius, and turns with it on the inner condyle of the femur. It is at first covered by it, and is then situated below it, and blended with it in its anterior and inferior part, and is finally inserted a little lower down, in the upper part of the inner face of the tibia. It bends the knee, turns the leg inward, and draws the anterior face of the iliac bones from the side to which it is attached. II. EXTENSORS OF THE LEG. § 1223. The leg has four extensors which may very properly be considered as one muscle with four heads, since they are attached to a common tendon. They are situated directly below the fascia lata aponeurosis on the anterior face, and on the sides of the thigh, and form most of its muscular mass. A considerable mucous bursa exists between them and the aponeurosis of the thigh. They are termed the rectus femoris, the vastus internus, the vastus externus, and the crureeus muscles. A. RECTUS FEMORIS. § 1224. The rectus femoris muscle, llio-rolulien, Ch. (M. rectus femoris, s. extensor cruris medius superficialis), is a strong elongated 1) Huber, Act. n. c, vol. x. p. 114.—Rosenmuller, loc. cit., p. 7.—Gantzer, p. 14. 1) Kelch, loc. cit., p. 42, p. xxxv. MYOLOGY. 153 pointed muscle situated on the anterior face of the thigh, directly under the fascia lata aponeurosis in most of its length, except its upper part, where it is covered by the sartorius muscle. It arises by two points from the iliac bone by a very strong but short tendon. In fact, this tendon is divided above into two heads, an upper and a lower or external tendon. The upper head, which goes directly downward, comes from the anterior and inferior spine of the ilium. The lower, which is curved in a semicircle, arises from the upper part of the edge of the cotyloid cavity. These two heads soon unite to give rise to the upper common tendon. This tendon soon disappears on the posterior part of the muscle, but becomes much broader on the anterior, and descends to its centre, gradually becoming thinner. The central fleshy portion is composed of an outer and an inner layer of fibres, which unite at an acute angle on the median line, so that the arrangement of these fleshy fascicuh resembles in some mea- sure a roof. The fibres are much longer, and ascend much straighter the nearer they are to its lower extremity. They are attached on both sides to a prolongation of the upper tendon, the direction of which is from before backward, which descends into the substance of the muscle from its anterior face, and gradually diminishes from above downward. It however continues perceptible to near the lower end of the fleshy belly, that is, much lower than the broad and anterior part of the upper tendon descends on its outer face. It is nowhere connected with the posterior and inferior tendon. The lower tendon is much longer but is weaker than the upper. It ascends on the posterior face of the muscle, much higher than the upper, descends on the anterior, so that the fleshy belly is situated for several inches before and behind between two tendinous expansions. It begins to be visible forward only towards the lower third of the thigh, and is seen first on the two sides of the fleshy belly, which gradually contracts. It is entirely loose after quitting the last fifth of the thigh. When approaching the patella below, it becomes broader, and is attached to the upper edge of this bone, and is intimately united with the tendons of the other extensors. This muscle extends the leg when the thigh is fixed, and the thigh when the leg is fixed ; in the latter case it also bends thc^elvis a little and turns its anterior face obhquely to the opposite side. D. VASTUS EXTERNUS. § 1225. The vastus externus muscle, (J\f. extensor cruris vastus, $. extemus),(l) the largest of all the extensors of the leg, although much shorter than the preceding, forms almost solely the muscular mass on the outside of the thigh; at the same time it extends very much (1) This and the next two muscles are termed the Trifemoro-rotulien by Chaussier. Vol. II. 20 154 DESCRIPTIVE ANATOMY. backward and forward. It is considerably thick, but it is broader from before backward than from within outward. It arises by a shghtly concave edge which inclines from before back- ward, from within outward, and from above downward, from the lower part of the anterior and outer face of the great trochanter. The upper half of its posterior edge, situated along the rough line of the the femur, comes from the inner face of the outer wall of the fascia lata aponeurosis. From all these points it gradually descends forward, becomes narrower, and is finally attached, by an inferior tendon, to the upper and outer edge of the patella. The inner part of this tendon is covered some distance above its insertion by the tendon of the rectus femoris muscle, to which it is even slightly united, although it is easily separated from it as far as where it is inserted in the patella. The muscular fascicuh go directly downward. The upper tendon extends below the centre of the muscle on its outer face, and tho lowci only to the centre of its inner face. The vastus externus muscle extends the knee, and most generally raises the leg at the same time, and turns it a httle outward. C. VASTUS INTERNUS. § 1226. The vastus internus muscle (JVf. extensor cruris, s. vastus internus) is a little shorter and much weaker than the preceding, with which it is blended outwardly in a small portion of its upper extremity. It arises by its upper edge, which descends obliquely inward, from the anterior intertrochanterian line ; by a small part of its lower edge, from a part of the anterior face of the femur situated below this line ; and by the upper part of its posterior edge, from the upper part of the ante- rior lip of the linea aspera. Its lower tendon is attached to the inner part of the upper edge, and to the inner edge of the patella. The inner part of this tendon is covered below by that of the vastus externus which passes obliquely over it, and is attached to the patella before it; it adheres to this tendon, but is easily separated from it. The upper tendon of this muscle descends over almost the whole of the inner and loose face on the posterior half of the muscle, while the lower disappears already below the centre of its outer face, principally at its upper part. This muscle extends the leg and turns it a httle inward. D. CRURJEUS. § 1227. The cruraus muscle, (JVf. cruralis, s. cruraus, s. femoraus) the shortest of the four extensors of the leg, is also nearly as strong as the preceding. It arises by its posterior and inner face, directly below this last, from the larger part of the anterior and the outer face of the femur, excepting a small portion above, and from its lower third. The posterior edge comes from the outer lip of the linea aspera. This MYOLOGY. 155 muscle covers also most of the anterior and outer faces of the femur. It is attached by its lower tendon behind the vastus internus and the vastus externus to the upper edge of the patella, and usually also at its lower and outer part, by short fibres, to the synovial capsule, and to the outer edge of the patella.' This lower and outer part is generally separated from the others, particularly from their tendon. The upper edge of this muscle is attached to the bones without any appearance of a tendon. The lower tendon, the loose portion of which is longer than that of the two preceding, begins on the contrary from the middle of the anterior and loose face. The cruraeus muscle is mostly covered above by the vastus externus and the vastus internus ; it is entirely covered below by the rectus muscle, excepting however its outer and lower lateral face, where it is concealed by the vastus internus muscle. Its lower part also is inti- mately connected with the two vasti, especially the externus. A capsular ligament exists between its tendon, that of the vastus externus, the capsular ligament and the patella; this frequently opens into the femoro-tibial articulation. It extends the knee. § 1228. The common tendon of these four muscles, after envelop- ing the patella, goes to attach itself to the tuberosities of the tibia, where we find a considerable synovial capsule between it and the bone. E. SUBCRURALIS. § 1229. The subcruralis muscle is a small triangular muscle, which always exists and is entirely covered by the lower part of the preced- ing. It arises from the lower fourth of the anterior face of the femur, and is attached to the upper part of the anterior wall of the synovial capsule of the knee. It draws this capsule in the motion of extending the leg, and also prevents it from being injured. III. FLEXORS OF THE LEG. § 1230. The flexors of the leg are situated on the posterior face of the thigh. We number three, two internal and an external; but the latter arises by two heads. All arise at the side of each other from the sciatic tuberosity, and are attached posteriorly to the bones of the leg. They consequently bend the knee or draw the posterior faces of the thigh and of the leg towards each other. They also extend the coxo-femoral articulation when the leg is extended. I. INTERNAL FLEXORS. § 1231. The two inner or tibial flexors arise from the sciatic tube- rosity and are inserted in the upper end of the tibia. They are called the semimembranosus and the semitendinosus. 156 DESCRITTIVF. ANATOMY. A. SEMITENDINOSUS. § 1232. The semitendinosus muscle, Ischio-pretibial, Ch. (.If semi- tendinosus, s. seminervosus), is an elongated muscle broader and thicker above than below, partially covering the following, because it is ex- tended more below it and nearer the surface. It arises from the inner part of the posterior face of the sciatic tuberosity by a tendon which is very distinct outwardly, while its summit adheres very intimately to the inner edge of that of the long head of the biceps femoris muscle. This muscle is the most internal of the three flexors, and goes directly downward. Its lower tendon commences on its inner edge, a little be- low the centre of the fleshy belly; from about the last fourth of the thigh it forms a very strong rounded cord, which passes behind the inner condyle of the femur to arrive at the tibia, and is attached, after enlarging and becoming thinner, to the inner face, directly below the gracilis muscle. It blends with the lower edge of the tendon of this latter muscle, and generally divides below into an upper and a lower slip. We find a mucous bursa directly near its insertion, between its upper tendon and that of the semimembranosus and the long head of the biceps. There is also another, and sometimes two or three, even between its lower tendon ; that of the sartorius, that of the gracilis, and the internal lateral ligament of the knee. This muscle bends the leg and turns it a little inward ; when it acts in an opposite direction it draws the pelvis and the trunk backward, and bends them with the thigh in the same direction. B. SEMIMEMBRANOSUS. § 1233. The semimembranosus muscle, Ischio-popliti-tibial, Ch. (M. semimembranosus), follows a direction to a certain exent directly oppo- site to that of the preceding. Of the three flexors this arises farther forward, upward, and outward from the outer part of the sciatic tubero- sity by a very long, strong, broad, and perfectly distinct tendon, which gradually enlarges and becomes thinner as it descends to the centre of the thigh and to the end of the fleshy belly, to which it is united by an edge oblique from within outward. This belly is elongated, rounded, thicker, but shorter than that of the semitendinosus, and is formed of an internal and an external layer of fibres which are turned upward towards each other, and are attached by radiations to the upper tendon. This latter exists only on the outer face of the upper part of the muscle; but from its centre to its lower end, where it appears externally as a narrow band, it penetrates deeply inward to the centre of its substance. The lower tendon, which proceeds nearly to the centre of the muscle on its anterior face and on its inner edge, passes on the outer face of the inner condyle of the femur, between it and the semitendinosus MYOLOGY. 157 muscle, and is inserted to the inner part of the inner condyle of the tibia, after passing freely a short distance. A mucous bursa exists between the upper tendon and the quadratus femoris or the adductor magnus. Sometimes there are two. Another is found between the lower tendon, the upper internal head of the gas- trocnemius and the capsular Hgament of the knee. This bursa often encloses another which is smaller, and adheres very intimately to the tendon of the semimembranosus muscle. The action of this muscle is the same as that of the preceding. II. BICEPS FEMORIS. § 1234. The biceps femoris muscle, Ischio-femoro-peronier, Ch. (JVf. flexor cruris externus, s. fibularis, s. biceps femoris), arises above by two separate heads, which are attached below by a common tendon. The long head arises from the posterior face of the sciatic tuberosity by a short but firm tendon, which is inserted between the two preceding muscles. A short distance from its upper extremity this tendon begins to receive the fascicuh of the fleshy belly, and descends along its inner edge. The belly descends at first in a straight hne, behind and at the side of the upper part of the semimembranosus muscle ; but it then goes outward, passes over the adductor magnus, and thus arrives at the outside of the thigh. The short head is much smaller, and its form is an oblong square. It arises by very short tendinous fibres from the central two fourths of the outer lip of the linea aspera, directly at the side of the adductor magnus, goes obliquely downward, and is attached to^the inner face of the lower tendon of the long head, from the lower fourth of the thigh to near its lower end. The common inferior tendon, which goes nearly to the centre of the large belly, on its posterior face, descends on the outer face of the outer condyle of the femur, and is inserted at the top of the head of the fibula, where there is a mucous bursa between it and the external lateral ligament of the knee. The biceps femoris muscle bends the knee, turns the leg a little out- ward, extends the pelvis, and inchnes it slightly downward and back- ward. § 1235. Sometimes the short head does not exist, a remarkable ana- logy with animals, in most of which it is deficient. But in other sub- jects we find a third, which is thinner, and comes sometimes from the sciatic tuberosity, and is attached below the common tendon of the muscle,(l) and sometimes arises from the upper part of the long head, descends on the calf of the leg, and is joined by the lower end to the tendo Achillis ;(2) this deserves to be remarked because the biceps femoris muscle descends very low in the mammalia. (1) Gantzer, loc. cit., p. 15.—Soemmering', Muskelehre, p. 276. (2) Kelch, loc. cit., p. 42, no. xxxvi. 158 DESCRIPTIVE ANATOMY When this anomaly exists the biceps femoris resembles the normal structure of the biceps flexor cubiti, even as the latter, when it presents a third supernumerary head, represents the anomaly, of which the other sometimes gives an instance. ARTICLE FOURTH. MUSCLES OP THE LEG. § 1.236. The muscles of the leg occupy its posterior, external, and anterior faces; but they leave the internal loose, so that on this side the tibia is covered only by the skin. Most of them are attached, by their upper extremities, to the bones of the leg, and by their lower, to those of the feet as far as the toes. Some, however, come from the lower part of the thigh, their lower extremities are inserted in the bones of the leg. I. POSTERIOR MUSCLES. § 1237. The posterior muscles of the leg form two layers, a super- ficial and a deep layer. I. SUPERFICIAL LAYER. § 1238. The superficial layer of the posterior muscles of the leg is composed of two muscles, the triceps surre and the plantaris. A. TRICEPS SUH.E. § 1239. The triceps sura muscle (JVf. triceps sura, s. gemelli cum soleo) is extremely strong, and forms most of the muscular mass of the leg ; it deserves to be considered as a separate muscle with three heads, since these heads, although entirely separated above, are all attached below to a common tendon. Two of these heads are in pairs and the third is single. The first two called for this reason the gastrocnemii muscles, Bi-femoro-calca- niens, Ch. (JVf. gemelli sura), are situated at the side of each other. They arise by a short, broad, but thin tendon, which terminates above by a semicircular convex edge from the femur, above the upper edge of the posterior face of its inner and outer condyle. These two bellies are triangular and much narrower above than below. Above there is an interval of about four inches, which is filled by an abundant and very loose cellular tissue and also by the vessels and the nerves of the leg. Their fibres converge from above downward and meet the common tendon a little above the centre of the whole length of the muscle. The upper tendon, which is expanded along MYOLOGY. 159 the external edge and the posterior face, gradually becomes thinner and descends almost to the lower extremity of the fleshy belly. The latter terminates below in a rounded edge ; so that the two bellies unite and form a waved line, very concave in its central part. The inner belly is much stronger and descends much lower than the outer. The lower tendon, in which the two fleshy bellies are inserted, arises far above their anterior face, that which corresponds to the posterior face of the bones of the leg, from the union of the two bellies to the centre of their common lower edge: it forms a broad canal, through which pass the branches of the nerves and vessels which descend on the posterior face of the loose portion of the common tendon. The third belly, called also the solans muscle, Tibio-calcanien, Ch., is much stronger than the two preceding. It is situated below and before them. It arises by its upper edge, which is fleshy, serrated, and oblique downward and inward, from the posterior part of the head of the fibula, from the lower edge of the poplitaeus muscle, and from the pos- terior edge of the tibia. Its lower edge and a part of its anterior face arise for a considerable distance above from the posterior face and below from the inner edge of the tibia. Finally, its outer edge comes from the upper part of the posterior face and from the outer edge of the fibula. Its posterior and upper fasciculi go directly downward. The ante- rior and inferior of the tv/o sides meet each other below and are attached to the anterior face of the common tendon, covering its anterior face to some inches above its insertion, gradually becoming thinner and nar- rower, so that this belly consequently occupies nearly all the leg, and descends very much lower than its centre. The tendons by which the two lateral edges of this muscle arise from the fibula and the tibia gradually enlarge, descend on the anterior edge and on the posterior face, and do not stop except at some inches above the lower end of this fleshy belly. Hence most of the latter is enclosed between two aponeurotic expansions. The common inferior tendon, called the Achilles tendon (tendo Achillis), from its power, is slightly covered above and behind by the two posterior bellies and before by the third belly. A little above the lower edge of the posterior bellies it divides into an anterior and a pos- terior tendinous layer. The latter reascends on the anterior face of the gastrocnemius in the manner mentioned above: the other covers the posterior face almost to the upper edge, gradually becoming thinner. The tendon, considered as a whole, contracts very much from above downward, and also becomes thicker, and is attached by a very narrow ed-e to the upper part of the posterior face of the tubercle of the cal- caneum, between which and its anterior face we find a considerable mucous bursa above its insertion. The triceps extends the foot in raising the heel: hence why it acts principally in standing on the toes and other similar circumstances. 160 DESCRIPTIVE ANATOMY. When the foot is fixed, the two upper heads bend the knee and draw the thigh backward and downward. The lower head, when it con- tracts toward the heel, extends the foot, because it carries the leg down- ward. This muscle corresponds to the supinators and to the pronator quad- ratus of the fore-arm : the two superficial heads represent the supina- tors and the deep head is analogous to the pronator. B. PLANTARIS. § 1240. The plantaris muscle, Petit femoro-calcanien, Ch., arises by a short tendon from the posterior face of the external condyle of the femur, from the external head of the gastrocnemius muscle, to which it is united, and from the posterior wall of the synovial capsule. Pro- ceeding directly behind the capsule, it goes inward and downward and even becomes a long, thin, and flat tendon, which descends along the inner edge of the tendo Achillis, unites with it below, and disappears in the cellular tissue on the inner face of the calcaneum to arrive at the tendinous expansion of the sole of the foot. This muscle has no very manifest action. We see in it only a rudi- ment of that which is much more developed in some mammalia and an imperfect imitation of the palmaris brevis of the hand. § 1241. It is often deficient and much more frequently than the palmaris.(l) II. DEEP LAYER. § 1242. The deep layer of the posterior muscles of the leg is com- posed of the poplitaus, the tibialis posticus, the flexor longus digitorum communis, and the flexor longus pollicis proprius. A. POPLITiEUS. § 1243. The poplitaus muscle, Femoro-popliti-tibial, Ch. (M.popli- taus, s. sub poplitaus), is a triangular muscle, which arises from the inferior and posterior part of the outer face of the external condyle of the femur. It is formed of oblique fibres, becomes broader from without inward, and is attached to the upper part of the posterior face of the tibia. It is intimately connected, especially at its upper and outer part, with the posterior wall of the synovial capsule of the knee. We find a mucous bursa between it and the external condyle of the femur on one side, the external semilunar cartilage and the capsular liga- ment on the other. (1) Our observations authorize us to assert that Gantzer mistakes in stating that the plantaris is more constant than the palmaris (loc. cit., p. 4). MYOLOGY. 161 This muscle corresponds to the pronator teres of the fore-arm. It turns the leg a httle inward, draws the outer semilunar cartilage outward and backward, and contributes to bend the knee. § 1244. Sometimes it is double.(l) B. TIBIALIS POSTICUS. § 1245. The tibialis posticus muscle, Tibio-sous-tarsien, Ch. (JVf. tibialis, s. tibiaus posticus, s. nauticus), arises between the extensor digitorum communis longus and the flexor longus pollicis pedis (§ 1248). It is the longest of the three muscles of the deep-seated layer and is penniform. It arises in its whole length from most of the posterior face of the interosseous ligament and from the inner face of the fibula; some fibres of its upper part arise also from the outer part of the posterior face of the tibia. Even as in the two long flexors of the toes, the two layers of fibres are attached to a very strong tendon, which descends inward and for- ward, is contained within the posterior and fibro-cartilaginous groove of the internal malleolus, thence passes into an analogous groove hollowed along the upper part of the inner face of the astragalus, and thus goes to the inner and lower face of the sole of the foot, opposite the anterior part of the inner face of the astragalus. Its tendon incloses a rounded sesamoid bone and divides into two slips: the internal is shorter, the inferior is longer. The first is single and is attached to the inner edge of the scaphoid bone. The second divides into several bands, which are inserted in the lower face of the scaphoid, the cuboid, and the three cuneiform bones, at the same time that they blend with the aponeurotic expansion of the sole of the foot and with the tendon of the peroneus longus. The tendon of this muscle is surrounded with a mucous sheath where it arrives at the sole of the foot. This muscle corresponds to the radialis internus muscle (§ 1149). It extends the foot, turns its inner edge a little upward, and the sole inward; it also extends the thigh and draws it backward. C. FLEXOR L0NGCS DIGITORUM COMMUNIS. § 1246. The flexor longus digitorum communis muscle, Tibio-pha- langettien, Ch., (JVf. flexor digitorum communis longus, s. perforans, s. profundus), is a thin, elongated, and penniform muscle; it arises from the summit of the anterior face of the tibia, except its upper part, which is covered by the popliteeus. The fasciculi, by which it arises, and which converge downward are inserted in a strong tendon below, which ascends almost to the upper extremity of the muscle and proceeds along the inner edge. This tendon approaches the surface, descends on the (1) Fabricius, De motu locali animalium, in Op., p. 359. Vol. II. 21 162 DESCRIPTIVE ANATOMY. posterior face of the tibia, goes to the inner face of the tarsus, and enters a fibro-cartilaginous furrow which exists along the upper part of the inner face of the astragalus, and is there kept in its position by a tendi- nous sheath, and thus goes forward. After leaving this point it turns outward, is covered by the posterior head of the abductor pollicis pedis muscle, on which it continues to go forward, and soon divides into four bands, which go in their turn on the flexor digitorum brevis, which is consequently covered by it. At the place where the tendon of the flexor longus muscle passes on the flexor brevis, and before it divides into four bands, we see a small muscle attached to its external and inferior part. The form of this muscle is an oblong square. It may be called the small or accessory head of the flexor longus communis (accessorius perforanlis). This small head, which is covered on all sides by the flexor commu- nis digitorum brevis, arises by two slips, the posterior or external, which is longer and stronger and comes from the external anterior tuberosity of the calcaneum, and the anterior or internal, which is smaller and arises from the superficial calcaneo-cuboid hgament (§ 982). Its fibres are oblique. It goes forward and inward, and not only is it fitted by its inner edge to the tendon of the flexor digitorum longus, but contri- butes much by its anterior tendons to form those of this muscle. The small head principally forms almost the whole tendon of the second toe. Most usually this tendon is not at all derived from that of the slip of the common flexor, but only from the short head and from the tendon of the extensor longus proprius pollicis, with which the centre of the flexor communis communicates near the anterior extremity of the calcaneum. The tendons of this muscle have the same relation to those of the short flexor as those of the flexor digitorum sublimis have with those of the flexor profundus. They are situated upon them, perforate them above the second phalanx of the toes, enlarge a little, and are attached to the posterior part of the lower face of the third phalanges. It is surrounded by a mucous sheath in the place where its tendon passes at the side of the fibula and of the calcaneum. A second enve- lops this tendon and that of the flexor longus pollicis proprius at the posterior extremity of the sole of the foot. The tendon it gives to each toe and that of the flexor minimi digiti proprius are surrounded with a proper mucous sheath. This muscle bends the third phalanx of the toes and brings the leg backward. § 1247. Sometimes it is furnished with a fifth tendon, which replaces the fourth of the flexor digitorum brevis, which is then deficient. This tendon proceeds along the inner edge of the fourth tendon of the flexor longus, and divides to allow the latter to pass, and consequently pre- sents the same arrangement as the flexor sublimis.(l) This formation (1) Brugnone, loc. cit., p. 176. MYOLOGY. 163 evidently resembles that of the apes, in which the tendons of the flexor sublimis and flexor profundus are so blended that they are distinguished from each other with difficulty. D. FLEXOR LONGUS POLLICIS PROPRIUS. § 1248. The flexor longus pollicis proprius muscle, Peroneosous- phalangettien du pouce, Ch. (JVf. flexor hallucis longus), is shorter but much stronger than the preceding. It arises by an internal and an •external layer of fibres, which converge downward and proceed by fleshy fibres from almost all the lower half of the posterior face and from the outer edge of the fibula, excepting only its lowest portion. These two orders of fibres are inserted in a strong lower tendon, which mostly remains concealed in the midst of the muscular substance and becqrnes entirely loose only when its fleshy fibres cease.^ This tendon goes obliquely from without inward and from behind forward, and thus comes on the inside of the tarsus, whence it goes forward along a fibro- cartilaginous groove, which exists at the upper part of the inner face of the calcaneum, directly below the upper edge of this bone, and where it is retained by a special sheath. It is covered by the outer slip of the posterior head of the abductor pollicis pedis muscle and directly by the tendon of the flexor communis digitorum longus which is nearer the surface, and is consequently situated beneath it. It crosses the direction of the latter and sends to it a very strong tendon, which unites principally to that of the second toe. We may justly say that the tendon of the flexor longus pollicis pro- prius muscle divides into two slips where it passes under the abductor pollicis pedis, an external for the second toe and an internal for the large toe. The latter is the strongest; it goes inward and forward directly at the side of the abductor pollicis pedis, is situated outward before it, and is partly covered by it. At the anterior end of the meta- tarsal bone of the large toe it enlarges a little, at the same time be- comes thinner, and is attached to the posterior part of the lower face of the second phalanx of the large toe. This muscle corresponds to the flexor longus digitorum communis in its course and in its attachment to the anterior phalanx of its toe. There is in fact a short flexor of the large toe; but this muscle has no perforated tendon which is attached to the posterior phalanx. On the contrary, we sometimes see an aiTangement analogous to that of the tendons of the flexor brevis perforatus. In fact a strong but nar- rower tendon, which however gradually enlarges as it advances, ex- tends from the head of the first metatarsal bone to the posterior end of the second phalanx, over the tendon of the flexor longus: this tendon is firmly attached in its whole extent and breadth of its upper face to the lower face of the phalanges, by a fold of the synovial capsule: it contains a single and transverse sesamoid bone : immediately behind its anterior extremity and below the articulation of the first phalanx with 164 DESCRIPTIVE ANATOMY. the second, it is finally attached to the lower face of the first phalanx, directly behind the tendon of the flexor longus. This tendon which has no muscle, is not found in the other toes; so that decidedly we should consider it as a rudiment of the flexor longus communis perforatus : it is however but an imperfect rudiment, since it is never perforated, which depends probably on the absence of the second phalanx of the large toe. The tendon of this muscle is enveloped with a mucous bursa in the canal of the astragalus and os calcis. A second covers its tendon and that of the flexor longus at the posterior part of the sole of the foot. A third incloses its tendon along the metatarsal bone of the first toe. It flexes the large and small toe. § 1249. We sometimes find at the lower part of the posterior face of the leg a small supernumerary muscle, which does not always present exactly the same arrangement. Sometimes it ascends from the cal- caneum and from the tendo Achillis, and is attached to the aponeurotic expansion of the leg, acting as its tensor muscle ;(1) so that we may then consider it as a fourth head of the triceps. It sometimes arises from the lower part of the fibula, goes downward, and is then lost around the articulation of the foot. It is sometimes attached to a spe- cial bone found in this place,(2) or to the lower face of the calcaneum, or finally to the small head of the flexor longus digitorum communis.(3) The second anomaly is very probably a repetition of the pronator quadratus of the upper extremity, but it is developed lower toward the foot, in accordance with the same law as that to which the other mus- cles are subjected, especially the flexors and extensors of the toes. The first corresponds probably to the palmaris brevis; the arrange- ment of the muscle in the upper and lower extremity differ in the same way as the palmaris brevis and the plantaris, as the latter does not arrive at the aponeurotic expansion of the sole of the foot. II. EXTERNAL MUSCLES. § 1250. The external muscles of the leg are the peroneus longus and the peroneus brevis. They extend from the fibula to the outer edge and to the lower face of the foot. I. PERONEUS LONGUS. § 1251. The peroneus longus muscle, Peroneo-sous-tarsien, Ch. (JVf. peroneus longus, s. primus, s. posticus), arises from the upper and smaller half of the anterior face, and by fibres which proceed obliquely from above downward and converge. Its upper tendon arises from the outer edge of the fibula and covers the upper and posterior part of this bone. (1) Mayer in Heymann, loc. cit., p. 15. (2^ Rosenmiiller, loc. cit., p. 8. (3) Gantzer, loc. cit., p. 15-17. MYOLOGY. 165 The lower tendon, which is very long, very strong, flat, and entirely loose from the lower third of the leg, conceals itself partially above this point between the muscular fibres ; so that it entirely disappears exter- nally toward the bottom of the upper third of the leg. But it appears again within the muscle, near its upper extremity, as a semicircular band, which gradually diminishes and to which the fleshy fascicuh are attached outward and inward. This tendon goes behind and on the outside of that of the peroneus brevis, along the outer and posterior face of the leg, and descends be- hind the external malleolus across a hgament formed of oblique fibres, within which is a sheath which sends prolongations to it. Arrived at the foot, the tendon winds forward and downward/around the outer edge of the cuboid bone, and thus comes on the sole of the foot, where it pene- trates ; thence it goes inward, covered by all the muscles of this region and directly by the calcaneo-cuboid hgament, which keeps it in place: then gradually enlarging, it is attached to the lower face of the cuboid bone and also to the lower face of the posterior head of the fifth, also of the fourth and third, and particularly of the second metatarsal bones: it sometimes also reaches the first metatarsal bone and the first cunei- forrcfbone before dividing. At the place where the friction of the tendon is the greatest, espe- cially opposite the external malleolus, the tuberosity of the calcaneum, and the cuboid bone, sometimes also in its plantar portion, we find sesa- moid bones or cartilages, the third of which is the largest, while the first is very small and often scarcely perceptible. There is also a considerable mucous bursa where the tendon of the muscle descends on the outer malleolus and astragalus: this bursa en- velops it and also the tendon of the following muscle. We find another below, which extends to the plantar face. The peroneus longus muscle extends the tibio-tarsal articulation and draws the foot backward and the leg downward: it also turns the foot, making its outer edge the upper and the plantar face look upward. It corresponds to the flexor carpi ulnaris of the fore-arm. II. PERONEUS BREVIS. § 1252. The peroneus brevis muscle, Grand peroneo-sus-metatarsien, Ch. (JVf. peroneus, s. fibularis brevis, s. anticus, s. secundus, s. medius, s. semifibulaus), is an elongated muscle, which terminates above in a point and is formed of two layers of fibres ; those of the anterior layer go from before backward and those of the posterior go from behind for- ward. These two layers converge toward the base: they arise from the second fourth of the anterior face and from the posterior edge of the fibula to near the outer malleolus. The lower tendon, which is long, strong, and flat, extends within the muscle, and like that of the preceding ascends almost to its upper extremity. It becomes visible externally sooner than that of the pero- 166 DESCRIPTIVE ANATOMY. neus longus, and descends between the fibres of the muscle to arrive at its outer face. Once disengaged it goes before that of the peroneus longus, behind the outer malleolus, and is retained in the groove which exists there by a ligament, common to it and the preceding muscle. This ligament, called the retinaculum musculorum peronaorum, extends from the ante- rior, to the posterior edge of the groove like a bridge. The tendon having thus reached the upper face of the foot goes forward; enlarging along its anterior edge. Near the base of the fifth metatarsal bone it usually divides into two slips, the outer of which is attached to the tuberosity of this bone while the inner is longer, subdivided likewise into two parts, one of which is attached to the centre of the upper face of its body ; the second is inserted partly in the outer edge of the fourth tendon of the extensor and partly on the posterior face of the fourth external interosseous muscle. Besides the common mucous bursa (§ 1229)'the tendon of this mus- cle has a special bursa situated lower on the outer edge of the foot, and which surrounds it. The peroneus brevis muscle acts like the preceding ; it flexes the tibio-tarsal articulation, consequently carries the foot upward, and depresses the leg; it also turns the sole of the foot outward and its outer edge upward, but less so than the peroneus longus. It corresponds to the extensor carpi ulnaris, and paitially also to the extensor brevis minimi digiti. § 1253. It is sometimes double. III. ANTERIOR MUSCLES. § 1254. On the anterior face of the leg we find one after another the extensor longus digitorum communis, the extensor longus hallucis proprius, and the tibialis anticus. I. EXTENSOR LONGUS DIGITORUM COMMUNIS. § 1255. The extensor longus digitorum communis muscle, Peroneo- sus-phalangettien commun, Ch. (JVf. extensor digitorum communis lon- gus), is a very long muscle,,occupying almost all the leg. Its fibres descend obliquely from behind forward. It arises above from the outer face of the head of the tibia, and, in the rest of its course, from the anterior face of the interosseous ligament, and also from the anterior edge of the fibula. It is attached to the tendon which commences near its upper extremity and which descends on its anterior edge. This tendon generally divides below the crucial ligament of the foot into five slips, which separate from each other. The outer is the shortest, and is inserted into the posterior extremity of the upper face of the fifth, and sometimes also of the fourth, metatarsal bone. This slip is sometimes connected with a special fleshy belly entirely distinct MYOLOGY. 167 from the extensor longus,but which most generally forms only the lower part, and which is called the small or the peroneus tertius muscle. It is not unfrequently deficient, and is then replaced to a certain extent by the inner part of the tendon of the peroneus brevis muscle: it also frequently forms a small special tendon which is sometimes attached forward to the metatarsal bone, and sometimes unites either to the fourth external interosseous muscle or to the tendon sent by,the common extensor to the fifth toe. The four other slips go obhquely forward and outward ; they are attached to the dorsal faces of the second, third, fourth, and fifth toes. Arrived at the base of the poste- rior phalanges they become broader and a httle thinner, and give off also, the fourth outwardly, the other three inwardly, a thin triangular prolongation, formed of perpendicular fibres, which go downward, and are attached partly to the base of the first phalanx, and are partly blended with the tendon of the interosseous muscles. This tendon sometimes assumes the nature of cartilage when pass- ing over the synovial capsule of the first phalangean articulation. On the articulation between the second and third it enlarges or divides more or less completely into two lateral slips, which converge forward, and after uniting are attached to the upper face of the third phalanx, directly before its posterior edge. We find an oblong mucous bursa on the articulation of the foot, between the tendon of this muscle and the capsular ligament. The extensor digitorum communis longus raises the four smaller toes, extends them, and with the peroneus brevis muscle, bends the tibio- tarsal joint, and thus raises the foot or draws the leg forward and down- ward. This muscle and the preceding act principally in standing on the toes, because they fix the leg. The extensor digitorum communis longus corresponds to the com- mon extensor of the fingers. The proper extensov of the little finger is represented by the peroneus tertius, and when that is deficient by a part of the peroneus brevis. This analogy becomes still more evident when the portion of the flexor longus belonging to the little toe, and the peroneus tertius muscle, are entirely separated from the rest of the muscle.(1) II. EXTENSOR LONGUS HALLUCIS PROPRIUS. § 1256. The extensor longus hallucis proprius muscle, Peroneo sus- phalangettien du pouce, Ch., is a thin and semipenniform muscle, which arises, by fleshy fibres, from the lower two thirds of the inner face of the fibula, and from the anterior face of the interosseous ligament. It also receives below some fibres from the outer face of the tibia. Its fasciculi are attached to a tendon which proceeds along the anterior edge of the muscle, gradually becomes broader, passes across a particular groove of the crucial hgament of the back of the foot, goes (1) Brugnone, loc. cit.—We have seen it several times. 168 DESCRIPTIVE ANATOMY. inward and forward along the inner edge of the tarsus, and is attached to the upper face of the ungu^al phalanx of the first toe. On the back of the tibio-tarsal articulation the tendon of this muscle is inclosed in a special mucous sheath. It raises all the first toe. § 1257. This muscle is often more or less completely double. In this case we sometimes find another which is smaller, and which arises more externally from the fibula, and from the anterior face of the inter- osseous ligament, goes to the large toe, and unites to the tendon of this muscle, or > attached to the first metatarsal bone, or finally loses itself in the cellular tissue. Sometimes and most generally another smaller tendon is detached, even in the leg, from the inner edge of the normal tendon, which is inserted in the tibial side 6f the two phalanges. These anomalies are important because they approximate the forma- tion of the proper extensor of the large toe to that of the proper exten- sor of the thumb; so too on the other hand, the deficiency of the short extensor of the thumb, or its blending with the large, approximates the formation of the hand to that of the foot. III. TIBIALIS ANTICUS. § 1258. The tibialis anticus muscle, Tibio-sus-tarsien, Ch. (JVf. tibi- alis, s. tibiaus anticus, s. catena musculus, s. hippicus), is the strongest of the three anterior muscles of the leg; it arises directly at the side of the peroneus longus muscle, and is covered in this place by a broad tendon, which expands on its anterior face from the lower face of the outer part of the head of the tibia, and still lower from the outer face of this bone, nearly to its lower third, so that its fibres gradually come only from the most posterior portion, and even the inner edge of this face in all its course. At the same time it receives some which arise from the periosteum. All these fibres, which go obliquely forward, are attached to an anterior tendon, which is loose only in a very small point of its extent downward, but which extend within the muscle even beyond its centre. This tendon, which is very strong, descends obliquely inward, passes on the anterior face of the tibio-tarsal articu- lation, comes upon the inner edge of the foot, where it is retained by a ligamentous band, obhque downward and backward, which extends from the scaphoid to the first cuneiform bone, and is finally attached by two short slips to the inner part of the lower face of the large cune- iform bone,' and also to the base of the metatarsal bone of the large toe. Opposite the articulation of the foot its tendon is enveloped in a mucous sheath. It raises the foot, turns it on its axis, so that its sole looks inward and its inner edge upward. It corresponds to the radiales muscles of the hand. MYOLOGY. 169 ARTICLE FIFTH. MUSCLES OF THE FOOT. § 1259. The muscles of the foot arise from the tarsus and metatarsus, and are all attached to the phalanges of the toes. They are situated on the back of the foot, on its sole, on its internal and external edges. Some are common to several toes, others belong exclusively to some of them, namely to the large and small toes. The latter are only repetitions of those which are divided between several of them. I. MUSCLES OF THE BACK OF THE FOOT. § 1260. Besides the tendons of the extensor digitorum communis longus and of the two peronei muscles, we find also on the back of the foot the extensor communis digitorum brevis. EXTENSOR COMMUNIS DIGITORUM BREVIS. § 1261. The extensor communis digitorum brevis muscle, Calcaneo- sus-phalangettien commun, Ch. (JVf. extensor digitorum pedis communis brevis, s. pediaus externus), is a flat muscle, formed of four elongated and rounded bellies, which arises from the back of the anterior process of the calcaneum, goes forward and inward, its bellies separating from each other, and is attached by four tendons to the four inner toes. These tendons in their course on the metatarsus cross those of the extensor communis digitorum longus, but on the toes they are situated on the outside of them. The outer three are very intimately blended, by their internal edge, with the outer edge of the tendons of the extensor longus, and consequently form their outer half; but the most internal, that which goes to the great toe, does not unite to the corresponding tendon of the flexor longus, but is attached below it to the posterior edge of the back of the first phalanx of the large toe. This muscle extends the four inner toes and directs them a little outward. § 1262. Often and even most generally its inner belly is separated much more from the others than the latter are from each other. Very frequently it forms an entirely distinct muscle, which deserves to be noted because of the more striking resemblance established between the upper and lower extremities by this peculiarity. Sometimes the other bellies and even all are entirely detached from each other, a curious analogy with what exists in birds. Again, the extensor brevis often presents supernumerary belhes. Most commonly a small fleshy fasciculus exists between the internal and what is commonly called the second ; its tendon is attached either to the second metatarsal bone or to the tibial face of the second toe. This accessory muscle, men- Vol. II. 22 170 DESCRIPTIVE ANATOMY. tjoned by Albinus,(l) and which we have often seen, is curious, as it must evidently be considered as a repetition of the indicator muscle. The second belly is also sometimes divided at its anterior extremity into two fasciculi, or sends two tendons to the second toe. The tendons of the third and fourth bellies are often divided, so that there is for the third toe an extensor muscle or at least a tendon; this arrangement resembles the doubling of the proper extensor of the index finger in the hand for a proper extensor of the third finger. After this anomaly the one most frequently found consists in the presence of a small special belly for the fifth toe. We have also seen this several times, and it is interesting as an analogy either with the apes(2) or with the extensor proprius minimi digiti. II. MUSCLES OF THE SOLE OF THE FOOT. § 1263. Most of the muscles of this part of the lower extremity are found in the sole of the foot.(3) In fact, besides the short head of the extensor digitorum communis already described (§ 1245), we find the flexor communis digitorum brevis, the adductor and flexor of the large and little toes, the adductor hallucis, the lumbricales, and the interossei muscles. The adductor hallucis occupies the inner edge of the foot and that of the httle toe the outer edge. A great part however of these muscles project likewise in the sole, so that it is best to study them at the same time as the other muscles of the toes, to which they belong, and to consider them as the lower muscles of the foot. We shall describe first the common muscles, next the special mus- cles : first, however, their common aponeurosis. I. PLANTAR APONEUROSIS. § 1264. The plantar aponeurosis (aponeurosis plantaris) is a very firm tendinous layer, formed of longitudinal fibres, which arises from the lower face of the tuberosity of the calcaneum, directly under the skin, with which it is intimately connected. Thence it goes forward, where it enlarges very much. Arrived at the anterior edge of the metatarsus it divides into five shps, which correspond to the five toes, and which are attached to each other by transverse fibres. This aponeurosis protects and fixes the muscles of the sole of the foot, and at the same time increases the surfaces of insertion of several. (1) Hist, muse., p. 602. (2) Meckel, Beytrdge zur vergleichenden Anatomie, vol. ii. part i. (3) A. F. Walther, Tractationes de artvculis, ligamentis et musculis incessu diri- gendis supplemenlum tabulamque novam plantce humani pedis exhibens, Leipsic, 1731.—D. C. de Courcelles, Icones musculorum plantce pedis, sorumque descriptio, Amsterdam, 1760. MYOLOGY. 171 II. COMMON MUSCLES OF THE SOLE OF THE FOOT. a. Flexor digitorum pedis communis brevis. § 1265. The flexor communis digitorum brevis muscle, Calcaneo- sous-phalanginicn commun, Ch. (JVf. flexor digitorum pedis communis brevis, s. perforatus, s. sublimis, s. pediaus internus), is elongated, quadrilateral, thicker behind, and broader but thinner before. It arises by very strong tendinous fibres, which extend on a considerable portion of its lower face from the lower face of the tuberosity of the calcaneum, and by fleshy fibres by almost all its lower face, from the upper face of the plantar aponeurosis, to which its posterior tendon also adheres. Posteriorly it is very intimately united internally with the outer edge of the adductor pollicis, and above with the short head of the extensor communis digitorum longus. Nearly in the centre of the sole of the foot it divides into four very short fleshy fasciculi, which soon become as many single tendons. The latter are attached to the second, third, fourth, and fifth toes. They cover those of the extensor longus and are much smaller. They are arranged in the same manner anteriorly as those of the extensor digitorum sublimis. In fact a rhomboidal fissure begins a little before the posterior extremity of the first phalanx, which extends to before the centre of this bone. The tendons of the extensor communis digitorum profundus pass through these fissures. The two halves of the tendon which pass through this division unite for a short extent; then again separate, enlarge and diverge from before backward, and are separately attached by straight edges to the centre of the lower face of the second phalanx. Each tendon of this muscle is attached with the corresponding tendon of the flexor longus, to the lower face of the toes by synovial and fibrous ligaments, exactly like those which retain the tendons of the flexor sublimis and profundus of the fingers. This muscle flexes the first and second phalanges of the four outer toes. § 1266. The fourth tendon is sometimes deficient, and then it is often but not always replaced by a tendon of the flexor longus. In some subjects there seems to be an antagonism between the short extensor and the short flexor of the toes ; for we have sometimes found in this case the number of tendons of the second is greater than usual. Sometimes also another portion of the muscle is deficient; it is usually the most internal or the most external. It is then replaced by other fasciculi which come from the flexor of the large and that of the little toe, which reminds us of the insulation of the internal head of this muscle in apes, and the disappearance of the short common flexor as a separate muscle in all the other mammalia and in all birds. 172 DESCRIPTIVE ANATOMY. b. Lumbricales. § 1267. The lumbricales muscles, Planli-sousphalangiens, Ch., correspond to those of the hand in number, form, and situation. They arise by fleshy fibres from the tendons of the flexor digitorum longus, and are attached, partly by short tendons, to the posterior head of the first phalanx of the four outer toes, and partly by thin tendinous ex- pansions, to the tendons of the extensor digitorum longus. c. Interossei. § 1268. We find in the foot as in the hand seven interossei muscles, JVEetatarso-phalangiens lateraux, Ch. (JVf. interossei), which fill the intervals between the metatarsal bones. They arise from the posterior part and from the lateral faces of these bones, and their anterior tendons blend below with those of the extensor communis. We distinguish them into external and internal. The first are four and the second three in number. a. External interossei. § 1269. The upper and external or dorsal interossei muscles (JVf. interossei externi, s. superiores, s. dorsales) are situated directly below the extensor communis digitorum brevis, in the first, second, third, and fourth interosseous spaces. The first, which is the most internal, differs from the other three in its form and arrangement. In fact it comes only from the tibial side of the second metatarsal bone and is attached forward by a short, broad, and flat tendon to the inside of the first phalanx of the second toe. It is however almost always divided into two heads, the upper of which is longer and much thinner than the lower. The second, third, and fourth have two heads each, which are in- serted by short tendons on the outer or fibular side of the first phalanx of the second, third, and fourth toes. The outer head is much larger, arises from the posterior part of the inner face of the metatarsal bone, which is placed directly on the out- side of the toe to which the tendon is attached, and descends as deeply as the internal, on the side of the sole of the foot. The inner is the smallest, and arises from the posterior part of the outer face of the me- tatarsal bone of the toe in which its tendon is inserted, and descends a little lower than the preceding. The fibres of these two heads unite at a very acute angle and are implanted in a common tendon. The first external interosseous muscle brings the first toe inward; the second, third, and fourth carry the toes to which they are attached outward. MYOLOGY. 173 6. Internal interossei. § 1270. The internal, inferior, or plantar interossei muscles (JVf. interossei interni, s. inferiores, s. plantares) are smaller than the exter- nal and have only one head. They arise from almost all the posterior part of the inner or tibial face of the third, fourth, and fifth metatarsal bones, and are attached by a considerable tendon to the inner face of the first phalanx of the third, fourth, and fifth toes. This tendon is closely united to the capsule of the metatarso-phalangean articulation, and sends a prolongation to that of the extensor communis. These muscles direct the third, fourth, and fifth toes inward toward the large toe. III. PROPER MUSCLES OF THE TOES. § 1271. We may consider as proper muscles those of the large and small toes. a. Muscles of the large toes. a. Abductor hallucis. § 1272. The abductor hallucis muscle, JVEetatarso-sous-phalangien du premier orteil, Ch., is the strongest short muscle of this toe. It arises by several slips from the inside of the tarsus and the metatarsus, and is attached to the inside of the large toe. To simplify the descrip- tion, we may refer these several shps to two heads. The posterior head, which is the larger, arises by two bands, of which the inferior is longer, from the lower part of the inner side of the tuberosity of the calcaneum, and the upper, which is shorter, from the upper and projecting part of the inner face of the body of the calca- neum. The anterior head, which is the smaller, arises by three or four dis- tinct shps from the inner and anterior face of the astragalus, scaphoid, the first cuneiform, and first metatarsal bone. The posterior tendon of these two fasciculi covers them from their origin to near their anterior extremity below. The anterior, which is much stronger, begins near the centre of the posterior belly and is situated on its inner side ; so that the fibres of the two bellies which go forward and inward are inserted at acute angles. This last tendon, after it disappears from the surface, extends very far within the muscle, whence it goes backward and divides into seve- ral very considerable shps. Anteriorly, it is sometimes attached by two shps to the lower and inner face of the head of the first metatarsal bone, to the inner face of the capsular ligament of the first me- tatarso-phalangean articulation, and principally to the inner and lower 174 DESCRIPTIVE ANATOMY. part of the base of the first phalanx of the large toe, where it adheres intimately to the flexor digitorum brevis. This muscle brings the large toe inward and flexes it a little. b. Flexor brevis pollicis pedis. § 1273. The flexor brevis pollicis pedis, Tarso-sous-phalangien du premier orteil, Ch. (JVf. flexor hallucis proprius brevis), is much shorter than the abductor. It arises behind from the tendinous sheath of the peroneus longus, intimately united to the long head of the adductor of the large toe. Most generally its posterior extremity may be divided into an external and an internal belly. Thence it goes inward and forward. It is attached by a short tendon, more or less divided, to the posterior part of the lower side of the base of the first phalanx of the large toe. This tendon is generally united to that of the adductor out- ward ; it contains anteriorly, below the two parts of the head of the first metatarsal bone, two sesamoid bones placed one at the side of the other. This muscle flexes the first phalanx of the large toe. c. Adductor pollicis pedis. § 1274. The adductor pollicis pedis muscle, Calcaneo-sous-phalan- gien du premier orteil, Ch. (JVf. adductor hallucis), is a considerable muscle which has two bellies. The posterior is much stronger than the other and is placed above and outside of the flexor brevis pollicis pedis. It arises from the lower side of the base of the third and fourth and also often of the second me- tatarsal bone, and from the sheath of the peroneus longus, above the flexor brevis pollicis pedis. Before, on its outer and lower face, are strong tendinous expansions, which unite to give rise to the anterior tendon. This latter is united to the external tendon of the flexor brevis (§ 1212), and is attached to the outer face of the base of the first meta- tarsal bone. The anterior head is much smaller and weaker than the posterior, and arises from the lower and inner face of the capsular ligament, be- tween the metatarsal bone and the first phalanx of the fourth and fifth toes, sometimes also from the anterior part of the fifth metatarsal bone. It goes obliquely forward and inward, directly below the anterior end of the interossei muscles, between these and the tendons of the flexor communis digitorum profundus. It is attached by a thin and short tendon to that of the abductor of the great toe. MYOLOGY. 175 b. Muscles of the little toe. a. Abductor minimi digiti. § 1275. The abductor minimi digiti muscle, Calcaneo-sous-phalan- genien du petit orteil, Ch. (JVf. abductor digiti quinti), is the longer of the two muscles of this appendage, has two bellies like the abductor pollicis pedis ; the posterior belly is greater. The posterior belly is covered below and behind by a strong aponeu- rosis, and arises from the posterior and from a little of the anterior part of the lower face of the tuberosity of the calcaneum. The anterior belly comes from the lower edge of the tuberosity of the fifth toe. Both are attached outwardly to a broad and strong tendon, which extends far back into the substance of the muscle and which is attached to the outer part of the lower face of the base of the first phalanx. b. Flexor minimi digitf brevis. § 1276. The flexor minimi digiti brevis muscle, Tarso-sous-phalan- gien du petit orteil, Ch. (JVf. flexor digiti quinti proprius brevis), is much smaller than the preceding. It arises from the inner part of the lower side of the base of the fifth metatarsal bone and from all the lower face of its body. It may almost always be divided into an outer and inner belly. Most frequently also it is attached by two distinct tendons to the inner part of the lower side of the base of the first phalanx. § 1277. The muscles of the large and small toes may be referred to the other muscles of the foot, as we have seen those of the thumb and little finger could be to the other muscles of the hand. The abductor pollicis pedis is the first external interosseous muscle, and the posterior belly of the abductor the first internal interosseous muscle. The ante- rior belly of the latter represents the first lumbricalis. The flexor bre- vis digitorum pedis muscle corresponds to the flexor digitorum com- munis. The abductor minimi digiti is the last external interosseous muscle. Finally, the flexor minimi digiti brevis may be considered as belonging to the flexor digitorum communis, because of the slight de- velopment of the fourth tendon of the latter in most subjects. COMPARISON OF THE MUSCLES OF THE DIFFERENT REGIONS OF THE BODY. § 1278. We have already compared the muscles of the different regions of the body with each other in different directions, while de- scribing each one particularly. They also conform to the law that the analogy betweeen the upper and lower halves of the body is more marked than that between the anterior and posterior. In fact we ob- serve, 1st, that many muscles which succeed from above downward 176 DESCRIPTIVE ANATOMY. are repetitions of one another, as is evident with those between the vertebrae or between these bones and the head ; 2d, the muscles of the limbs correspond very evidently, and the differences they present, like those between the bones and the ligaments, depend on the greater solidity of the lower limbs and the greater mobility of the upper, either when considered as a whole and in their relations with the trunk, or when viewed in detail and in regard to the relations of their different parts with each other. An abnormal arrangement of the muscles belonging to the two extremities frequently renders their similitude more perfect and more evident than it is generally ; and if we do not err, of all the organic systems, the muscular most frequently presents anomalies in the configuration, which cause an unusual similitude be- tween the anterior and posterior faces of the body and also between its upper and lower portions. In this respect we often find an anterior sternal muscle, which de- termines a resemblance between man and animals, and the existence of which is so curious in another respect; and we not unfrequently find a short head of the biceps flexor cubiti and a short extensor of the middle finger. So too the muscles of the lower limbs are frequently repetitions of those of the upper. The latter however seem to us more disposed to present assimilating anomalies in their configuration, which probably depends on a general law, amply supported by the vascular system, viz. that anomalies in the pelvic members are more frequent than in the pectoral extremities. GENERAL REMARKS ON THE MOTIONS OF THE HUMAN BODY. § 1279. Having described successively the different organs of loco- motion, we must now briefly examine the principal motions(l) which result from their joint action. We must first endeavor to prove that the erect posture on the lower limbs is natural to man. A. ERECT POSTURE. I. OSSEOUS SYSTEM. § 1280. We may also point out in this place the conditions which arise from the other organic systems, not yet described, and which refer to the general form of the body, because the osseous system serves as the basis for all the others. In considering the body from below upward, we discover successively in the osseous system all the conditions which render the erect posture natural to man. (1) F. Roulin, Recherches theoriques et experimentalessur le mecanisme des mouve- ments et des attitudes dans I'homme; in the Journ. de physiol. cxp., vol. i. p. 209, 301, vol. ii. p. 45, 156, 283. MYOLOGY. 177 I. In the lower extremities. § 1281. 1st. The predominance of the bones of the lower over those of the upper extremities. 2d. It is only in the erect posture that the articular surfaces of all the bones are exactly fitted to each other. 3d. The breadth of the foot. 4th. The size of the tarsus and metatarsus in proportion to the toes. 5th. The number and size of the sesamoid bones. 6th. The union of the bones of the leg with the tarsus at a right angle. 7th. The length and the obliquity of the neck of the femur. 8th. The breadth, concavity, and lowness of the iliac bones. 2. In the trunk. § 1282. 1st. The lowness, breadth, and curve of the sacrum, and also the curving inward of the coccyx, upon which and also on the arrangement of the iliac bones the peculiar shape of the human pelvis depends, which seems well adapted only for the erect posture. 2d. The breadth and lowness of the vertebrae. 3d. The considerable curve of the ribs, whence results the breadth and convexity of the thorax. 3. In the head. § 1283. 1st. The anterior, posterior, and horizontal position of the condyles and foramen magnum of the os occipitis. 2d. The direction of the cavities of the orbits and nose forward in the erect posture and downward in that on the four limbs. 4. In the upper limbs. § 1284. 1st. The shortness and feebleness of these members in pro- portion to the lower. 2d. The forced position of the bones of the fore-arm and of the radio- carpal articulation in walking on all fours. 3d. The mobility of the radius. 4th. The concavity and breadth of the bones of the metacarpus and of the phalanges. These latter circumstances indicate that the bones of the upper extremities are intended to grasp external objects, while the corresponding parts of the lower limbs prove they are designed to support the body. Vol. II. 23 178 DESCRIPTIVE ANATOMY. II. LIGAMENTOUS SYSTEM. § 1285. The peculiarities of the ligamentous system are as follow : 1st. The ligaments of the lower extremities are stronger than those of the upper, and this strength increases progressively from below upward. 2d. The looseness of the cervical ligament, although the head is very much developed, in regard to the occipital foramen which is situated farther forward. III. MUSCULAR SYSTEM. § 1286. The muscular system also furnishes several strong argu- ments : 1st. The greater power of the muscles of the lower extremities. 2d. The extreme force and the arrangement of some of them, viz. a. The thickness of the peronei muscles in the leg, the lower head of which always draws the leg backward and extends it, while the upper two prevent the body from falling forward. b. The arrangement of the flexors of the leg compared with that of the flexors of the fore-arm ; for one of the three long flexors of the first of these limbs is manifestly developed only in part; so that the number of the corresponding muscles in the fore-arm is much greater than in the leg. c. The thickness of the gluteei muscles, particularly the glutaeus maximus. d. The multiplication of the muscles of the fore-arm to execute the peculiar motions of the bones of the fore-arm: so likewise the differ- ence between the number and development of the special muscles of the thumb and little finger and those of the large and small toes. e. The deeper situation of several of the muscles of the fore-arm in the upper extremity, and the foot only in the lower : such are particu- larly the flexor brevis and the extensor communis brevis. /. The slight extent of the insertion of the flexors of the leg, which favors the extension of this limb and prevents the continued forced flexion it experiences in quadrupeds. g. The smallness of the small muscles of the head, which, in con- nection with the looseness of the cervical ligament and the anterior position of the occipital foramen, forms a very striking character, espe- cially when we regard the great development of these parts in quadru- peds, the head of which is however smaller than that of man. § 1287. All these circumstances united prove sufficiently that the erect posture on the lower limbs is natural to man. We must next examine how the erect posture is preserved in a state of repose, and how the body when erect exercises the motion of progression, or of standing and o{ walking, treating of the modifications of each. MYOLOGY. 179 B. OF STANDING. § 1288. The trunk and the lower limbs act in standing. The part taken by the trunk consists, 1st. In the support of the head by the vertebral column. 2d. In the action of the very strong long muscles of the back which fill the channels between the vertebras and the ribs. They prevent the body from falling forward, to which it is in some measure disposed from the portion of the pectoral and abdominal viscera before the verte- bral column. In fact, they are much more developed in their lower part than at their summit. In this part also we'feel fatigue and pain most sensibly after standing a long time and especially after leaning forward. The trunk is supported by the lower extremities. Whenever the position changes the pelvis presents a broad point of support for its weight, and that of the head which is sustained by the vertebral column. The articulation of the ossa femoris with the iliac bones in front of their union with the spine increases the extent of this base of support. In standing, the weight of the body passes from this base to the thigh, next to the leg, and finally to the foot, so that the body rests upon the latter. In the usual position on the two feet, besides the peculiarities relative to the lower extremities and which we have mentioned above, their separation caused by the breadth of the pelvis and the length of the neck of the thigh bones is very advantageous, as it increases the extent of the base of support which falls between the soles of the feet; thus the attitude becomes unsteady and less firm when the breadth is diminished by approximating the feet. Standing, inasmuch as it depends on the lower limbs, results from the action of all the muscles which arise from the trunk, and from the different sections of these members. These muscles contract from above downward, and thus move the divisions immediately above them, and act in a direction the inverse of that which results in pro- gression, since they approximate the least movable point to that which is most movable. Thus the most active are, 1st, the glutaei, which draw the trunk backward; 2d, the three flexors of the leg, which prevent the pelvis from inclining forward ; 3d, the extensors of the thigh, except- ing the rectus, which prevent the limb from falling backward ; 4th, the lower head of the triceps suras, which keeps the leg on the foot in a direction intermediate between flexion and extension. The other muscles, which confine the action of those we have men- tioned, have little or no action, and this action is counteracted by that of the others. Standing on one foot, where the whole weight of the body rests on one of the lower extremities, is practicable, especially by the length of the 180 DESCRIPTIVE ANATOMY. neck of the femur and the breadth of the sole of the foot. This posture of the body is preserved by the action of the muscles on the outside of the lower limbs, by the broad abdominal muscles, and by the quadratus lumborum, which act from below upward, preventing the body from falling to the opposite side, where it is unsupported. In standing on the toes there is no change except in the relations of the bones of the leg and the action of its muscles. The toes are ex- tended as much as possible on the metatarsal bones and the foot on the leg, and the weight of the body then rests wholly on the toes and also on the sesamoid bones of the foot, which are numerous and large. This position is caused principally by the simultaneous ac- tion of the muscles situated on the anterior and posterior faces of the leg and foot; the tibialis anticus, the peronei, especially the peroneus brevis, the extensors of the toes anteriorly, and the triceps sura posteriorly, are the principal agents. At the same time the toes are forcibly pressed against the ground by the action of their flexors, hence they are more firmly fixed and afford a more solid point of attachment to their muscles. C. OF WALKING. § 1289. Walking is produced by the displacement of the lower extremities, which move alternately either forward, backward, or laterally, so that a distance exists between them, and consequently the rest of the body is supported by only one of them. Each motion, by which a limb is raised from the ground, separated from the other, and is replaced on the ground, is a step. This motion, in whatever direction it is performed, depends princi- pally on the displacement of the femoral articulation, which is flexed in walking forward or sideways, and, on the contrary, extended in walking backward. When we walk forward or backward the knee-joint is generally slightly bent, which serves to raise the foot still more. The metatarso- phalangean joint is most generally forcibly extended, articular when the lower limb which is to be moved is behind the other. In walking, the flexion of the haunch carries one of the two limbs more or less before the other; when left to itself, and the coxo-femoral articulation is not bent, the foot falls again to the ground and the step is finished. If we take long steps the pelvis also turns more or less around the limb which remains fixed as around an axis; hence the limb which moves, and the corresponding side of the body, are carried farther for- ward. This effect is caused partly by the flexion of the other sections of this limb and partly by the extension of the metatarso-phalangean articulation. It is merely necessary to mention these motions to know the muscles which perform them. MYOLOGY. 181 Running is a quick walk, most generally withlarge steps, which differs from the ordinary walk not only by its rapidity, but also because all the lower face of the foot rests on the ground. Jumping is a sudden movement by which the body rises into the air. In order to perform it all the joints of the lower limbs are flexed and then suddenly extended ; from the shock which the body expe- riences from the soil against which it strikes it is carried upward until its weight exceeds the motion communicated to it, and causes it to return to the earth. The leap in a straight hne is always shorter than the oblique leap because the weight of the body presents more resistance in the first case than in the second. In kneeling the articulation of the foot is flexed by the anterior muscles of the leg, which act from above downward, and the articula- tion of the knee is changed in the same manner by the action of the upper heads of the triceps suras muscle. In stooping the gastrocnemii muscles of the leg exercise all their power; at the same time the coxo-femoral articulation is flexed more or less forcibly in order to lean the body forward, and to prevent its centre of gravity from falling behind its base of support, and in this manner to prevent its fall. § 1290. The motions of the trunk(\) are very limited. This is proved by the vertebrae and also by the pieces of the sternum, which are firmly united. Thus the motions of the trunk in every direction depend but slightly on the displacement of the bones which form it, but almost entirely on the lower limbs, and those in the coxo-femoral articula- tion, are performed by the muscles which extend from the thigh and leg to the vertebral column and to the iliac bones. The mobility of the ribs is much greater ; the changes in their situation produce the con- tinual alternate changes which take place in the capacity of the chest, and which result in inspiration and expiration. The examination of these changes and of those which occur in the capacity of the abdo- minal cavity will be more in place after describing the pectoral and abdominal viscera than here. § 1291. The head moves on the vertebral column; it bends forward, is extended backward, inchnes to the side, and turns on its axis. The last two motions take place almost entirely between the second and first vertebras, the last of which only accompanies the head. The other two occur between the head and the atlas, and not between the atlas and axis, because the odontoid process and the transverse portion of the crucial ligament almost entirely prevent every displacement in this direction between the first and second vertebras. Luxation cannot take place in flexion and extension on account of the firmness of the attachments ; but it easily supervenes in the rota- (1) Winslow, Sur les mouvemens de la tete, du cou et du reste de I'evine du dos, in the Mem. de Paris, 1730, p. 492-508. 182 DESCRIPTIVE ANATOMY. tion of the first vertebra and of the head on the axis, when this motion is performed quickly. The cervical portion of the vertebral column must always be fixed in order that these different motions may be executed. § 1292. Thekupper limbs are much more movable than the lower both in regard to the trunk and their different sections, which doubtless depends on the arrangement of these bones and the ligaments. The motion of rotation on the axis particularly is much easier in the first than in the second. The greater mobility of the upper limbs, consi- dered as a whole, is also increased by the difference remarked in the mode of articulation, of the first section of the bones of the two extre- mities, for the iliac bones are almost motionless on each other and on the vertebral column, while the clavicle and scapula on the contrary are very movable both on each other and on the trunk. Hence the motions of the upper limbs are not performed solely in the scapulo-humeral joint as those of the lower extremities are in the coxo-femoral articulation, but take place at the same time in the sca- pulo- and sterno-clavicular articulations ; hence they are not only more free, but also keep the bones together in the different motions they perform. Hence the bones are much less firm, but they require less strength, since the upper extremities are rarely obliged to sustain such heavy loads as happens for instance in creeping, walking, or standing on the hands. If we except the fingers and toes, mobility diminishes from the peri- phery of the limbs to their centres. A great difference between the partial motions of the two limbs consists in the power of turning the radius on its axis and around the ulna, while the leg cannot move around the thigh, except as a whole, the fibula being immovable on the tibia. The leg is capable only of flexion and extension, while the fore-arm can execute also the motions of pronation and of supination.(1.) Although in the two latter motions the radius is the principal part displaced, the ulna is not however motionless; for it is slightly ex- tended in pronation and a little flexed in supination. (1) Winslow, Obs. anat. sur la rotation, la pronation, la supination et d'autres mouvemens en rond, in the Mem. de Paris, 1727, p. 25-33.—Vicq d'Azyr. (Buvrcs, vol. v. p. 343-351. ANGEIOLOGY. 183 BOOK IV. ANGEIOLOGY. § 1293. The vascular system(l) is composed of a central part, the heart, whence all the blood departs and where all this fluid returns; of vessels which carry it away, the arteries; and of vessels which (1) We have already mentioned (vol, i. p. 280) the most important works on the general conditions of the structure and external form of the vascular system in the normal and abnormal state. We shall now mention the principal descriptive treatises. They are, I. For the whole system.—J. C. A. Mayer, Anatomische Beschreibung der Blutgefasse des menschlichen Korpers, Berlin, 1777, 1778.—F. A. Walter, Angiologis- ches Handbuch, Berlin, 1789. II. For the heart.—1st. Complete description of this organ in all its parts, both in the normal and the abnormal state; Senac, Traite de la structure du cceur, de son action et de ses maladies, Paris, 1747, 1778.—2d. Complete description of it in the normal state; R. Lower, Tractatus de corde, item de motu colore et transfusions sanguinis, London, 1669.—J. N. Pechlin, Defabricaet usu cordis, Kiel, 1676.—Wins- low, Sur les fibres du ceur et sur ses valvules, avec la maniere de le preparer pour le demontrer, in the Memoires de Paris, 1711, p. 196, 201.—Vieussens, Traite de la structure et des causes du mouvement natural duceur, Toulouse, 1711.—Santorini, Obs. anat., Venice, 1724, ch. viii., Deiis quae in thoracemsunt.—Lieutaud, Obs. anat. sur le ceur, in the Mem. de Paris, 1752, 1754.—3d. Development of the heart; Meckel, Sur Phistoire du developpment du casur et des poumons dans les mammiferes, in the Journal complem. du Diet, des sc. midic, vol. i. p. 259.—Rolando, Sur la for- mation du cceur et des vaisseaux arteriels, veineux et cajnllaires, same journal, vol. xv. p. 323, vol. 16. p. 34.—Prevost et Dumas, Developpment du ceur et formation du sang, in the Annates des sciences naturelles, vol. iii. p. 46.—4th. Structure of the heart in respect to the arrangement of its fibres ; C. F. Wolff, Dissertationes de ordine fibra- rum muscularium cordis, in the Act. Acad. Petropol., 1780-1781, in the Xova act., vol. i.-viii.—J. F. Vaust, Recherches sur la structure et les mouvemens du ceur, Liege, 1821.—S. N. Gerdy, Memoire sur t'organisation du ceur, in the Journ. compl. du Diet, des sc. med., vol. x. p. 97.—5th. Pathological state ; A Burns, Observations on some of the most frequent and important diseases of the heart, London, 1809.—Pelle- tan, Mcmoires sur quelques maladies et vices de conformation du ceur, in the Clinique chirurgicale, Paris, 1810, vol. iii.—Testa, Delle malattie del cuore, loro cagioni, specie, cura, Bologna, 1810,1813.—Corvisart, Essaisur les maladies etles lesions organiques du ceur et des gros vaisseaux, Paris, 1818.—Kreysig, Ueber die Herzkrankheiten, Berlin, 1814, 1817.—Laennec, Delauscultation mediate, or Traite du diagnostic des maladies des poumons et du ceur, Paris, 1819, p. 195-445.—Bertin, Traite des maladies du ceur et des gros vaisseux, Paris, 1824. III. For the arteries.—Haller, Icones anatomice, Gottingen, 1745, 1756.—A. Murray, Descriptio arteriarum corp. humani tabulis redacta, TJpsal, 1783, 1798.—J. F. S. Posewitz, Physiologie der Pulsadern des menschlichen Korpers, Leipsic, 1795. —J. Barclay, A description of the arteries of the human body, Edinburgh, 1818, 8vo. —Tiedmann, Tabulce arteriarum corporis humani, Carlsruhe, 1822,1824.—Hodgson, Diseases of the arteries and veins. IV. For the veins.—Besides the tables of Loder see Breschet, Sur le systeme veineux, now publishing. V. For the Lymphatics.—The works mentioned in the first volume contain also a description of this system. 184 DESCRIPTIVE ANATOMY. return it, the veins and the lymphatics. The last mentioned carry a fluid different from the blood, they are the annexes or appendages of the venous system. SECTION I. OF THE HEART. CHAPTER I. GENERAL REMARKS. § 1294. The heart (cor) is a hollow muscle irregularly conical or pyramidal, situated in the centre of the chest, between the two lungs, and inclosed in a special envelop called the pericardium. Its vessels are numerous, but it has few nerves ; it is formed of several cavities, some of which are separated, while others communicate together. Its tissue is formed of fibres united in superimposed layers, and is connected on one side with the large venous trunks of the lungs and body, and on the other with the large arterial trunks of both. Each of these characters deserves to be specially considered. I. FORM. § 1295. The shape of the heart is that of a cone or an irregular pyramid. We distinguish in it a broad and thick base (basis) and a summit (apex), which is generally blunt and bifurcated, an upper and anterior face which is concave, and an inferior and posterior which is smaller and flatter; two edges, a posterior which is thick and pointed, the anterior is smaller, shorter, thin, and sharp. The base of the heart is formed, properly speaking, by that part of the organ directly connected with the veins : we may then term it the venous portion of the heart (pars cordis venosa). However we gene- rally apply the term base of the heart to the upper region of the arterial portion. The venous portion is formed of two auricles. It is separated from the next by a large groove, called the groove of the base, the auri- cuto-ventricular groove, or circular groove (sulcus baseos, s. atrio-ventri- cularis, s. circularis). Its form is an oblong square and its breadth exceeds its height. The succeding portion, which is situated before the auriculo-ventri- cular groove, is directly connected with the large arterial trunks. We may then term it the arterial portion of the heart (pars arteriosa cordis). It is formed by the two ventricles. It terminates in a blunt summit, which is usually more or less evidently grooved. This groove is some- times very large. ANGEIOLOGY.. 185 The longitudinal groove (sulcus cordis longitudinalis superior et infe- rior) exists on both faces of the heart, from its base to its summit, and consequently in all its length. The principal branches of the nutritious vessels of the organ are situated in these grooves: they communicate on the side of the base by a groove, which descends perpendicularly between the two auricles, and on the summit by the depression observed in this place. They mark the course of the septum within the heart (septum cordis). § 1396. The septum passes also across the venous portion of the heart or the auricles as well as its arterial portion or the ventricles. It separates completely these two synonymous parts, and consequently divides the heart into a right or an anterior and a posterior or left half. That part which passes between the auricles is called the septum atri- orum, and that between the ventricles is called the septum ventriculorum. The right part of the heart is called the pulmonary heart (cor pulmonale), because the pulmonary artery arises from it, or the heart of the black blood, from the color of this fluid within it. The left is termed the aortal heart (cor aorticum), because the aorta arises from it, or the heart of red blood, from the color of the blood within it. We employ sometimes also the terms of first ventricle, to designate the anterior, and second ventricle, to mark the posterior; but these are less convenient. II. WEIGHT AND SIZE. § 1297. The weight of the heart in a fully grown man is about ten ounces ; whence it is to that of the whole body as 1 is to 200. Its length, measured from the centre of the auricles, is between five and six inches; its mean length is five and a half inches, four of which are for the ventricles and one and a half for the auricles. The breadth of the ventricles united is generally three inches at their base and that of the auricles is three and a half inches.(l) III. SITUATION. § 1298. The heart is placed obliquely from right to left, from behind forward, and from above downward; so that its base is nearly opposite (1) A knowledge of the perfectly normal proportions of the heart in the healthy state is very important to the physician, since without it he can establish no certain diag- nosis of the diseases of the central organ of the circulation. We cannot do better than to quote the following passage of Laennec on this subject: " The heart in- cluding the auricles, should be equal to, a little less, or a little larger than the first ot the subject. The walls of the left ventricle should be a little more than twice as thick as the walls of the right ventricle; they should not collapse on cuttin°- into the ventricle. The right ventricle, a little larger than the left, presenting smaller fleshy pillars, although its panetes are thinner, ought to collapse after the incision " (De I auscultation mediate, vol. ii. p. 270.) "Reason teaches and observation proves, that in a well formed subject the cavities of the heart are nearly equal; but as the parietes of the auricles are very thin and those of the ventricles are much thicker, it follows that the auricles form only one third of the whole volume of the organ or the half of that of the ventricles." (lb.) p i< Vol. II. 24 186 DESCRIPTIVE ANATOMY. the eighth dorsal vertebra, from which it is separated "by the esopha- gus and aorta, and its summit corresponds to the cartilage of the sixth rib, or to the interval, which separates it from the next. Its lower face, which is flattened, corresponds to the upper face of the central tendon of the diaphragm, and the upper to the central and left portion of the anterior wall of the chest. IV. TEXTURE. § 1299. The heart is formed of several layers of muscular fibres, situated between two thin, smooth, and polished membranes, the inner and outer membranes of the heart. The latter is the inner layer of the pericardium. The outer surface of the heart is smooth and uniform in relation to the inner, even when we have removed the outer membrane. The inner surface is very uneven and reticulated, which arises from its- being formed of numerous rounded, flat, and distinct muscles, which intercross continually and which are called fleshy pillars (trabccula carnea). The mnscular substance of the heart is generally harder, more solid, and more elastic than that of other muscles. As the arrangement of these fibres(l) differs wholly in the venous portion from what it is in the arterial portion, as it is not exactly the same in the right and left portions, and as it finally differs according to the subject, all that can be said generally may be reduced to the following corollaries :(2) 1st. The directions of the layers are more or less opposite. But in the recent state, far from being entirely separated from each other, they intercross differently ; so that all those of one portion of the heart con- stantly contract uniformly and diminish the cavity they circumscribe in every direction. The union of the different layers takes place partly by more or less manifest muscular fibres. 2d. The fibres which form the layers are united in fasciculi of va- rious sizes, which vary more or less in their origin and their direction, and which are often separated by greater or less spaces. These fas- ciculi are sometimes rounded and sometimes flattened,—a difference which seems to depend on determinate laws, since it is constant in the different regions of the heart. For instance the right and left ventricles (1) Wolff, De ordinefibrarum muscularium cordis, diss. vii. De stratis fibrarum in universum. In nov. act.petrop., vol. iii., 1785, p. 227-249.—Gerdy, loc.cit.,x>. 101.- Vaust, loc. cit., p. 102, etc. (2) Gerdy has established a law, that all the fibres, whatever is their extent, situa- tion, and direction, form webs, which are convex toward the point of the heart, and which are nearly superficial at one extremity and deep at the other; so that for instance the external or internal fibres are the same reversed, and having- passed through the thickness of the ventricle. The extremities of these muscular webs are constantly inserted in the base of the heart, around the different auricular and arte- rial orifices of the ventricles, either directly or by tendons attached to the auriculo- ventricular valves (loc. cit., p, 101). p T ANGEIOLOGY. 187 are not similar in this respect nor in regard to the arrangement of their fibres, and the same is true of other parts also. Thus the inner layers are generally rounded and form fleshy pillars. The auricular appen- dages of the auricles are formed of rounded fasciculi, and the auricles of flattened fascicuh. From this arrangement we may deduce that the firmest parts are formed of rounded fasciculi. But the fibres and the fasciculi formed by them are united by intermediate fibres, which may be distinguished with facility. The fibres and fasciculi are every where interlaced with each other, conformably with all thein voluntary muscles. They are united principal- ly in two ways : sometimes the ends of the fibres and fasciculi join, and sometimes they are united by intermediate filaments, which arise from their lateral portions. In the first case, either the fasciculi go to meet each other and the extremities of those which continue together intermix like the teeth of a saw, as is the case with the digitations of several adjacent muscles, or some fibres are attached obhquely to others at acute angles, as the fibres of the penniform muscles are implanted in their tendons, and finally, as is the case most generally, the fibres or fasciculi which go side by side unite at very acute angles. The lateral union takes place principally between the insulated fibres and the small fascicuh of fibres, especially in the outer layer. Some- times it is irregular; so that those fibres which are evidently separated in the rest of their course are placed one against another in a part of this same course, whence the reticulated structure is more or less evi- dent. It is sometimes regular, and we see oblique fibres going from each side, which unite. The redness and determinate form of the inter- mediate filaments always demonstrate that they are not formed of cel- lular tissue but of real muscular substance. The mode in which the filaments are united also presents determi- nate differences in the different regions of the heart. 3d. In the ventricles, the external layers go obliquely downward, backward, and from right to left. The direction of the central is oppo- site, and the most internal, which form the fleshy pillars, extend longi- tudinally from the summit to the base. On the contrary, the transverse direction predominates in the auricles. The external layer, which is the strongest, proceeds in this direction, while the internal, which forms only insulated fasciculi, has a longi- tudinal direction. 4th. All the external layers are not equally extended. Generally the external layers are those only which cover all the surface of the ventricles; the central are smaller and occupy only a third of the heart. If we except the most internal, that which forms the fleshy pillars, they diminish in direct ratio to their depth. They disappear first at the summit of the organ, and in reascending from this point to the base of the ventricles, they are deeper and deeper; so that the deepest 188 DESCRIPTIVE ANATOMY. are found only at the base. Hence this part of the heart is the thickest. We observe also occasional spaces between the layers, which ex- tend the whole length or all the breadth of the ventricles. 5th. The outer layers differ from the central ones, inasmuch as they are stronger and their fibres are more intimately united together. Thus the fibres and the fasciculi of the inner layers are more easily demonstrated. But the external forcibly embrace and compress these latter; so that they contribute essentially to the firmness of the heart., 6 th. The fibres of the two portions of the heart are not continuous, at least not all of them, with each other, so that the same layers are reflected on the two; but the fibres of the two ventricles terminate in the septum. The upper and lower faces of the heart are not arranged in precisely the same manner: the separation is seen with more difficulty in the first than in the second. We remark also three different arrange- ments in the upper face. In fact, either we cannot distinguish the least trace of separation and the fibres are uninteruptedly continuous with each other, or two fibres are in fact applied one on the other, but a species of suture serves as a line of demarkation between them, or finally they mingle with each other by digitations. Wolff states that on the lower face, the fibres of the two ventricles are separated by a distinct and very broad band, formed of longitudinal fibres, and which diminishes insensibly from the base to the summit, to which these fibres are attached on the two sides. But we have usually found but a shght, and often no trace of this arrangement. 7th. The upper extremities of the fibres of the heart are attached to a fibro-cartilaginous tissue,(l) formed a. Of two oblong, rounded projections or tubercles, usually three or four lines long, little less than a line thick, seen on both sides of the ori- fice of the aorta. b. Of a thin band, which surrounds the posterior part of the circum- ference of the aorta and unites the two tubercles. c. Of four filaments, placed in the circular groove on the base of the heart, two on the right and two on the left, an anterior and posterior on each side. Below these four filaments the two anterior arise from the tubercles. The right anterior goes into the anterior and upper part of the circular groove; the left into the upper and posterior part. The posterior two arise by a very short common trunk, which is only a few lines long, from the band which unites the two tubercles, near that of the right side, and proceed in an opposite direction to the lower part of the circumference of the circular groove. These anterior and posterior filaments are situated at the venous orifices of the ventricles. They do not surround the base of the heart (1) C. D. F. Wolff, De ordine fibrarum muscularium cordis, Diss, ii., dc textu carti- lagine ocordis, sive defilis cartilagineo-osseis eorumque in basi cordis distributione. In Act. Petropol., 1781, vol. i. p. 211.—Gerdy, loc. cit., du tissu albugine cardiaque, p. 97. ANGEIOLOGY. 189 and form a complete ring, but terminate near the edges of each orifice and gradually lose themselves in the cellular tissue. This cartilaginous tissue is surrounded entirely by a thin, firm, but loose sheath, a real perichondrium. It is covered more externally by the outer membrane of the heart and internally by its inner membrane. The external muscular or superficial fibres arise principally from the cartilaginous tubercles and filaments, and from the cellular tissue be- tween the extremities of the latter; so that the fibres, which come from the tubercles and from the origin of the filaments, adhere to them very intimately, while the others are united only by a cellular sheath which surrounds them. v. VESSELS.(l) § 1300. The blood-vessels of the heart are proportionally very large and are called the coronary vessels (vasa coronaria cordis). The coro- nary arteries and veins resemble each other in many respects : 1st. These vessels (the arteries) arise directly from the beginning of the trunks of the vessels of the body, or they (the veins) open directly into the heart. 2d. They turn around the base of the heart in the circular groove, whence they send toward the summit large branches which arise at almost right angles : these go to the ventricles and proceed along the heart, while the others are smaller and follow an opposite direction, proceeding to the auricles. 3d. The large trunks and the large branches extend on the outer face of the organ and ramify internally. 4th. The veins have valves at the places where they open but not in their course. There are two arteries of nearly equal calibers, while we find only a single large coronary vein, which is constant; but be- side this last we observe several, which are smaller, which open directly into the heart, but not constantly, except into the right part of the organ, and particularly into the right auricle : they do not open, even, except into the septum, and they do not empty their blood into the left part of the heart,(2) as some anatomists have pretended, and among others Vieussens(3) and Thebesius.(4) In fact, Abernethy has very recently supported this latter opinion, viz. that the venous blood of the heart mixes with the arterial blood which nourishes the body, without passing through the lungs ; he has only modified it by saying, that these orifices of the coronary veins in the left portion of the organ serve principally to prevent repletion of the right portion in those cases where the passage of the blood through the lungs is obstructed; because, (1) Haller, De vasis cordis propriis, Gottingen, 1737.—Iterate observationes, 1739. —Geisler, Commentatio de sanguinis per vasa coronaria cordi motu, Leipsic, 1743. (2) Sabatier, Sur lesveines de Thebesius ; in the Traite d'anat., vol. iii. (3) Nouvelles decouvertes sur le ceur, Montpelier, 1706.— Traite duceur, 1715. (4) De circulo sanguinis in corde, Leipsic, 1708.—De circulo sanguinis per cor, Leipsic, 1759. 190 DESCRIPTIVE ANATOMY. having injected the cardiac arteries and veins in a subject whose lungs were diseased, he has seen the fluid penetrate into the left ventricle by broad openings. But as generally injections, even when very fine, transude on all the inner face, although no venous orifices are percep- tible on the left side, we have reason to admit that the openings exist- ing in the cases observed by Abernethy were produced accidentally, either during life or after death, by obstacles to the course of the injec- tion, on account of the feeble resistance of the tunics of the veins weak- ened by disease, and considerably distended, both by the blood accu- mulated in these vessels and by the injected mass. VI. NERVES. § 1301. The nerves(l) of the heart are proportionally smaller than those of the voluntary muscles. They arise from the upper and lower cervical ganglions of the great sympathetic nerve, from the cervical portion of the nerve between these two ganglions, or from the central ganglion sometimes found in this place. Some arise directly from the nerve, others from the plexuses formed by the filaments which come from the ganglions and by others sent off by the pneumo- gas trie nerve. The relations of the nerves of the heart with its muscular substance have been the subjects of dispute. Some anatomists, Behrends(2) among others, deny that this substance, and consequently that the heart, possesses nerves, which they pretend are distributed only to the cardiac vessels. Others on the contrary, as Scarpa, Munniks,(3) and Zeiren- ner,(4) maintain that they really go to the heart as well as to all other muscles. The partisans of the first hypothesis adduce the following arguments: 1st. Anatomical examination, whence it results that the cardiac nerves, which we cannot follow except to the third ramification of the coronary arteries, do not enter the substance of the heart but go only to the arteries.(5) 2d. The origin of the cardiac nerves; they arise from the great sympathetic nerve, the ramifications of which go only to the arteries.(6) (1) J. E. Neubauer, Descriptio nervorum cardiacorum, Frankfort and Leipsic, 1772. He has figured the nerves of the right side.—E. P. Andersch, De nervis; in the Nov. comm. Gett., vol. ii., and Konigsberg, 1797. He has represented those of the left side. These figures have been copied in Haase, Cerebri nervorumque corporis humani repetita, Leipsic, 1781.—A. Scarpa, Tabula; neurologicce ad illustrandum historiam anatomicam cardiacorum nervorum cerebri, glossopharyngeal et pharyngei ex octavo cerebri, Pavia, 1794. (2) J. Behrends, Diss, qua demonstratur cor nervis carere, addita disquisitione de vi nervorum arterias cingentium, Mayence, 1792.—A. T. N. Zerrenner, An cor nervis careat iisque carere possit ? Erford, 1794. (3) Observaticm.es varice. Diss. auat. med., Groningue, 1805,1-17. (4) Zerrenner, An cor nervis careat iisque carere possit ? Erford, 1794. (5) Behrends, loc. cit, p. 5, 8. (6) Id., ibid., p. 8. ANGEIOLOGY. 191 3d. The smallness of those nerves which is in direct ratio with the thinness of the fibrous coat of the arteries,(l) and which contrasts on the contrary with this law, that the number and size of the nerves correspond to the power and frequency of the motions of the mus- cles.^) 4th. The insensibility of the heart, the motions of which are inde- pendent of the nervous system, since it beats regularly although removed from the body,(3) and the excitement of the nerves, whether mechanically or dynamically, by means of galvanic electricity, do not alter its motions,(4) and its pulsations are not deranged when the ner- vous system is paralyzed as in apoplexy.(5) 5th. The integrity of the motions of the heart, notwithstanding the administration of opium.(6) But all these arguments can be refuted with greater or less facili'y. In fact: 1st. The manner in which the cardiac nerves are distributed and their proportion both to the muscular substance and to the vessels, do not differ essentially from what is seen in the same respects in the voluntary muscles.(7) Here also the nerves and the ramifications of the vessels are very compactly situated in regard to each other, and we do not see the nerves unite to the muscular suMtance. Besides the cardiac nerves are closely connected with the vessels only in their largest branches, and not at all in many animals. 2d. The muscular substance of the heart is only a greater develop- ment of the fibrous membrane of the vascular system, so that the dis- tribution of the branches of the great sympathetic nerve within it does not present an aberration from the type of this nerve. 3d. The cardiac nerves possess more medullary substance than those of the voluntary muscles. They arise from the ganglions of the great sympathetic nerve, and through them from all the spinal marrow.^ Their action is probably favored by the mutual contact of the blood and of the inner face of the heart; very probably also the size of the nerves which go to the voluntary muscles relates to their functions which is to conduct the influence of the will. 4th. The facts cited in the fourth paragraph are explained partly by the smallness and partly by the texture especially the softness and gelatinous nature of the cardiac nerves, and from the circumstance that they arise from the ganglions. Besides they are correct only to a certain extent, since the motions of the heart are not entirely inde- pendent of the nervous system. The passions have a marked influ- ence on the number and strength of its pulsations. Impressions of (1) Behrends, loc. cit., p. 8, 9. (2) Id., ibid., p. 10. (3) Id., ibid., p. 11. (4) Id., ibid., p. 20. (5) Id., ibid., p. 12. (6) Id., ibid., p. 11. (7) Scarpa, loc. cit., § 13.—Munniks, loc. cit., p. 6. 192 DESCRIPTIVE ANATOMY. every kind on the nervous system modify its motions more or less sen- sibly^ 1) In fact several observers, particularly Valli, Volta, Klein,(2) and Bichat, have doubted the influence of electricity on the motions of the heart; but the observations of Fowler, Schmuck, Pfaff,(3) Rossi,(4) Giulio,(5) Humboldt,(6) Munniks,(7) and Nysten, and our own also, prove it to be real. The non-affection of the heart in paralysis of the brain proves nothing in regard to the relations between the nerves and this organ, since the irritability of the voluntary muscles is not altered in apoplexy. This apparent^difference depends only on that between the excitants of the voluntary and involuntary muscles. In fact the excitant of the first is the influence of the brain, and that of the second the substance contained in their cavity, which in the present case is the blood. The motions of the heart continue also in cerebral paralysis, while those of the other muscles are not performed ; the activity of these last seems extinct while it is only no longer seen. 5th. The observations of Haller, of Fontana, of Whytt,(8) and of Alexander,(9) prove that the heart, like the voluntary muscles, is sen- sible to the influence of opium, whether the narcotic acts directly upon it, or is placed hi contact with the nervous system or with any organ whatever. These observations and experiments prove that the rela- tion between the heart and the nerves is perfectly like that between the nerves and muscles generally, and more, because the effect of opium upon the heart is much more evident when this substance is placed in relation with the nervous substance than when applied directly to the heart. VII. VENOUS PORTION. § 1302. The characters of the venous portion of the heart,(10) the auricles, are, 1st. The muscular substance of its parietes is so thin that the two membranes of the heart touch in several places. 2d. Its form is irregularly quadrilateral, (1) See on this subject Legallois, Experiences sur leprincipe de la vie, Paris, 1812, —Wilson Philip, in the Phil. Trans., 1815, part i. p. 65-97; part ii. p. 224-246.—Id. An experimental inquiry into the laws of the vital functions, London, 1818. (2) In Pfaff, Veber thierische Electricitdt und Reizbarkeit, p. 119. (3) In Ptaff, loc. cit., p. 140. (4) Mem. de Turin, vol. vi. (5) Voight, Magazin, vol. v. p. 161. (6) Veber die gereizte Muskel-und Nervenfaser, vol. i. p. 340-349. (7) Loc.cit.,p. 115. (S) In Pfaff, he. cit., p. 140. (9) Memoirs of the Manchester society, vol. i. p. 98. (10) Ruysch, Epist. anat. problemata decima de auricularum cordis earumque jibrarum motricium structura, Amsterdam, 1725.—A. F. Walther, De structura cordis auricularum, Leipsic. ANGEIOLOGY. 193 3d. It is composed of a part into which the veins open directly the cavity of the auricle, the sac (sinus), and another upper and anterior, the auricular appendix (auricula), which projects above the sac. The exact limits of these two parts cannot be pointed out, or rather anatomists do not distinguish them according to the same principles on the right and left sides. On the left side the appendix is readily dis- tinguished from the sac, because it suddenly forms a very rounded pro- jection, which is much narrower, and has thicker walls on the upper anterior and left angle. On the right side, on the contrary, this name is applied to a part, the walls of which are very thick, which is formed on the left by the confluence of the two venae cavae, terminates above in a blunt summit, and which is not sensibly separated from the rest, while, if we remained true to the analogy, this term should be applied only to the small appendix which terminates the auricle above, and which is elevated on the left along the vena cava superior. 4th. It is directly continuous with the venous trunks which open into it. VIII. ARTERIAL PORTION. § 1302. The characters of the arterial portion of the heart, the ventricles, are, 1st. Their parietes are thicker, so that the internal and the external membranes are every where separated from each other by a muscular substance. The thickness of the parietes of each portion of the heart is then in direct ratio with the extent passed through by the blood it sends forward. 2d. The arterial portion is considerably larger and broader than the venous portion. 3d. Its external form is elongated, rounded, and pyramidal, and determines, properly speaking, the form of the whole heart. 4th. At its upper extremity are two openings, the venous and the arterial, which establish the communication, the first between the ven- tricle and the auricle, and the second between the ventricle and the artery w hich arises from it. The venous orifice is almost perpendicular; its direction is from before backward and from right to left; the arterial is almost horizontal and is situated a little above the former farther in- ward and nearer the septum. Both are rounded ; the venous is broader than the arterial. Its form is elliptical, while the latter is nearly circular. Neither the venous nor the arterial opening is perfectly loose ; both have valves. The valves placed at the arterial opening are very similar in their arrangement to those found in the common veins ; they are however much larger and are usually three in number. Their convex and attached edge looks toward the heart while the loose edge, which has two concavities and which is thicker than the rest of the membrane, is turned toward the cavity of the artery. In the centre Vol. II. 25 194 DESCRIPTIVE ANATOMY. of the latter we observe a fibro-cartilaginous tubercle (nodulus). The blood which comes from the ventricle pushes them toward the circum- ference of the artery and against its parietes. On the contrary the blood which tends from its specific gravity to return from the artery into the ventricle separates them from these same parietes, their loose edges then touch, and they form a horizontal septum between the cavity of the artery and the ventricle, which prevents the reflux of the blood into the latter. The tubercles complete this septum and close the space in the centre of the artery between the three valves. The valves of the venous orifice differ from those of the arterial opening, and from all other valves, since they are attached much more firmly, hence they close more completely the opening around which they are placed. A narrow cartilaginous ring, which is not however perfect, exists on all the circumference of the venous opening; this sometimes ossifies in advanced age, especially in the left portion of the heart, and is situated deeply between the muscular fibres of the ventri- cle and those of the auricle. This is the cartilaginous tissue already described as the origin of the external muscular fibres of the heart. The venous valve is attached to this tissue by its posterior edge, but its opposite and uneven edge, unlike that of all the other valves, is not loose; many flat and solid tendinous filaments, which extend from the base to the summit of the heart, arise from the valve, on which they are often united or pass over it and go to the opposite part of the circumference of the heart, soon unite into larger cords, and are attached to the parietes of the heart, and principally to its fleshy pillars. As the latter shorten when the heart contracts, the different parts of the valves then approach each other and the opening is forcibly closed. It is necessary that the loose edge of these valves should be thus attached since they must resist not only the weight of the blood like the other valves, but also the action of the muscular parietes of the heart, which forcibly push forward the arterial blood. 5th. The arterial portion of the heart is divided into an upper and lower half, which are separated by the upper part of the valve of the venous orifice at the upper and posterior parts of the ventricles, and which blend together at the summit of the heart, so that the ventricles, although resembling externally an elongated cone, form in fact two arched canals, convex forward, and the greatest convexity of which corresponds to the summit, and are more extensive in this part than in any other. 6th. The reticulated structure of the ventricles is much more dis- tinct than that of the auricles. Some of the fleshy pillars form rounded, elongated projections, terminating in blunt summits (musculi papillares), which go toward trie base of the heart, and from the extremity of which several tendinous filaments proceed to attach themselves to the loose edges of the venous valves. Farther, those fleshy pillars which are attached by their two extremities, as well as those which have ANGEIOLOGY. 195 one end loose, communicate with each other at intervals by tendinous fibres. The direction of the principal fasciculi is longitudinal, the smaller which unite the preceding are oblique. Near the summit the reticulated texture is more and more developed, and the parietes be- come thinner in the same proportion. IX. RIGHT AND LEFT PORTIONS. § 1303.1st. The right half of the heart is considerablythinnerthan the left. This difference is very striking between the two ventricles, where the relation is generally as one to four or to five. Even then we find, as between the auricles and the ventricles generally, that the power of the parietes is in direct ratio with the space passed through by the blood which comes from them. The greater thickness of the walls of the left ventricle determines the form of the whole arterial portion of the heart. The right wall formed only by the septum is convex, and the left appears fitted to it hke a sling. 2d. The substance of the right side, especially that of the ventricle, is softer and looser than that of the left side. 3d. The right side is broader than the left after death.(l) This difference also is most marked between the two ventricles, but it is not yet determined if it exists constantly during life or supervenes only after death. Many anatomists, particularly Lower,(2) Santorini,(3) Weiss,(4) Lieutaud,(5) and Sabatier,(6) have adopted the latter opinion, while most others favor the first. This hypothesis has been supported sometimes by the result of measurement, and sometimes by the fact that the left ventricle is as much longer as the right is broader, and sometimes by experiments and observations, from which it has been concluded that the right side appears broader after death, only because it is more distended by the blood which remains stagnant in the lungs from their inaction, while previously the passage of the blood from the left ventricle was not obstructed; whence the left ventricle seems to be narrower com- pared to the right, in proportion to the less quantity of pulmonary blood received by it through the pulmonary veins. In men and ani- mals who have died suddenly from the injury of the large vessels, or of those which communicate with the right portion of the heart, when consequently this cause of the distention of the right ven- (1) Helvetius, Sur Vinegalite de capacite qui se trouve entre les organcs destines a la circulation du sang, dans le corps de I'homme, et sur les changemens qui arri- vent au sang enpassant par le poumon, in the Mem. de Paris, 1718, p. 222-281. (2) Loc. cit., p. 34. (3) Loc. cit., p. 144, 145. (4) De dextro cordis rentriculo post mortem ampliore, Altdorf, 1745. (5) Essais anat., p. 230, 231. (6) Sur I'inegale capacite des cavites du ceur et des vassieauxpulmonaires, in the Mem de Paris. (7) Lieutaud has brought forward this argument. 196 DESCRIPTIVE ANATOMY. tricle did not exist, the capacity of the two portions has been exactly or nearly the same.(l) Finally, when the left ventricle is placed in the same condition by means of a ligature as is the right ventricle at the time of death ; while on the contrary the blood is removed from the latter by cutting the pulmonary artery, or the vena cava, we find that the relation between the two ventricles is the inverse of that which commonly exists, that is, that the right ventricle is narrower than the left.(2) The veins appear much larger than the arteries after death, undoubt- edly from the same cause. To these experiments we may add that we sometimes find the right ventricle narrower than the left from the effect of disease, such as ossi- fication or some other malady of the valves of the aorta, in which case the difference must be explained precisely in the same manner. We have before us several preparations in which, beside a considerable dilatation of the left ventricle arising from this cause, there is at the same time a great contraction of the right ventricle, proving that the results drawn from these facts cannot be opposed, by saying that the dilatation of the right cavity of the heart in the usual state of things should extend also to the left portion from the influence which it exer- cises on the veins and arteries of the body, and consequently that the right half is really larger during life since the left is itself distended. Since the cause of the greater distention of the right portion, that is, the more difficult passage of blood through the lungs, supervenes only at the moment of death, the opinion that the right ventricle is also more capacious during life cannot be sustained.(3) That the cause above mentioned is that which increases the capa- city of the right portion of the heart at the period of death only, is proved by the fact that the difference between the two portions of the organs varies with the cause of death, and that it increases in a direct ratio with the increase of the obstacle to the circulation of the blood in the lungs. Thus, in those animals killed by drowning, hanging, and suffocation, Colman has found the right ventricle generally twice the size of the left, although its proportions commonly mentioned are much smaller.(4) In fact, Haller asserts that in one subject he found it three times as large as the left,(5) but the usual estimates are much less than this. Gordon says the relation is sometimes as 5 : 4,(6) Lie- berkuhn as 3 : 2,(7) Portal as 7 : 5,(8) Helvetius(9) and Legallois,(10) (1) Weiss, loc. cit.—Sabatier, loc. cit. (2) Sabatier, loc. cit. (3) Haller, Elem. phys., vol. ii. p. 134. (4) On suspended respiration from drowning, hanging, and suffocation, London, 1791. (5) Loc. cit., p. 133. (6) System of human anat., vol. i. p. 38. (7) Hamberger, Physiologie, p. 708. (8) Mem. de Paris, 1770, p. 245. (9) Loc. cit. (10) Diet, des sc. med. vol. v. p. 440. ANGEIOLOGY. 197 as 6 : 5, Brown Langrish as 11 : 10.(1) Gordon has found the two ventricles nearly equal in some cases,(2) and Portal asserts that their capacity is the same in young people.(3) These differences in the estimates of authors furnish a new argu- ment against the common opinion, since we should presume that they depend on greater or less accidental obstacles to the pulmonary circula- tion. We cannot however deny but that the capacity of the right portion of the heart is a little greater than that of the left, because the blood brought by the vena cava has received the fluid contained in the tho- racic canal. It is also proved by the difference relative to the age in the degree of disproportion, this being, directly after birth, less than at a more advanced period of life.(4) Legallois has also found the right portion of the heart a little broader than the left in every kind of death, both after strangulation and from the loss of blood. (5) The facts related prove only that the right por- tion of the heart can contract as much as, and even more than the left, in certain circumstances, and that the left is also susceptible of becoming larger than the right, but not that the capacity of the latter exceeds that of the former during life. 4th. The fibres of the right side, especially those of the ventricle, are not arranged in the same manner as those of the left side. a. The thinness of the right ventricle is attended also with fewer fibrous layers, a fact already pointed out by Senac,(6) but which Wolff has indicated more precisely in saying that the right ventricle is formed of three layers only, while that of the left side presents six, counting the fleshy fasciculi of its internal face.(7) We have not however been able to find this number of layers. Usually we have observed on each side only three distinct layers, two oblique, and one internal longitudinal. b. The fibres of the right ventricle are flatter and thinner than those of the left. Thus the former form flattened fasciculi, and the second rounded and thicker fasciculi. The latter ramify more; they are separated by fat, and have spaces between them, while we can hardly distinguish the former from each other except by the direction of their fibres. c. The fibres of the right ventricle are more obhque and annular, while those of the left are more longitudinal. d. The layers of the right ventricle, although thinner, are much more distinct than those of the left ventricle ; besides the latter are still (1) De part, corp hum. fabric., vol. ii. p. 133. (2) Loc. cit., p. 38. (3) Loc. cit. (4) Portal, loc. cit. (5) TV. du ceur, vol. i. p. 200. (6) De stratis jibrarum cordis in universum, in the Nov. act. Petrop. vol. iii. an. 1785, p. 234-238. (7) Loc. cit., p. 234. 198 DESCRIPTIVE ANATOMY. more similar in regard to direction, which doubtless contributes to make the left ventricle firmer, but proves at the same time that we should exercise some judgment in determining the number and direction of these layers. Such at least is the positive result of our researches. This also is the opinion of Wolff himself, who has studied the arrange- ment of the heart with too much exactness. 5th. The primitive form of the heart, that of a canal curved on itself, is more evident in the left ventricle than in the right. 6th. The nerves of the left side are larger and more numerous than those of the right side. CHAPTER II. SPECIAL REMARKS ON THE HEART. § 1304. We usually describe first the right half of the heart; and in order to follow the direction of the circulation of the blood, we begin with the right auricle. I. RIGHT AURICLE. § 1305. The right auricle (atrium anterius, s. venarum cavarum, s. dextrum), forms that portion of the base of the heart situated farthest on the right and forward. Its form is almost square ; the vena cava superior descends obliquely from right to left, and from behind forward, towards its upper and right angle, and the vena cava inferior ascends in a contrary direction towards its lower and right angle. Notwithstanding this difference in the direction of the two vena? cava?, we must admit that they unite and form a single trunk in the cavity of the auricle, for they unite on the right forward and backward, and the absence of the left side of their circumference is only apparent, since this side in fact exists, but is dilated to produce the muscular part of the auricle. The upper and left angle of the latter extends into a small blunt appendage, formed hke a rounded square, which is observed before the lower pait of the aorta. The lower and left angle is rounded. We observe transverse fibres on all the circumference of this auricle, directly below the inner membrane of the heart, which, becoming thinner and separating from each other above and below, are prolonged for a small distance around the superior and inferior venae cavae. They are thinner where they surround the point of union of the two venae cava? forward, and are extended more uniformly, and are smoother on the right side, both on thair outer and on their inner face. But the left part of the posterior face of the anterior and unattached wall of the right auricle, which is the most extensive, is uneven inter- nally. This unevenness depends on much larger and transverse fasci- ANGEIOLOGY. 199 culi, which are united by other smaller obhque fasciculi, so as to pre- sent a reticulated appearance. These fascicuh, with which the trans- verse fibres of the auricle are united, appear between two longitudinal smooth bands which proceed only along its internal face. One of these two bands, the left, descends a short distance from the anterior part of the venous orifice of the left ventricle; the other, the right, situated almost in the centre of the anterior wall, a little however to the right, descends toward the left side, along the union of the two venae cavae. These fleshy fascicuh have been called the pectinaal muscles (JVf. pectinati). The posterior wall of the right auricle forms the anterior face of the interventricular septum. We discover in it several remarkable parts, some of which belong to the history of the development of the heart. On the right side and toward the centre is the fossa ovalis (fossa ovalis, s. valvula foraminis ovalis, s. vestigium foraminis ovalis), an oblong and rounded depression, which varies much in size. This fossa is very distinct from the posterior wall of the auricle at its upper part, a little less so on its sides, especially on the right, and is generally blended with it below, particularly on the right side. The more exten- sive it is, the less evident are the limits which separate it from the other parts of the posterior wall. It however not unfrequently pre- sents a similar arrangement even when it is very small. Most generally it exactly fills the space between the edges of the projection which surrounds it, and it is very tense, but not unfrequently it is much larger, and forms a valve, the loose edge of which corres- ponds to the left auricle. We almost always observe a greater or less depression above, between its extremity and the upper part of the pro- jection v/hich surrounds it. Very often also we see in this place one or more openings by which the cavity of the two auricles communicate. This arrangement is not constant, and it is entirely independent of the extent either of the valve or of the depression, although it occurs parti- cularly when the valve is very broad. Even when the openings are large and numerous, they seldom descend below the central part of the projection which surrounds the depression, so that the septum of the auricles is complete in regard to the separation of the blood contained in the two cavities. This place, especially in its upper part, is the thinnest portion of the septum and of the auricle generally. We however always observe muscular fibres between the two layers of the internal membrane of the heart, that of the right and that of the left auricle. The projection which surrounds this depression is formed of reticu- lated muscular fibres. It is called the ring or the isthmus of Vieus- sens (annulus, s. isthmus Vieussenii). Its right portion separates the right and left halves of the septum. Although it does not project at its lower part, it is however complete in this place also. We observe in its circumference several openings of the cardiac veins, called the foramina of Thebesius (foramina Thebesii). At the 200 DESCRIPTIVE ANATOMY. lower end of the inferior edge of the ring a circular fold of the inner membrane of the right auricle commences, this is called the Eustachian valve, or the anterior valve of the foramen ovale (valvula Eustachii, s. foraminis oralis anterior).(I) This fold extends more or less to the right, along the anterior part of the orifice of the vena cava ascendens into the right auricle, so that its lower edge is concave and attached while the upper is convex and loose within the right auricle. It im- perfectly separates below the right and left halves of the right auricle. This valve varies much in regard to size, form, and texture. It is usually more perfect and proportionally larger in the fetus than at any time after birth. In the adult it is often entirely changed, at least at its upper part, into a reticular tissue, and in many cases some filaments only trace the valve, and these frequently do not exist. It usually contains some muscular fibres, but it is often only a simple fold of the internal membrane. An intimate relation generally exists between the Eustachian valve and the fossa ovalis, the former being more developed in proportion as the septum formed by the latter between the two auricles is less per- fect, and vice versa; but to this rule there are numerous exceptions. The valve acts principally in the fetus. At this period of life it con- ducts the blood of the vena cava superior toward the opening of the septum or the foramen ovale. Hence the relation between it and the valve of this opening. In the adult it may prevent to a slight degree the reflux of the blood from the vena cava superior, and from the right auricle generally into the vena cava inferior. Directly at the left side of the left branch of the isthmus of Vieussens, between this branch and the venous orifice of the right ventricle, there is a large and rounded opening, the orifice of the large coronary vein of the heart (orificium vena coronaria cordis magna).(2) This opening is sometimes divided more or less distinctly into several, and generally is more or less perfectly closed by a valvular fold, which arises at its lower part. This fold, called the valve of The- besius (valvula Thebesii), has its upper and concave edge unattached, while its lower and convex edge adheres. Sometimes it does not exist; in other cases it is replaced by one or more imperfect transverse bands; finally, in some subjects there are several, even as many as six, situated one behind another. (1) Winslow, Description d'une valvule singuliere de la rcine cave inferieure, a Voccasion de laquelle on propose un sentiment nouveau sur la fameuse question du trou ovate, in the Mem., de Paris, 1717, p. 272. Eclaircissemcnt sur un Mem. de 1717, Ibid. 1725.—Haller, De valvula Eustachii, Gottingen, 1737.—L. Crell, De valvula vene cave Eustachian^,, Wittenberg, 1737.—Brcndel, De valvula Eustachiana inter venam inferiorem dextramque cordis auriculam posita, Wittenberg, 1738.—Haller, Dc valvula Eustachii progr. ii. Gottingcn, 1748.—J. M. Diebolt, De foramine ovali, Strasburg, 1771— J. F. Lobstein, De valvula Eustachii, Strasburg, 1771.—C. F. Wolff, De foramine ovali ejusque usu in dirigendo sanguinis motu observationes nove, in the N. C. Petrop, vol. xx. p. 357.—H. L. Leveling, De valvula Eustachii et foramine ovali, in the Obs. anat. rarfasc. i. 1786. (2) Wolff, De orificio vene coronaria magne; in the Act. Petrop. 1777, p. 234-257. ANGEIOLOGY. 201 II. RIGHT VENTRICLE. § 1306. The anterior, pulmonary, or right ventricle (ventriculus an- terior, s. dexter, s. pulmonalis) is composed of an upper and lower por- tion, which are separated by the upper part of the venous valve. The former unites directly to the right auricle, the latter to the pulmo- nary artery, and its walls are thinner than those of the former. It terminates in a conical extremity, which projects upward and backward above the left ventricle and the septum of the heart. The pulmonary artery arises from this part. The internal or posterior wall is formed by the septum of the heart and is shghtly convex ; the anterior is still more so. The posterior wall is smoother than the anterior at its upper portion and very often entirely so below the arterial opening. The net-work formed by the projecting muscular fasciculi is much more complete toward its sum- mit than toward its base. The anterior wall of the pulmonary ventricle is thinnest above toward the septum and thickest below also near the septum. Its thickness when the heart is strong and not very much distended is more than two fines, but less than this in the latter point. The two parts are scarcely a line thick even in those hearts which are neither very much distended nor small. The quantity of blood in the right ventricle after death varies from one ounce and a half to three ounces. § 1307. The venous valve of the right auricle arises from the cir- cumference of its venous orifice. It is called the tricuspid valve (val- vula triglochis, tricuspis), because, although it forms a single membrane, it is higher in three points than in the short spaces between them, and thus three slips are formed. Of these, one, which is the largest, arises from the external and an- terior part of the circumference of the venous orifice. The other two are smaller and arise from the inner and posterior part of this circum- ference, one over the other ; so that consequently there is an external and larger slip, and two internal, an upper and a lower slip. The last two are separated from each other by a space not so deep as those between them and the external. It is then more correct to admit only two slips, an anterior and external and a posterior and internal. The first is much higher than the second. The tendinous filaments of the upper extremity of the anterior or external slip are attached to this upper part of the septum. They are few in number. We usually find in the space only one or at most two short muscles, to which are attached those filaments farthest to the left; the others are inserted in its smooth wall. Most of those filaments which come from the central and lower parts of the edge of Vol. II. 26 202 DESCRIPTIVE ANATOMY. this slip are attached to the summits of five or six of the fleshy pillars coming from the middle and lower parts of the anterior wall. The filaments which arise from the posterior slips are mostly attached to the smooth folds of the septum, except a few, which are inserted in two or three small fleshy pillars, all of which except the lowest come from the septum. The arterial orifice generally extends about three fourths of an inch higher than the venous. The sigmoid valves are thin. Their tuberclee (noduli Morgagnii) are slight swellings, which however are often well marked in the young fetus. III. LEFT AURICLE. § 1308. The left, posterior, ox pulmonary auricle (atrium sinistrum, s. posterius, s. venarum pulmonalium, s. aorticum) is of an oblong square form, considerably more broad than high. It is separated below and posteriorly from the left ventricle by a circu- lar groove, upward and to the right from the right ventricle by a similar depression. The pulmonary artery, the aorta, and the vena cava superior are also found upward and outward, between it and the right ventricle; so that the external part of its right and left extremities is alone visible. Its upper left angle rises into an auricular appendage (auricula sinis- tra), which goes forward to the left and upward, directly behind the pulmonary artery, separating very much from the rest of the auricle. This appendage, which is narrower, longer, and on the whole larger than that of the right auricle, is circumscribed by rougher edges. It curves three or four times and finally terminates in a sharp summit, below and before the pulmonary artery. The posterior wall of the lower part, the sinus of the auricle (sinus venarum pulmonalium), receives where it is continuous with the lateral parietes the four pulmonary veins, two on each side, the upper being larger than the lower. One of the two veins of the same side opens directly above the other, while between those of the two opposite sides is the whole breadth of the auricle; so that the two pairs occupy the whole height of the posterior wall. The parietes of the whole auricle are muscular and formed principally of transverse fibres. They are smooth with the exception of the ap- pendage. We observe in its whole length an anterior and a posterior series of very prominent transverse fasciculi, united by other smaller and oblique fasciculi, which proceed between two longitudinal bands, situated one on the right the other on the left. The anterior wall is formed by the septum of the auricles and is also, like the posterior face of the septum, irregular in another respect. In fact we there observe a constant semicircular valve, which is however more or less developed. This valve leaves the upper edge of the trans- parent point which corresponds to the fossa ovalis of the right auricle (§ 1305). It is turned upward and toward the left. Its lower edge ANGEIOLOGY 203 is convex and attached, and its upper edge is loose in a greater or less extent. Sometimes there is only a slight projection in its place. This valve extends behind the interauricular septum. Its lower edge is attached to the posterior face of the centre of the isthmus of Vieus- sens, and the space between it and this isthmus forms a small cavity (sinus septi), which terminates below in a cul-de-sac. This is only the upper part of the valve of the foramen ovale (§ 1305), which in the normal state always ascends on the posterior face of the isthmus. Of this we are readily convinced when it does not adhere to the isthmus in the centre; for then the continuity is totally uninterrupted. IV. LEFT VENTRICLE. § 1309. The left ventricle (ventriculus sinister, posterior, s. aorticus) is the strongest of all parts of the heart and forms its figure. Its pos- terior wall and its anterior wall which forms the posterior face of the septum, are convex externally and concave internally; so that its whole form is oval. The internal face of the posterior wall is very much reticulated ; the anterior wall is smooth at its upper part and reticulated in the lower, but less so than the posterior wall. The fleshy pillars are rounded. The thickness of the parietes is less toward the summit and greater at the base than in all other parts. In the adult it is five or six lines thick at the base and only three at the summit. The capacity of the left ventricle varies in the adult from eight to twenty drachms. § 1310. Before the round venous orifice we find the mitral valve (valvula mitralis), composed of an upper and a lower slip. The upper arises directly below or rather before the ring of the sigmoid valve of the aorta, and is attached by slips to three or four fleshy pillars, which all come from the internal face of the posterior wall of the ventricle, some above, others below, and among which we distinguish two particularly, an upper and a lower, which are much larger than the others. The inferior and external shp, which is much narrower, is attached by ten- dinous filaments to a short but very thick fleshy pillar. All these fleshy pillars arise from the posterior wall of the left ven- tricle ; so that those of the upper slip arise near the summit of the heart, and cover those of the lower, so that we cannot perceive the lower slip until we have removed the upper or have detached it from its fleshy pillars. The orifice of the artery is situated directly over that of the vein. Its sigmoid valves are thick and are generally supplied with tubercles (noduli Arantii), which are very distinct. 204 DLStRIFTlVE ANATOMY. V. SEPTUM. § 1311. In the normal state the septum of the heart completely separates its two halves, even when the valve of the foramen ovale is not united with the isthmus of Vieussens at its upper part. In the venous portion of the heart it is much thinner than the auricles, which it separates, and is much lower, as they project above it. It is not muscu- lar in every part, and generally there are no muscular fibres in the upper part of the old valve of the foramen ovale. In the arterial portion, on the contrary, the septum is very muscular and is formed almost entirely by the fibres of the left ventricle. It projects considerably into the right ventricle, while in its posterior face, which forms the anterior wall of the left ventricle, there is a deep depression. Its height equals that of the ventricles. It is triangular and terminates in a point toward the summit of the heart. It is generally from four to five lines thick, and even more than a half an inch thick in those parts where the large fasciculi project above the surface in those subjects which have large hearts. It is thickest below the orifices of the large arterial trunks, and thinnest beyond this point toward the interauricular septum. It is almost always weaker at the summit, where the layers which constitute it are less compact and more easily separated from each other. CHAPTER III OF THE PERICARDIUM. § 1312. The pericardium (pericardium) (§ 1293)(1) is a fibro-serous membrane (§ 354), which entirely envelops the heart and the origin of the large vessels, and unites them with the adjacent parts. The fibres which strengthen its outer layer and which are very ap- parent in old men, arise from the central aponeurosis of the diaphragm and extend longitudinally over the serous membrane. They are very much developed, particularly forward and upward. Its lower face, which corresponds to the lower and flat face of the heart, is intimately united to the upper face of the central aponeurosis of the diaphragm by a very short cellular tissue. It is covered on the sides and forward by the inner walls of the pleura?. Behind, it is attached to the esophagus and to the root of the right lung. (1) J. M. Hoffmann, Diss, de pericardia, Altdorf, 1690.—A. B. Heimann, Deperi- cardio sano et morboso, Leyden, 1729.—Lanzoni, De pericardia; in Opp. omn., Lau- sanne, 1738. ANGEIOLOGY. 205 & 1313. The pericardium incloses not merely the heart but also the origins of the large vessels, whence it is reflected on itself in every direction to arrive at the centre of the heart. When examined from before backward and from above downward, we notice the following arrangement: It envelops the aorta and the trunk of the pulmonary artery forward for about two and a half inches, unites these two vessels very closely, and passes uninterruptedly from one to the other; so that the corre- sponding parts of their circumference are retained by a cellular tissue. The posterior part of these vessels is not covered in the same extent by the pericardium. From the aorta this membrane passes to the right on the vena cava superior, to about an inch above its entrance into the right auricle, de- scends obhquely from left to right on its anterior portion, then arrives at the right pulmonary veins, on which it descends to about half an inch from their entrance into the left auricle, then goes on the anterior part of the vena cava inferior, directly below its opening into the right au- ricle, and wholly surrounds it except a small part of its posterior por- tion. \Thence it goes to the left, on all the surface of the left pulmo- nary veins, and finally covers the left branch of the pulmonary artery below. From all these parts the pericardium is reflected on itself. It adheres feebly to the large vessels, but much more strongly to the auricles and ventricles. As in all other serous membranes, the inner and reflected portion of the pericardium is thinner than the external. It closely envelops the surface of the parts inclosed by the membranous sac, and, except in those parts where it is reflected, it is entirely separated from the outer layer, although they touch; so that the circumference of the heart is perfectly loose and is attached only by its upper part. CHAPTER IV. OF THE DIFFERENCES OF THE HEART WHICH DEPEND ON THE DEVELOPMENT AND ON THE SEX. § 1314. The differences presented by the heart in regard to its de- velopment are considerable.(l) They relate to its volume, situation form, and texture. 1st. Volume. The heart is much larger in proportion to the body in the early periods of hfe than at a more advanced period. The relation (1) The principal works on this subject arc mentioned in Danz, Grundriss der Zergliederungskunde des ungebornen Kindes in den verschiedenen Zeiien der Schwangerschaft, vol. ii. Giessen, 1793, p. 185-188.—See also Meckel, Memoirc sur le developpement du ceur; in the Journal complementaire, vol. i. p. 259.—Rolando Memoire sur la formation du ceur; same journal, vol. xv. p. 323, vol. xvi. p 34 ' 206 DESCRIPTIVE ANATOMY. between it and the body is as 1 : 120 in the full grown fetus and in the early years of life, while before this period, in the second and third month of pregnancy, it is as 1 : 50. 2d. Situation. At first the heart is not oblique, but its summit looks directly forward and a little downward. It is only at the fourth month that it begins to turn slightly toward the left side. 3d. Form. The differences in its form are the most important and relate both to the circumference of the whole organ and to the mode of limiting its cavities. Observers have not decided whether there is or is not in the human fetus a period very near its origin, when the heart forms only a single cavity, composed of several compartments placed near each other. But if this period exists, it passes rapidly, since all the external parts are developed in the fetus at the end of one month. A. OUTER CIRCUMFERENCE. a. At first the arterial portion of the heart is much smaller in propor- tion to the venous. The right auricle especially remains for a long time the largest portion of this organ. The permanent relation how- ever begins to establish itself during the last half of uterine existence. b. The arterial portion is at first flat and rounded : soon however its breadth exceeds its length. Its summit is at first single and blunt; but as it enlarges it bifurcates. This phenomenon depends on the fact that the right ventricle from its situation does not at first concur to form the summit of the heart; but it gradually extends downward and remains separated from the left ventricle by a considerable depression. This groove sometimes continues during life, but almost always disappears after the middle of uterine existence. c. The right ventricle is at first much smaller than the left: they are soon equal in size : for a certain time the right ventricle is even a little larger, but it becomes smaller during most of uterine existence ; so that it is narrower in the full grown fetus and in the young child. The greater size of the right ventricle seems to result from the obstacles which often disturb the pulmonary circulation at an advanced period oflife.(l) (1) This at least has been observed by Portal (Sur la capacite des ventricules du ceur; in the Mem. de Paris, 1770, p. 244-246). In the heart of a full grown fetua the left ventricle contained seven drachms of water, while the right contained only six and a half. The capacity of the two ventricles was the same in that of a young child; in that of an adult the right ventricle contained eighteen drachms of water, and the left only seventeen. The experiments of Legallois (Diet, des sc. mid., vol. v. p. 440,) prove that we can introduce gr«. of mercury T „j„n S Into the right ventricle, 1172 Inanadult'......\ Into the left ventricle 1068 f Into the right ventricle, 828 _ , .,. I Into the left, not softened In a child, - - -j by prea8Ure) . . 658 Into the left, softened, 822 ANGEIOLOGY. 207 d. In the early periods of hfe the upper and pyramidal extremity of the upper part of the pulmonary ventricle is less distinct from the rest of the organ than at more advanced periods : it elevates itself also less above the left ventricle and the septum. This peculiarity is very curi- ous, as precisely the contrary is seen in many mammalia, especially the ruminantia and the hog. B. INTERNAL ARRANGEMENT OF THE HEART. The principal difference presented by the? heart in this respect is, that its septum is imperfect in the early periods of life, whence its right and left portions then communicate with each other. a. The interauricular septum is perforated during all fetal existence by an opening called the foramen ovale. This foramen is much greater as the fetus is younger; so that we may consider the septum as primi- tively deficient and the two auricles then form a single cavity. The foramen ovale gradually grows smaller and occupies the lower and cen- tral part of the septum. The Eustachian valve is found very early di- rectly before it and on the right, so as to occupy all its height. Hence as it arises from the anterior part of the circumference of the vena cava in- ferior, it separates the right and left auricle in such a manner, that this vein empties directly into the left auricle only. On the contrary, there is no trace of the closing of the foramen ovale on the left side till the com- mencement of the third month. But about this period this foramen begins to be obliterated by the formation of its valve, which arises from the posterior part of the vena cava. grs. of mercury f Into the right ventricle, 34 In a still-born child,.....^ Into the left ventricle, In a seven months' fetus, In another about the same age, not softened, - - 37 |_ Into the left, softened, 78 C Into the right ventricle, 23 < Into the left, not softened C nor flaccid, - - 34 (Into the right ventricle, 21 (Into the left, softened, 54 In repeating these experiments, also with mercury, we have obtained the following results: In a man 50 years old, - In a woman 46 years old, In a woman 40 years old, In a man 34 years old, - « 30 " - « 26 " --- In a boy 16 " ... In a girl 7 months old, - - - In a new born boy which had breathed, In a still-born boy, ... R. ventricle L. ventricle L. auricle R- auricle oz. drs. oz. drs. oz. drs- oz. drs. 30 10 25 20 40 22 4 22 15 55 40 41 35 32 15 4 21 25 32 4 28 4 25 22 4 28 20 4 20 18 41 4 21 4 37 29 2 4 1 4 1 4 1 6 1 6 2 1 6 1 2 1 4 2 together 4 ounces. 208 DESCRIPTIVE ANATOMY. As this enlarges, the Eustachian valve diminishes and recedes from the septum, while on the contrary that of the foramen ovale approaches it. The latter also becomes narrower and more tense, especially in the latter months of pregnancy ; so that it closes the opening more exactly. The termination of the vena cava inferior in the heart suddenly changes, and this vessel empties itself no longer into the left auricle but into the right. This change is also favored by that which takes place in the situation of the heart, which varies so that its summit corresponds to the left; the right auricle is more than usually elevated above the vena cava inferior, at the same time that the Eustachian valve is re- moved from the septum and is carried forward. The valve of the foramen ovale increases from below upward along the lateral edges of this foramen. At the sixth month of pregnancy it has already arrived at its upper part; it then passes beyond it; so that the interauricular septum is entirely filled, except a small space, which is no longer an opening but a very short canal, formed forward by the upper part of the ring of the foramen ovale and backward by the upper part of the valve. b. It is not yet well demonstrated whether the ventricles, like the auri- cles, form at first only a single cavity without a septum, although the development of the heart in the animal series, and the deviations of formation of this organ lead us to this opinion. We have always found a trace of the interauricular septum at the summit of the heart, even in the youngest fetuses we could examine. During the first two months however, or at least till the middle of the second, this septum presents at its upper part a foramen, at first rather large, but it gradu- ally diminishes, and is found below the origin of the large vessels, so that the two ventricles form only one, which is imperfectly divided into two portions. This opening is obliterated at the period when the artery which arises from the ventricles becomes double, instead of single, as it was at first; that is, when the pulmonary artery, which before was blended with the aorta, becomes a proper and distinct vessel. Its obliteration then much precedes that of the foramen ovale. 4th. Texture. The thickness of the parietes is much greater com- pared to the size of the cavities during the early periods of life than subsequently, and the greatest size of the heart then depends on this cause.(1) The parietes on both sides are then equally thick. The difference which always exists afterwards, and which is scarcely perceptible even in a full grown fetus, does not begin to be developed till the second half of uterine existence. The fibrous texture and the different layers of fibres are always more apparent at the early periods of life than at a more advanced age. (1) Gordon is mistaken in saying that the parietes of the heart are proportionally thinner in the early periods of life than at a more remote period (System of human anatomy, vol. i. p. 53.) angeioloCy. 209 5th. Color. The color of the heart is much brighter when the subject is younger. No fat has as yet accumulated on the surface of this organ in the early periods of fetal existence ; but this is generally the case with all parts of the body. The pericardium is then proportionally thicker than at subsequent, periods, and its internal or reflected layer adheres less intimately to the heart. C SEXUAL DIFFERENCES, § 1315. The only sexual difference seen in the heart is that it is proportionally a little larger in males. CHAPTER V. MOTIONS OF THE HEART. § 1316. The circumstances in the history of the motions of the heart, or in the heart in its active state, which deserve examination, are, 1st. The changes in its form. 2d. The succession and simultaneousness of the motions in its different parts. 3d. The relation between the cavities of the heart in its different states and the blood. 4th. The number of its motions. 5th. The changes in its situation. 6th. The duration of its motions. 7th. The conditions on which they depend. § 1317. 1st. The heart diminishes in contraction and enlarges in dilatation in every directional) 2d. The auricles and ventricles contract and dilate alternately, so that the two auricles and the two ventricles execute the same motions at the same time. (2) The auricles in contracting send the blood into (1) Sur le changcment du figure de ceur dans le style, in the Mem. de Paris, 1731, hist. p. 33, 40. (2) The motions of the heart have been carefully analyzed by Laennec with the aid of the stethoscope, by which we can study them more correctly than by openine and inspecting living animals (De Pauscultation mediate, vol. ii. p. 195-227). Prom this analysis are deduced numerous important practical facts. In the motions of the heart we must consider their extent, its impulse, the nature and intensity of the sound and the rythm, according to which the different parts of the organ contract, 1st. Extent. In a healthy and moderately fleshy subject, the pulsations of the heart are heard only in the space between the cartilages of the fifth and sixth true ribs, and under the lower part of the sternum. Those of the left cavities correspond principally to the first point, and those of the right to the second. If the sternum is short, we hear the pulsations in the epigastrium also. When the subject is so fet that Vol II, 27 21U DESCRIPTIVE AN ATOM 1 ihe ventricles, which then contract on it, and throw it into the arteries at their base. A small quantity of the fluid however always returns from the arteries into the ventricles, from these into the auricles, and thence into the veins which open injo them. 3d. The cavities of the heart are almost entirely empty when they contract. However a little blood always remains, which is attached especially to the reticulated surface of their inner face. 4th. When the ventricles contract the apex of the heart beats against the anterior wall of the chest, notwithstanding that the organ shortens. This arises principally because that the auricles are then filled, both by the blood disgorged by the veins and by that which i hey cannot be felt by the hand, the space in which they can be heard by the stethoscope is sometimes only about a square inch. In thin persons, when the chest is narrow, and even in children, they always have more extent. They may be heard in the lower third, or even in the three lower fourths, of the sternum; sometimes also, under all this bone, at the left anterior and upper part of the chest to near the clavicle, and • sometimes, but less manifestly, under the right clavicle. The subject rarely enjoys perfect health when the extent of the pulsations exceeds these limits, so that Jhey are heard in the left side of thcche3t, from the axilla to the region corresponding to the stomach; and to a similar extent on the right side, at the left posterior part of the f best; finally, on the right posterior part, a successive progress, which would seem fp be constant, and which is attended with a progressive diminution in the intensity uf the sound. In this respect wc may state as a principle, that the extent of the heart's pulsations is directly as the feebleness and the thinness of its parietes, especially those uf the auricles, and inversely as their force and thickness. 2d. Impulse of the heart. In contracting, the heart g-ives a sensation of percus- sion, raising or repelling the hand, or any other part placed upon the anterior walls of the thorax. In some individuals this impulse J3 visible, and sometimes causes a very extensive motion, which raises the parietes of thd chest, the epigastric region, and even the clothing. It is however but slightly marked when the proportions of the heart are normal, and is often imperceptible in fat people. It is perceptible only during the systole of the ventricles. If the contraction of the auricles sometimes produces a similar phenomenon, it maybe distinguished from the first, inasmuch as most generally it consists only in a kind of rumbling, which is heard very deeply in the mediastium. This impulse is generally perceptible only between the cartilages of the fifth and sixth true ribs, or, at most, in the lower half of the sternum, andin some subjects, when the sternum is very short, in the epigastrium. Generally speak- ing, it is inversely as the extent of the pulsations, and directly, as the thickness of the ventricles. 3d. Nature of the sound. On listening attentively we distinguish during the pul- sations of the heart two distinct sounds: one, duller and continued; the other, quicker, and more distinct. The first is simultaneous with the pulsations of the arteries and marks the contraction of the ventricles; the second is caused by the contractions of the auricles. That heard at the lower part of the sternum belongs to the right cavi- tLesi r distinffuished between the cartilages of |the fifth and sixth ribs depends on the left cavities. In the normal state, this noise is similar and equal on both sides; and is no where so loud as in the precordial region. It is as much stronger as the parietes of the ventricles are thinner, and as the power of impulse of the heart is less. *u * Rythv\\ The duration of the sound caused by the auricles is shorter than of that produced by the ventricles; hence, the contractions of the auricles do not con- tuiuc as long as those of the ventricles. There is a well marked but short interval ol rest between these two sounds. This observation proves that the heart, like all other muscles, is alternately m a state of action and of rest. We may admit, that of the twenty-four hours, the ventricles have twelve and the auricles eighteen hours of rest; in supposing also that the cavities of the heart are entirely passive in their dilatation. u-u \u aennec a.dK"t8 that in the most general state of the whole duration of time in which the successive contractions of different parts of the heart, occur, a third at most, or even a quarter, is occupied by the systole of the auricles; a fourth, or a little less. by absolute rest, and a little more than a half by the systole of the ventricles. F. T ANGEIOLOGY. 211 flows back from the ventricles, so that the latter are pushed forward; but it depends also a little on the extension of the arterial trunks at the moment when the arterial blood which is sent from the ventricles passes through them.(l) From not attending to these last two cir- cumstances it was for a long time impossible to explain the pulsations of the heart during its contractions, except by admitting that it length- ened in performing this motion, which is very improbable. 5th. The mean number of pulsations of the heart in the adult is seventy per minute. But it varies much according to the individual. The pulsations are generally more feeble and fewer in the female If we except the early periods of life when the contractions of the heart are few, the number of its pulsations is much greater the nearer it is to the period of its formation. 6 th. We generally consider the heart as that part in which irrila- tability continues the longest. But it follows from the observations of Haller, Zimmerman, and Oeder, that there are exceptions to this law ; and the observations of Fontana, Creve,(2) and Nysten,(3) with which our own agree, demonstrate that this is not true, at least to the arterial portion, since the ventricles lose their irritability before the other mus ■ cular parts of the body; but the auricles preserve it the longest,(4) and that the right auricle remains initable longer than the left. Hal- ler has attempted to prove that this latter difference depends on the circumstance that the right auricle is stimulated longer by the blood within it,(5) but we have often seen it in hearts which were removed from the chest and totally destitute of blood. Nysten has observed it also in persons who were beheaded. We then have reason to say it depends on the greater tenacity of life in this part of the heart, and the more as the tenacity increases in animals in a direct ratio with the predominance of the venous system in them. 7th. The conditions of the action of the heart are the same as those of muscular action generally. For this then we refer to the details already mentioned in the first volume. (1) When the ventricles contract, the point of the heart strikes the left lateral «"aii of the chest, between the cartilages of the filth and sixth ribs. The two causes men- tioned by the author, the filling of the auricles and the extension of the trunks of tin; arteries, doubtless contribute to produce this phenomenon; but we may admit als^ that Vhile the ventricles contract, their moveable point rises, and performs the motion of a pendulum on the base of the heart, which, being more fixed, serves as a point ot support. 1\ T. (2) Vom Me.tallreize, Leipsic, 1796, p. 100. (3) Recherchcs dephysiol. et de chimie, Paris, 1811, p. 307. (4) As Davy observed in experiments for another purpose. See his Researches nv nitrous oxide, London, 1800, p. 352. |5) Decordis motu a stimu'.o nato, in the Comm. frntt.,v^]. i. 212 UE&CRIPTIVE ANATOMY CHAPTER VI OF THE HEART IN THE ABNORMAL STATE. § 1318. The anomalies of the heart are divided into two sections, according as they affect the form or the texture of this organ. We shall mention here only the first, having spoken of the latter in the first volume, when treating of the alterations in the texture of the vessels, of the muscles, and of the serous membranes. § 1319. The deviations in the formation of the heart embrace ano- malies which may exist in number, situation, volume, and figure. § 1320. In regard to number, the heart may vary from the normal state in two opposite modes, that is, may be either wholly or partially deficient, or may have supernumerary parts. The heart is entirely absent only when the upper half of the body is very imperfectly developed, and the head is then usually deficient. However, this rule presents but rarely exceptions of two kinds: for, first, the heart sometimes appears when the head does not exist ;(1) and secondly, this organ is sometimes wholly(2) or partly deficient(3) in monsters where the trunk and head are not very much deformed. We shall speak of the partial absence of the heart hereafter. The plurality of the heart, the body being simple, is infinitely more rare, however common it may be when the body is double, but is not seen constantly even in the latter case. We know of but one instance of a perfect plurahty of the heart where the body was single. We are led to this anomaly by the fissure of the ventricles and by the conge- nital existence of abnormal and hollow appendages to the heart.(4) § 1321. The anomalies in the situation of the heart are congenital or accidental. In the first case the organ exists sometimes within, and sometimes outside of the cavity of the thorax. When found in the chest it may be, 1st. Straight, and then either perpendicular, or horizontal, or finally placed so that its summit looks upward.(5) 2d. Reversed, having its base to the left and its summit to the right, an anomaly which exists singly or which is attended with the more or less perfect inversion of the other organs.(6) (1) We have collected all the instances of this anomaly in our Handbuch derpatho- legischen Anatomie, vol. i. p. 165. (2) See our Handbuch der path. Anat,, vol. i. p. 414. Besides the cases there men- tioned, two have been published since; one by Brodie (Phil. Trans. 1811), and the other by Lawrence (Med. Chir. Trans.), vol. v. (3) Rcederer, in the Comment. Gott., vol. iv.—Meckel, Handb. der path. Anat., vol. i. p. 421. r ' (4) We have collected all the cases of this anomaly in Meckel, De duplic. monstrosa. p. 53, and Handb. der path. Anat., vol. ii. p. 33-45. (5) Meckel, Handb. der path. Anat-, vol. i. p. 418.—Bertin in hit work has figured a heart which was situated transversely in the cavity of the thorax. (61 One case of this kind now before us has been figured in Meckel, De conditionihm rordjs nbnorm., Hallo. 180& vol j ANGEIOLOGY. 213 3d. Deeper than usual.(l) When it exists out of the chest two cases are possible. 1st. The anomaly being slight the heart hangs loosely outward, either in its usual place(2) or higher than it is generally, in the cervical region.(3) In this case the pericardium is usually but not always deficient. On the other hand it sometimes but very rarely happens that this membrane is not found even when the heart is situated in the chest, and then it is replaced by the pleura.(4) 2d. The anomaly existing in a greater degree which is also still more rare, the heart is found in the abdomen,(5) a deviation of formation to which the very sloping situation of this organ in the pectoral cavity leads. The accidental anomalies in the situation of the heart depend on the accumulation of solids or hquids within the chest or the penetra- tion of foreign bodies there, and follow no constant and fixed laws. § 1322. Anomalies in the volume of the heart are congenital much less frequently than accidental. They however sometimes have the character of a primitive formation, and are even hereditary in many families. The heart is then too small or too large. We often find both of these anomalies in the different parts of the same heart. The smallness of the heart(6) is much more rare than its excess in volume. It is often carried to an extreme point although the forma- tion of the organ is unchanged.(7) As to the excessive size of the heart, we must distinguish the pure ^.nd simple increase in its mass, the thickening of its parietes,(8) from the thickening of its parietes with an increase in its capacity,(9) and from its simple dilatation or an increase in its capacity(10) with or without a thinness of its parietes, since we find all these states sometimes insu- (1) Meckel, Handb. der path. Anat., vol. i. p. 417. (2) Id. Ibid. vol. i. p. 406. (3) Id. Ibid. vol. i. p. 98,99. (4) See our Handb. der path. Anat., vol. i.p. 110. (5) Deschamps has mentioned an instance of this in Sedillot, RecueU periodique, vol. xxvi. p. 275-279. (6) We have mentioned several cases in our Handb. der path. Anatomic, vol. i. p. 470-472. (7) Consult also, on the wasting of the heart, Laennec (De Pause. Med. vol. ii. p. 291), and Bertin (Des mat. du ceur, p. 387). The latter admits two kinds; one where the walls of the heart are collapsed, the other where the same parietes, especially those of the ventricles, are, on the contrary, dilated, and at the same time become thinner; this is the state termed passive aneurism. F. T. (8) Different instances of the simple increase of the mass of the heart have been reported by Vetter, Aphorismen aus der pathologischen Anatomie, p. 99.—Legallois, in the Bullet, de I'Ec. de Med., 1813, 1814, p. 69.—Morgagni, Ep. anat. mcd., 30 to 20—Burns. (9) We find several cases of it in Morgagni, Epist. anat. 18 to 28, and 30.—Corvi- sart, Malad. du ceur. p. 61. (10) Many instances of this anomaly are mentioned in Burns.—Morgagni, Epist, anat., 18 to 2, and 14.—Dundas, On a peculiar disease of the heart, in the Med. surg. Trans., vel. i. p. 37. 214 DESCRIPTIVE ANATOMY. lated and sometimes united.(l) The last two are termed aneurisms of the hbart, which in the first case is called active, and passive in the second. The active aneurism is more common on the left side and the passive on the right. These two states usually coexist, the left side being dilated actively, and the right side passively, to a greater or less degree.(2) Sometimes the parietes of the left side have only become thicker, and those of the right side are on the contrary thinner, with or without dilatation at the same time.(3) However it often happens that one part or the other is diseased, each in its (1) This distinction neglected by Corvisart who understands by the terms active aneurism and passive aneurism only a dilation of the heart with a thickening or thin- ness of its parietes, was made by Bertin in 1811, in a memoir presented to the Insti- tute. Bertin admits three distinct^orms of hypertrophy of the heart, that is, of its total or partial fleshy thickening: 1st, simple hypertrophy, in which the cavities of the organ preserve their natural capacity, at the same time that the parietes are more or less thickened: 2d. aneurismal hypertrophy, in which the cavities are dilated and the parietes are thickened; this is the active aneurism of Corvisart: 3d, concen- tric hypertrophy, in which the thickening of the parietes is attended with a greater or less contraction of the cavities. He also distinguishes two kinds of aneurismal hypertrophy ; one in which the parietes are thickened, and the other where the pari- etes preserve their natural thickness, so that the increase takes place in some mea- sure according to the extent and the circumference, or according to the surface. He has also remarked, that in the hypertrophy of the ventricles the thickness often dimi- nishes from the base to the point, but it is sometimes about the same at the point as at the base, and in some cases is more marked in its centre, and diminishes toward the point and even toward the base. It may be equal to fifteen lines, and more, although Laennec asserts that it never exceeds four or five lines. Sometimes we find in the same ventricles one portion which is dilated and thickened, and another contracted and thickened, or one part thin, while tbe other is thick. We sometimes observe a great difference between the parietes of the ventricles, especially on the right side, and the fleshy pillars, the. latter being doubled or tripled in extent, while the parietes are not, or but very slightly, thickened. In other cases, the hypertrophy of the left ventricle seems to take place at the expense of the pillars, which are effaced or are hardly visible. The hypertrophy of the left ventricle is generally attended with that of the septum. We sometimes observe also a hypertrophy of the inter- ventricular septum only. The fleshy pillars of the right ventricle have been found so thickened and intercrossed that there was hardly any cavity. Hypertrophy also of- ten affects both ventricles at once, but not unfrequently they present an opposite state. The point of the thickened ventricle always descends lower than that of the other! The three forms of hypertrophy are observed in the auricles, but the aneurismal is the most common. The thickening is nearly equal in all the extent of the parietes ' especially in the left auricle. The muscular fasciculi of the right auricle sometimes increase in volume. Finally, in certain cases, the parietes of this auricle are so much thickened in all their parts, that they imitate those of the corresponding ven- tricle. Again, whatever may be the form of the hypertrophy, Bertin admits, as its immediate and proximate cause, an irritation applied to the heart, which increases the activity of the phenomena of nutrition in this organ (Des maladies du ceur p ^^J-i^Ltf^lilt^u .thj;e5.kindf °,f dilatation of the heart, or to proper aneurism: 'pertrc Corvi usual thickness, or simple dilatation," whTch'has' not" hitherTo' beeT re "arded.UTo ^"k &T™S?T «r "^^.a/ourth, which is doubtful; the mixed dilatation, in which the Parietes of the dilated cavity are thicker in some parts and thinner in others, and of their natural thickness in the rest. (Ibid. p. 368.) Consult also on hypertrophy ofthe heart, La^ rarcoses du ceur, in the Archiv. gen. de mid. vol v p 520 ««» «^ic/ (2) Morgagni, Ep. anat., an. m. 40 m 23.-Testa, Mai. 'del cuore. iii c Xv ' ?A Morgagni. Ep. anat. m. 30 to ?o. tHV - '"•l • x^ ■ ANGEIOLOGY 215 usual inanner.(l) The disease does not necessarily effect an entire half. Generally, passive aneurism exists only in the right auricle, and active aneurism only in the left ventricle, whether these two states exist alone, or whether they are both found in the same heart. Sometimes however, but rarely, the right side is entirely or partially thicker than usual, or at the same time dilated ; and then sometimes the left side is also affected and sometimes it is not: sometimes also it prebents a passive aneurism, or at least its walls have become thinner. Perhaps the passive aneurism is still more rarely confined to the left ventricle, while all the other parts of the heart are in the normal state.(2) These affections are confined to one part of the heart only, much more generally than they are extended to the whole of it. Nevertheless, if we except the active aneurism of the left side, combined with the pas- sive aneurism of the right side, which is frequently observed, we some- times find hearts which are affected equally in every part.(3) . The diseased cavity of the heart is most generally dilated in its whole extent. A partial dilatation in the form of a cul-de-sac rarely ex- ists. The substance of the heart is sometimes, but very rarely, thicker in some parts from round excrescences which project on its internal face. We know of but one instance of this arrangement, and the specimen is in our cabinet. This is still more curious, as it throws much light on the formation of the polvpi of the heart, which are ex- plained with difficulty unless we admit that one or more of these ex- crescences are detached from their place of origin.(4) § 1323. The anomalies in the form of the heart relate either to its external or to its internal arrangement, or finally to both. They are congenital much oftener than accidental. § 1324. The congenital anomalies in the external form are, (1) We find instances of the active aneurism of the left ventricle in Lancisi, De rep. mart., p. 137.—Lafaye, in the Mim. de Paris, hist., p. 29.—Corvisart, Journ. de mid. vol. xi. p. 257.—We find cases of the passive aneurism of the right ventricle only in Fleury, Bull, de VEc. de mid., 1807, p. 124.—Morgagni, Epist. anat., m. 18 to 6. (2) We find one case in Corvisart, p. 99. (3) Different cases which prove this proposition, both in respect to the simple thickening of the parietes, and also to passive aneurism, are mentioned in Vetter, loc. cit., p. 99.—Burns.—Morgagni, Ep. anat., m. 18 to 2, 28, 30. ep. 53 to 9.—Corvi- sart, p. 61, 87.—Testa, loc. cit., vol. iii. ch. xvi. a, 7, 8, p. 361-367. (4) Laennec relates several cases of this abnormal arrangement (Dc Vauscultation mediate, vol. ii. p. 344) which he terms globular excrescences of the heart, and which he compares to the excrescences of the valves. Meckel's mode of explaining them cannot be maintained. Bertin (loc. cit., p. 444) not only admits with Corvisart, Testa, Burns, Creysig, and Laennec, that polypi, or rather fibrinous concretions, may form, during life, in the heart, as in all other portions of the sanguineous system; but he also adopts Kreysig's theory, and regards them as resulting from an effusion, which occurs after inflammation of the inner membrane of the heart. These concre- tions are most generally free from all adhesions, at least organic; but sometimes also they are perfectly organized, and have numerous vessels injected in bright red or black. This important fact, of which Bouillaud has published two remaikable instances (Obs. et cons. nouv. sur Voblitir des veines, in the Arch. gen. dc mid., voi. v 216 DESCRIPTIVE ANATOMY. 1st. The form of the heart is more rounded; this is sometimes met with alone, but is usually attended with several other anomahes already mentioned, or which remain to be described, as prolapsus, perpendicular position, &c. ... 2d. The deep fissure of the summit of the heart, to wmch our remarks on the preceding anomaly apply. The accidental anomalies in the external formation are principally the solutions of continuity, which must not be confounded with those which are congenital, for the latter implicate the inner form, and they consist essentially in anomahes of the connection of the two portions of the heart. Solutions in continuity of the heart axe fissures or wounds. Fissures( 1) occur most generally after those pathological changes which supervene in the substance of the heart itself, or in the arterial trunks. They less commonly depend on external injuries, which do not directly affect the substance of the heart, but act either on the parietes of the thoracic cavity, or on the organs within it. 1st. The changes in the substance of the heart giving rise fissures, are produced principally by inflammation, ulceration, and gangrene,(2) which soften this substance,(3) and gradually destroy it in one or more parts, so that there is finally a solution of continuity during the systole or the diastole. One can imagine that tins species of fissures is equally frequent in all parts of the heart. 2d. Those on the contrary which depend on morbid changes super- vening in the arterial trunks occur in some points more frequently than in others, and are probably more common in one sex than in the other. E. 95, and 101), throws great light on the theory of the formation of polypi of the eart, inasmuch as we can no longer doubt that their organization takes place in the same manner as that of the false membranes, and depends en the same cause. F. T. (1) Bland, Mimoirc sur le dichirement sinile du ceur, in the Bibliothcque midi- cale, voL lxviii. p. 364.—Rostan, Mimoires sur les ruptures du ceur, in the Nouveau journal de medicine, vol. viii. p. 265.—A. J. L. Bayle, Observation de rupture du ceur, in the Revue midicale, vol. iii. p. 96.—Carrier, Observation sur une double rupture des parois du ventriculc gauche du ceur, in the Journ. univ. des sc. medi- cates, vol. xxxv. p. 358. (2) Although, strictly speaking, gangrene of the heart is not impossible, it is at least so rare that those observers in whom the fullest confidence can be placed have not seen it. Thus Corvisart does not hesitate to say that no well authenticated case of it exists. Most of the facts which have been reported, being stated in a faithless manner, should be received only after strict examination and admitted with distrust. Such is the very wise opinion of Bertin (Des malad. du cavr, p. 408), who thinks that these facts should be considered as acute softenings of the heart rather than real gangrenous affections. p. T. (3) Laennec first called the attention of pathologists to softening of the heart, of which he admits two species, one where the substance of the organ is more deeply colored, and the other where it is discolored, or rather has a whitish or yellowish tinge (De Vauscultation, vol. ii. p. 186). He asserts that he has found this softening in all cases of fevers called essential, when he has attended to them. He does not however consider this as a character of inflammation. Bertin thinks it is caused by inflammation of the heart, which is acute when it is of a deep red or even brownish, and Aronic, when the muscular tissue of the organ is discolored and becomes pale or yellowish. F. T. ANGEIOLOGY. 217 Thus the part of the heart most frequently ruptured is the left ventricle, and this accident is more common in the male than in the female, be- cause the ossification of the valves and the contraction of the arterial orifice, which is a consequence of it, are observed in the left more fre- quently than in the right, and in the male oftener than in the female. When this occurs, the substance of the heart is thinner less frequently than it is thickened and hardened. The normal difference between the right and left portions of the heart also accounts for the greater frequency of the fissures on the left side, since the right side is less tense and more extensive than the other. The normal arrangement of the heart explains also why fissures occur in one part of the ventricles rather than in another. This point is commonly the place where the arterial trunk unites to the ventricle/1) because there is no continuity in this place between the fibres of the heart and those of the arteries. The place where fissures occur most frequently, next to this, is the apex of the heart, as there the substance of the organ is thinnest. Contusions of the chest or the forcible penetration of foreign bodies, as of musket-balls, also tear the heart, even when the parts surrounding this viscus are uninjured. Besides these fissures, which are visible externally and which pass through the heart entirely, there are others which are much less frequent, and where either the tendons of the venous valves or the fleshy pillars are detached from their points of insertion. The latter almost always result from violent efforts or emotions.(2) Wounds of the heart are or are not attended with the presence of the wounding body. In both cases they pass through all the substance of the organ or affect only its surface. Wounds attended with the presence of the foreign body are seen principally after musket-wounds, when the ball, not having power enough to pass through the heart, remains within it or probably insinuates itself by degrees, the wound cicatrizing behind it as it advances. In both these cases the individual has sometimes survived so severe an injury, but this is rare.(3) (1) This assertion is not correct. Ruptures of the heart occur always, or most generally, toward the apex and the anterior part, that is, in the thinnest part. In this respect, Rostan has observed that the disproportion of the diameter is such, that often, when the diameter of the upper part of the ventricle is sixteen or eighteen lines, which he asserts is the greatest development which it can attain, the apex is only two lines thick. Bayle has mentioned, that of nineteen instances of rupture of the heart, fourteen existed in the left ventricle, principally its anterior face near tho apex, three in the right ventricle, one in the apex, and the other in the interventricular septum. In most of the cadavers the heart was remarkably soft, and in some cases a brownish color was observed around the perforation. These two circumstances sup- port Bertin's opinion, who (Des maladiet du ceur) thinks that the preceding erosive inflammation plays an important part in these perforations, as in those of the stomach and intestines. F. T. (2) Corvisart, loc. cit., p. 256, De la rupture partielle du ceur. (3) We find an instance of the first case in the Diet, des sc. mid. vol. iv. p. 217, and one of the second in Penada, Saggi sc. diPadova, vol. iii. part 2, p. 59 Vol II .28 216 DESCRIPTIVE ANATOMY Penetiating, cutting, or pricking wounds are always and almost im- mediately mortal.( 1) In order to conceive of a contrary case, we must admit that the wounding instrument penetrates gradually.(2) § 1325 Most of the deviations in form in the inner parts of the heart are congenital. They comprise, 1st, those which cause no derange- ment except in the circulation of the blood; 2d, those which derange the formation of the blood. . ..... § 1326. The deviations of form in the first class consist principally in the abnormal arrangement of the several orifices of the heart. Among these are: 1st. The abnormal narrowness of the venous orifices of the ventri- cles.^) This anomaly occurs most frequently on the left side, and is not rare. The mitral valve is then always thickened, more or less hardened, and often ossified. It is very doubtful if this anomaly ever be congeni- tal. At least it is not so generally. 2d. The abnormal narrowness of the arterial orifices of the ventricles. This congenital aberration occurs most frequently on the right side, and almost always results from a contraction, often also from an ad- hesion of the valves. (1) Wounds of the heart are generally mortal after a few moments, or at most some hours. Some wounded persons have been known to survive one or five, seven, thir- teen, seventeen, and twenty days, after penetrating wounds. See the surgical part of the article Cceur, by Begin, in the Diction, abrege des sc. medic, vol. iv. p. 493. b. 1. (2) Although it did not form apart of our author's plan to speak of the alterations in the texture of the heart, we think it necessary to say a word upon its hardening, the theory of which appears to be intimately connected with that of its hypertrophy, its polypi, and its softening, that is with its irritation more or less approaching to the degree usually considered as inflammation. General hardening of the heart has not yet been noticed; but it may be more or less extensive and sometimes invade an entire half of the heart. It is often confined to the internal or external face, where it is presented under the form of incrustations. The fleshy columns and the septum' may also be the exclusive seat of it. It presents several degrees. Simple hypertrophy is the first and ossification the last. There are different shades between these two extremes; sometimes the substance of the heart, of a bright red color and almost healthy in appearance, resembles in hardness a fibro-cartilage, and resists or grates when cut: sometimes it presents a cartilaginous density and solidity: again it is still harder and sounds like horn, as Corvisart says; sometimes it resembles earth or sand (Bertin, Des mal. du ceur, p. 401). Ossifications of the heart are not rare in man. Meckel has collected several instances in his Dissertatio de cordis conditioni- bus abnormibus, Halle, 1802, and in his Manual of Pathological Anatomy. It is cu- rious that in many animals, especially in the ruminantia, there is very often a bone in the heart. This has long been known in regard to the ox and the stag. See on this subject Keuchen, Diss, de ossiculis e cordibus animalium, Groningen, 1772.— Jaeger, Veber des Vorkommen eines Knochen im Herze des Hirsches; in the Deut- sches Archivfur die Physiologic, vol. v. p. 113.—F. S. Leuckart, Bemerkungen iiber den Herzknochen des Hirsches; same journal, vol. vi. p. 136.—We think it worthy of mention, however, that Masuyer has found 1,7 of phosphoric acid, 2 of uric acid, 3 of animal matter, 5,3 of lime, in twelve grains of the ivory substance coming from the ossification of the valves of the heart, from its external face at the base of the right ventricle, and from the aorta, and also from the large branches which arise from it (Journal de la sociite des sciences, agriculture, et arts, de Strasbourg, 1824, No. 3). The presence of uric acid in this case is remarkable as an analogy with what is seen in arthritic concretions F. T. (3) Abernethy, On a diminution in consequence of disease of the area of the aper- ture, by which the left auricle of the heart communicates with the ventricle of the same; in the Med. chir. trans, vol. i. p. 27. angeiologt 219 3d. The deficiency or adhesion of the valves, especially those of the arteries, sometimes occurs, and is not generally congenital but acci- dental. The absence of the valves is caused by their destruction by suppuration, and their adhesion results from inflammation and ossifi- cation. 4th. An excess or deficiency in the number of the valves, which is seen particularly, but yet seldom, in the pulmonary artery, and much less frequently in the aorta. We find four valves more commonly than two. § 1327. The essence of the deviations in form of the second division is an abnormal communication between the systems of red and black blood. They have no influence on the formation of blood, or when they possess it, the arrangement is such that the black blood becomes less venous or the red blood less arterial. In both cases the abnormal union of both the systems of blood may take place in very different parts. 1st. The abnormal communication of the first kind depends, a. On the insertion of one, of several, or of all the pulmonary veins in the vena cava superior. We have a case of this land before us. b. On the existence of an accessory pulmonary artery, which arises from the ascending aorta.(l) 2d. The abnormal communications of the second kind occur either between the auricles, or the ventricles, or in the large vascular trunks. Many or all these anomalies are not unfrequently combined in the same subject.(2) a. The most simple form is a single heart, consisting of one muscular cavity. b. Next follows the formation where only one auricle and one ven- tricle exist, whence a single vessel, the aorta, arises, from which the pulmonary artery branches off, while the pulmonary veins open into the auricle, or even, by a formation still more abnormal, into the vena cava superior. The formation is more perfect when the heart is divided by a septum into two halves, and the aorta and the pulmonary artery arise by sepa- rate trunks, but the septum is imperfect. c. In this case the septum of the ventricles and of the auricles is per- forated and the foramen ovale is open, which is the case most fre- quently; or, d. Only the septum between the ventricles is perforated, a more un- frequent formation; or, e. Only the foramen ovale is open; this is the most usual. (1) We have collected all the known cases of this anomaly, in the De monstrosd duplicitate, p. 55, and in Handb. der pathol. Anat., vol. ii. p. 134. (2) The different degrees and in general most of the species of this class of ano- malies are described in our Handbuck der pathol. Anat., vol. i. p. 422-470, vol. ii. p. 133 134.—Farre, Pathological researches, Essay 1, On malformations of the human heart, London, 1814.—J. C. Hein, De cordis deformationibus que sajiguinrm vrnosvm <~«m artrrinso misceri permittunt, Gottingen, 1816. 220 DESCRIPTIVE ANATOMY The septum of the ventricles is perforated generally in one determi- nate place, viz. the base; so that sometimes the aorta, sometimes but more unfrequently the pulmonary artery, arises from both ventricles: in the latter case the aorta arises as usual, but forms only an ascending portion, and terminates in the left subclavian artery, and the descending aorta comes entirely from the pulmonary artery. The interauricular septum is frequently developed imperfectly, that is, its formation has not followed the course mentioned above (§ 1305), but the pressure of the left auricle can then complete it; so that the passage of the blood from this auricle into the right becomes impossi- ble. Sometimes however, but more unfrequently, from the absolute or relative smallness or deficiency of the valve of the foramen ovale, this opening is so large, that the right and left auricles communicate freely. This continuance of the foramen ovale is more unfrequent than the perforation of the septum, although its imperfect closure, produced in the manner stated above (§ 1305), is an anomaly still more frequent. than this. The abnormal arrangements of the large vascular trunks, which render the hematosis imperfect, are, / The obliteration or the considerable contraction or deficiency of the pulmonary artery, states which commonly but not always attend one of the anomalies mentioned above. g. The continuance of the-arterial canal, which seldom occurs alone, but is generally attended with one of the anomalies already described or which remain to be mentioned. h. The existence of a second pulmonary artery, which arises from the right ventricle and terminates in the aorta. Finally, The transposition of the origins of the arterial or venous trunks, viz. i. The origin of the pulmonary artery from the left and of the aorta from the right ventricle, while the venous trunks empty themselves in their proper places.(l) k. The insertion of the veins of the body into the left portion of the heart, or into the pulmonary veins, or frequently into the pulmonary artery. This occurs in different ways. We have before us a prepa- ration where the large coronary vein of the heart, instead of terminating in the nght portion, opens into the left auricle of the heart. In another case, the vena azygos is divided near the heart into two branches, one of which goes to the right, the other to the left auricle. Sometimes the pulmonary arteries evidently anastomose with the azygos vein lhe physiological influence and importance of these anomalies are not the same. t In the first point of view, we may state it as a principle, that the first six arise because the formation of the heart is arrested at an early period of development, and because it is a repetition of the formation of the ^St^. ANGEIOLOGY. 235 trunk in common with the superior thyroid artery, but more frequently, and nearly once in seven times, with the facial artery. It is generally a little larger than that we have mentioned. This artery curves considerably, and its convex part looks upward, passes then directly over the large hom of the hyoid bone, goes hori- zontally forward, glides between the middle constrictor of the pharynx and the hyoglossus muscle, and then ascends towards the base of the tongue, where it recommences, and then goes horizontally forward, along the inferior face of this organ. From its posterior part arise, 1st, several branches, which go to the hyo-glossus muscle and middle constrictor of the pharynx, and which, having passed through the latter, enter the digastricus and the thyro- hyoideus muscles, and the submaxillary gland; 2d, a branch which goes downward and inward, between the genio-glossus and the genio- hyoideus muscles directly on the hyoid bone, gives branches to these muscles, especially to the first, and anastomoses with that of the oppo- site side. It is called the hyoid branch (R. hyoideus). From the central ascending part arise one or more dorsal arteries of the tongue (R. dorsales lingua), which go downward to the posterior part of the tongue, on the inside of the hyo-glossus muscle, ascend upon the back of this organ, and advance to the epiglottis. The lingual artery divides, in front of the hyo-glossus muscle, into a ranine and a sublingual artery. The ranine artery (A. ranina) is larger than the other, and is a continuation of the trunk. It extends deeply between the lingualis and genio-glossus muscles, proceeds forward, gives off several branches in its course, and finally anastomoses with that of the opposite side, behind the summit of the tongue, at the upper end of its frenum. The sublingual artery (A. sublingualis) is more external and more superficial than the preceding. It passes over the mylo-glossus muscle, between it and the sublingual gland, gives off branches to it, to the hyo-glossus muscle, to the lingualis muscle, and to the proper membrane of the mouth, passes over the mylo-hyoideus muscle, and anastomoses with the inferior maxillary branch of the facial artery. This artery sometimes arises from the facial. III. FACIAL ARTERY. § 1351. The third branch, the facial or external maxillary artery {A. facialis, facialis anterior, angularis, maxillaris externa), varies in respect to its origin, size, and extent; it is commonly the largest of the three anterior branches of the external carotid, and supplies all the anterior part of the face ; but sometimes also it extends only to the angle of the mouth, and. the other branches are supplied from the temporal artery. There is scarcely a vessel which varies so much as this, even in the two sides of the same body. 2&i DESCRIPTIVE ANATOMY It passes under the posterior belly of the digastricus muscle to go to the angle of the lower jaw. In this place it proceeds first horizontally behind and within the inferior edge of the lower jaw, then goes ob- liquely upward and forward on the inside of this bone and of the upper jaw. It frequently gives off, directly above its origin, the inferior or ascending-palatine artery (A.palatina ascendens, s. inferior), which usually arises from the ascending or- inferior pharyngeal artery (A. pharyngaa ascendens); we shall describe it with'that. It then gives small ramuscules to the digastricus and stylo-hyoideus muscles. Farther on, it gives off considerable branches which go to the sub- maxillary gland '(R. glandulares), and goes forward in one of its grooves. Farther onward, it gives off one or more ramuscules to the pterygoideus internus muscle. It then furnishes the submental artery (JJ. submentalis). This arises near the lower edge of the lower jaw, and proceeds along it, directly below the attachment of the mylo-hyoideus muscle, and over the ante- rior belly of the digastricus muscle, gives ramuscules to both of these muscles, anastomoses with the sublingual artery, and thus goes forward, where it communicates with that of the opposite sidi, on the centre of the lower edge of the lower jaw. Thence it reascends into the sub- stance of the lower lip, to which it gives twigs, as also to the skin of the chin, and anastomoses with the descending branches of the coro- nary artery of the lower lip, and also with those of the inferior, dental artery, which emerges from the mental foramen. When the sublingual artery is a branch of the'facial it arises a little, and even in most cases directly before the submental. The continuation of the trunk, or the proper facial artery, turns upon the lower edge of the lower jaw, generally directly before the anterior edge of its ascending branch, thus attains the outer face of this bone, de- scends very obliquely between the masseter and the triangularis oris muscles, arrives at the angle of the lips, and gives off in this place several branches, which enter the masseter, the triangularis and the buccinator muscles and the skin. About the centre of the space between the angle of the mouth and the under edge of the lower jaw, it generally divides into two branches. One, the continuation of the trunk, goes directly upward ; the other is smaller, and proceeds more obhquely inward and forward. The latter is the inferior coronary artery of the lip (A. coronaria labii inferioris). It passes under the triangularis oris muscle and proceeds toward the lower lip, gives several branches to this muscle, to the levator menti, and also to the membrane of the mouth, and anastomoses both with its fellow of the opposite side and with the twigs of the submental and inferior dentar artery. This artery is sometimes much smaller on one side than on the other. In some subjects it is even entirely deficient, and is then replaced by ANGEIOLOGY. 237 that of the opposite side. Sometimes it arises much higher and comes from'the superior coronary artery of the lip. In some cases it is double: one of the two then arises much above the other; but the two arteries taken together are not larger than that of the opposite side: sometimes the two branches into which the lower coronary artery of the lips is divided are very small. After giving off this branch, the facial artery winds tortuously up- ward and inward. Arrived as high as the angle of the mouth, it gene- rally divides, a little above this point, into two branches. The larger goes inward and forward, between the fibres of the orbi- cularis oris, and is called the superior coronary artery (A. coronaria labii superioris). This artery proceeds directly over the loose edge of the upper hp, gives ramuscules to the orbicularis oris, to the levator labii superioris, to the skin, to the buccal membrane, meets that of the opposite side and anastomoses with it by a broad communication similar to that between the inferior coronary arteries. The two coronary arteries usually anastomose together in two places by large branches: some- times the anastomosis between the arteries is very small on one side, but is replaced by a very large branch, which arises higher up from the facial and which communicates with the artery of the septum of the nose. Both coronary arteries are very tortuous, but the upper is more so than the lower. Both anastomose with the synonymous arteries of the opposite side, and these anastomoses are proportionally the largest in the body, when we consider the vessels between which they occur. The superior coronary artery always gives off from its centre, where it anastomoses with that of the opposite side, a branch, which goes upward toward the nasal septum, which is called the artery of the sep- tum of the nose (A. nasalis septi). Sometimes this artery is single, some- times double, and even triple, at its origin: in the last two cases it is fre- quently given off by the coronary artery of one side; but however this may be, it divides near the septum of the nasal fossa into at least two branches, a right and a left, each of which proceeds along the lower edge of the septum and the inner part of the corresponding nostril to the end of the nose, and also sends ramuscules, which reascend on the cartilaginous septum. Besides these branches, the coronary artery gives off sometimes be- fore, more externally and on one side only, or on both, another consi- derable branch (R. pinnalis), which goes to the ala and the outer part of the nostril; but this branch more frequently comes from the next one. The facial artery, after giving off the superior coronary, consists only >of a smaller branch, which may be called the common external nasal artery (A. nasalis externa communis). This artery is very tortu- ous, and ascends obliquely forward under the levator labii superioris muscles, to which it gives ramuscules, goes toward the nose, and anas- tomoses by considerable branches with the infra-orbitar artery. It 238 DESCRIPTIVE ANATOMY. usually gives off, opposite the nostril, the lateral arteries of the nose (R. pinnales, s. laterales nasi), and also sends off numerous smaller arterial twigs, which anastomose with each other and also with those of the septum and their corresponding ones of the opposite side, which are called the dorsal arteries (R. nasales dorsales), and which always communicate on the nose by several large or small branches with the ophthalmic artery. Finally, it terminates on the back and side of the nose, and never, even in its greatest degree of extension, goes beyond the upper edge of the cartilaginous portion of this organ. The two coronary and the common external nasal artery, and more frequently only the superior coronary and the latter, sometimes arise not only from the above facial but also from the transverse facial artery, which then is much larger, while the other is smaller, although the facial artery is not necessarily more developed at its lower part; we likewise observe in other subjects that this artery is very much de- veloped at its upper part, although the lower part does not produce more branches than usual. We have seen the sublingual artery coming from it at least several times, and the facial artery at the same time was as large as usual. In other cases, on the contrary, it gives off neither of the two coronary arteries, while the sublingual artery arose as usual; but the submental artery was uncommonly small. Hence it appears that the facial artery is always the principal source of communication, 1st, between the superficial and the deep-seated branches of the external carotid by its anastomoses with the infra-orbitar, the nasal, and the dentar arteries ; 2d, between the external and the internal carotid arteries by its anastomosing with the ophthalmic artery. § 1352. Numerous small branches, which go to the masseter and pterygoidei muscles and to the parotid gland(J2. masseterici,pterygoidei, et parotidei), arise externally and internally from that part of the carotid artery situated between the ascending branch of the lower jaw and the ear. A larger anterior branch, the transverse facial artery, which will be described hereafter, rarely arises from its upper extremity, directly below its division. B. INNER BRANCH. I. ASCENDING OR INFERIOR PHARYNGEAL ARTERY. § 1353. Most generally only one branch arises from the inner face of the external carotid artery; this is the ascending or inferior pharyn- geal artery (A. pharyngaa ascendens, s. inferior, s. posterior), which comes sometimes from the bifurcation of the primitive carotid, some- times from the origin of the internal carotid, but more frequently from ANGEIOLOGV. 239 the occipital artery,(l) and is sometimes replaced by the branches of the facial artery. If it is.a branch of the external carotid, it arises very deeply, most generally above the inferior thyroid artery; so that it is the second branch from the trunk. but sometimes it comes higher up and even above the facial artery.(2) It is sometimes double: then the two inferior pharyngeal arteries rarely come from the external carotid; one arises from the latter, and the other from one of the secondary branches above described, or from the internal carotid artery.(3) It is always the smallest branch of the external carotid artery. It goes perpendicularly upward, on the inside of the external carotid artery, and in the same direction with it, between it and the pharynx. It gives off first the descending branches to the constrictors of the pharynx, and to the anterior and lateral muscles of the neck. A httle farther it divides into two branches, one of which, the pha- ryngeal branch, (R. pharyngaus) is distributed principally to the con- strictors of the pharynx, and communicates with the pharyngeal branches of the superior thyroid artery; the other is termed the poste- rior meningeal artery, (A. meningaa posterior) ascends through the posterior foramen lacerum of the skull, or through a special opening near the occipital condyle, and is distributed to that part of the dura mater which fines the lower part of the skull. C. POSTERIOR BRANCHES. § 1354. The posterior branches of the external carotid artery are, 1st the occipital, and 2d the posterior auricular artery. 1. OCCIPITAL ARTERY. § 1355. The occipital artery (A. occipitalis) is a considerable branch, but much smaller than the three anterior branches, which usu- ally arise opposite the lingual or the facial artery; seldom or never above or below them. It rarely comes from the internal carotid artery. It is very deeply situated; goes upward and backward, often gives off, soon after arising, branches which go to the posterior belly of the di- gastricus muscle of the lower jaw, then a descending branch, which (1) Scemmerring states that it sometimes arises from the superior thyroid artery. We have never seen this, nor is it mentioned by any other anatomist. Scemmerring, it is true, quotes Mayer; but the laryngo-pharyngean artery (A. laryngo-pharyngea) described by Mayer, is the laryngeal branch of the superior thyroid artery, and de- scribes the inferior pharyngeal artery as the posterior artery of the throat. (2) Bichat asserts that it arises between the facial and lingual arteries. Our ob- servations lead us to think that Scemmerring is more correct in saying that it rarely arises higher than the lingual. Murray places it behind the facial, but adds that its origin is near that of the lingual. Portal also places it nearly opposite this latter, as do Sabatier and Mayer. Boyer states that it arises opposite the facial. (3) Soemmering asserts that when it is double, the lower trunk arises from the pri- nt tive carotid, and the superior from the internal carotid. This arrangement exists ,sometimes, but it is not the law. That mentioned by us is much more common. 240 DESCRIPTIVE ANATOMV goes to the sterno-cleido-mastoideus muscle and the upper lymphatic glands of the neck, higher up, gives off wholly or partially the ascend- ing pharyngeal artery, then extends below and deeply between the transverse process of the first cervical vertebra and the mastoid process of the temporal bone, continues its course backward, passing under the complexus minor muscle, then assumes a horizontal direction, gives branches to the upper extremity of the sterno-cleido mastoideus, to the complexus minor, to the transversalis colli, to the small lateral and posterior muscles of the head, and then ascends on the occipital bone, covered by the upper part of the splenius muscle, to which it gives branches. It is then called the superficial occipital artery, proceeds directly below the skin, on this bone to the vertex, terminates in a large anastomosis, formed by its branches with each other and with those of the frontal, the superficial temporal and the synonymous artery of the opposite side. At the place where the occipital artery leaves the space between the transverse process of the first cervical vertebra and the mastoid process of the temporal bone, to pass on the obliquus capitis major muscle of the head, it always gives a deep or descending branch. This branch being sometimes very considerable, and nearly as large as the continu- ation of the trunk, we may then admit that the artery divides at this place into a superficial and deep-seated branch. When this is the case, it descends to the middle of the back, between the splenius, com- plexus, digastricus and transversalis colli muscles. Sometimes, how- ever, it is very small, and then it is distributed in the small poste- rior muscles of the head. The deep-seated branch anastomoses many times with the vertebral artery, and with the cervical branches of the inferior thyroid artery. From the superficial occipital artery constantly arise one of several branches, which pass into the cranium through the mastoid foramina; more rarely through the large occipital foramen or the foramen lace- rum, which are distributed to the posterior and inferior part of the dura mater. They are termed the posterior meningaal arteries. (A. meningeoz posteriores ab occipitali.) 2. POSTERIOR AURICULAR ARTERY. §1356. The posterior auricular artery (A. auricularis posterior) is generally much smaller than the preceding, and arises a httle above it, in the substance of the parotid gland, and is generally separated from it only by the stylo-hyoideus muscle. Sometimes it arises from this artery, and rarely somewhat higher, directly below the division of the external carotid artery into the superficial temporal and the internal maxillary artery. It goes upward, at the side and behind the trunk of the external carotid artery, and passes through the parotid gland, near the mastoid process. There it gives, 1st at its lower posterior ANGEIOLOGY. 241 part, branches which go to this gland, to the posterior belly of the digas- tricus muscle, to the stylo-hyoideus and to the upper part of the sterno- cleido-mastoideus muscles ; 2d, from its superior and anterior part, an ascending branch, the stylo-mastoid artery (A. stylo-mastoidea), which furnishes ramuscules to the auditory passage, penetrates into the canal of the facial nerve through the stylo-mastoid foramen, distributes itself to the mastoid process, to "the tympanum, and also to a portion of the laby- rinth, and anastomoses with a branch of the middle meningeal artery. The trunk of the artery then divides at the level of the mastoid pro- cess into two branches, an inferior or muscular and a superior or auri- cular branch. The inferior branch goes transversely outward, over the upper part of the splenii muscles, gives ramuscules to these muscles, to the trape- zius and to the skin, anastomoses with the superficial occipital artery, and advances toward the occiput. The superior branch goes upward and backward. It usually divides into two or three branches, one of which, the more transverse, goes backward to the mastoid process, and gives branches to it, also to the occipitalis muscle ; while the other, or the others, attain the posterior part of the concha, distribute the small arteries to the retrahentes auriculae, and to the transversus auriculas muscles, then pass over the concha, and thus come on its internal face, where they lose them- selves in the skin and the mucous membrane. D. TERMINATION OF THE EXTERNAL CAROTID ARTERY. § 1357. The external carotid artery terminates at the neck of the lower jaw in two trunks, a superficial, the temporal artery; the other deep-seated, the internal maxillary artery. I. TEMPORAL ARTERY. § 1358. The temporal artery (A. temporalis) is smaller and more superficial than the internal maxillary, and continues in the direction of the trunk. It goes upward and outward. Its branches may be divided into anterior and posterior. The anterior branches are principally the following: 1st. The first branch is often the upper masseteric artery (A. masse- terica superior) which penetrates sometimes to the external and some- times to the internal layer of the masseter muscle, but frequently comes from the next. 2d. The transverse facial artery (A. transversa, s. transversalis faciei)(l) is the second, often the first branch of the artery, and arises (1) Soemmering (loc. cit.. p. 196) mentions it as arising from the external carotid artery, before it bifurcates, and says also that it sometimes comes from the internal carotid artery, and cites as authorities Mayer, Murray, and Walter. But Murray states expressly that it is the fourth branch of the external temporal artery (p. 17). Vol. II. 31 242 DESCRIPTIVE ANATOMY. directly above the bifurcation of the external carotid artery. Some- times, but unfrequently, it arises from the external carotid artery, and most generally from the bifurcation. It goes forward, with the canal of Stenon, on the masseter muscle, directly below its upper edge, gives off the superior masseteric artery, when this does not come from the temporal artery, sends several ramuscules to the skin, penetrates for- ward into a greater or less portion of the orbicularis palpebrarum mus- cle, and anastomoses, by a considerable number of ramifications, with the facial artery, which it meets, and with the infra-orbitar artery. Sometimes this gives off all the upper part of the facial artery. In some subjects its ascending ramuscules extend much higher, and reach the outer extremity of the edge of the orbit. The middle temporal artery (A. temporalis media) generally arises some fines above the transverse facial artery, a httle below the malar bone, a considerable branch, which proceeds first from below upward, gives off one or several ramuscules to the upper part of the masseter muscle, then curves backward at a right angle, between the trunk and the temporal muscle, and terminates partly in small twigs, which penetrate into the substance of the muscle where they anastomose with those of the deep temporal artery, and partly in superficial branches, which are distributed on the auditory passage, where they communicate with those of the posterior auricular artery. After giving off this artery, the trunk of the temporal artery goes upward and forward, on the temporal muscle, directly under the skin, and describes a considerable arch, which is convex posteriorly and terminates as the anterior temporal artery (A. temporalis anterior), anastomosing several times with the superciliary artery, and giving branches to the frontalis muscle, and to the skin of the forehead. Small inconstant branches come from the anterior and concave part of the arch which it describes, these go forward into the outer part of the orbicularis palpebrarum muscle, and communicate with the ascend- ing branches of the transverse facial, and also with the upper ramus- cules of the anterior temporal artery. The posterior branches of the superficial temporal artery are, 1st. The anterior inferior auricular arteries (A. auriculares anteriores inferiores), usually three or four in number, which arise directly above one another from its lower part, and are expanded in the inferior and anterior part of the concha. 2d. The anterior and superior auricular artery (A. auricularis ante- rior superior) which is often single, rarely double; it arises nearly opposite the preceding branches, and goes to the upper and anterior part of the concha, and to the attollens auriculas muscle. Mayer describes it as the tenth branch of the external carotid artery (p. 84), but asserts positively that it arises about a line above the internal maxillary artery. The descriptions of Portal (p. 186), Boyer (p. 42), Bichat (p. 152), and Menon (p. 267), agree, like that of Murray, with the results of our observations. ANGEIOLOGY. 243 3d. Two or three larger branches usually go backward, inward, and upward, and anastomose with each other and with those of the opposite side, and with the superficial occipital artery, which some- times partly replaces them. They are called the posterior temporal arteries (A. temporales posteriores), and they are usually wrongly con- sidered as forming, in opposition to the anterior temporal artery, but one branch. II. INTERNAL MAXILLARY ARTERY. § 1359. The internal maxillary artery (A. maxillaris interna, A. orbito-maxillaris) is larger than the preceding, but differs more from the direction of the primitive trunk, and is situated more deeply, so that it cannot be seen entirely till the zygomatic arch and the outer part of the body of the upper maxillary bone is removed. Its direction changes several times in its course. First, it goes transversely inward and a little forward, behind the neck of the jaw; then it goes directly inward, and passes between the two pterygoidei muscles, or curves again a httle forward. Arrived at the pterygoid process, it goes perpendicularly upward, over the pterygoideus externus muscle, and is reflected on itself as high as the floor of the orbit, so that its direction becomes horizontal. Thence it divides into several branches which descend more or less, by which it terminates, distri- buting itself on one side on the inner and posterior part of the nose, on the other to the outer part of the face. Proceeding in this manner, it distributes the blood to the dura mater, to the internal ear, to the pterygoidei muscles, to the temporalis muscle, to the teeth, to the interior part of the nose, to the upper part of the pharynx, and to a part of the face, and communicates with several branches of the external and internal carotid, by the following branches, which are successively given off. It usually sends one or two to the ear, viz : a. The deep-seated auricular artery (A. auricularis profunda), which goes to the organ of hearing. b. The artery of the tympanum (A. tympanica), which is distributed to the temporo-maxillary articulation, and then penetrates into the cavity of the tympanum, through the fissure of Glaser, These two branches often arise from the external carotid artery, or from the facial or temporal artery. c. The small meningeal or the external pterygoid artery (A.meningea parva, s. pterygoidea externa) is an inconstant branch, which often arises from the middle meningeal or from a pterygoid artery; it gives branches to the pterygoidei muscles, to the muscles of the soft palate, and to the dura mater, near the sella turcica, and sometimes pene- trates into the skull through the foramen ovale. 244 DESCRIPTIVE ANATOMY. d. The middle, or great meningeal, or spheno-spinal artery (A. me- ninges media, s. magna, s. spinosa),(\) is the largest branch of the internal maxillary artery. It arises from the upper part of the origin of the internal maxillary artery. It goes directly upward and gives off branches to the ptery- goidei muscles, to the upper constrictor of the pharynx, to the temporal muscle, and to the muscles of the soft palate; these are sometimes, although rarely, deficient. When they do not exist they are replaced by the small meningeal artery. The artery then, either simple or divided, enters through the spheno- occipital hole of the sphenoid bone, into the skull, and then gives off some ramifications posteriorly, which glide into the fissure of Fallopius, penetrate into the cavity of the tympanum and the canal of the facial nerve, are distributed to the membrane of the tympanum, to these nerves, and to the muscles of the tympanum, and anastomose with the stylo- mastoid artery. Others, which are anterior, sometimes penetrate into the orbit, through the malar bone or the large wing of the sphenoid bone, and to the lachrymal gland. But this trunk, covered on the outer face of the dura mater, above which it projects, and of which it is the largest artery, expands principally in the anterior and central part of this membrane. It arises, near the anterior edge of the parietal bone, at the median line of the skull, and gives off, forward and back- ward, numerous branches, which anastomose with the other branches of the middle, and also with those of the anterior and posterior menin- gceal arteries. Besides3 these branches communicate also with those of the temporal and occipital arteries. As they project above the dura mater, and follow the grooves of the skull-bones, these indicate their course very well. c. The inferior maxillary or inferior dental artery (A. maxillaris, s. alveolaris, s. dentalis inferior), which sometimes arises from the middle meningceal artery, and always comes from the lower point of the origin of the internal maxillary artery, descends between the two pterygoidei muscles, to which it gives twigs, and also sometimes to the temporal muscle ; penetrates into the dental canal, through which it passes for- ward, gives ramifications to all the teeth and to all the lower dental nerves, which occupy the same canals as they do, then emerges from the mental foramen, and anastomoses above with the inferior coronary or labial, and below with the submental artery, and produced, like the preceding, by the facial artery. (1) Some anatomists, as Sabatier, Boyer, and Bichat, state that it is the first branch of the internal maxillary artery. We have always seen it preceded by one or more of those we have mentioned, and we have never found it, as Mayer states, arising directly from the bifurcation of the external carotid artery. According to our obser- vations, it does not normally arise before the inferior dentar artery, as Soemmering, Murray, and Munroe assert. We have seen that Portal was correct in saying that it is given off as frequently after it or at least opposite to it. ANGEIOLOGY. 245 This emerging branch most commonly arises at some distance from the mental foramen, within the dental canal, and on a level with the small malar teeth, at the place where the inferior maxillary artery bifurcates to produce it and the continuation of the trunk. / g. Two or more deep-seated temporal branches (R. temporalis profundi) arise from the upper part of the maxillary, and are distri- buted to the buccinator and the pterygoidei muscles, and especially to the temporal muscle; penetrate also into the orbit, where they send branches into the lachrymal gland and the eyelids, and anastomose extensively with the ophthalmic artery. h. The masseter artery (R. massetericus) is not constant, and arises sometimes from the external temporal, or even the external carotid, or finally from one of the deep pterygoid arteries. It passes over the semicircular notch of the lower jaw into the upper part of the masseter muscle. It gives branches also to the temporal muscle, and to the two pterygoidei muscles, especially to the external. i. The buccal artery (A. buccalis, s. buccinatoria) is a very con- stant branch, although it often arises from the deep temporal artery, or from one of the following branches. It comes from the lower part of the inferior maxillary artery, goes downward and forward, along the outer face of the body of the upper jaw, distributes its branches in the buccinator muscles, the muscles of the upper hp, the lower part of the orbicularis palpebrarum muscle, the buccal membrane, sometimes also the anterior teeth to which it comes by several openings which exist in the upper part of the superior maxillary bone, and anastomoses with the branches of the facial, and also with those of the infra-orbital, artery. k. The superior maxillary or alveolar artery (A. maxillaris supe- rior, s. alveolaris) arises sometimes from one of the deep temporal or from the infra-orbital artery. It is larger than the preceding, goes a httle downward and forward, turns on the upper maxillary bone, and sends off numerous large and small branches, one of which is termed the superior dental artery (R. dentalis superior) into the teeth of the upper jaw. These branches nourish the dental capsules, the perios- teum, the germ, the buccinator muscle, the zygomaticus major mus- cle, and anastomose with the branches of the facial and infra-orbital arteries. /. The infra-orbital artery (A. infra-orbitalis) is generally smaller than the preceding, and arises near the bottom of the orbit. It soon engages itself in the infra-orbital foramen, and the infra-orbital canal sends some branches into the orbit and the maxillary sinus, emerges by the infra-orbital foramen, behind the levator labii superioris thus comes on the front of the face, and terminates in a great many ra- muscules, some of which go to the muscles of the upper lip while the others anastomose with the upper dental artery, the dorsal 'artery of the nose, the orbitar and the palatine artery. Finally, at the upper end of the zygomatic fossa, the internal max- illary artery divides into an ascending and a descending branch, which goes inward. 246 DESCRIPTIVE ANATOMY. m. The superior palatine artery (A.palatina suprema, s. descendens, s. pterygo-palalina) gives off,first, the superior or descending pharyngeal artery (A.pharyngaa suprema, s. descendens). This passes through the pterygo-palatine foramen, and expands in the pterygoid process of the bone,and theEustachian tube and the upper part of the pharynx. Some- times it arises from the internal maxillary artery by a distinct trunk. The superior palatine artery descends in the pterygoid canal and divides into several ramuscules, which pass through different openings, to go to the soft parts of the palate. The trunk passes through the posterior palatine canal, comes on the palatine arch, rests directly on its lower face, describes a right angle to go forward, forming numerous curves, in its course gives off twigs to the mucous membrane of the palate and to the muciparous glands, and anastomoses forward with that of the opposite side, and sends its latter branches through the anterior palatine foramen into the nasal cavity, where they extend to the lower turbinated bone, communicating' with the branches of the artery of the septum and of that of the dorsum of the nose which arise from the facial artery. n. The last branch, the posterior nasal or spheno-palatine artery (A. nasalis posterior, s. spheno-palatina), enters through the spheno- palatine hole into the posterior part of the nasal fossa, and divides into two branches, an external and an internal, and sometimes into three. The internal branch, the posterior artery of the septum of the nose (A. septi narium posterior), descends along the posterior part of the septum of the nose, sends ramuscules to the upper part of the pharynx, and penetrates into the posterior cellules of the ethmoid bone, and also into the upper turbinated bone. The external branch descends along the outer edge of the posterior opening of the nasal fossae, and usually divides into two ramuscules, which go, the upper to the middle, and the lower to the lower turbinated bone. These ramuscules are distributed principally in the posterior part of the nasal fossa and of the maxillary sinus. II. INTERNAL CAROTID ARTERY, § 1360. The internal carotid or anterior cerebral artery (A. carotis interna, s. cerebralis, s. cerebralis anterior, s. encephalica) is usually smaller than the external, ascends behind it, before the internal jugular vein, on the outside of the pneumo-gastric nerve, directly before the vertebral column, to the lower orifice of the carotid canal. It does not generally bend much, although it is sometimes very tortuous, and it is rarely straight. It seldom gives off branches in this course. It rarely in fact furnishes one of the internal or posterior branches of the external carotid or of the occipital artery. The latter comes from them less frequently than the others. Upward it gives off sometimes a small branch, which goes to the palatine region and to the velum palati. ANGEIOLOGY. 247 Immediately below its entrance into the carotid canal it is generally almost horizontal, or at least goes obhquely upward and forward. At the lower part of this canal it goes vertically upward. It afterwards goes forward at nearly a right angle, and becomes almost horizontal, although it ascends a little. After leaving the canal it resumes its pri- mitive direction upward, but proeeeds at the same time forward and inward, and thus comes on the side of the sella turcica. At the poste- rior part of this excavation it curves a second time at a right angle, goes horizontally in the lateral carotid groove, going outward and a httle downward. In this part of its course it accompanies the ca- vernous sinus of the dura mater, both being inclosed in the same por- tion of the dura mater, but separated by its proper membrane from the blood which it contains. At the anterior extremity of the lateral face of the sella turcica, below the anterior clinoid process, it describes a third right angle, and goes upward, backward, and inward. In its course it gives off very trifling branches to the internal ear, to the dura mater, and to the third, fourth, fifth, and sixth pairs of nerves. Opposite the internal extremity of the upper orbitar fissure it divides into two branches, the continuation of the trunk which goes to the brain, and the ophthal- mic artery. Thus it changes its direction five times at least, and this arrange- ment retards the course of the blood much more, inasmuch as all the curves are sudden and do not occur on the same plane. The internal carotid artery is intimately united by a very short cel- lular tissue to the canal through which it passes and which it almost entirely fills. I. OPHTHALMIC ARTERY. § 1361. The ophthalmic artery (A. ophthalmica) is a very conside- rable branch, which exceeds in volume all those hitherto mentioned. It is always single. It leaves the skull through the optic foramen, usually on the outer and lower side, rarely at the upper part of the optic nerve, penetrates into the orbit, sends numerous branches to all parts of the eye, and also larger or smaller branches into the nasal fossae and the face. Having come into the cavity of the orbit, it soon ascends on the optic nerve, goes upward and inward, passes between this nerve and the rectus superior muscle of the eye, and thus arrives at the inner part of the orbit and goes forward to the internal angle of the eye. Its branches vary surprisingly in respect to their origins, their number and their volume. The principal are : 1st. Usually but not always an external posterior ciliary artery (A ciliaris posterior), which arises from the outer side of the ophthalmic artery, goes forward along the optic nerve on its outer and lower side, and penetrates the sclerotica directly before the anterior extremity of this nerve. 248 DESCRIPTIVE ANATOMY. 2d. The lacrymal artery (A. lacrymalis) arises from the upper part of the ophthalmic artery, generally far backward and sometimes very far forward. It rarely arises from the middle meningeal artery, in which case it enters into the orbit, through the upper orbicular fissure, or through a special opening either in the malar bone or in the large wing of the sphenoid bone. It proceeds outwardly under the rectus superior muscle, to which it gives branches, and also to the rectus ex- ternus and to the levator palpebrarum muscles. It sometimes sends several through the malar bone into the temporal muscle, where they anastomose with those of the deep temporal artery. In some subjects one or several ciliary arteries arise from it. It then passes across, above or below the lacrymal gland, leaves the orbit at the external angle of the eye, anastomoses with the palpebral artery given off by the ophthalmic artery to form the palpebral arch, and terminates in the orbicularis palpebrarum muscle, the skin of the eyelids, and the tunica conjunctiva. 3d. The posterior upper ciliary artery (A. ciliaris posterior, superior) is distributed in the same manner as the external, but gives off no branch after passing through the tunica sclerotica. • Sometimes all the posterior ciliary arteries arise after the posterior ethmoidal artery; but they always proceed very tortuously on the surface of the optic nerve, and after dividing into numerous branches, pass through the posterior part of the sclerotica to enter the eye, where they are distibuted in the manner stated in describing that organ. 4th. Next, a small inconstant branch arises and goes to the posterior part of the rectus superior muscle. 5th. The posterior or middle ethmoidal artery (A. ethmoidalis poste- rior, s. media) is also inconstant, and often arises from the lacrymal artery, from the anterior ethmoidal, or from the supra-orbitarartery.(l) It gives first branches to the origin of the obliquus superior, rectus internus and externus muscles, then goes inward over the obliquus superior muscle, passes through the ethmoidal or posterior internal or- bitar foramen, comes into the nasal fossae, and is distributed to the pos- terior ethmoidal cellules, the sphenoidal sinus, and the antrum High- morianum; it anastomoses with the branches of the posterior nasal or spheno-palatine artery and with the anterior ethmoidal artery, then re- enters the skull through a small canal in the ethmoid bone, gives ramuscules to the periosteum which covers the anterior and central fossa of the base of the skull, and terminates by again passing into the nasal fossae through the openings in the cribriform plate. 6th. The central artery of the retina (A. centralis retina), arises far- ther back, directly from the ophthalmic artery, or from the preceding, or from the lacrymal artery, or from one of the two muscular branches; (1) But it is not always the smallest, as Bichat asserts; we have remarked several times that it was one of the largest branches and much larger than the anterior. ANGEIOLOGY. 249 it goes into the optic nerve, proceeds forward along its axis, and distri- butes itself to the retina, as we shall mention in describing the eye. 7th. The inferior muscular artery (A. muscularis inferior), is a con- siderable and rather constant branch, which sometimes gives off the central artery of the retina and one or more of the ciliary arteries, goes inward, sends branches to the rectus internus and inferior muscles of the eye, and penetrates even into the nasal fossa. 8th. The superior muscular or supra-orbitar artery (A. muscularis superior, s. supra-orbitaria) is less constant than ilie preceding, but it comes from the lachrymal less frequently than from the ophthalmic artery. It proceeds forward directly below the orbitar plate, leaves the orbit through the supra-orbitar foramen, gives off branches to the frontal bone, to its periosteum, to the supraciliaris and orbicularis palpebrarum muscles, and to the skin of the forehead, and anastomoses with the other branches of the ophthalmic and with the temporal artery. The anterior ciliary arteries (A. ciliares antica) arise from this branch and from the preceding; they divide into fewer branches than the pos- terior, and enter the sclerotica much farther forward than the latter, near the transparent cornea. The branches we have described generally arise near the floor of the orbit, not far from each other; hence why they are generally long. After giving them off, the ophthalmic artery is usually smaller and proceeds along the internal wall of the orbit, describing numerous curves. Towards the anterior opening of the orbitar cavity it gives off, 9th. The anterior ethmoidal artery (A. ethmoidalis anterior), which goes directly inward, passing over the obliquus superior muscle, and penetrates through the ethmoidal or anterior internal orbitar foramen into the nasal cavity, where it is distributed to the anterior ethmoidal cells and the frontal sinuses, and anastomoses with the other nasal arteries. It also sends off branches to the anterior region of the dura mater. The ophthalmic artery now proceeds a short distance within the orbit, afterwards leaves this cavity at the inner angle of the eye, and terminates in giving origin to, 10th. The palpebral arteries (A. palpebrales). These arise some- times by a common trunk (palpebralis communis) and sometimes sepa- rately, the superior a little before the inferior, and go outwardly. They are distributed partly to the conjunctiva, partly and parti- cularly to the eyelids, in which they disappear between the skin and the orbicularis muscle. They divide there principally into two branches, one of which proceeds near the edge (ramus marginalis), while the other goes obliquely outward along the base of the eyelid. The superior palpebral artery anastomoses in this place with the lachrymal, the superciliary branch of the frontal, and even some branches of the anterior temporal artery. It also forms a single or double supe- rior palpebral arch (arcus tarsens superior), which communicate with. each other by numerous ramuscules, and thus form a net-work. Vol II. 32 250 DESCRIPTIVE ANATOMV The inferior palpebral arch (arcus larseus inferior) is produced in the same manner, by the anastomosis of the inferior palpebral with the infra-orbitar, the lachrymal and the nasal arteries. All the parts of the eyelids are abundantly provided with vessels by these arterial branches. 11th. The frontal artery (A. frontalis), which also ascends soon after arising, usually divides immediately into three branches, the supra- ciliary artery (A. supraciliaris), the superficial or subcutaneous frontal artery (A. frontalis subcutanea), and the deep frontal artery (A. fron- talis profunda). By this division it is distributed, 1st, to the upper part of the orbicularis palpebrarum and corrugator supercilii muscles ; 2d, to the frontalis muscle and to the skin of the forehead ; 3d, to the frontal sinus. It extends to the coronal suture and to the temporal region, where it anastomoses with the branches of the external temporal artery; it also communicates in other parts with those of the supra-orbitar and lachrymal arteries. 12th. The nasal artery (A. nasalis) varies much in volume. Some- times it is a very small branch, terminating at the root of the nose; sometimes it forms the continuation of the trunk of the ophthalmic artery, descends very low, contributes with the lateral nasal branch of the facial artery to produce the dorsal artery of the nose, extends to the end of the nose, proceeding on the side of this organ, always anas- tomoses with the inferior palpebral and the facial artery, and gives ramuscules to the integuments and to the nasal bones, to the frontalis muscle, to the internal part of the orbicularis palpebrarum, to the mus- cles of the nose, and even to the pituitary membrane. II. CEREBRAL ARTERIES. § 1362. After giving off the ophthalmic artery, the internal carotid artery is distributed entirely to the cerebrum, particularly to its anterior portion, the posterior being supplied with blood from the vertebral artery. It properly deserves then to be called, from this point, the anterior cerebral artery (A. cerebralis anterior). § 1363. It gives off, first, small ramuscules, which go inward, and are designed for the posterior part of the optic nerve, for the infundi- bulum, for the pituitary gland, and for the third ventricle. § 1364. It then gives off four branches ; these are the communicating artery, the choroid artery, the anterior cerebral artery, and the artery of the corpus callosum. The first two generally arise directly after each other; and the carotid artery bifurcates farther on to give rise to the last two. Sometimes, but more rarely, three or all of these branches arise from the same point. § 1365. The first, or the posterior communicating artery (A. com- municansposterior), goes backward and inward. It approaches that of the opposite side, opens into the posterior cerebral, which comes from the vertebral, artery, or if we prefer it anastomoses with a branch analogous to it, which it meets. ANGEIOLOGY. 251 This anastomosis gives rise to the posterior part of the circle of Willis (circulus Willissii). The size of this communicating artery varies extremely. It is gene- rally considerable, and only about one half smaller than one of the succeeding branches, into which the internal carotid artery divides. It is sometimes however very small; in this case the anastomosis between the internal carotid and the vertebral artery, frequently but not always takes place by means of another and larger branch of the anterior cerebral artery, which opens more outward into the posterior. The communicating artery is sometimes larger on one side than on the other. Sometimes this artery is a branch of the anterior cerebral.(1) It arises more rarely not from this but directly from the basilar artery, when the posterior cerebral artery does not come from it. and it is given off by the internal carotid. But the anastomosis almost always exists ; and it is constantly sim- ple or at most double, on each side, when it occurs by considerable branches, although we find others which are accessory and smaller in the cerebral peduncles. We consider its total absence as one of the rarest anomalies. We have never yet seen it, and Barclay alone mentions one case where the injection penetrated neither from the carotid into the vertebral artery, nor from the vertebral into the carotid.(2) Several vessels arise from the communicating artery and go to the pia-mater or to the floor of the third ventricle, to the mamillary emi- nences, to the posterior part of the optic nerves, to the thalami optici, to the cerebral peduncles, to the inner face of the anterior part of the large cerebral lobe, and to the choroid plexuses. § 1366. 6. Above the communicating artery, the internal carotid always gives off a special branch, the choroid artery (A. choroidea) which also arises from its posterior part.(3) This artery goes a little backward and outward, along the posterior edge of the origin of the optic nerve, ascends above the upper part of the cerebral peduncle, and expands partly in the pia-mater of the anterior part of the posterior (1) This anomaly, however, is proportionally very rare. Portal then estimates in- correctly, the relation between the rule and the exception, in saying that the internal carotid artery usually divides into two branches, the smaller of which is the artery of the corpus callosum, the larger the anterior lobate artery; the latter giving off the communicating artery, which sometimes arises directly from the internal carotid. Hilderbrandt seem3 to think that the two cases are equally frequent, which is just as fabe. (2) Loc. cit., p. 47. (3) We have always found this branch very constant, although several anatomists particularly Mayer, Murray, Portal, Hilderbrandt, and Scemmerring, do not mention it. Haller states (Ic. anat., vol. vii. p. 5) that it sometimes exists. Sabatier, Boyer, and Bichat assert that is constant, which agrees with our remark. But Bichat errs in saying thatthe choroid is always smaller than the communicating artery. This case frequently. occurs, since, as we have observed, the communicating artery is usually large; but we have often found, when this was small, that the choroid artery was as large or even larger than it. 252 DESCRIPTIVE ANATOMY'. cerebral lobe and of the thalami optici, and partly also penetrates through the anterior opening of the lateral ventricle, into this cavity, where its ramifications expand in the choroid plexus. § 1367. The internal carotid now divides, at a very obtuse angle and at the anterior extremity of the fissure of Sylvius, into two unequal branches ; these are the artery of the corpus callosum and the anterior cerebral arter}', § 136S. The artery of the corpus callosum (A. callosa, s. corporis callosi, s. anterior cerebrica, s. anterior hemisphari, s. mesolobica) is always smaller than the posterior branch. It goes forward and inward, directly before the union of the optic nerves, proceeds to meet that of the opposite side, towards which it converges very much, and after giving off superiorly generally several ramuscules for the posterior extremity of the anterior lobe, for the olfactory and for the optic nerves, it anas- tomoses with it between the posterior extremities of the first two lobea by the anterior communicating artery (A. anterior communicant, s. anostomotica). This branch is generally very short; sometimes how- ever, it is three or four lines long ; it is generally much larger in the former case and often very narrow in the second. Its direction is always transverse. Sometimes it is entirely double; and we not unfrequently find it double in one half its extent.(l) It gives off, par- ticularly when longer than usual, ramuscules, which go upward and backward, into the septum lucidum, the fornix, and the corpus callo- sxim. The trunk also generally sends off one or more small branches which proceed forward and outward to the inner part of the inferior face of the anterior lobe of the cerebrum. After this, it is situated directly near that of the opposite side, turns on the anterior extremity of the corpus callosum, ascends to the inner face of the cerebral hemis- pheres, and divides into several branches, the anterior of which enter into the circumvolutions of this internal face, while the posterior pro- ceed on the corpus callosum, as far as its posterior extremity, where they begin to change their direction and to go upward. All these branches extend to the upper face of the cerebrum and anastomose with those of the succeeding artery, and with those of the posterior cerebral artery, given off by the vertebral artery. Besides these large branches, into which the artery of the corpus callosum divides above, it also gives off, from its lower and concave part, numerous smaller branches, whtch distribute themselves in the corpus callosum. Rarely, a large posterior branch is detached on both sides at the place where the two arteries of the corpus callosum meet, and the anterior anastomosing branch becomes the single trunk of the anterior part of the artery of the corpus callosum, which shortly divides into two large branches, a right and a left, or the two arteries arise (l) Bichat is incorrect in stating that this arrangement is very rare ANGEIOLOGY. 253 from a common trunk, and do not give off a branch posteriorly."' This arrangement is remarkable because of the analogy it establishes with the union of the two vertebral arteries into one, the basilar, which is situated on the median line. § 1369. The anterior or more properly the middle cerebral artery (A. cerebri anterior, s. media, s. hemispharica media, s. fossa Sylvii, s. sylviana), the last and the most posterior branch of the internal carotid, is always much larger than the preceding. Soon after its origin it goes outward, and only a httle inward ; it enters the fissure of Sylvius, gives off, at its upper and posterior part, numerous, generally small, ramuscules, some of which penetrate into the anterior extremity of the posterior lobe, others into the posterior extremity of the anterior lobe, and afterward divides generally about half an inch from its origin into two, three, or four large branches. The largest of the latter are turned backward, soon bifurcate, and proceed, closely against each other, into the bottom of the fissure of Sylvius, where they go upward and back- ward. The anterior attain the posterior and external part of the ante- rior lobe, and the posterior the anterior central part of the posterior lobe, gliding in the circumvolutions of the posterior face of the first and the anterior face of the second, but penetrating mostly into their substance, through their outer face, and thus extend to the upper edges of the hemispheres, where they anastomose with the ascending branches of the anterior and posterior cerebral arteries. § 1370. The anterior and middle cerebral arteries are not always arranged symmetrically. The two large middle arteries not unfre- quently arise (as Haller states and as we have verified) from the right carotid only, and the anterior, which is smaller, from the left carotid, an arrangement which deserves to be remarked as indicating the pre- dominance of the right side over the left. Sometimes also only the left anterior artery comes from the internal carotid of the same side, and the other three come from the right. We have seen this anomaly in several subjects. If we add the union of the arteries of the corpus callosum at their origin, which we mentioned above, we here find a remarkable repeti- tion of several of the varieties to which the origins of the trunks coming from the arch of the aorta are subject. ARTICLE FOURTH. ARTERIES OF THE UPPER EXTREMITIES. § 1371. The arteries of the upper extremities, for which we cannot find a better term than that of the brachial arteries(l) (A. brachiales), (1) This term is generally applied only to that portion of the artery which corres- ponds to the arm, and which might more properly be termed the humeral artery. 254 DESCRIPTIVE ANATOMY. arise on each side by a single trunk, generally called the subclavian artery (A. subclavia). I. SUBCLAVIAN ARTERY. § 1372. The two subclavian arteries (A. subclavia) arise from the ascending aorta, and extend to the scaleni muscles. They differ in their mode of origin; for the left subclavian artery arises directly from the arch of the aorta, while the right proceeds indirectly from it, as it is the external branch of the trunk of the innominata (truncus communis innominatus), which bifurcates and gives origin to it and to the right primitive carotid. This at least is the most common arrangement. Sometimes, but rarely, the subclavian arteries arise directly from the arch of the aorta. We may there find two principal differences. Sometimes in fact the trunk of the innominata gives off the right subclavian and the carotid, the subclavian artery arising on the right, outside of the carotid, which is the least but also the rarest anomaly. Sometimes the right sub- clavian artery arises more to the left, until it is the extreme left trunk of those which arise from the arch of the aorta, below the left subcla- vian artery, and goes to the right, towards the corresponding limb, passing behind the other trunks, rarely directly, more frequently be- tween the trachea and the esophagus, anfl still more frequently between the esophagus and the vertebral column. § 1373. The first branches of the subclavian artery are never con- stant. They often and in fact almost always arise from its upper ex- tremity, directly before its passage between the scaleni muscles. But sometimes the artery gives off much sooner, and even near its origin, considerable branches, which go to the thymus gland, to the upper part of the pericardium, also to the trachea, to the bronchia^, and to the esophagus (A. thymicos, pericardiaca superior, anterior et posterior, bronchica, asophagea, broncho-asophagea), but they rarely or never belong to these parts alone, although they distribute branches to all. Even when these branches arise from the subclavian artery (which occurs on the left side more frequently than on the right, because it descends deeper) its course is no shorter, but it gives off no branch until just before passing between the scaleni muscles. Here, however, several large branches arise from it. These may be distinguished generally speaking into the upper or posterior and the lower or ante- rior branches; and they vary much, for, 1st, the same twigs do not always arise from the same branches, so that the latter are not always of the same caliber ; 2d, small branches sometimes arise from the subclavian artery, by a common trunk, whence their number varies : 3d, they do not always emerge from the same point of the subclavian artery, the inferior arising somelimes farther forward, and the superior farther backward than usual. ANGEIOLOGY, 255 A. UPPER POSTERIOR BRANCHES. § 1374. The most constant of the upper and posterior branches are two, the vertebral artery and the inferior thyroid artery. I, VERTEBRAL ARTERY. § 1375. The vertebral artery (A. vertebralis) is generally the first and largest of the two upper branches of the subclavian artery. Shortly after arising, it enters the arterial canal of the cervical vertebrae, and goes from below upward. This artery shows a great disposition to change its origin, and to arise directly from the arch of the aorta. We shall remark, 1st, that this anomaly, however common it may be, is seldom seen on the right side (at least to our knowledge), and that it rests always on the left ;(1) 2d, that when it occurs, the vertebral artery is almost always inserted between the left carotid and the left subclavian arteries. If this branch arises directly from the arch of the aorta more frequently than the others, it may be attributed, we think, to the following facts: 1st, in the normal state it is the first branch of of the subclavian artery ; 2d, the vertebral vein normally empties itself into the common trunk of the subclavian and jugular veins. The other fact, that the anomaly appears almost entirely on the left side, seems to us to depend on this, that the division of the trunk into branches characterizes the left side of the ascending aorta even in the normal state, since the subclavian arteries there arise separately, and are not blended in a single trunk, as on the right side. The greater length of the left trunk of the innominata vein may contribute to it, since this anomaly should be considered, as we have remarked, an imitation of the arrangement of the venous system. Finally, the situ- ation of this artery between the left carotid and the left subclavian arteries probably depends on its arising, in the normal state, from the internal and posterior side of the subclavian artery. We sometimes but rarely find on the right side a similar anomaly where the vertebral artery arises from the bifurcation of the trunk of the innominata; this is still more curious, because in comparing this arrangement with that on the left side we have a new proof that the anomaly does not destroy in the two sides the character of the normal type. We know of only one case where the right vertebral artery arose from the arch of the aorta; but that of the left side also presented the same anomaly. (1) This might be easily proved by numerous quotations. Of all the authors who mention this variety Mayer is the only one who asserts the contrary; for, without speaking of the left vertebral artery, he asserts only that the right sometimes arises directly from the arch of the aorta. This assertion is so contradictory to observa- tion that it can be explained only by considering it as a typographical error. 256 DESCRIPTIVE ANATOMY. A second anomaly of the vertebral artery consists in its division into several trunks. Sometimes then one of the trunks arises directly from the arch of the aorta; the other, which is generally smaller, from its usual place ;(1) or both come from the subclavian artery, at a greater or less distance from each other. Perhaps the first arrangement also is found only on the left side; at least in a specimen before us, and where the anomaly exists on the right, the two vertebral arteries are branches of the subclavian artery. In both cases one of the trunks, particularly the largest, enters the vertebral canal higher than usual. Sometimes it unites with the other, which enters at the normal place; sometimes it unites with it before entering this canal; sometimes, finally, the smallest branch extends into the vertebral canal after passing over one or more vertebral foramina. Even when the vertebral artery is normal in respect to its origin, it enters the vertebral canal at several different points. Its proper place is the vertebral foramen of the sixth cervical vertebra.(2) In extremely rare cases this artery enters through the vertebral foramen of the seventh cervical vertebra.(3) Even when it arises lower than usual, from the arch of the aorta it however enters into the hole of the sixth cervical vertebra, and we have frequently seen it in this case not enter the vertebral canal until it reaches the fifth vertebra. More frequently, although not very often, the vertebral artery, even if not double,enters through the vertebral foramen of the fifth,fourth,third, or even the second cervical vertebra. We know of no case in which it has been found entirely out of the vertebral canal, and we have never known it to leave this channel lower than the upper vertebra, or to leave a vertebra, pass through a certain extent on the anterior face of the transverse processes, and enter again into the vertebral canal. Finally, the vertebral artery of one side is very frequently much larger than that of the other, although according to our observations the sides of the body have no effect on this disproportion. This anomaly confirms the general rule that the synonymous arteries which go to the single organs on the median line of the body often differ in volume and enlarge on one side at the expense of the other. (1) Henkel, Anmerkungen von weidernaturlichen Geburten, zweite Sammlung, p. 10, II.—Hulier, De arcus aorte ramis; in the Act. Helv., vol. viii. p. 68-102. (2) We have always observed this, except in a very few instances. Haller (Ic. anat.fasc. ii., explic. icon. 2, art. thyr. infer., not. c) and Scemmerring (p. 177) are then correct in saying that this arrangement is normal. Mayer mistakes in saying (p. 110) that there is for the vertebral artery a special opening, through which it en- ters into the vertebral canal, sometimes in the seventh and sometimes only in the sixth cervical vertebra. This opening always exists except in a very few instances in the seventh cervical vertebra; but the vertebral artery rarely or never passes through it and always enters through the sixth. What Mayer considers the normal Btate is a rare anomaly, and vice versa. Monro (Outlines, epe, vol. iii, p. 301) is also mistaken in thinking that the artery enters through the seventh cervical vertebra as often as it does through the sixth. (3) Bichat (p. 193) is correct in saying that it sometimes but rarely enters through a similar foramen of the seventh cervical vertebra. This arrangement is rare, as Haller, Murray, and Scemmerring have not spoken,of it, although they mention the next. ANGEIOLOCfY. 257 § 1376. The vertebral artery ascends in an almost straight line to tire second cervical vertebra ; but at this point it becomes tortuous and de- scribes several curves, four of which are very remarkable. First, it penetrates into that part of the canal which belongs to the transverse process of the second vertebra, forming a right angle, assuming an en- tirely horizontal direction, and going transversely outward ; then pass- ing through this opening, it describes another right, acute, or obtuse angle, resumes its first direction, and'becomes perpendicular again at the upper cervical vertebra. When it has passed through the vertebral foramen it inclines again at a right angle, resumes a second time a horizontal direction, and goes backward and inward, turning around en the articular process of the first cervical vertebra, along its posterior groove. From the posterior extremity of the articular process it goes gradually and at an obtuse angle inward and upward, and soon enters the cranium, passing through the dura mater and the large occipital foramen directly above the occipital condyle. Having entered the skull, it is situated first on the side,.then on the lower face of the me- dulla oblongata, and ascends forward and inward on the basilar pro- cess of the occipital bone. There the two arteries approach each other, and after passing usually more than an inch within the cavity of the skull, they unite at an acute angle, either a short distance behind the posterior edge of the pons Varohi, or on this edge, or even in its centre. They always, as far as we know, unite and give origin to a single U'unk, the basilar artery (A. basilaris), which is much smaller than the two branches which produce it. In size it nearly equals the internal carotid artery after it gives off the ophthalmic artery. It proceeds for- ward to the centre of the lower face of the pons Varolii, and divides at its anterior extremity into two large branches, a right and a left. § 1377. In this, course the vertebral artery generally gives off no branches, or at least but small and inconstant ones. These branches are distributed to the anterior deep muscles of the neck. In this respect the vertebral artery resembles the internal carotid. § 1378. From the portion within the vertebral canal several small branches pass forward, outward, and backward, generally betweai every two vertebrae, and go to the vertebrae, to the inter trans versarii, to the multifidus spina?, to the anterior deep muscles of the neck, and to the small muscles of the head. ' Internal branches, which are also very small, pass through the inter'- vertebral foramina, either alone or attended with small arterial twigs from the other branches of the subclavian artery, penetrate the verte- bral canal and are distributed partly to the nerves, others to the anterior and posterior sides of the dura mater and to the pia mater of the spinal marrow. They anastomose with those of the opposite side and with the anterior and posterior spinal arteries. Considerable branches arise from that part of the vertebral artery between the first and the second cervical vertebree, and also between tho Vol. U. 3*3 ■Ida DESCRIPTIVE ANATOMY latter and the occipital bone. Some go outward, are expanded in the transversalis colli and the complexus minor muscles, and anastomose with the branches of the ascending cervical artery, and sometimes en- tirely replace it. The others proceed backward and outward and are distributed in the posterior and lateral small muscles of the head. Some go imvard and anastomose with the synonymous branches of the other side. Finally, many enter the tissue of the dura mater. § 1379. The largest branches arise from that part of the vertebral artery within the skull. From the difference of cahber between the branches which it sends out of the cavity of the skull, this part is fre- quently much larger on one side than on the other, although both have primarily the same diameter at their origin and although the side of the body has no necessary influence upon this difference. The branches which arise before the two vertebral arteries unite are the anterior spinal artery, the posterior spinal artery, and the inferior artery of the cerebellum. § 1380. The posterior spinal artery (A. spinalis posterior) is the smallest, and often comes from the inferior artery of the cerebellum. It arises the lowest and from the outside of the vertebral artery, goes inward on the posterior face of the spinal marrow, and descends on each side along the posterior spinal groove to the end of the spinal marrow. The two arteries are very tortuous and are parallel to each other. They are always enlarged by the accessory ramuscles of the vertebral, the deep cervical, and the intercostal arteries which pass through the inter- vertebral foramina, and anastomose by numerous transverse branches, which generally correspond to the intervertebral spaces; so that each portion of the spinal marrow between two vertebrae has its special vas- cular circle, even as the four cerebral arteries form one by their anas- tomoses. § 1381. The inferior artery of the cerebellum (A. inferior cerebelli) also arises from the outer side of the vertebral artery and is usually double on both sides. One, the posterior inferior artery of the cerebellum, arises farther backward, and goes backward, upwaid, and inward, proceeds on the lateral parts of the medulla oblongata, distributes its branches to the tela choroidea of the cerebellum and to the floor of the fourth ventricle, and ascends between its two hemispheres to its vermiform eminence and to the inner face of its two hemispheres. This branch often exists on one side only, and then it is observed particularly when the inferior artery of the cerebellum arises very far forward. The anterior inferior artery of the cerebellum sometimes arises at the origin, sometimes also at the extremity of that portion of the vertebral artery within the skull. In some subjects, particularly when the vertebral arteries unite early, it comes from the basilar artery. These varieties are observed even on both sides of the body at once. The anterior inferior artery of the cerebellum not only frequently exists alone but it is generally much larger than the posterior. It is some- \NGEI0L0GV 2o9 mies much smaller on one side than on the other. It proceeds very tortuously outward and backward to the lower face of the cerebellum, where itjDasses on the grooves which it crosses and divides into branches, some of which go backward and others forward. These branches also cross the direction of the grooves of the cerebellum; the small ramifr- cations alone become parallel and finally penetrate into them. § 1382, The anterior spinal artery (A. spinalis anterior) generally commences a short distance from the lower edge of the pons Varolii, even when the two vertebral arteries unite much higher than usual. It arises from the internal part of the trunk and soon unites with that of the opposite side in a single trunk on the median line, which descends along the anterior groove of the spinal marrow. Generally, particularly when the two vertebral arteries unite higher than usual, we find a small anterior and superior spinal artery, which is sometimes single and arises from the top of the angle of union, and sometimes double, which blends likewise with that of the opposite side, and which, pro- ceeding also from above downward, soon anastomoses with the lower. The single trunk of the latter, which corresponds to the median line, is often divided in its course and thus forms considerable islands. Its upper part receives also from all or most of the intervertebral foramina considerable branches, which are given off by the vertebral or the other cervical arteries to the anterior face of the spinal marrow and anasto- mose with it. During its course, which is very tortuous, it sends off on each side numerous branches to the spinal marrow. II. BASILAR ARTERY. § 1383. The basilar artery (A. basilaris, s. meso-cephalica) is corir stant, and arises, proceeds, and varies in the manner mentioned above. We however sometimes remark in its arrangement a tendency to a want of union or to the separation of the vertebral arteries, since it forms islands, especially at its posterior part. This artery is however the only one in which we have observed this arrangement. It very soon divides into two parts, which almost immediately unite. We consider this anomaly as very rare, not only because we have never seen it but twice, but because it is not mentioned by the most correct angeiolo- gists.(l) It is curious not only as an anomaly, but because it increases the analogy between the basilar and the anterior spinal arteries, which are already so similar. It is not unimportant to say, that in the two] subjects which presented this unusual arrangement the anterior com-' municating artery of the two internal carotids presented analogous (1) An arrangement has been figured by Heuermann (Physiologie, vol. ii. tab. 8J where the two vertebral arteries were connected behind their union by a large trans* verse branch, to give rise to the basilar artery, which seems to have some relation with this anomaly; but more probably it consisted only in the union of the anterior Fpinal arteries, since the two vertebral ;?rteTtes cfre not v^rt united twbind fRi's br 294). Bichat also mentions the frequency of this last origin. Wardrop says he has observed it in many subjects. The details on the origin and distribution of this artery given by Burns are most correct; they perfectly agree with our own observations. He says the obturator artery is usually regarded as a branch of the internal iliac artery, but wc have as good right to assert that it arises from the trunk or from one of the branches of the external iliac. We have often seen it come from this vessel an inch above Poupart's ligament. It frequently arises by a trunk in common with the epigastric artery. These details are given in his treatise on diseases of the heart. Farther (Observations on the structure of the parts contained in crural hernia ; in the Edinb. Med. and Surg. Journ., vol. n. p. 272), he says that the obturator and the epigastric arteries often arise by a common trunk; perhaps however this arrangement may be considered as a rare anomaly, but he has observed it more than twenty times. Cooper (The anatomy and surgical treatment of crural and umbilical hernia, 1807, Edinb. Med. and Surg. Journ., vol. iv. p. 231) also states, when speaking of the origin of the obturator and epigastric arteries by a common trunk, that it is not rare. Monro (Anat. of the gullet, p. 429) establishes the relation between this case and those where it does not exist as 1 : 10. Bekkers also mentions (Diss, de hernia inguinali, Paris, 1813) three cases observed by himselt, in which these two vessels arose in common from the external iliac artery. We have mentioned these cases, which support our observations, because Hesselbach (Neueste anatomisch-pathologisck Untersuchangen uber den llrsprung und das b ortschreiten der Leisten-und Schenckelbruche, Wurzburg, 1815) is wrong on this subject. He maintains, which seems impossible in so distinguished an anatomist, not only-toM this variety is very rare but adds, that, as to his knowledge the lesion of this arterj has been observed only in females, the injury of the obturator artery in the male is not to be feared. Vol. II. 40 314 nF.RCniPTIVK ANATOMY pelvis to be distributed to the upper and internal part of the thigh. It usually gives off also, before leaving the pelvis, a branch, which anas- tomoses with a corresponding branch of the opposite side on the sym- physis pubis, and always gives origin to a branch, which varies in size and anastomoses with the epigastric artery above the horizontal branch of the pubis In or directly before the obturator foramen, the obturator artery usually divides into two branches, an external and an internal. The internal branch is smaller and passes above the obturator exler- nus muscle, gives branches to it and also to the adductor brevis and longus, to the gracilis, to the pectineus, and to the skin of the internal part of the thigh, the scrotum or the labia pudenda, commonly anasto- moses with the internal circumflex artery of the thigh, and with the external branch on the circumference of the obturator foramen, and with the external pudic artery in the scrotum and the labia pudenda. The external branch descends deeply outward between the obturator internus and externus muscles, gives branches to these muscles in which it sometimes terminates, is reflected from within outward on the articu- lar capsule and the inner part of the articulation to emerge from the ob- turator foramen, and passing behind the quadratus femoris muscle goes transversely to the posterior part of the extremity ; then it is distributed to the quadratus femoris, to the gastrocnemii, to the adductor longus and brevis, to the upper extremity of the flexors of the leg, finally, to the substance of the external condyle of the femur ; anastomoses with the internal branch on the circumference of the obturator foramen and with the ischiatic artery above, and within with the internal circumflex and the internal hemorrhoidal arteries. § 1478. The varieties in the origin of the obturator artery are very important to the surgeon. When this artery arises at the usual place from the hypogastric or from the crural artery within the pelvis, and even from the epigastric artery, but far above the crural arch, it is not exposed to be wounded in any of the common operations. But when its origin is situated very low, and it comes either from the crural artery or by ajrunk in common with the epigastric artery, as it then al- ways re-enters the pelvis over the branch of the pubis, it is exposed to wounds in the operation for crural hernia. When the common trunk of this and the epigastric artery is short, it is generally thrown outward toward the ischium in crural hernia, so that it would be divided if the incision should be made in this direc- tional) When, on the contrary, this same trunk is long and the obturator artery consequently goes farther inward, it is pushed down by the crural hernia and proceeds before the neck of the tumor inward.(2) (1) See a. case of this kind figured in Monro, Morbid anatomy of the human gullet. Edinburgh, 1811, tab. xiv. fig. 1. ° ' (2) Wardrop has figured a case of this kind (Edinb. Med. and Surg. Journ. vol ii p. 203), and points out the means of avoiding the obturator artery in this case. See ANGEIOLOGY, 315 We must however in this case determine whether the crural hernia is situated more or less outwardly. If an external and an internal crural hernia exist on one side, the obturator artery sometimes passes to the inside of the external tumor, even when the common trunk of this vessel and of the epigastric artery is short, and enters the cavity of the pelvis between the two tumors. This has been observed by Burns. If the obturator artery rises far below the usual place and from the crural artery, either directly or by a trunk in common with the epi- gastric artery, it generally proceeds deeply, along the pectineus muscle, on the inside of the crural vein, so that, being situated behind the tumor, in case of crural hernia it cannot be wounded in the operation. But if it was nearer the surface, it might be situated also on the anterior face of the tumor. We have never seen this latter arrange- ment. Burns and Monro have observed only the first. IV. GLUTEAL ARTERY. § 1479. The gluteal or posterior iliac artery (A. glutea, s. iliac a posterior, s. externa), the largest artery of the posterior branch of the hypogastric artery, which may be considered as its continuation, arises very often by a trunk in common with the ischiatic artery. Some- times it furnishes the lateral sacral, the obturator, and all the other arteries which usually come from the posterior branch of the hypo- gastric artery. It goes downward, forward, and outward, toward the lower part of the ossa ilia, usually sends off, in this course, branches to the iliacus intumus muscle, to the obturator internus, to the pyri- formis, to the levator ani, and to the os pubis, then emerges from the pel- vis through the ischiatic notch, between the pyriformis and the gluteus minimus muscle, is reflected from below upward, penetrates between the gluteus medius and minimus muscles, and divides into numerous branches, which are distributed to the pyriformis and to the three glutei muscles and anastomose above with the epigastric, the last lumbar, and ilio-lumbar arteries, below with the ischiatic and with the external circumflex artery. § 1480. The anterior branch of the hypogastric artery gives off, first, the ischiatic artery, the internal pudic, and the umbilical arteries. The vesical, uterine, and vaginal arteries come from one of the latter; sometimes also they arise by a common trunk. V. ISCHIATIC ARTERY. § 1481. The ischiatic artery (A. ischiadic a) arises separate from the internal pudic artery less frequently than by a trunk, which varies in length, in common with the latter, and often by a trunk in corn- Bums, Observations on the structure of the parts contained in crural hernia, in the Edinburgh Med. and Surg. Journ., vol. ii. p. 273, fig. 1. 316 DESCRIPTIVE ANATOMY. mon with the gluteal artery. It descends before the latter, but at the ischiatic notch it turns backward, continuing still to descend, and emerges from the pelvis, below the pyriformis muscle. The common trunk of the ischiatic and of the internal pudic arteries frequently does not bifurcate, except in this place, to give origin to two arteries; and from its portion within the pelvic cavity arise branches which are distributed to the pyriformis, to the obturator internus, and to the levator ani muscles. On emerging from the pelvis the ischiatic artery sends, to the pos- terior part of the ilio-femoral articulation, branches which anastomose with the circumflex arteries. It afterward goes backward, toward the gluteus maximus muscle, into which it penetrates from within out- ward, and within which it is almost entirely distributed. It often gives off the middle hemorrhoidal, the uterine, the vaginal, and the vesical arteries, especially when it arises by a long trunk, in common with the internal pudic artery. It not unfrequently gives off an inferior lateral sacral artery when the usual artery of this name does not descend very low, and is unu- sually small. It constantly anastomoses by large branches, above, with the ischi- atic artery, and with the circumflex arteries below, around the coxo-femo- ral articulation of the large trochanter. VI. INTERNAL PUDIC ARTERY. § 1482. The internal piidic artery (A. pudenda interna, s. communis, s. circumflexa, s. pudica pelviena, s. hamorrhoidea externa) descends into the pelvis, directly before the ischiatic artery, which is generally larger than it, and when it is not given off in this place or even after- ward by the latter, emerges with it from the cavity of the pelvis, between the pyriformis muscle and the large sacro-sciatic ligament, between the latter and the small sacro-sciatic ligament, afterward re-enters the pelvis, where it continues to the symphysis pubis, descends along the posterior edge of the descending branch of the ischium, on its internal face, to the tuberosity of the ischium, then reascends, always on the inner side Of the bone, along its ascending branch and the descending branch of the pubis, between the obturator internus and the levator ani muscles, and having come above the symphysis pubis, terminates in the external organs of generation. Thus the pudic artery usually emerges from the pelvis through the sciatic notch, and re-enters it between the two sacro-sciatic hgaments to leave it a second time below the symphysis pubis ; but not unfre- quently, especially in the male, it always continues in the cavity of the pelvis, and then, proceeding on the lower and lateral portion of the bladder, it goes forward, across the upper part of the prostate gland, where Burns remarks it may be wounded in the operation of lithotomy particularly when the summit of the prostate gland is cut. ANGEIOLOGY 317 It often gives off within the pelvis one or several vesical arteries, the middle hemorrhoidal, the vaginal, or the uterine, and even the obtu- rator arteries. It also sends smaller branches to the internal parts of the genital and urinary apparatus. In its course along the descend- ing branch of the ischium, besides several small branches which go to the bone, to the obturator internus muscle, to the upper extremity of the flexor muscles of the thigh, to the lower part of the rectum, and to the sphincter ani, it gives off others also, of which the principal are, 1st. A considerable branch which goes outward, between the large trochanter and the ischium, divides into several branches, descends on the neck of the femur and the capsule of the ilio-femoral articulation, between the obturator internus and externus muscles, gives ramuscules to these muscles, and also to the quadratus femoris and to the gemelli muscles, and anastomoses with the circumflex arteries. 2d. One or more rather large internal branches, which go to the inferior part of the rectum, also to the anus, and form the external or inferior hemorrhoidal artery (A. hamorrhoidea externa, s. inferior). A little above the tuberosity of the ischium, the internal pudic artery divides into two branches, an interrfal transverse, and an external anterior ascending branch. The internal branch, the perineal artery (R. internus, s. transversus, s. superficialis, arteria perinaa, s. transversa perinai) is smaller than the external. It goes inward and a little forward along the transver- salis perinei muscle, usually between it and the skin, distributes branches to these parts, and also to the other muscles of the penis, and to the constrictor vaginae in the female; gives some branches to the lower part of the rectum, and to the sphincter ani, which are termed the external or inferior hemorrhoidal arteries (A. hamorrhoidales infe- riors, s. externa,) and sends others also to the skin of the perineum, labia pudenda, and scrotum. The external, anterior, superior, or deep branch (R. anterior, s. supe- rior, s. profundus, s. pudendus) is called the artery of the penis (A. penis) in the male, and the artery of the clitoris (A. clitoridea) in the female. When the internal pudic artery gives off considerable branches within the pelvis, this artery not unfrequently arises mostly from the other adjacent branches of the hypogastric artery, especially from the obturator artery, less frequently from the external iliac artery, particularly from an external pudic artery, an anomaly which is indi- cated in the normal state by the more or less manifest anastomoses between the internal and the external pudic arteries. This artery is much larger in the male than in the female on account of the greater proportional size of the parts to which it is distributed. In both sexes it proceeds from below upward, around the inner face of the pubis and ischium, between the bone and the corpus cavernosum of the penis and clitoris, and distributes branches to the vagina and prostate gland, the labia pudenda, and the scrotum, finally to the cli- toris and the penis, which branches are arranged after the same type. 318 DESCRIPTIVE ANATOMY. The branches which go to the prostate gland and the scrotum in the male, to the vagina and to the labia pudenda in the female, are given off the first, directly above the sciatic tuberosity. After these the trunk descends along the ischium and the pubis, covered by the erector penis (levator penis, clitoris), and thus comes .into the triangular space below the symphysis pubis, where the roots of the corpus cavernosum of the penis in the male, and of the clitoris in the female unite. In both sexes, the artery then divides into two branches, the super- ficial and the deep branch. The superficial or the dorsal branch, the dorsal artery of the penis or clitoris (R. dorsalis, s. superficialis penis vel clitoridis), passes through the suspensory ligament. It is very tortuous when the penis is not erected, and proceeds under the skin at the side of the synonymous artery of the opposite side, with which it sometimes unites, after a very short course, advances thus on the back of the penis, and gives branches to its skin and its fibrous membrane, and sends off others which descend into the scrotum. At the groove behind the glans, it forms a crown around it, and finally penetrates into its substance. The deep branch or the cavernous artery (A. profunda, s. cavernosa penis, s. clitoridis) passes through the fibrous membrane of the corpus cavernosum of its side, thus penetrates into the substance of this body, and soon divides into several branches. These proceed from behind forward, along the penis, expand in the corpus cavernosum of both the penis and urethra, and frequently anastomose with those of the oppo- site side.' The two deep branches often unite in a single common trunk. Sometimes the internal pudic artery terminates much sooner than we have mentioned, in the transverse perineal artery, and the dorsal artery of the penis or clitoris arises wholly or in great part from the obturator artery. VII. UMBILICAL ARTERY. § 1483. The third artery of the anterior branch of the hypogastric artery, the umbilical artery (A. umbilicalis), is before birth the continu- ation not only of the trunk of this artery, or even of the primitive iliac artery, but is larger than the hypogastric and femoral arteries, and is the continuation of the aorta. At all periods of life the umbilical artery goes a little obliquely for- ward and inward, toward the upper part of the lateral wall of the bladder, to which it is attached by mucous tissue. Thence it proceeds along this wall, toward the posterior face of the anterior wall of the abdomen, and thus goes from behind forward and from below up- ward to the umbilicus. In the fetus it is open in its whole extent, but soon after birth it is gradually obliterated after leaving the umbilicus, so that finally it ANGEIOLOGY. 319 affords a passage to the blood only in the part between its origin and the bladder, the rest of it being changed into a full and solid ligament, enveloped by a fold of the peritoneum, and which may be generally traced to the umbilicus. During fetal existence, the lower and anterior part of the umbilical artery which is convex, gives off not only the branches of the hypo- gastric artery, which we described above, but also, first, the inferior vesical, then the vaginal, next the uterine, and finally one or more superior vesical arteries, which generally are very distinct from each other. But as it is gradually obliterated, and as at the same time the lower extremities and their vessels are developed, these arteries approach each other, and seem to be in part the upper arteries of the anterior branch of the hypogastric artery. These branches arise in the following order, which we adopt, since in following it the arteries to be described, correspond from behind for- ward to those already mentioned. VIII. VESICAL ARTERIES. § 1484. The vesical arteries (A. vesicates) are distinguished into inferior and superior. The inferior are larger than the superior, and generally there is only one. They arise from the umbilical or from an anterior branch of the hypogastric artery, which is usually the internal pudic, or from the trunk of the hypogastric artery ; they go downward and forward to the lower and posterior part, and also to the neck of the bladder, the commencement of the urethra, to the prostate gland and to the vesiculse seminales in the male, and to the lower part of the vagina in the female. The superior are generally smaller and more numerous; they always arise from the lower part of the umbilical artery, consequently from the most anterior part or from the extremity of the hypogastric artery, and go to the middle and superior part of the bladder. IX. MIDDLE HEMORRHOIDAL ARTERY. § 1485. The middle hemorrhoidal artery (A. hamorrhoidea media) often follows the inferior vesical artery from below upward, and from behind forward ; but frequently also it arises lower than it, being even sometimes deficient, and is given off by the ischiatic or by the internal pudic artery. Sometimes it arises from the upper or lower hemor- rhoidal arteries, with which it always anastomoses, and is distributed on the anterior face of the rectum and also on the posterior part of the bladder, where it communicates with the proper vesical arteries. 320 DESCRIPTIVE ANATOMY. X. VAGINAL ARTERIES. § 1486. One or two vaginal arteries (A. vaginalis) usually follow the inferior vesical artery. But this artery is frequently deficient, and it is then replaced by the ramifications of the vesical, the hemorrhoidal, or the uterine arteries. Sometimes also, even when it forms a distinct branch, it does not arise in the order mentioned, but comes from some one of the arteries of the anterior or of the posterior branch of the hypogastric artery. It goes forward, inward, and downward. Its branches are distri- buted to the inferior and middle regions of the lateral part of the bladder and of the vagina. XI. UTERINE ARTERY. § 1487. The uterine artery (A. ulerina) generally succeeds the vaginal artery, but it frequently varies from this order. It is however constant. It goes inward, toward the upper part of the vagina, to which it gives off some branches, as well as to the bladder; it then reascends in the broad ligament along the lateral wall of the uterus. In its course which is very tortuous, it gives off numerous ramifications which are also curved, to the anterior and posterior faces of the uterus. Some of these ramifications are distributed on the surface and others in the substance of this organ. Its upper part expands by several branches in the folds of the peritoneum; they go to the internal organs of generation, to the Fallo- pian tubes, and to the ovaries, where they frequently anastomose with the spermatic arteries. § 1488. In man, the vessels which correspond to the uterine or the vaginal arteries are small secondary branches of the vesical and of the external hemorrhoidal arteries. ARTICLE SECOND. EXTERNAL ILIAC ARTERY. § 1489. The external or anterior iliac artery (A. iliaca externa, s. anterior, s. cruralis iliaca, s.femoralis), from its origin, descends from within outward, on the inside of the psoas magnus muscle, sends nu- merous small branches to this muscle, and also to the lower part of the iliacus muscle. It usually gives off, at a greater or less distance from the crural arch, two large branches, the epigastric artery, and the circumflex ANGEIOLOGY 321 iliac artery, which are very important in a pathological and surgical point of view on account of inguinal and crural hernias. The first usually arises a little and sometimes much higher than the second, and even above the crural arch; besides, it always comes from the inside of the iliac artery, while the other constantly arises from its outside. I. EF1GASTRIC ARTERY. § 1490. The epigastric artery (A. epigastrica) is rarely a branch of the common or deep crural artery,(l) but it often arises by a trunk, in common with the obturator artery, so that we may consider it as giving off this latter(2) (§ 1476), although, for all this, its origin is not neces- sarily displaced and carried higher than usual. It is often given off, sometimes higher and sometimes lower, from the external iliac artery, so that the place where it arises varies to the extent of two inches, although the obturator artery is not necessarily one of its branches.(3) Thus we may consider erroneous the opinion of Hesselbach, who asserts that this artery rarely varies in its origin and in its course,(4) and also that of Mayer,(5) who, like Burns, asserts that it always arises directly below the crural arch. The latter case exists very seldom, for the epigastric artery almost always arises above Poupart's ligament. On the contrary, the place where it detaches itself from the external iliac artery varies much, although it never comes from any other vessel.(6) It however generally arises directly above the crural arch,(7) and its origin is normal when situated one inch or even two inches above this arch.(8). (1) Monro, Morbid anatomy of the human gullet, Edinburgh, 1811, p. 426. (2) At least we have never found in this case that the epigastric was a branch of the obturator artery, although we have often seen both arise by a common trunk, and have now several cases of the anomaly before us. Hesselbach, ( Veber den Or- prung und das Fortschreitcn der Lcisten-und Schenkelbriiche, Wurtsburg, p. 17) and Bekkers (loc. cit., p. 315), mention in fact one case where the epigastric arose from the obturator artery. But it is evidently wrong, as it follows from the descrip- tion of this anomaly given by the former, in saying that the obturator artery came from the inside of the crural more than an inch above the crural arch; since it fol- lows from it we say that the common trunk arose, as is commonly seen in this case, from the external iliac, and not from the internal iliac, or hypogastric artery, as would be the case provided the expressions of Hesselbach were correct. This ano- maly however may sometimes occur. Monro (loc. cit., p. 427) seems to have observed it, for he says that in one preparation before him the epigastric arose from the obtu- rator artery, and afterward went upward and inward, toward the rectus abdominus muscle. (3) Which Hesseloach seems to think necessary. (4) Hesselbach, loc. cit., p. 17-52. (5) Mayer, Beschreibung der Blutgefasse des menschlichen Korpers, p. 206.. (6) Monro is very correct in saying (loc. cit., p. 254) thatthe epigastric artery varies much in its origin. (7) As has been correctly stated by Bichat (loc. cit., p. 311) and Murray, (loc. cit., p. 89). (8) Outlines, p. 354. (9) According to Scemmerring, loc. cit., p. 307. Vol. II 41 * 322 DESCRIPTIVE ANATOMY When the epigastric artery arises unusually high it descends near the crural arch, sometimes very low, even below this arch, and always passes behind the commencement of the spermatic cord, above the inguinal ring, so that it is situated on the inside of this cord. There it suddenly curves and reascends vertically on the posterior face of the rectus abdominis muscle, first between this muscle and the peritoneum, then between it and the posterior layer of the sheath. Soon after it is reflected around the spermatic cord, it gives off, di- rectly above the inguinal ring, a constant branch, which divides into two branches; one goes downward and backward and anastomoses with the iliac artery, the other is transverse and goes inward, proceeds along the horizontal branch of the pubis, behind the inguinal ring, and communicates with that of the opposite side. It also sends to the spermatic cord or to-the round ligament of the uterus, some ramifica- tions which penetrate to the scrotum and the labia pudenda, and anas- tomose below with the spermatid arteries, and above with the uterine arteries in the female. These ramifications, which go to the spermatic cord and to the round ligament of the uterus, sometimes come from the trunk of the external iliac, even above the epigastric artery, when the latter arises lower than usual. This arrangement coincides with the very high origin of the spermatic arteries notwithstanding the sloping situation of the testicles and of the ovaries, since it manifestly depends on the spermatic cord being situated at first higher and more internally. The trunk of the epigastric artery divides below into two branches, the external, which is generally the larger, and the internal, the smaller; it then ascends on the posterior face and in the substance of the rectus abdominis muscle, sends off several branches outwardly, one of which is frequently larger than the others, in the internal part of the broad abdominal muscles, gives branches to these, the recti, and to the pyramidales muscles, and to the peritoneum, and terminates near the centre of the abdomen, by anastomosing with the branches of the ex- ternal thoracic, the inferior intercostal, and the internal mammary arteries. The epigastric artery is situated on the outside of the tumor in in- ternal inguinal hernia, and on the inside in external inguinal hernia; so that in the former case it is wounded when the incision is carried out- ward and in the latter case when the history is directed inward. It is rarely so far distant from the inside that it is raised with the umbilical artery or with the remnant of this vessel, and consequently proceeds on the inside of the tumor, even in an internal inguinal hernia.(l) In crural hernia it is usually found outward, so that we run the risk of opening it when we cut in this direction. It is however difficult to wound it when it does not arise lower than usual, while this is easy when it comes from the crural artery, in which case it sometime? f:l) Bekkers, loc. cit., p. 316. ANGEIOLOGY 323 .'oceiids on the outside of the inguinal ring, sometimes passes before this opening to go to its inside ; it may also be divided, when, although it does not arise lower than usual, it descends first superficially and resumes its situation afterward to go toward the umbilicus. § 1491. Sometimes a considerable branch arises from the inside of the iliac artery, below this artery, the following, or finally the crural arch. This is half as large as the epigastric artery, and ascends out- side of the inguinal ring, between the external face of the obliquus ab- dominis muscle and the skin, gives branches to this muscle, particularly to the integuments, extends to the umbilical region, anastomoses below with the epigastric artery, and may be considered as the second epigas- tric artery. When this branch exists, it is also found on the outside of the tumor in an external inguinal hernia, and it is wounded if the his- tory is carried in that direction. II. CIRTUMFLEX ILIAC ARTERY. § 1491. The circumflex or anterior iliac artery (A. abdominalis, s. circumflexa iliaca externa, s. iliaca externa minor, s. epigastrica externa) usually arises on the outside of the iliac artery, opposite the epigastric artery, which is generally a Httle larger than it. As however it is more constant in its origin than the latter, it is not unfrequently placed more or less below it. It frequently comes from above the epigastric artery, although the latter arises at its usual place. In some subjects it even arises from the crural artery, directly below the crural arch, but always at least from its outside. It goes directly outward and upward toward the iliac crest, frequently sends branches to the tensor fascise lata? and sartorius muscles, always give them to the iliacus muscle, and following the direction of the crest of the ilium, proceeds from be- fore backward and from within outward, in the lower and middle part of the broad abdominal muscles, between which its principal branches penetrate. The latter anastomose with the ileo-lumbar and epigastric arteries. Others, which go outward, toward the great trochanter and the sartorius muscle which they accompany, communicate with the ramifications of the crural artery. This artery is not unfrequently divided into two trunks, one of which generally arises a little below the epigastric artery. The external branch is generally much larger than the other, but sometimes becomes a small branch, while the principal branches of the artery go obliquely inward and upward. In this case, when one or more of these branches are considerably large, the operation of para- centesis might give rise to a formidable hemorrhage^ 1) (1) Ramsay, Account of some uncommon muscles and vessels, in the Edinb. mat. and surg. journ,, vol. viii. p. 282, tab. 1, fig. 1. 324 DESCRIPTIVE ANATOMY ARTICLE THIRD. CRURAL ARTERY. § 1493. The external iliac artery after emerging from the crural arch, under the centre of which it passes, is called the crural or femoral artery (A. cruralis, s. fetnoralis communis s. cruralis inguinalis, s. cruri inguinalis). It is situated in this place on the neck of the femur, almost directly below the skin, covered only by the fascia lata aponeu- rosis, the fat, and the lymphatic glands of this region, over the vein which accompanies it, and occupies nearly the centre of the space between the symphysis pubis and the anterior and superior spine of the ilium, between the adductor muscles of the thigh on one side, the. rec- tus anticus and the sartorius muscles on the other. Beside the small inconstant ramifications which it distributes to the skin, to the muscles, and to the lymphatic glands of this region, it gives off, sometimes higher and sometimes lower from its inside, one, two, and even three external pudic, scrotal, or vulvar arteries, the upper, the lower, and the lowest (A. pudenda externa, superior, inferior et infima, s. tertia). These arteries, which proceed directly under the skin, go from with- out inward in the integuments and the fat of the pubis and of the lower part of the abdomen, the inguinal glands, the scrotum, and the labia pudenda, where they form the anterior scrotal and labial arteries (A. scrotales et labiates anteriores). To this is referred the second epi- gastric artery mentioned above. § 1494. The crural artery has not always the same extent. Its length is principally determined by the origin of the deep femoral artery, which always arises from its posterior and inner side, so as to be covered by it. This branch is generally given off from the trunk one or two inches below the crural arch, rarely higher,(l) but some- times also it arises directly below the arch or even, which is always very rare, above it. On these differences depend also those in the size of the superficial and deep crural arteries or of the continuation of the trunk. When the crural artery arises very high it is usually much larger than common, nearly equal to the superficial in size, and then it frequently gives off the upper branches of the latter, particularly the external pudic arteries, but more frequently still the circumflex arte- ries, which we shall mention directly. Sometimes the latter and the deep crural artery arise from a common trunk and at the same place. (1) Burns has already corrected the error made by Bell, who asserted that this division usually occurred four inches above the crural arch. ANGEIOLOGY. 325 I. DEEP CRURAL ARTERY, § 1495. The deep crural artery (A. cruralis, s. femoralis profunda) gives off frequently, not far from its origin, two branches, called the circumflex arteries of the thigh (A. circumflexa femoris), which are distinguished into external and internal. This however is not always the case. Sometimes, but very rarely, these two arteries (more fre- quently one of them, particularly the internal, and very rarely the external) arise from the common crural or even from the superficial crural artery, below the origin of the deep femoral artery. I. CIRCUMFLEX ARTERIES. § 1496. The internal circumflex artery (A. circumflexa femoris interna) generally arises higher than the external. Its origin is some- times two or three inches above that of the latter; hence it comes more frequently than the other from the common crural artery, directly below the crural arch and the epigastric artery, higher even than the three external pudic arteries, and it is thus sometimes given off by the external iliac artery. It generally comes from the inside, but in some subjects from the outside of the common crural artery. In this case it gives one or more branches, which go outward and upward, into the inguinal glands, the iliacus and the sartorius muscles, and anastomose with those which arise from the crural artery. The trunk goes inward, passing in the second case below the crural artery, and at the same time descending a little when not unusually high. It gives branches to the lower part of the psoas and iliacus, the pectineus, to the short and long adductor muscles, afterward goes deeply inward and back- ward, below the pectineus muscle, and immediately around the neck of the femur, and divides behind the pectineus into two branches, a superior, or anterior and an inferior or posterior. The superior is smaller and soon subdivides into two branches ; the external and smaller is called the artery of the cotyloid cavity (A. ace- tabuli) \ it goes to the capsular hgament and to all parts of the articu- lation, turns on the head of the femur, anastomoses by a. large ramus- cule with the obturator artery, and distributes branches to the obturator externus muscle. The internal is larger, passes behind the adductor longus and brevis, and is expanded in the upper part of the adductor magnus muscle. The inferior branch is much larger than the preceding, and is the con- tinuation of the trunk. It descends backward, behind the adductor mag- nus muscle, is distributed principally to the gracilis muscle, the three long flexors of the leg, the long head of the biceps femoris, the semi- membranosus and the semitendinosus, and finally becoming sometimes one, sometimes two branches, called the trochanterian, which are dis- tinguished into an upper and lower (R. trochanterics superior et infr- 326 DESCRIPTIVE ANATOMY rior), it is reflected from before backward, on the inner part of the femur, then outward and upward, to arrive at the great trochanter, ascends before the gemelli and quadratus femoris muscles, between them and the obturator externus muscle, gives branches to these mus- cles, and also to the tendon of the obturator internus and pyriformis, and anastomoses with the external circumflex, the gluteal, the ischiatic the inferior hemorrhoidal, and the obturator arteries. This inferior branch is sometimes smaller, and is distributed only to a portion of the adductor magnus and to the gracilis muscles ; all the other ramifica- tions, especially the anastomotic, arising from the superior. Beside the anastomoses between the external and the internal cir- cumflex arteries at the posterior part of the thigh, these two arteries often unite by a very large transverse branch on the anterior face of the bone, which, added to their communication with the crural artery, completes the circle of anastomosis. By all these anastomoses the internal circumflex artery is the prin- cipal channel through which the blood comes to the lower extremity when the external iliac artery is tied. It is consequently one of those vessels which are considerably dilated after this operational) § 1497. The external circumflex artery (A. circumflexa femoris ex- terna) arises still more frequently than the preceding, although not always from the outside of the deep crural artery. It comes some- times from the place where this latter is given off from the common femoral artery, and sometimes much lower. It goes obliquely outward, turning on the anterior face of the femur, directly on the upper part of the cruraus muscle, gives small branches to the lower extremity of the iliacus muscle, and soon divides into an ascending and a descending branch. The descending branch which arises sometimes wholly, sometimes partially, from the superficial or from the deep femoral artery, gives ramuscules to almost all the outer part of the triceps extensor, also to a small portion of the rectus femoris muscle, and sends upward, across this muscle, a transverse vessel which goes to the large trochanter, penetrates into its substance, and forms a net work on its surface by anastomosing with the ramifications of the internal circumflex artery. The ascending branch penetrates from before backward and from within outward, principally into the gluteus medius muscle, passes above the great trochanter, and anastomoses in this place with the internal circumflex, the gluteal, and the ischiatic arteries. These anastomoses are also very much dilated when the external iliac artery is tied. II. PERFORATING ARTERIES. § 1498. The deep femoral artery after giving off the circumflex arteries goes backward, inward, and downward, so that it descends (1) A. Cooper, Account of the anastomoses of the arteries of the groin; Med. Chir. Trans., vol. iv. p. 424. ANGEIOLOGY 327 on the inside of the femur, between the vastus internus externally, the adductor longus and brevis internally, and the superficial femoral artery forward. In this course it generally gives off some anterior and several posterior branches ; the latter are larger and more constant. The anterior generally arise very high from* the outer and inner sides of the artery. Sometimes there is only one and sometimes we find several on each side. The external goes to the vastus internus and penetrate also to the crurales muscle. The internal "go to the adductor magnus and adductor brevis muscles, and, passing between these two muscles, arrive at the upper and middle part of the gracilis internus muscle, of which they are the principal nutritious vessels. Properly speaking, the trunk of the deep femoral artery divides to give rise to the posterior branches, since it penetrates much farther back, to the posterior part of the thigh behind the femur. These branches have been termed the perforating arteries (A. femo- ris perforantes), because they pass through the adductor magnus muscle to the parts behind it. They vary in number from one to five; for sometimes the whole trunk, or at least that part from which the perforating arteries generally arise, goes backward,-after passing through the summit of the adductor magnus muscle, and then descends behind this muscle, while in other cases it proceeds before it, and gradually gives off branches, which pass through it to arrive at the posterior part of the thigh. This dif- erence is sometimes observed in the two lower extremities of the same subject. • The saperior or first perforating artery commonly divides into two branches, an upper which ascends, and a lower which descends. The superior branch ascends toward and around the great tro- chanter, on which it anastomoses with the ramifications of the external circumflex artery, and penetrates into the lower part of the gluteus maximus muscle, where it communicates with the gluteal artery. The inferior branch turns around the femur forward and outward; it is distributed to the vastus externus and to the rectus, and to the long head of the biceps muscles. It also gives off the nutritious artery of the femur (A. nutritia ossis femoris). The second and third perforating arteries sometimes arise opposite each other, one from the outside the other from the inside of the femoral artery. The external goes to the triceps extensor muscle, the internal is distributed to the biceps, the semitendinosus, and the semimembra- nosus muscles. Sometimes we find also two other perforating arteries, an external and an internal, which are distributed in the same manner. In some subjects the upper branch, then unusually-large, is the only one which passes through the adductor magnus muscle. It divides into two branches, an ascending which gives all the internal ramifications to the flexor muscles ; the inferior is larger, and gives off all the external ramifications except the first. The latter is not visible 32S DESCRIPTIVE ANATOMY externally, but directly where the adductor magnus muscle is inserted it passes through this muscle to empty itself from within outward, in the vastus externus and the rectus femoris muscles. The sciatic nerve also receives considerable branches from the per- forating arteries. A large branch, the anterior extremity of the trunk of the deep femoral artery, always descends before the adductor magnus muscle, between it, the adductor longus and brevis muscles, distribute branches to these muscles, and near the centre of the thigh give off the inferior nutritious artery of this bone. Many of these branches, especially the lower, sometimes arise from the superficial, and not from the deep femoral artery. They all anasto- mose with each other. Farther the superior, as we have already observed, communicate with the external femoral and the gluteal arteries. The lower and the middle are connected by large anasto- mosing branches with recurrent branches, which arise from the lower part of the superficial femoral and the popliteal arteries. Thus when the common or superficial artery is obliterated to a greater or less extent, the perforating branches of the deep femoral artery, and generally all its ramifications, are very much dilated, larger even than the trunk, as is proved by the observations of Deschamps,(l) Dupuy- tren,(2) and Astley Cooper.(3) The deep femoral artery supplies the blood to most of the muscles of the thigh, to almost all the skin of this extremity, and to its bone ; it also gives origin to the accessory vessels for the circulation of the blood in the lower extremity. II. SUPERFICIAL FEMORAL ARTERY. § 1499. The superficial femoral artery (A. femoralis superficialis, s. cruralis femoralis, s. cruri-femoralis, s. femoro-tibialis), after the origin of the deep, penetrates a httle farther, between the vastus internus on one side and the adductor longus and brevis on the other, passes below the sartorius, to arrive at the inner side of the thigh, proceeds before the adductor muscles to the commencement of the lower fourth of the thigh, enters in this place the tendon of the adductor magnus muscle, and thus comes on the posterior face of the limb, where it is called the popliteal artery. In its course it gives off branches, of which the principal are the internal and the external; but it also sends off anterior and particularly posterior branches, especially at its lower part. The internal branches are distributed in the adductor, the gracilis and the sartoius muscles. (1) Observ. anat. faites sur un sujet operi suivant le procede de Hunter, d'un anevrysme de Vartere poplitee; in the Mem. pris. a VInstil., 1805, vol. i. p. 251. (2) Journ. de Corvisart, vol. vii. p. 536. (3) Dissection of a limb, on which the operationfor popliteal aneurysm had been performed, in the Med. chir. trans., vol. ii. p. 250. ANGEIOLOGY. 329 The external are distributed in the latter, to the rectus, and particu- larly to the vastus internus ; the deep pass behind the femur, and go to the vastus externus. The anterior distribute blood to the sartorius muscle and to the skin, to which also go some ramifications of the other branches. The posterior go to the vastus internus, but particularly to the lower part of all the flexors of the leg, and as they turn around the femur they also penetrate into the vastus externus and extend to the skin. They anastomose by large branches above with the perforating arte- ries, below with the superior and inferior articular arteries. The superficial, femoral artery deserves its name, because, during its whole course, it is situated near the skin. It is covered for a short distance by the sartorius muscle which crosses it. We may then easily find it in operations. The place where it is exposed in Hun- ter's operation for aneurism is directly below the lower edge of the sartorius muscle at the inner part of the anterior side of the thigh.(l) The objection that when we operate in this place the articular arteries are lost and the circulation cannot continue is unfounded,(2) since when the superficial femoral artery is entirely obliterated, the anasto- moses of the branches of the deep femoral artery with the lower branches of the superficial, and with those of the popliteal artery, supply channels which are large even in the normal state, and through which the blood may pass from the branches of the deep femoral into the articular arteries, and into all the parts below the ligature. III. POPLITEAL ARTERY. § 1500. The popliteal artery (A. poplitaa, s. cruri-poplitaa, s. femoro-poplitaa) is the lowest portion of the femoral artery, a'nd descends into the calf of the leg, inclining a little from within outward ; it extends from the beginning of the lower fourth of the femur to the summit of the upper fifth of the leg. Sometimes it is much longer, because the superficial femoral artery penetrates the adductor magnus higher, and also divides a little higher. It is separated at its upper part'from the femur and from the posterior face of the capsular hgament of the femoro-tibial articulation at its central part, by an abundance of fat and cellular tissue. The tibialis posticus muscle separates it below from the tibia. Behind, it is separated at its upper part from the skin by the sciatic nerve and the popliteal vein, by fat and by mucous tissue; in its lower part, by the muscles of the calf of the leg, and the plantaris muscle. Above, it is separated by abundance of fat and cellular tissue, out- ward from the biceps femoris muscle, and inward from the semitendi- (1) Home, An account of Hunter's method of performing the operation for the cure of popliteal aneurysm, in the Trans, of anass. for the improv. oi med. and surg. knowl., vol. i. no. 4. Additional cases, &c. ibid. vol. ii. no. 19. (2) Deschamps, loc. cit., vol. i. p. 254. Vol. II 42 3.30 DESCRIPTIVE ANATOMY nosus and the semimembranosus muscles. The two upper heads of the triceps extensor muscle closely envelop it at its lower part. It is then looser and also nearer the bone above and below, but is every where surrounded with an abundance of fat and cellular tissue. This circumstance, added to the prominence of the flexor muscles of the tibia and of the fibula, renders it difficult to fix it and to compress it. § 1501. Beside certain inconstant branches which, when it passes through the tendon of the adductor magnus muscle higher than usual appear near its origin, on the posterior face of the thigh, it gives off, 1st. From its upper part or crural portion, particularly from the posterior and inner side of this portion, several branches, which go to the lower part of the flexor muscles of the tibia. 2d. Lower down three superior articular arteries (A. s. rami articu- lates superiores), which are distinguished into internal, external, and middle, which sometimes, even usually, all, or at least two, arise by a common trunk from the anterior side of the popliteal artery. Some of these arteries are double in some subjects, then only one is detached from the trunk before the other, and the superior anastomoses with the muscular branches mentioned before. The internal and external are usually larger than the middle. § 1502. The external superior articular artery (A. articularis genu superior externa) rests directly on the tibia, and passes between this bone and the common tendon of the biceps muscle, usually goes from below upward, but always from behind forward and from within out- ward, and gives off, in its course, ramifications to the inferior belly of the biceps muscle, also to the lower part of the vastus externus, is dis- tributed on the outer condyle of the femur, penetrates into the articular capsule, gives branches to all the ligaments of the keee, and communi- cates, by a very large anastomosing branch which proceeds across to the anterior face of the femoro-tibial articulation, on the common tendon of the extensors of the thigh, on one hand, both on the side and forward with the ascending branches of the external inferior articular artery on the other, on the median line and forward, with a similar branch of the internal superior articular artery. § 1503 . The internal superior articular artery (A. articularis genu superior interna) varies more than the external and the middle in respect to its origin, for it not only forms a distinct trunk much more frequently than the latter, but it also not mifrequently, in fact almost normally, arises very high, as it sometimes comes from the superficial femoral artery, and then descends along the inner edge of the vastus internus muscle, to which it distributes ramifications. In this case, we find at the most normal place of its origin, a small artery, which is sometimes a branch of a common trunk of the articular arteries, and sometimes arises directly from the popliteal artery, and anastomoses with the superior internal articular artery. When the origin of the latter is placed low, it goes a little from above downward, like the external, before it proceeds inward and forward. It divides into one or severa' a NGElOLOGY. 331 muscular branches, which go to the lower part of the vastus internus muscle; another median artery is situated lower, and passes behind this muscle and the common tendon of the extensors of the thigh, goes into the inner condyle of the femur and to the inner part of the ligaments of the knee; finally, a third, which is superficial; this proceeds on the anterior face of the femoro-tibial articulation, directly under the skin, anastomoses below with the branches of the internal inferior articular artery, and outwardly and transversely with the transverse branch of the external superior articular artery. Both the external and the internal superior articular arteries give off considerable and recurrent branches, which communicate with the branches of the deep and superficial femoral arteries. § 1504. The middle articular artery (A. articularis genu media azygos) very rarely forms a distinct trunk, and is generally given off by the external superior articular artery. It goes forward and down- ward, penetrates from behind forward between the two condyles of the femur, and is distributed near the centre of the knee, in the femoro- tibial articulation, to the crucial ligaments, to the articular fat, to the posterior and middle part of the capsular ligament, and anastomoses with the branches of the inferior and also of the other two superior arti- cular arteries. § 1605. Some small external and internal ramifications arise from the middle and inferior part of the popliteal artery and of its crural por- tion ; these are not constant and go to the lower part of the flexor muscles of the tibia and fibula. This portion then gives off the arteries of the gastrocnemii muscles and the inferior articular arteries. § 1506. The arteries of the gastrocnemii muscles (A. gemella) usu- ally arise, at least in part, above the inferior articular arteries and come from the posterior side of the popliteal artery. They are generally two, an external and an internal, one for each of the two upper heads of the triceps surae muscle. They rarely arise opposite each other. We fre- quently find also several other smaller gemelli arteries, which However do not always exist. These vessels furnish the blood to the plantaris muscle, which however sometimes receives a proper and distinct branch. § 1507. The inferior articular arteries (A. articulares genu inferiores externa et interna) are usually two, an external and an internal, which generally form two distinct trunks. They arise from the anterior and lateral side of the popliteal artery, rarely at the same height. Some- times one and sometimes the other is higher. Generally they are of the same size. § 1508. The external sends branches to the lower and middle head of the triceps surae muscle. These branches however sometimes arise, at least in part, from a special branch of the popliteal artery. The artery then, passing directly above the external head of the tibia, below the external lateral ligament of the knee, and on the capsular ligament of the articulation, goes thus from behind forward. In its course it 332 DESCRIPTIVE ANATOMY gives branches to the articular capsule, and anastomoses on one side by ascending lateral branches with the descending branches of the external superior articular artery, on the other by a large transverse branch, which passes above the lower part of the anterior face of the tendon of the extensors of the thigh, below the patella, with a similar transverse branch from the internal inferior articular artery. § 1509. The internal usually proceeds a little downward, goes from behind forward and from without inward, below the internal head of the triceps surae muscle, directly surrounds the inner condyle of the tibia, gives numerous branches to the popliteus muscle, sends downward other branches, which anastomose, on the internal face of the tibia-with the recurrem branches of the posterior tibial artery, gives also others, which are larger and transverse, which communicate directly above the insertion of the common tendon of the extensors of the thigh with the recurrent branches of the anterior tibial artery, and finally goes upward and forward on the external anterior face of the ligament of the patella, where it anastomoses by several ramifications with the internal superior and with the external inferior articular arteries. § 1510. Besides these two inferior articular arteries, we sometimes find a middle articular artery (A. articularis inferior media, s. azygos). which however arises oftener from the internal, and which penetrates from behind forward in the femoro-tibial articulation, on the median line, between the two condyles of the tibia. The popliteal artery generally gives off no other branches than those which have been described; it is then the principal source of the anas- tomotic articular branches, by which, from the communication estab- lished between the upper and the posterior branches of the deep femoral artery, or between the inferior and recurrent branches of the arteries of the knee, the circulation of the blood may continue regularly in the leg, even when the superficial femoral and the popliteal arteries are oblite- rated. Thus these vessels are very much dilated after an operation for popliteal aneurism, where the superficial femoral and the popliteal arteries are obliterated. ARTICLE FOURTH. ARTERIES OF THE LEG. § 1511. The popliteal artery generally, after passing an inch with- out giving off any branches except those which go from its lower part into the soleus or to the third head of the triceps suras muscle, divides about an inch below the knee, very rarely higher and opposite the ar- ticulation, into two branches, called the tibial arteries (A. tibiales, s. cnemiales, Barclay). Of these two branches, the posterior is the larger, and may be considered from its direction as the continuation of the trunk, and is the common trunk of the posterior tibial and peroneal ANGEIOLOGY, 333 arteries; the anterior is smaller, separates from the trunk, and is the anterior tibial artery. The common posterior trunk is always larger than the anterior; sometimes it exceeds it greatly in size, in which case the latter is arrested in the middle of the leg, and all the branches which it generally gives off then arise from the posterior tibial and from the peroneal artery. It sometimes divides very high. Thus, in a case observed by San- difort,(l) the crural artery divided directly below Poupart's ligament. Portal(2) has also found it to divide higher than usual. Ramsay(3) has seen it bifurcate, not in fact above the knee, but at least above the popliteus muscle ; the anterior tibial artery passed before this muscle, between it and the tibia, and was there compressed by him. I. ANTERIOR TIBIAL ARTERY. § 1512. The anterior tibial artery (A. tibialis antica, s. rotularis)(4) describes a shghtly acute angle to go forward above the upper edge of the interosseous membrane. On the anterior face of the leg it divides into two branches, the smaller of which is the ascending or recurrent branch; the other is the continuation of the trunk; the latter descends on the anterior face of the limb and is distributed on the tibial side of the leg and foot. § 1513. The recurrent artery (A. rccurrens) gives branches to the tibialis posticus muscle, and is situated directly on the outer face of the upper extremity of the tibia; it proceeds from below upward, to be dis- tributed partly in the head of the tibia, partly also to the external and lower part of the ligaments of the knee and the common tendon of the extensor muscles of the leg. It anastomoses with the inferior articular artery, and by means of it with the superior and likewise with the rami- fications of the femoral artery. We must place it among the accessory vessels of the lower extremity. § 1514. The trunk of the anterior tibial artery descends on the an- terior face of the interosseous membrane, between the peroneus brevis muscle, the extensor digitorum communis longus, and the extensor longus pollicis proprius, and is covered bv the two latter. It gives outward and inward numerous short and small branches, some of which are distributed in these muscles, while others pass through them to go into the peronei muscles and even to the skin. (1) Obs. anat. path., book iv. p. 97. The crural artery divides there into an anterior and posterior tibial artery, and we cannot admit that there is any doubt in regard to its high division into a superficial and a deep crural artery, since Sandifort expressly Bays, that on the left side the division occurred as usual in the calf of the leg. (2) Anat. mid., vol. iv. p. 230. (3) Account of an unusual conformation of some muscles and vessels; in the Edinb. Med. Journ., vol. viii. p. 283.—Barclay, loc. cit., p 263. (4) We describe this artery first, although from its direction and its small size it is not the continuation of the trunk, because it corresponds to the radial artery in its distribution. 334 DESCRIPTIVE ANATOMY When the posterior tibial or the peroneal artery is unusually large. the anterior tibial artery terminates on the back of the foot or in the leg. Sometimes it does not exist as a separate trunk, and is replaced in the leg by the perforating branches of the posterior tibial artery and on the back of the foot by the peroneal artery. In some subjects also it is ob- literated at the articulation of the foot, while above and below this part it admits the blood and is distributed as usual.(l) It generally fur- nishes the dorsal arteries of the foot and those of the large toe. Near the lower end of the leg, it gives off the two malleolar arteries (A. malleolares), an external and an internal, which vary much in their size and place of origin. § 1515. The external malleolar artery (A. malleolaris externa) often arises a little higher than the internal, then descends from behind for- ward between the tibia and the fibula, resting directly on these bones and below the tendon of the peronei muscles, goes outward, expands on and in the external malleolus, frequently sends branches also to the anterior part of the lower end of the tibia, gives ramifications to the extensor hallucis brevis and abductor minimi digiti muscles, and anastomoses by a large branch with the recurrent branches of the tarsal artery on the anterior face of the articulation of the foot, and also with the anterior branches of the peroneal artery on the outside of the os calcis. This branch is constant, but it varies in size, and when large it partially or wholly gives off the dorsal artery of the foot. Sometimes it does not arise from the anterior tibial but from the peroneal artery, when the latter is unusually large. It is rarely given off by the peroneal artery, and arises still less frequently from the posterior tibial artery. § 1516. The internal malleolar artery (A. malleolaris interna) usually arises a httle below the preceding. It not unfrequently divides into several branches, which are given off from the anterior tibial artery, one on the tibia and the other on the tibio-tarsal articulation. It proceeds from without inward, under the tendons of the tibialis anticus and the extensor digitorum longus muscles, resting directly on the tibia and in the second case on the capsular ligament, arrives at the internal malleolus, distributes branches to this eminence, to the cap- sule of the articulation of the foot, to the astragalus, and anastomoses with the branches of the tarsal and posterior tibial arteries. When two internal malleolar arteries exist, they communicate with each other. This artery also sometimes arises, but more rarely than the prece- ding, from the peroneal or the posterior tibial artery. § 1517. After giving off the malleolar arteries, the trunk of the an- terior tibial artery passes under the tendons of the extensor digitorum communis longus, on the outside of the extensor hallucis proprius, and Comes on the back of the foot, giving off right and left small branches, (1) This arrangement does not necessarily arise from the primary formation; it may, as Burns correctly remarks (or Barclay, loc. cit., p. 293), • e accidental and be produced by compression. This ougnt also to be admitted in the second case ANGEIOLOG1 335 which go into the periosteum, the dorsal ligaments of the tarsus, and the tendons of the extensor and peroneus brevis muscles. In this place it is called the dorsal artery of the foot (A. pediaa). The latter is rarely the continuation of the trunk of the peroneal or of the posterior tibial artery. § 1518. Internal and external branches arise from the dorsal artery of the foot. The latter are more numerous, larger, and more constant than the internal. We observe two particularly, the tarsal and the metatarsal artery. The tarsal artery (A. tarsea) arises from the outside of the dorsal artery of the foot, sometimes higher and sometimes lower on the back of the foot, even above the lower extremity of the tibia, in which case the external malleolar artery is very small; this vessel is considerable, and its caliber almost equals that of the continuation of the trunk of the anterior tibial artery; thus it would be more convenient to term it the external tarsal artery (A. tarsea externa), in opposition to another branch which corresponds to the inside. This tarsal artery goes transversely outward on the astragalus and os calcis, gives branches to these bones and also to the external part of the ligaments of the tibio-tarsal articulation and to the tarsus, sends off toward the external malleolus a large branch which anastomoses with the external malleolar artery (§ 1515), communicates on the out- side of the os calcis with the branches of the peroneal artery, gives off forward other branches which unite to those of the metatarsal artery, penetrates to the cuboid bone, to the posterior extremity of the fifth metatarsal bone, anastomoses also with the external plantar artery on the outer edge of the foot, and distributes branches to the extensor digitorum brevis and to the abductor minimi digiti muscles. § 1519. Next comes the metatarsal artery (A. metatarsea), which also arises from the outside of the dorsal artery of the foot, and varies so much in regard to its origin that it is sometimes a branch of the tarsal artery, and sometimes arises several inches distant from it, and from the dorsal artery of the foot, directly behind the anterior edge of the tarsus. It is generally smaller than the preceding. Its direction, like that, is from within outward, assuming a course more transverse as it arises farther forward, and is always situated below the extensor digitorum brevis muscle. It is more or less evidently convex forward, and forms an arch, which is completed outwardly by the anastomosis constantly existing between it and the tarsal artery. This arch, on the outer edge of the tarsus, is changed by the smaller but constant branches of the tarsal artery into a vascular net-work, which covers most of the back of the foot. When this artery arises far backward, we usually find a second, which is smaller and proceeds on the anterior edge of the dorsal face of the tarsus, and which communicate with the posterior by very analogous longitudinal branches, which correspond in number and situ- ation to the three external interosseous spaces. This second artery is not so much a branch of the dorsal artery of the foot as the result of 336 DESCRIPTIVE ANATOMY anastomoses between these longitudinal branches and the dorsal inter- osseous arteries. Sometimes there are even three metatarsal arteries, a third existing between the two we have mentioned. A transverse arch, the convexity of which looks forward, con- stantly forms on the anterior part of the dorsal face of the tarsus or on the posterior part of the metatarsus. This arch contributes more or less but constantly with the posterior perforating arteries given off by the inferior tibial artery to form the dorsal interosseous arteries (A. inter- ossea dorsales), This vascular net-work is termed the dorsal arch of the tarsus (A. dorsalis tarseus). It varies much in extent and complexity. A dorsal interosseous artery proceeds in each space between two metatarsal bones. These arteries are always very large and some- times of an enormous caliber. They are four in number; but the first or the most internal, comprised between the first and second metatarsal bones, is considered as the continuation of the trunk and is called very improperly the external dorsal artery of the large toe (A. hallucis dorsalis). All these dorsal interosseous arteries are similar in the following respects: 1st. They anastomose by their posterior extremity with the posterior perforating arteries. 2d. They communicate with the anterior perforating arteries by their anterior extremity, between the bases of the first phalanges of the toes. 3d. They give off, outward and inward, branches, by which they anastomose with each other on the back of the tarsus, and which are distributed in the external interosseous muscles, the bones of the meta- tarsus, the abductor pollicis longus, and the skin of the dorsal face of the tarsus and of the toes. The branches which go to the toes, each of which receives at least two, the tibial and the peroneal, are called the dorsal arteries of the toes (A. digitales dorsales tibiales et peronea). These superior interosseous arteries sometimes divide anteriorly into two branches, the tibial and the peroneal, each of which always goes to a different toe. From the outer part of the tarsal arch a branch usually arises, which is also connected with the superior interosseous arteries, but which goes to the abductor minimi digiti muscle, and sometimes arises from the fourth interosseous artery, or, according to the usual way of numbering them, from the third. This last also most generally gives off another branch to the fibular side of the little toe, the dorsal peroneal branch of this appendage, while itself gives off the dorsal tibial branch. Sometimes butrarely the second superior interosseous artery, generally called the first, does not arise from the metatarsal artery, but from the continuation of the trunk of the dorsal artery of the foot, and then the latter corresponds more than usual to the middle of the dorsal face of 'he tarsu?. ANGEIOLOGY. 337 § 1520. The internal branches of the dorsal artery of the foot are smaller than the external. They are generally as numerous, but usually there is only one very large. That arises about the centre of the tarsus, a little before the anterior extremity of the astragalus. It is well called the internal tarsal artery (A. tarsea interna). This artery proceeds obliquely from without inward and from behind forward, distributes branches to the internal half of the bones of the tarsus and also to the first metatarsal bone, to part of the extensor digi- torum brevis and of the abductor pollicis pedis, and anastomoses with the dorsal artery of the back of the foot on the dorsal face of the tarsus, with the first interosseous artery, with the internal plantar artery on the inner edge of the foot, finally with the internal malleolar artery, and thus contributes to form the dorsal arch of the tarsus. § 1521. The trunk of the dorsal artery of the foot divides, between the posterior extremities of the first and second metatarsal bones, into two branches: one is the continuation of the trunk, the first metatarsal artery, usually termed the dorsal artery of the great toe (A. dorsalis hallucis) ; the second, the deep anastomosing branch (R. anasiomoticus profundus), passes directly to the sole of the foot, between the two bones, and forms with the external plantar artery the deep plantar arch (A. plantaris profundus), whence arise most of the plantar arteries of the toes (A. digitales plantar es). The dorsal artery of the large toe usually proceeds from behind for ward on the back of the foot, along the external edge of the toe, and there divides into two branches, which become, one the common dorsal artery of the large toe, the other the dorsal tibial branch of the second toe. It anastomoses most generally either at its place of origin or by one of its two branches with the plantar artery of the large toe. II. POSTERIOR TIBIO-PERONEAL ARTERY. § 1522. The common trunk of the posterior tibial andperoncal artery, called also the tibio-peroneal artery, or simply the posterior tibial artery (A. iibio-peronea, s. tibialis postica, s. tibialis poplitea), descends verti- cally behind the interosseous membrane, covered by the heads of the peronei muscles, and generally, soon after the origin of the anterior tibial artery, gives off two considerable branches, an external and an internal. The internal branch sends off small twigs to the poplitcus muscle, penetrates principally into the tibia as the upper nutritious artery (A. nutritia tibia superior), and gives off from behind forward, into the periosteum of this bone, ramifications which anastomose on its internal face with those of the inferior and internal articular artery (§ 1509). The external branch gives off ramuscules to the lower or middle head of the triceps suras muscle, proceeds below it, around the upper extremity of the fibula, sends off ramifications to the upper part of the Vol IJ 43 333 DESCRIPTIVE ANATOMY. peroneus longus muscle, and anastomoses both with the anterior tibial (§ 1511) and with the descending branches of the external inferior articular artery. These two branches consequently contribute to en- large the system of the accessory vessels of the leg. § 1523. After giving them off, the tibio-peroneal trunk, which sends only inconstant branches to the soleus muscle, divides generally from one to two inches below the origin of the anterior tibial artery into two branches, the peroneal artery and the posterior tibial artery. I. PERONEAL ARTERY. § 1524. The peroneal artery (A. peronaa, s. fibularis) generally but not always arises at the place mentioned. Sometimes, but much more rarely, and only when the popliteal artery divides unusually high, it arises above, more frequently below, this point, and in the second case it is smaller in proportion as its origin is lower. Sometimes, in fact often, it does not exist, and it is re- placed by the branches which are successively given off from the posterior tibial artery. Independently of its point of origin it varies very much in respect to its volume, a circumstance in regard to which it increases and diminishes inversely with the anterior tibial artery. It is generally smaller than the two tibial arteries ; but sometimes when one of the latter is deficient it is much larger than usual. It descends on the posterior face of the interosseous hgament, covered by the soleus muscle, on the inside of the flexor longus digitorum com- munis muscle, gives its largest branches to these two muscles and also to the peronei, usually sends off, near the lower extremity of the leg, rather a large branch, which, passing under the posterior tibial artery, is called the posterior internal malleolar artery (A. malleolaris interna postenor) and goes to the internal maUeolus, on the surface of which it frequently communicates with the anterior internal malleolar artery furnished by the anterior tibial artery (§ 1516), and terminates on the outer face and the tuberosity of the os calcis by ramuscules, which enter partly into this bone, and partly by large branches by which it anastomoses with the posterior tibial artery, thus forming the inferior plantar arch. § 1525. At various heights of the leg, but generally toward its lower extremity, it gives off a branch which also varies much in size and which goes to the anterior face of the limb, passing between the two bones. When this branch is considerable it is termed the anterior peroneal artery (A. peronaa anterior). It proceeds, near the surface, on the outer and anterior face of the leg, frequently descends to the external face of the tarsus, unites to the external malleolar artery, given off by the anterior tibial (§ 1515), concurs to form the dorsal arch of the tarsus, anastomoses with the branches of the external plantar artery, and distributes twigs to the tendons of the extensor digitorum communis, to the posterior part of the extensor minimi digiti ANGEIOLOGY. 339 muscle, to the external malleolus, to the astragalus, and to the cuboid bone. This branch does not always arise from the peroneal artery ; it is then generally very small, and does not descend to the lower extremity of the leg or is entirely deficient. It is normally replaced by a branch of the anterior tibial given off by the external malleolar artery (§ 1515) less frequently, although more commonly than when it arises from the peroneal artery, it comes from the posterior tibial artery, and then it passes, at the us ual place, on the anterior face of the leg. The anterior peroneal artery much more rarely not only arises higher than usual, sometimes even not far from the middle of the ante- rior face of the leg, so that it sends off in this place ramifications to the peronei and to the extensor digitorum communis "muscle, but it is also so large that it gives off the external malleolar artery; and the dorsal artery of the foot is even the continuation of its trunk, and then the anterior tibial artery is very small, terminates on the back of the tarsus, and anastomoses with it. Not more frequently the peroneal artery, extends farther than usual in the sole of the foot, and gives off the external and the internal plantar arteries. We have before us only one specimen of this ano- maly. At the same time the anterior tibial artery is extremely small; it stops at the middle of the leg, and all the branches it generally gives off below this point arise from the posterior tibial artery, which passes to the anterior face of the limb, about the level of its lower fourth. II. POSTERIOR TIBIAL ARTERY. § 1526. The posterior tibial artery (A. tibialis postica) is generally much larger than the peroneal artery, but its direction varies more than that of the primitive trunk, and it proceeds slightly inward. It is generally a little larger than the anterior tibial artery and sometimes very much exceeds it in size. It descends, covered above by the third head of the triceps sura muscle, between this muscle, the flexor longus digitorum communis and the'tibialis posticus, and is entirely loose at its lower part, being covered only by the crural aponeurosis and the skin and the posterior face of the tibia, on the inside of the tendo-Achillis. In its course it gives off posteriorly numerous small branches to the soleus muscle and the tendo-Achillis, and anteriorly to the tibialis posticus on flexor longus digitorum communis muscles. At the lower part of the leg it sends off several larger branches both outward and inward ; these anastomose frequently, on the two malleoli, with the internal and external malleolar arteries, given off by the anterior tibial artery. Theposterior tibial artery, proceeding between the tendons of the flexor longus digitorum communis and the tibialis posticus muscles, situated on its inside, and that of the extensor pollicis pedis on the outside, so that it passes on the latter, leaves the posterior face of the leg, and arrives at the sole of the foot, where it is situated on the posterior face of the os calcis. 440 DESCRIPTIVE ANATOMt Very rarely it passes from the posterior to the anterior face of ihe leg. thus becoming the dorsal artery of the foot. It most generally sends off, at the place where it enters the sole of the foot, a considerable branch, which goesrnto the os calcis and also into the lower extremity of the tendo-Achillis ; this branch anastomoses on the tubercle of the os calcis, before this tendon, with the final branches of the peroneal artery, and by means of them with the external malleolar artery ; thus a vascular plexus is formed which may be termed the inferior or plantar tarsal arch (rete, s. arcus tarsus plantaris). Not unfrequently another external and large branch goes to the posterior part of the abductor pollicis pedis muscle. The posterior tibial artery then divides below the internal malleolus, about the centre of the inner face of the calcaneum, but a little behind it, into two branches, the external and internal plantar arteries. These two branches, and the two branches described previously, very rarely arise from the peroneal artery, which happens when the poste- rior tibial artery replaces the lower portion of the anterior tibial artery (§ 1525). III. PLANTAR ARTERIES. I. INTERNAL PLANTAR ARTERV. § 1527. The internal plantar artery (A. plantaris interna) is always smaller than the external, and varies in size less than the latter. It follows the direction of the trunk and goes forward, under the tendons of the flexor digitorum longus muscle, above the long head of the abductor pollicis, not far from the inner edge of the foot. In its course it sends superficial branches to the abductors and the flexor pollicis brevis, and to the flexor communis digitorum brevis, gives deep branches to the inner half of the plantar face of the ligamentous envelop of the tarsus, to the os calcis, to the astragalus, and to the scaphoid bone; anastomoses, in several places above the inner edge of the foot, with the branches of the internal artery of the tarsus and of the dorsal artery of the foot, and gives off anteriorly, between the first and second toes, generally one, often also two, branches, which form the plantar artery of the large toe, and frequently anastomoses, by an external branch, with the deep plantar arch. II. EXTERNAL PLANTAR ARTERY. § 1528. The external plantar artery (A. plantaris externa) is deeper than the internal. It varies in size more than this latter. It is often scarcely visible, and again is sometimes three times the size of the internal. These differences depend principally on those in the size of the dorsal artery of the foot (§ 1517), for there is always an inverse relation between the caliber of these two vessels. The external plantar artery immediately goes far outward. It pro- ceeds between the abductor pollicis pedis and the flexor digitorum ANGEIOLOGY, 341 brevis below, and the accessory muscle above, toward the outer edge of the sole of the foot, where it extends forward, on the inner edge of the abductor minimi digiti muscle, gives branches to all the muscles mentioned, and anastomoses, by several branches which reascend above the outer edge of the foot, with the arteries of the tarsus and metatarsus. At the posterior extremity of the fifth metatarsal bone it goes inward, and gives off, either in this place or a little before, a considerable branch, the peroneal plantar artery of the fifth toe (A. digitalis plan- taris peronea .digiti quinti), which goes forward on the flexor minimi digiti muscle, along the fibular edge of the toes to the anterior extre- mity, sends branches to its flexor muscle, to the third internal inter- osseous muscle and to the skin, and finally anastomoses, on the ungdeal phalanx of the little toe, with the tibial branch. The deep or internal plantar artery then goes almost transversely forward and inward, between the internal interossei and the other muscles of the sole of the foot, and anastomosing with the deep anas- tomotic branch of the dorsal artery of the foot, between the first and second metatarsal bones, forms the deep plantar arch, which is con- cave backward and convex forward, and is situated very deeply on the posterior extremities of the metatarsal bones. III. PXANTAR ARCH. § 1529. The digital arteries and the anterior and posterior perfo- rating arteries arise from the deep palmar arch, a. Digital arteries. § 1530. The digital arteries (A. digitales) arise forward, from the convex part of the arch. Their general characters are, a. They are situated deeply in the sole of the foot, and proceed from behind forward, on the square belly of the flexor digitorum longus communis, and the transverse belly of the adductor hallucis. 6. Between the posterior extremities of the toes they divide into two branches, which go one to the tibial side of the outer, the other to the peroneal side of the inner toe. c. The two branches unite on the ungueal phalanx, and also anas- tomose with each other and with the dorsal branches. d. They anastomose forward with the superior and inferior meta- tarsal arteries at their bifurcation. But they differ very much in regard to their origin. The deep arch most generally gives rise to the deep plantar arteries of the three outer and the peroneal branch of the second toe, less frequently to the tibial branch of this and the plantar branch of the large toe. The peroneal branch of the little toe often comes directly from the plantar arch, and even farther behind it, from the external plantar 342 DESCRIPTIVE ANATOMY. artery (§ 1528), but it not unfrequently arises, by a common trunk, with the tibial branch of the fifth toe and the peroneal branch of the fourth. We have never observed that when this first digital artery gave off also the tibial branch, it was destined solely for the fifth toe, and did not proceed at the same time to the peroneal side of the fourth. Even when the peroneal branch of the fifth toe forms a distinct and separate trunk, it generally communicates by large anastomosing branches, both on the metatarsus and on the first phalanx of the toe, with the second digital artery, and the tibial branch of the fifth toe. The second digital artery when it does not form a trunk with the preceding, goes to the tibial side of the fifth toe and to the peroneal side of the fourth. Next comes the third, which goes to the tibial side of the fourth toe and to the fibular side of the third. Sometimes this artery is double as far as the arch from Whence it arises to the anterior part of the metatarsus; but its two trunks there unite in one, which soon divides into two branches, the tibial branch of the fourth and the peroneal branch of the third toe. This arrangement occurs particularly when the usual number of digital arteries is diminished in any manner whatever, as, for instance, by the union in one trunk of the peroneal branch of the fifth toe and of the two following branches. Next comes usually a fourth, which divides in the same manner for the second and third toes. The fifth constantly forms the tibial branch of the second toe. Sometimes, when the anterior tibial artery is much smaller and the posterior on the contrary is larger than usual, it forms the common plantar artery of the large toe, from whence the tibial branch of the second also arises. The plantar artery of the large toe and the tibial branch of the second vary the most in their origin and arrangement. This artery is generally the continuation and termination of the trunk of the dorsal artery of the foot, which comes to the first phalanx of the large toe, goes to its plantar face, and gives origin to all the plantar and dorsal branches of this toe, sending off first the peroneal dorsal branch, then the peroneal plantar branch, next the tibial plantar branch, and finally the tibial dorsal branch, which anastomose as usual. More rarely the continuation of the trunk of the dorsal artery of the foot divides, soon after giving off the deep anastomosing branch to the sole of the foot, into two branches, a superior, which becomes the com- mon trunk of the dorsal artery -of the large toe and the tibial branch of the second; an inferior, or the common trunk of the two plantar arteries of this toe, which bifurcates near the centre of the plantar face of the large toe, to give rise to two plantar branches. But we must remark that here we find a similarity between the anomaly and the normal or more common arrangement first described, since the two ANGEIOLOGY. 343 branches communicate at the base of the first two toes by a large anastomosing branch. The superficial internal plantar artery given off by the posterior tibial artery always contributes to form the two plantar branches of the large toe and the inner branch of the second; since it constantly anastomoses near the anterior extremity of the first metatarsal bone with the trunk of these branches, and thus forms the superficial plantar arch (arcus plantaris superficialis). When the anterior tibial artery is smaller than usual, it sometimes but not always gives off only the dorsal artery of the large toe; some- times too it sends off in. part the tibial artery of the second. On the contrary, the trunk from which the plantar branches of the large toe and the plantar branch of the second arise, the internal plantar artery, is unusually large, and is always increased by a branch, which varies in size ; this arises from the deep plantar arch, and communicates with it toward the extremity of the first metatarsal bofie. Finally, sometimes but rarely all the arteries of the first and second toe arise only from the posterior tibial artery, particularly from the deep arch. The anterior tibial artery, which is very small, then terminates simply by a deep anastomosing branch in the deep plantar arch, and a large branch arises from the latter, which soon divides into two: one is deeper and larger, and is the continuation of the trunk; it goes from behind forward on the first metatarsal bone, and is also enlarged by one or two branches arising from the internal plantar artery, which is also in this case unusually large, and bifurcates to give rise to the common plantar artery of the large toe and also to the tibial artery of the second; the other is smaller and more superficial, ascends to the back of the foot between the first two metatarsal bones, gives off the dorsal branches of the large toe, and becomes, with a second digital artery given off by the deep branch, the common trunk of the tibial branch of the third toe and of the peroneal branch of the second. 6. Anterior perforating arteries. § 1531. The anterior perforating arteries (A. perforantes anteriores) arise on the anterior part of the deep plantar arch, sometimes between the digital arteries. They are small and go only to the interosseous muscles, to the transverse head of the adductor hallucis muscle, and the metatarsal bones. A part of its ramifications communicate anteriorly with the digital arteries and the dorsal artery of the foot. c. Posterior perforating arteries. § 1532. The posterior perforating arteries (A. perforantes poste- riores) arise from the posterior and upper surface of the deep plantar arch. They give branches to the posterior part of the interosseous muscles, and also recurrent branches to the anterior part of the tarsal 344 DESCRIPTIVE ANATOMY. ligaments and bones, and passing through the posterior extremities of the interosseous spaces, come on the back of the foot, where they anastomose with the upper interosseous arteries. These arteries are generally small, and can be considered only as the anastomoses between the dorsal and plantar arches. However, as these latter and the dorsal interosseous arteries are generally much larger than their corresponding parts in the hand, the posterior perfo- rating arteries are sometimes unusually developed; so that the trans- verse tarsal artery sends only small anastomosing branches to their posterior extremities, in the place where they appear on the back of the foot. But in this case they are not the only origin of the dorsal interosseous arteries, which arise also from the plantar arteries of the toes and are much larger than the common trunks of the digital arteries, and which give all the digital branches commonly arising from the anterior side of the deep arch. In this case the usual anterior branches of the plantar arch still exist, but they are merely branches for the deep muscles of the sole of the foot and the anterior perforating arteries; so that they are as shghtly developed as the dorsal interosseous arteries generally are. There are many degrees between this state of the dorsal interosseous arteries and the common one ; so that for instance many or all the dorsal interosseous arteries contribute equally to form the digital arteries, and thus the dorsal and plantar arteries have about the same size, although it does not necessarily follow that the dorsal interosseous arteries arise from the deep plantar arch, as in the anomaly described. On the contrary, they sometimes become unusually large, but are however only the branches of the dorsal arch. SECTION III. OF THE VEINS OF THE BODY. § 1533. The veins of the body generally unite in three large trunks, which open into the right auricle (§ 1305), the large coronary vein of the heart and the two vena cava. CHAPTER I. OF THE VEINS OF THE HEART. I. LARGE CORONARY VEIN. $ 1534. The large coronary vein of the heart (vena coronaria maxima cordis) opens into the right auricle, on the left and lower side of the interauricular septum, a little way from the venous orifice of the right ANGEIOLOGV 3.r (5) Human anatomy, vol. i. p. 177. (6) Dell' apoplcssia, Rome, 1709. (7) Lettre dunmedecin, 1710, p. 11. (8) Septemdecim tabul., p. 28-29, vol. ii. 19) Loc. cit., p. 598. (10) We instance Bartel's opinion, who considers respiration as a motion depend- ent on the brain. (11) De diss. part. carp, hum., b. iii. Paris, 1545, b. iii. c. xxxv. p. 341. OF THE NERVOUS SYSTEM. 417 one which was very large, five fingers long.(l) Portal seems to have observed it in the same place: but once he found it comprised all the spinal marrow, and that it appeared to be covered with a very thin membrane: and another time it extended only to the fourth cervical Vertebra. Gall, however, describes two canals existing all the length of the medulla, one on the right, the other on the left, which do not communicate with each other, or with the cerebral ventricles, but ter- minating in culs-de-sac, in the thalami optici, where they enlarge and produce a cavity the size of an almond, while the single and median cavity of the other writers is considered by them only as a prolonga- tion of the fourth ventricle. We have never found in man after birth, a median canal or two lateral canals. The circumstances under which they have been found by Gall and Portal, prove them to have been morbid. From Gall's ob- servations, it cannot be doubted that the canals he saw were produced by art, since he remarks that they could be demonstrated only by divid- ing the spinal marrow in such a manner that air might be introduced for six or eight lines. The smoothness and distinctness of the surfaces do not prove the real existence of the canals in question, for the first circumstance depends on the softness of the nervous substance, and the second on th ecentral prolongation of the pia-mater. We shall add one observation which we have always made, viz. that the ease with which these canals may be demonstrated, is in a direct ratio with the softness of the medulla oblongata; and it is much more easy by con- tinuing the inflation to make these communicate with the fourth ventri- cle, than to follow them into the thalami optici. We have succeeded, when the spinal marrow was soft, in pushing air into its whole length, without employing any cutting instrument, and without thinking that the existence of a normal cavity was proved by the space found in a soft and viscous mass, after having employed such a mode. We discover only at the top of the spinal marrow, a rounded and extremely narrow canal, from six to nine lines long, terminating below by a cul-de-sac, and continuous above with the floor of the fourth ven- tricle. III. WEIGHT OF THE SPINAL MARROW. § 1720. The absolute weight of the spinal marrrow, in the adult when deprived of its envelops, and entirely separated from its nerves, is more than an ounce. It is to the brain as 1 : 40.(2) (1) Adv. anat., vi. anim. 14. (2) Chaussier establishes a ratio more favorable to the spinal marrow, as he giyea the proportion as 1:19-25, but this is evidently wrong, doubtless because the origins of the nerves were not removed. Vol. II. 53 418 DESCRIPTIVE ANATOMY. IV. CONSISTENCE OF THE SPINAL MARROW. § 1721. It is generally thought that the spinal marrow is softer than the cerebrum. When, however, it is observed in the recent state, we remark, that although it is less consistent than some parts of the ence- phalon, particularly the annular protuberance, it is at least harder than the cerebrum and cerebellum.(l) CHAPTER II. ENCEPHALON. § 1722. The encephalon (encephalum), or that part of the central portion of the nervous system contained in the skull, has a rounded and oblong form. It is composed of two parts, which differ in size and ar- rangement ; an inferior which forms its base, and a superior which ex- tends upwards and on the sides. These two parts are however directly continuous with each other, and with the spinal marrow. The upper part very naturally divides into two portions, the cerebrum and the cerebellum, which differ in respect to situation size and structure. But it is more difficult to establish divisions in the lower part, since the different segments which form it, pass into each other by less evident shades. Hence, also, the difference which exists between authors in regard to the extent of the parts embraced by the same name. Thus the term medulla oblongata has been used to designate a greater or less segment of the lower part of the encephalon: but some give this name to all the parts which form the lower region of this viscus, while others apply it only to some of them, and are not agreed in respect to the number of the parts which are thus collectively desig- nated. Many have limited the meaning of the word still more, and employ it only to designate the lower part of the nervous substance, which ex- tends from the occipital foramen to the annular protuberance. Such is, for instance, the method of Haller, Scemmerring, Cuvier, Chaussier and Bichat. Some of these anatomists, however, particularly Scemmer- ring, Bichat, and Chaussier, have considered the medulla oblongata not as a particular portion of the central mass of the nervous system, but only as the upper extremity of the spinal marrow, as we have already remarked. The middle region of the encephalon is situated in front of this part, and is considered by some writers, as Chaussier and Bichat, as a special segment of this mass, called the cerebral protuberance (protuberantia cerebralis) by Bichat, and the mesocephalum by Chaussier. But these two authors do not give it the same limits, for Chaussier (1) Chaussier, p. 116.—Gordon, p. 182. OF THE NERVOUS SYSTEM. 419 states it to be composed only of the annular protuberance,, the tubercula quadrigemina, and of the valvula cerebralis, while Bichat includes in it also under the term prolongations, those medullary fasciculi which extend from the annular protuberance forward to the cerebrum, and backward to the cerebellum. Others, as Gordon, consider the annular protuberance as belonging to the cerebellum.(l) Vicq-d'Azyr had already said with more justice, that it must be described separately, and that it belongs neither to the cerebrum nor to the cerebellum. ARTICLE FIRST. MEDULLA OBLONGATA. § 1723. The best mode, in our opinion, is to include under the term medulla oblongata, not only what Haller and his successors have so termed, but also the annular protuberance; to insulate this part from the rest of the encephalon, and then to divide the remainder into two other portions, the cerebrum and the cerebellum. We also maintain this po- sition, as the portion we include under this term still belongs in common to the cerebrum and cerebellum, while that which is found in front of it, belongs only to the cerebrum, and that which is behind it makes a part of the cerebellum. We also ground ourselves on the fact, that what Haller and others term the medulla oblongata, differs so much from the rest of the spinal marrow in respect to structure, that we must consider it separately(§ 1713). The medulla oblongata, in our opinion, occupies all the length of the base of the skull, from the large occipital foramen, to the posterior edge of the sella-turcica. Its form is irregularly quadrilateral as it gradual- ly enlarges from behind forward. It is continuous below with the upper extremity of the spinal marrow, anteriorly with the cerebrum, laterally and superiorly with the cerebellum. We must therefore consider it the point of union, or the focus of these three segments of the central por- tion of the nervous system. The posterior and inferior part, the proper medulla oblongata of several writers, may perhaps be termed the rachidian bulb, as Chaus- sier^) and Bartels(3) call it; the anterior and upper will retain its usual name of annular protuberance. I. RACHIDIAN BULB. & 1724. The rachidian bulb (bulbus rachidicus, bulbus rachidicus superior, s.medulla oblongata, Haller, pars cephalica, s. extremum cepha- licum, s. spinalis medulla principium) is the most posterior and the most (1) Loc. cit., p. 112. (2) Loc. cit., p. 120. (3) Vom. Athmen, p. 108. 420 DESCRIPTIVE ANATOMY. inferior part of the encephalon, the direct continuation of the spinal marrow. It extends from the first cervical vertebra to the centre of the body of the basilar bone, and exactly fills the posterior part of the upper and concave face of this body. It has the form of an elongated triangle, and swells insensibly from behind forward, and from below upward. It generally does not exceed an inch in length, and its greatest breadth is about eight lines. I. EXTERNAL FORM. A. LOWER FACE. § 1725. The lower face of the rachidian bulb is slightly convex, and di- vided by a groove two or three lines deep, into two halves, a right and a left, which is continuous with the anterior groove of the medulla oblongata, from which, however, it is shghtly separated by the decus- sation of the anterior cords.(§ 1718) This inferior face presents two pairs of eminences, the pyramids and the olivary bodies. a. Of the pyramids. § 1726. The pyramids (eminentia, s. corpora pyramidalia, s. corpora pyramidalia antica, s. eminentia oblonga, Gordon, mediana interna) are visible with the intercrossing of the anterior cords of the spinal mar- row (§ 1718), and are situated entirely inward, so that their internal faces touch. They occupy the whole length of the medulla oblongata. They are from about two and a half to three lines broad. They gradu- ally become broader from below upward, and at the same time their upper projects more than their lower part. They terminate anteriorly by a contracted and rounded extremity, at the posterior edge of the an- nular protuberance, which projects downward and forward much be- yond it. At the same time, they separate slightly from each other, so as to leave in the median line, between them and the posterior edge of the protuberance, a small triangular hollow, into which the pia-mater penetrates. The anterior groove of the spinal marrow extends between the two pyramids, and becomes deeper at their upper part. Although these eminences terminate as such at the annular protuberance, they however pass uninterruptedly through it, and go forward. There is no decussation above the point we have already mentioned (§ 1718). The pyramids are also separated from each other by the anterior groove, in the rest of their length, always excepting the place directly below their upper extremity, where they are reunited by a small transverse medullary commissure, about a line and a half high. This reunion occurs at least frequently, just before they separate from each other, as if in this place their substance was pressed forward. OF THE NERVOUS SYSTEM. 421 Prochaska asserts(l) that there is no gray substance within them: we have succeeded no better than Vicq-d'Azyr(2) in finding it. In passing from below upward, they send off filaments which are entwined around the olivary bodies.(3) b. Olivary bodies. § 1727. The olivary bodies, the olivary eminences, the lateral emi- nences (oliva, s. eminentia olivares, Vieussens, s. laterales, Chaussier, s. ovales, Scemmerring, Gordon), are situated on the outside of the pyramids. They go a httle obliquely from below upward, and from behind forward, and form a rounded very elongated prominence, the largest diameter of which is from above downward. The prominence which disappears gradually above and below, passes from the lower face to the lateral face of the medulla oblongata, and is about seven lines long, two and a half broad, and one high. The olivary eminences do not extend so high as the pyramids : they cease about a line below the posterior edge of the annular protuberance. The roots of the hypoglossal nerve arise from the groove between them and the pyramids. These eminences are medullary externally, but the thin layer of white substance which covers them, is easily raised, and we then per- ceive a solid gray elongated nucleus, surrounded by an uneven and serrated edge, the centre of which is white, and the circumference of a deep gray. This nucleus is always loosely imbedded in medullary substance, and is called the corpus fimbriatum (corpus oliva fimbriatum, s. denticuiatum, s. rhomboideum). When cut longitudinally, tranverse- ly, or horizontally, we see very evidently that the gray border of the olivary bodies is interrupted inward, and consequently that the white substance which they inclose, is continuous on this side with the pyra- mids. This gray edge, on the contrary, unites below with the gray substance of the spinal marrow. From the place of decussation, and even by this decussation, the gray nucleus of the spinal marrow is di- vided anteriorly into two halves (§ 1718). The olivary bodies seem to be only a development of this arrangement. In fact, new medullary substance develops itself in the gray substance as the spinal marrow enlarges in this place, and is continuous internally with the pyramids. It perhaps would be more correct to say that the latter enlarges out- wardly, and that it penetrates into the gray substance in the same man- ner as the two halves of the spinal marrow separate from each other on the two sides, before it enters the skull, and are enveloped by the gray substance. (1) De struct, nerv., Vienna, 1779.—Opp. min. vol.i. p. 373. (2) Mem. de Paris, 1781, p. 587. (3) Santorini, Septemd. tab., p. 26—27. 422 DESCRIPTIVE ANATOMY B. LATERAL PACES. § 1728. Thetwo lateral faces of the medulla oblongata,are sloped and slightly convex outward. They are formed by a medullary projection situated outward and backward before the olivary bodies, which goes from below upward, and from within outward, and arrives at the cere- bellum. This projection is called the lateral pijramid, the restiform body, the crus of the cerebellum, the posterior eminence, the peduncle of the spinal marrow (eminentia pyramidalis lateralis, Tarin ; corpus, s. processus restiformis, Ridley; crus cerebelli ad medullam oblongatam, eminentia posterior, Chaussier; pedunculus medulla spinalis, Gordon). Those of the two sides unite at their inferior internal extremity. Each of them is a prolongation of the posterior cord of the spinal marrow at its side. Where they unite, they project shghtly inward. They separate from each other from below upward, from behind forward, and from within outward. A thin medullary layer about three lines long, and less than three broad, leaves the back part of the upper edge of the restiform body on each side; this goes inward. These two layers are separated by the pia-mater, which passes from the restiform body of one side, to that of the other, but they never unite in a state of perfect development. They may be termed the small bridges of the rhomboidal sinus(§ 1729), and may be considered as indicating the union of the two posterior cords. A second and larger, and particularly thicker medullary prolon- gation, arises from the anterior part of the restiform body, and is cover- ed by the root of the pneumo-gastric and hyoglossal nerves, and is at- tached to the choroid plexus of the fourth ventricle. C. UPPER PACE OR CALAMUS SCRIPTORIUS. § 1729. The lateral face is imperceptibly continuous with the upper face, by means of the restiform body. This upper face is very much grooved at its anterior and larger part, and these present a triangular de- pression, which terminates in a point, and is called the rhomboidal sinus, the sinus of the medulla oblongata, the ventricle ofArantius, the fossa of the fourth ventricle, the triangular fossa the calamus scriptorius, (sinus rhomboideus,sinus bulbi rachidici, ventriculus Arantii,foveola ventriculi quarti, Chaussier; fossa triangularis, Gordon). This depression ex- tends more or less into the upper extremity of the spinal marrow, where it gradually contracts to a considerable degree. On the superior face of the medulla oblongata, directly at the side of the median depression, we observe two medullary cords, which gradu- ally enlarge from behind forward, and are only the upper face of the anterior cords of the spinal marrow, which traverse the spinal marrow from below upward. Between them and the restiform bodies is a broader layer of gray substance. OF THE NERVOUS SYSTEM 423 a. Medullary strife of the upper face. § 1730. Near the anterior extremity of the upper face, we constantly observe white striae,(l) which go from within outward, usually project a little, and generally extend from the median depression to the outer part of the face, but which vary in respect to their existence, number, volume, progress, and direction. 1st. Existence. They are, in fact, very constant: but they are some- times deficient on one or even on both sides. We have never seen a case of the latter, but the former we have met with twice, and always on the left side. Prochaska(2) and Wenzel(3) have seen both. 2d. Volume. They vary in respect to the three dimensions. Some- times they are extremely narrow from above downward, almost ca- pillary, and at the same time single. In other cases they form con- siderable striae, which are more than two lines broad. Sometimes, also, they are very thin, and do not pass beyond the inferior face of the rhom- boidal sinus, and do not penetrate into it. They not unfrequently form a rounded projection above this same face, and penetrate more or less into the medulla oblongata, so as to arrive at its lower face. Finally their length varies much. Generally, but not always, some or all of them extend outward to the auditory nerve, and usually go inward to the median groove: but sometimes also they proceed beyond this groove, and blend with those of the opposite side. Not unfrequently they do not extend to it. We have generally remarked, that when they are large and numerous, they usually unite in part or entirely, on the me- dian line. 3d. Number. Their number varies sometimes; it is independently of their size, and most generally is inversely as the latter, from one only to fourteen. 4th. Arrangement. The stria of one side generally interlace differ- ently together.(4) They are however sometimes entirely distinct. 5th. Direction. Their direction, most generally, is more or less trans- verse, although a little oblique from behind forward. Sometimes they proceed almost directly forward. All, or at least some of these striae, most generally extend to the auditory nerve, as we have already stated, and very evidently form the most internal part of its origin. Very commonly also, the anterior which compose the smallest part of the mass, go obliquely farther forward and outward towards the trifacial nerve, although we cannot clearly demonstrate any con- nection between them and this nerve. The posterior are sometimes attached to the filaments of the root of the pneumogastric nerve. They frequently vary in a most striking manner, in every respect, on both sides of the body in the same subject. (1) Prochaska De struct, nerv., Vienna, 1779.—Wenzel, De penit. struct, cerebri, ch. xxiii. (2) Loc. cit., p- 388. (3) Loc. cit. p. 171. (4) Wenzel, loc. eit., p. 173—We have seen this several times. 424 DESCRIPTIVE ANATOMY. These striae are very probably not only the roots" of the auditory nerve, but are connected, although less evidently, both with the tri- facial and with the pneumogastric nerve, of which we shall speak more fully, when endeavoring to estabhsh a fewer number of cerebral nerves than generally admitted. b. Gray bands of the upper face § 1781. Before the white striae, we see on the upper face of the medulla oblongata, other larger and shghtly elevated striae,(l) which arise at some distance outside of the median line, so that their internal extremities are never blended. These striae extend from within out- ward, gradually swell, are convex forward, and pass over the anterior part of the posterior pyramids. They always unite with the auditory nerve„at their external extremity, and are very constant: for of ninety- seven cases they were deficient in only two.(2) They are called the gray bands (fasciola cinerea). They are also generally much marked, and are similar on both sides: but sometimes, although very rarely, those of the two sides are dissimilar, or they are scarcely perceptible on either: this peculiarity depends neither on the age nor on the sex. They arise generally by one, and rarely by two roots, and are always single on each side. Their intimate connection with the auditory nerve, is proved by the fact that it disappears in deaf people. II. TEXTURE. § 1732. The cords of the spinal marrow enlarge in the medulla ob- longata, and divide there into fasciculi, more evidently than in the spinal marrow. At the same time, thejposlerior separate from below upward, and distinct bodies, the olivary bodies, are developed in the substance of the anterior, which are unconnected with the organization of the spinal marrow. The anterior cords of the spinal marrow, divide evidently into at least two halves, an anterior which is smaller, and a posterior which is larger. Of these two halves, the anterior cross and form the pyramids (§ 1726), the posterior ascend behind the olivary bodies, enlarge and form the floor of the calamus scriptorius, and of the fourth ventricle. We also find another smaller fasciculus, which Gall asserts, is not con- stant, which Rosenthal has described more exactly,(3) and which our dissections have shown to be constant. This middle fasciculus, which touches the olivary bodies, surrounds them and passes through the an- nular protuberance to go forward into the tubercula quadrigenina. (1) The merit of having made profound researches on these striae belongs to Wenzel, but he neither discovered their existence nor constancy, nor their connection with the auditory nerve, since all these facts are already mentioned positively by Prochaska. (loc. cit. p. 387-391.) (2) Wenzel, loc. cit. p. 184. (3) Beytrege, p. 24—27. OF THE NERVOUS SYSTEM. 425 The division of the posterior cords of the spinal marrow into two fascicuh (§ 1717) is still more evident in the restiform bodies, on account of their enlargement. The internal, which are smaller, swell at the lower extremity of the calamus scriptorius, but disappear in a point before the restiform bodies have terminated their course towards the cerebellum. II. ANNULAR PROTUBERANCE. I. EXTERNAL FORM. § 1733. The annular protuberance, called also the bridge of Varolius (nodus cerebri, pons Varolii, eminentia, s. protuberantia annularis, pro- tuberantia encephalica, commissura cerebri), is a considerable and some- what regularly quadrilateral eminence, extending however rather more from right to left than from before backward; it is observed on the lower face of the cerebrum, projects more than three lines above the lower face of the medulla oblongata and the cerebral peduncles, gradu- ally becomes thicker on each side near its centre, and is separated from the medulla oblongata and the cerebral peduncles, by very distinct hmits. Its greatest length is one inch, its greatest breadth is one inch and some lines, and its greatest height, at its anterior extremity, is nearly one inch. Its anterior and posterior edges are convex on the sides, and concave in the centre, the anterior more so than the posterior. A superficial, but very evident groove, extends all along its inferior face from before backward; this is continuous with the serrated portion of the anterior and of the posterior edge. On the sides, the annular protuberance imperfectly divides internally into two halves, one of which is turned toward the tubercula quadrigemina, the other up towards the cerebellum, and both turn around the posterior crura of the cerebellum. II. TEXTURE. § 1734. The annular protuberance is formed externally of white fibres, transverse and convex forward, of which the central and the an- terior particularly incline very much backward, towards the cerebellum. It is very firm, and the firmest part of the centre of the nervous system. On examining it internally, which must be doneby horizontal, transverse, longitudinal, and even by perpendicular incisions, a little oblique from within outward, and from behind forward, we remark that its texture is very complex. Immediately below the external medullary layer, we discover a gray- ish substance. This substance is not pure: it alternates the whole length of the protuberance with transverse and very numerous bands of medullary substance, which are thin and convex inward, and are at- tached to the external. Vol. II. 54 426 DESCRIPTIVE ANATOMY. About two lines above the lower face of the protuberance, we observe on each side, almost in the centre of each lateral half, insulated longi- tudinal medullary fibres, which are directed from within outward, and from behind forward, and alternate with the transverse fibres. They are convex below, and concave above. They form a fasciculus, about four lines high, which contains in its centre only white substance, through which the cortical substance passes upward and downward. This fasciculus is the direct continuation of the pyramids. It con- tinues uninterruptedly forward with the lower face of the cerebral pe- duncles. Next comes always from below upward, a very thick layer of gray substance, interrupted by perpendicular layers of medullary substance, situated some behind the others; then, on this layer is another which is thinner, of longitudinal medullary striae, convex above, concave below, which arise behind the upper fasciculus of the anterior medullary cords of the medulla oblongata, pass above the central gray layer, blend for- ward with the lower and thickest layer of medullary substance, and thus arrive upon the upper face of the cerebral peduncles. Consequently the upper and lower fasciculi which result from the division of the anterior cords of the medulla oblongata, again unite at their anterior part, in the annular protuberance. The number of the longitudinal striae, especially the inferior, dimin- ishes much from without inward. They are separated from each other, upward and downward, by gray substance, and disappear entirely at about the centre of the annular protuberance. The central part is formed of gray and of white substance; it is much higher in this place, and only some longitudinal medullary striae pass above it. Thus the anterior medullary cords not only increase in size and di- vide in their course across the annular protuberance, but they are still directed from within outward. III. WEIGHT OF THE MEDULLA OBLONGATA. § 1735. The entire medulla oblongata generally weighs a little more than half an ounce. Its weight then is to that of the spinal marrow, as 1 : 2 ; to that of the cerebellum as 1:10 ; to that of the cerebrum as 1:74: finally to that of the whole central mass as 1:86. The rachidian bulb weighs three drachms; the annular protu- berance one. OF THE NERVOUS SYSTEM. 427 ARTICLE SECOND. CEREBELLUM. I. EXTERNAL FORM. § 1736. The cerebellum (cerebellum, s. parencephalis)(l) is situated below the posterior part of the posterior lobe of the cerebrum, from which it is separated by the tentorium, and occupies the inferior fossa? of the squamous portion of the occipital bone. We may divide it into the body and crura, and the body comprises the lateral parts, and a centre. § 1737. The body of the cerebellum has a rounded and oblong form. Its greatest breadth, which is from side to side, is about four inches. It is about two and a half inches from before backward in its broadest portion : it is two and a half inches from above down- ward in its centre, and only half an inch at its edges; in approaching which, it gradually becomes thinner, so that it seems a little flattened in the latter direction. Considered generally, it is circumscribed by two slightly convex faces, an upper and a lower, and by four obtuse edges, distinguished into anterior, lateral, and posterior. The upper face is sloped like a roof, that is, it projects most at its central part, whence it de- scends almost flat to the edges, backward, outward, and forward, al- though a little less in the latter direction. The inferior face, on the con- trary, is concave from before backward, at its centre, so that the an- terior and the posterior parts of this groove form the greatest hollow. The two faces are separated by a groove an inch deep in most of its extent, which corresponds to the posterior edge, and thence goes in- ward. This is called the large or the horizontal groove of the cerebel- lum (sulcus cerebralis magnus, Vicq-d'Azyr; sulcus magnus horizon- tails, Reil). This groove divides the cerebellum into an upper and a lower half, besides the two lateral halves into which it is divided by the median longitudinal groove. The anterior edge is the shortest, and is rendered very concave by a broad depression. The two lateral edges are straight, longer than the anterior, and oblique from before backward, and from within outward. They are continuous with the posterior, where the cerebellum is broader between their posterior extremities. The posterior edge is the longest, and is composed of two very convex lateral halves, which are separated by a median groove, about four lines deep and three broad. This groove is continuous with the median depression of the lower face. Thus the cerebellum is narrower in the centre than in the rest of its extent, and is divided by the anterior and posterior depressions of the edges, and by that of the lower face into two halves, called very im- (1.) Rolando, Osservazioni sul cerveletto, in the Memoria delta rcale academia delta scienza di Torino, vol. xxix. p. 163. 428 DESCRIPTIVE ANATOMY. properly, the hemispheres (hemisphara cerebelli). Each of these hemispheres has an irregularly quadrilateral form. The outer face of the cerebellum is not smooth. We observe in it numerous slight elevations, formed by the upper face of the layers (lamina). These elevations are convex externally, concave internally, and go unevenly from before backward, being separated by grooves, into which the pia-mater descends. These layers are not single, but they frequently subdivide and interlace, and are adapted to each other very exactly, even externally. The depth of the grooves, and consequently the height of the layers, are not every where the same. In the place where the grooves are very deep and very long, and where also the adjacent layers are entirely separated from each other, the cerebellum is perfect- ly divided into several segments, which are called lobes (lobi). The best mode of describing the form of the cerebellum, is to examine separately its lateral parts and its centre. I. LATERAL PARTS. § 1738. The two faces of the cerebellum, the upper and the lower, are divided very constantly by deep grooves into several lobes, which are superior and inferior. I. UPPER LOBES. § 1739. The two lobes of the upper half of the cerebellum, are the upper anterior and the upper posterior. 1st. The upper anterior or square lobe (lobus anterior, superior, s. quadrangularis) is irregularly quadrilateral, and narrower forward and outward than backward and inward. It is continuous with that of the opposite side by a central part which is not contracted, and is the highest point of the cerebellum. The two united lobes have a semi- circular form. Their posterior edge is convex and sharp, and is turned backward with the posterior face, while the anterior, which is concave, and which forms at the same time the anterior edge of the cerebellum considered as a whole looks forward. The blunt extremity which forms the anterior half of the lateral edge of the cerebellum, looks for- ward and outward. This lobe is separated from the upper posterior by a very deep groove, the superior groove of the cerebellum (sulcus superior cerebelli, Vicq-d'Azyr). 2d. The upper posterior or semilunar lobe, lobe semi-lunaire (lobus superior posterior, s. semi-lunaris), comes immediately next the prece- ding. It forms the posterior and external part of the upper half of each hemisphere. It is semilunar, thicker and broader forward than backward ; separated backward from the lower posterior by the large lateral groove, and forward from the upper anterior by the upper groove: it is attached inward to the synonymous lobe of the other OF THE NERVOUS SYSTEM. 429 hemisphere by a thinner and more sloping part, formed of white sub- stance, called the commissure of the upper posterior lobes. The con- siderable groove between the two upper posterior lobes, forms the com- mencement of the lower posterior median groove. II. INFERIOR LOBES. § 1740. There are four inferior lobes. 1st. The posterior or inferior semilunar lobe (posterior inferior, s. semi-lunaris), forms the posterior superior and external part of the lower half of each hemisphere. It is separated from the superior and anterior by the large groove, (§ 1737) and from the next by the infe- rior external groove (sulcus inferior externus), which is very deep. It is divided by two considerable but more superficial grooves, into three concentric portions which follow one another from behind forward, and diminish in size in the same direction. The two lateral halves are connected by a narrow and slanting com- missure, with which the middle of these three lobes is directly con- tinuous, while the anterior and the posterior only touch on its sides. The most internal segment has been considered a special lobe, and termed the small or thin lobe ;(1) but this distinction seems to us incon- venient, because we might just as well consider the middle and anterior segments as so many distinct lobes. 2d. The inferior anterior lobe, the cuneiform or internal inferior or digastric lobe (anterior inferior, s. cuneiformis, s. biventer), is much smaller. It is composed of layers, which proceed almost directly from before backward. It is broader and thicker forward and outward than it is inward, where it at first contracts very much, and then terminates together with the third segment of the preceding lobe, in a very bulging central part. 3d. The third inferior lobe, the lobe of the medulla oblongata, the spinal lobe, the monticule (lobus inferior internus, tonsilla, Malacarne; s. lobulus medulla oblongata, s. monticulus, Vicq-d'Azyr; lobus spinalis, Gordon), is smaller than the preceding, and is composed of layers which proceed directly from before backward, and is convex both out- ward and inward. Its anterior extremity rests in the restiform body of the spinal marrow.(§ 1728) Posteriorly it gives origin to the uvula, which is inserted between the two amygdala?. 4th. The fourth inferior lobe, the lobe of the pneumogastric nerve (flocculus, s. lobus nervi pneumogastrici, Vicq-d'Azyr, lobus subpedun- cularis, Gordon), arises a little above and before the preceding, from the posterior edge of the peduncle which goes from the cerebellum to the tubercula quadrigemina, directly where this peduncle unites with that which extends from the cerebellum to the medulla oblongata. It arises in this place from a thin pedicle, descends between the auditory (1) Malccarne, and Reil, loc. cit., p. 13. 430 DESCRIPTIVE ANATOMY. and pneumogastric nerves, and goes forward downward and outward. Almost all of its medullary nucleus is exposed forward and backward, fimbriated in its whole extent outward, and only in its lower part inward, and is covered both outward and inward with gray layers. The direction of this segment of the cerebellum, is precisely the op- posite of that of the others ; it is also the loosest. The two lobes become, upward and inward, a broad semicircular medullary layer, which rises above on the nodule, and is loose poste- riorly, called the posterior medulary vail (velum medullare posterius). This layer swells on its internal edge, into a thick mass of medullary substance, folded crosswise, and covered with cortical substance, which assists to form the posterior part of the fourth ventricle. II. CENTRAL PORTION. § 1741. Although, strictly speaking, the central part of the cere- bellum is no where separated from the two lateral parts, by a want of continuity in the substance; it however differs a little from them in form. The distinctive character of the formation of this central part is, that it is formed by transverse layers and plates, and that except in its middle posterior region, it presents a rounded form bulging from behind forward. On its anterior face is the most superior part of the cerebrum. The anterior part of its lower face is also very much elevated, but the pos- terior is lower. Its lateral faces and its anterior part are situated in a large depression, the direction of which is from before backward, which separates the two hemispheres. The middle region is usually termed the vermiform eminence (vermis cerebelli), and it is divided into an upper and a lower part. I. UPPER PART OF THE MIDDLE REGION. § 1742. The upper part of the middle region extends from the middle of the posterior edge of the upper face, above the anterior edge to the tubercula quadrigemina. It is composed of the upper or anterior vermiform process and the cerebral valve. The upper vermiform process may also be divided into three portions: 1st. The commissure of the two upper posterior lobes. 2d. The larger upper part, or the monticule (monliculus cerebelli). 3d. The lower part which is much smaller, or the anterior vermi- form process. The commissure of the upper posterior lobes, is thin, narrow, and lower than the lobes it unites. The monticule, which is the highest part of the cerebellum curves from behind forward, and from below upward, as high as the posterior edge of the tubercula quadrigemina. It is formed of five segments OF THE NERVOUS SYSTEM. 431 placed one after another from behind forwards, they become thicker from before backward, but the third is separated from the others by the deepest transverse grooves. These segments extend from the monticule into all the thickness of the hemispheres; but they gradually contract in approaching the anterior edge, so that the monticule, espe- cially on account of the rounded prominence in its centre, is almost three times as long, as are the lateral edges of the upper face of the cerebellum. The lower smaller part, or the proper anterior vermiform process, has a direction the inverse of that of the monticule, that is, it proceeds from above downward, and from before backward. It is reflected near its posterior extremity at an acute angle, and is continuous with the cerebral valve, on which it rests directly its entire length. II. CEREBRAL VALVE. § 1743. The cerebral valve, the large valve of the brain (valvula cerebri, valvula magna, velum medullare, velum medullare anticum, pars anterior veli medullaris), arises from the posterior extremity of the an- terior vermiform process, and is attached on the sides to the inner face of the prolongations sent by the cerebellum to the tubercula quadri- gemina, and terminates by its anterior extremity in the depression be- tween the posterior pair of the tubercula quadrigemina. It contracts from behind forward, becomes thin, and terminates in a convex edge. Its lower face is smooth. The upper presents posteriorly in nearly all its extent, transverse grooves, which generally extend only to the lateral edges; it is frequently, but not always, divided by a slight longi- tudinal groove into two equal lateral parts. Its anterior part is much less extensive than the other, and smooth; it is formed in its greater and posterior part, of gray substance. It is also formed anteriorly, at least on its lower face by this substance ; we however usually find at its anterior extremity, or directly behind it, on the median line, a white band from one to two fines broad, convex posteriorly and narrower on the sides: it is terminated forward by a small point, which is attached to the groove between the two posterior tubercula quadrigemina. This band generally gives rise to some filaments of the fourth cerebral nerve, but goes mostly only in the upper edge of the anterior peduncle of the cerebellum, and disappears on its outer face. III. LOWER PART OF THE MIDDLE REGION. § 1744. The lower part of the middle region of the cerebellum, com- monly called the inferior vermiform process, is a little lower posteriorly than the posterior part of the two lower posterior lobes which it unites, although it is not so low as the commissure of the upper posterior lobes situated above it. It is formed of two halves, separated by a superficial transverse groove, and situated one above the other. It presents a 432 DESCRIPTIVE ANATOMY. slight prominence in its centre, and is separated by a slightly per- ceptible contraction from the hemispheres which it unites. The central part or the pyramid (pyramis, Malacarne) is next to this prominence, and is separated from it by a very deep fissure. This central part projects in every direction much more than the posterior, and is attached, by much narrower and lower lateral parts, to the posterior half of the inferior external lobe, and to the inferior inter- nal lobe. Next to the pyramid, from which it is separated by a deep groove, comes a narrow part which is easily divided into several lobes situated one over another, and which generally is not perfectly symmetrical, being turned first to the right, and then to the left. This part also projects still more, in proportion to its breadth, and is continuous with the amygdala? by a narrow and deeply situated medullary band. Finally, we next observe the anterior and smallest part, called the nodule (nodulus, Malacarne), which is continuous on each side, with the posterior valve. Thus, the central portion of the cerebellum, considered as a whole, is so curved, first from before backward, then from below upward, next from above downward and from behind forward, that the two extremities of the vermiform process, which proceed toward each other, almost touch, and are separated only by the narrow face of the summit of the fourth ventricle. II. TEXTURE. § 1745. The gray substance surrounds all parts of the cerebellum, ex- cept its lower face which corresponds to the fourth ventricle ; this is covered with medullary substance. The latter is continuous in the three prolongations of the cerebellum, anteriorly with the tubercula quadrigemina, posteriorly with the medulla oblongata, below, and on the sides, with the annular protuberance, and extends within this organ in ramifications, the collection of which is termed the arbor vita; of this we may be convinced by vertical incisions. The medullary trunks follow a more or less curved direction, to near the circumference of the cerebellum, and give off, in this course, a greater or less number of branches, which arise from their convex edge. A thin layer of yellow substance, covered by a thick layer of gray substance, exists on the surface of each medullary branch. This arrangement causes the lamellar structure of the ceiebellum, since each layer incloses a layer of medullary substance, and each of the lamina? into which the principal layers divide always corresponds to a medul- lary branch. The middle and lower part of the cerebellum presents this arrange- ment most distinctly. We find, in this place, seven medullary layers, OF THE NERVOUS SYSTEM. 433 three anterior, three superior, and one posterior; the upper of which are the longest, and ramify most simply. All these layers become much larger from within outward, so that, with their covering of gray substance, they represent cones, the sum- mits of which are turned inward, and the bases unite with the parietes of the fourth ventricle, and are separated from each other forward by deep grooves. The medullary substance is proportionally much less in the central part, upon which circumstance alone depends its smallness ; but ex- ternally it accumulates in a direct ratio with the enlargement of the hemispheres of trie cerebellum. § 1746. A vertical section demonstrates that the medullary nucleus is thickest below, in the centre of the cerebellum, before the summit of the fourth ventricle, opposite the second and third segments, conse- quently in its anterior half. From this point to the circumference it grows thinner as it ramifies ; but we constantly observe that the medullarylayers of several lobes are much broader, toward the surface of the organ, than they are when they arise from the central nu- cleus. This arrangement is not observed in the fourth lobe, the uvula, the pyramid, the cerebral valve, and the anterior vermiform process ; but it is very perceptible in the other two segments. In the anterior lobes of the third segment the medullary layer, soon after leaving the nucleus, swells out considerably in passing through the lobes. The layer of the upper and the posterior lobes arises from a nucleus, almost as large as the central medullary nucleus, situated before the summit of the fourth ventricle. In the fourth segment we find a similar, but smaller, nucleus, more than six lines long, which is attached to the central nucleus by a thin filament. § 1747. In following this method, which is undoubtedly the strictest, we arrive at a new division of the medullary layers of the centre, and of the hemispheres of the cerebellum, very similar to the division men- tioned above, but different from it in some respects. The first of these seven layers belongs to the posterior part of the anterior valve. It is the smallest, and the folds of the posterior part of the valve rest upon it. The second is formed by the anterior vermiform process, and the anterior part of the upper anterior lobe. The third is much larger, and belongs to the anterior part of the monticule, and to the larger middle part of the upper anterior lobe. The fourth, the most posterior, corresponds to the most posterior part of the monticule, to the commissure of the upper posterior lobes, to that of the lower posterior lobes, to the most posterior part of the upper anterior lobe, to the upper posterior lobe, and to the upper part of the lower posterior lobe. The fifth is composed of the pyramid, of the lower smaller part of the lower posterior lobe, and of the digastric lobe. Vol. II. 55 434 DE8CRIPTIVE ANATOMY. The sixth corresponds to the uvula and to the amygdala?. Finally, The seventh, forms the nodules and fourth lobe ; it is the smallest of all, except the first. The last two are distinguished from the rest, as they are not cleft and covered with a gray substance, except in one part of their circum- ference, forward and backward. The first presents this arrangement in every part, and the latter at its upper posterior part. The others are divided several times on each side ; they however present tracesjof the arrangement above mentioned, because the lower anterior half of the segments, which are turned the most forward, and the lower poste- rior half, which are turned backward, present the most simple and shortest grooves and ramifications, the former downwardand backward, the latter downward and forward. CORPUS FIMBRIATUM. § 1748. In the centre of the medullary substance in each hemis- phere of the cerebellum, little more internally than externally, we find a rounded, oblong, very vascular body, medullary internally, surrounded with a serrated edge, and intimately united to the medullary substance, called the rhomboid or fimbriated body (corpus rhomboideum,, s. fim- briatum, s. dentatum). Its gray edge mostly surrounds it, except its lower anterior part, where the medullary substance within it is con- tinuous with that of the walls of the fourth ventricle, so that the hemis- pheres of the cerebellum are consequently composed of a double layer of medullary substance, and of gray substance ; the internal, formed by the corpus fimbriatum, and the external, comprising most of the external medullary substance and the external gray substance. We here then find the repetition of what is observed in the medulla oblongata, in the olivary bodies, and the pyramids ;(§ 1726-1727) only this form exists here in a greater degree, since the rhomboid body of the cerebellum is not only surrounded with a thin and smooth layer of white substance, as is seen in the medulla oblongata, but this layer is much thicker there, and not only forms several successive rami- fications, but is covered a second time with grey substance. § 1749. The medullary substance of the cerebellum is extended in three fasciculi, which, however, are not distinctly separated •, they are called the prolongations of the cerebellum (crura cerebelli). One is in- ferior and descending, another middle and anterior, the last is superior and ascending. The inferior descending prolongation (crus cerebelli descendens, s. ad medullam oblongatam) blends with the posterior cord of the spinal marrow or the restiform body. The superior ascending (crus cerebelli adscendens, s. ad eminentiam quadragesimam) goes to the posterior tubercula quadrigemina. The middle lateral or anterior (crus cerebelli ad portam) goes forward and downward, and blends with the annular protuberance. Of these three prolongations, the third is the largest. The first two are situated farther inward, and surrounded by it, so that OF THE NEnVOUS SYSTEM, 435 the rhomboid body exists between it and them. They blend forward and backward, and seem developed principally to form the middle region of the cerebellum, while the hemispheres of this organ rest on the lateral prolongations, so that the medullary layers which form them, are directed forward in the upper lobes, and backward in the inferior. When we separate longitudinally a cerebellum hardened by immer- sion in alcohol, it is divided into an upper and lower half; we also see on one side a very broad but thin transverse medullary layer, which contracts and at the same time becomes thicker from before, backward and outward, and which is expanded to form the lateral prolongations: we have on the other side, particularly towards the centre, fasciculi which intercross from before backward, so that the ascending and de- scending prolongations, at least to some extent, are not directly blended with each other, but reciprocally interlace. § 1750. The cerebellum forms most of a ring, which is constituted below by the lower part of the annular protuberance, embraces the cerebral peduncles, and unites by its anterior and posterior prolonga- tions, with the medulla oblongata, and with the cerebrum. III. WEIGHT. § 1751. The cerebellum, if separated at the place where its prolon- gations enter the annular protuberance, the cerebrum and the medulla oblongata, generally weighs five ounces. Its weight consequently, is to that of the rest of the encephalon, as 1:8, or as 1:7, rarely as 1: 10, or even as 1:11.(1) In the latter case, we must attribute its excess of weight to the suspended development of the encephalon. IV. CONSISTENCE. § 1752. The cerebellum has about the same consistence of the cerebrum, and like this, it is softer than the medulla oblongata, and harder than the spinal marrow. ARTICLE THIRD. CEREBRUM. I. EXTERNAL FORM. § 1753. The cerebrum forms most of the cephalic portion of the centre of the nervous system, and occupies its upper and anterior region. Considered as a whole, its form is a rounded oblong, and it is for the most part convex. Its length exceeds its breadth, and particularly its height. Its greatest length is six inches, its greatest breadth is five, and its height is four. It is broadest and highest in its centre. It is formed of two lateral and perfectly similar halves, called hemis- (1) Chaussier, loc. cit., p. 77. 436 DESCRIPTIVE ANATOMY. phercs or lobes (hemisphere:, iobi, Chaussier). These two halves are separated at their upper part by a longitudinal fissure (fissura longitu- dinatis), much broader backward than forward ; in the former direction its breadth is half an inch, but hardly a line in the latter. They are on the contrary, almost blended with each other at their middle and lower portion. Each hemisphere is divided into two lobes (lobi, lobuli, Chaussier), an anterior and a posterior. The anterior is more than twice as large as the posterior. They are separated by a groove more than an inch deep, the direction of which is oblique from above downward, and from behind forward ; this is called the groove of Sylvius (fossa Sylvii), Reil terms it the valley. This separation exists only below and on the side, for the groove does not extend to the upper face. The posterior lobe is also frequently divided into two others, termed the middle and posterior lobe. The latter forms that part of the cere- brum which rests on the tentorium. It cannot be distinguished exter- nally from the middle lobe, but is separated from it on its internal face by a fissure, the direction of which is obliquely from above downward, and from behind forward, and on the lower face by a slight depression. In each hemisphere we distinguish an inferior, an external, a superior and an internal face. I. INFERIOR FACE. § 1754. The inferior face should be examined first, for we there re- cognize most distinctly, that the cerebrum is directly continuous with the medulla oblongata. Of the three faces, this is the most irregular, and its central portion is entirely separated from the two lateral parts. I. MIDDLE REGION. I. CEREBRAL PEDUNCLES. § 1755. Wo first observe from behind forward, directly before the anterior edge of the annular protuberance, (§ 1733) the c< rubral pedun- cles, or the crura of the medulla oblongata (crura cerebri magna, crura ad medullam oblongatam). They are two large rounded bodies, about eight lines long, which become much larger from before backward, seven lines broad posteriorly, ten anteriorly, ten lines high, grooved lon- gitudinally, and entirely formed of substance, white externally. They diverge from each other behind forward, and are separated at their lower part by a very broad and deep groove; this is only the anterior groove of the spinal marrow, which is deepened by the development of the peduncles. This part forms above the floor of the aqueduct of Sylvius ; its lower face is gray, and numerous vessels pass through it, the direction of which is from below upward, and from without inward. Vicq-d'Azyr(l) terms it the middle perforated substance (substantia perforata media). (1) Loc. cit., p. 545. OF THE NERVOUS SYSTEM. 437 Near the posterior extremity of these bodies there is generally a transverse and shghtly projecting band which passes over all their lower face, and crosses the longitudinal groove. A second posterior transverse band is detached from where the anterior and middle pro- longations of the cerebellum unite, and is directed from behind forward, and from above downward between the two peduncles, proceeding on their lov/er face. This band is situated directly before the annular protuberance, and is often united with it, representing to a certain ex- tent a distinct edge. The cerebral peduncles are covered posteriorly by the anterior part of the annular protuberance, forward by the root of the optic nerve, which turns on them from above downward, from without inward, and from behind forward. § 1756. The cerebral peduncles are formed externally by a layer of white substance about two lines thick. Next comes a rounded and elongated layer of blackish substance, which has a semicircular form, as has the whole cerebral peduncle, being concave above and convex below. Next comes a third layer, the thickest; this extends upward to the surface, and is formed of a mixture of gray and of white sub- stance. § 1757. Between the anterior extremities of the two cerebral pedun- cles, is a broad triangular surface, which enlarges very much from behind forward, and is continuous posteriorly with the middle portion, anteriorly with the anterior part of the perforated substance of the lower face. The direction of this surface is from behind forward, and from above downward at its posterior part, from below upward, and from behind forward at its anterior part, which is more perpendicular than the other; it forms the floor of the third ventricle. We remark from behind forward the mammillary eminences, the infundibulum with the pituitary gland, the anterior part of the root, and the decussation of the optic nerve ; the rest of it 'is formed of gray substance. II. MAMMILLARY EMINENCES. § 1758. The mammillary eminences or pisiform tubercles, (eminentia medullar es, s. candicantes, s. mammillares, Chaussier) are situated side by side between the anterior extremities of the cerebral peduncles; they are two hemispherical prominences, formed externally of medul- lary substance, and internally of cortical substance, about half a line distant from each other in their v/hole height, but separated a little farther posteriorly. They are the inferior and anterior extremities of the fornix. When attentively examined, we observe that these triangular emi- nences are each composed of a larger inner, and a much smaller outer half. The anterior and inner faces are straight, the posterior is convex; the latter is the longest, the inner is much the shortest. The two halves of each eminence are very distinctly separated; the internal projects very much ; the outer terminates in a point on the outside of the gray substance, between the mammillary eminence and the optic nerve. 438 DESCRIPTIVE ANATOMY III. INFUND1BULUM AND PITUITARY GLAND. § 1759. We find a rounded and conical prolongation between the mammillary eminences, called the infundibulum ;(1) this descends ob- liquely forward, and terminates in the pituitary gland or body (hypo- physis cerebri, s. glandula pituitaria, Chaussier).(2) This is situated in the sella-turcica of the sphenoid bone below the dura-mater, which covers its upper face, and is closely surrounded on all sides. The lower extremity of the infundibulum, is connected with it by a narrow opening in the dura-mater. The lower and the upper parts of the infundibulum are thicker than its centre. In its first two parts it is about a hne thick. It is formed of gray substance. The pituitary gland has an oblong rounded form. It is about six lines broad, three long, and less than three high; it generally weighs, including the infundibulum, eight grains. It is always formed of an anterior and a posterior lobe, which are intimately united. The anterior is very large, and generally twice the size of the other. The anterior is bean-shaped; the posterior is more rounded, and is situated in the posterior and serrated edge of the anterior lobe. The pituitary body is generally very hard, but its posterior lobe is softer than the anterior. The anterior lobe is formed of two substances, an external reddish, and an internal which is white, which vary much in their degree of color and their proportional quantity. We rarely find one which is homo- geneous. We observe on the right and left side, on the limit between the two substances, a depression in which those small ducts which arise from the external substance terminate. The posterior part of this depression forms a small canal, which, converging with that of the op- posite side, goes towards the centre of the posterior edge of the lobes and the place where the infundibulum is continuous with the pituitary body ; the two canals unite in this place. The posterior lobe has uniformly a more or less grayish tint. Both lobes are directly attached to the infundibulum, which always descends on the upper face of the pituitary gland to the place where they unite, and are surrounded with it by a prolongation of the pia- mater. The infundibulum is formed of gray substance, a continuation of that of the floor of the third ventricle, and it is considerably narrower in its centre than above and below, where it is several lines thick. Il) A. Murray, Observations anatomice circa infundibulum cerebri, ossium capitis infetu structuram alienam partemque nervi intercostalis cervicalem, Upsal, (2) Wenzel, Observations sur le cervelet et sur les diverses parties du cerveau dans les epileptiques, 1811.—Rayer, Observations sur les maladies de I'appendiee sus- sphenoidaldu cerveau; in the Archiv. gen. de medecine, t. iii. p 320 —Sec also the extract fromGuersent's case same journal, v. iii. p. 312.-Ward, Case of amaurosis produced by enlargement oj the pituitary gland; in the Lond. med. repository 1823 t. xx. p. 217. r *' ' OF THE NERVOUS SYSTEM. 439 Opinions vary in regard to the nature of the infundibulum; some think it entirely hollow ; others on the contrary that it is solid ; and some assert that it is sometimes solid and sometimes hollow. Although a canal is not always visible within it, as some writers have asserted, particularly the old anatomists, and Murray among the moderns; it is sometimes hollow in all its extent, and we can always introduce into it air or liquids, pushing them from the pituitary gland into the third ventricle; but this is more difficult, and even fails when attempted in the opposite direction from the ventricle towards the pituitary gland. The infundibulum may serve to transmit into the cerebral ventricles, a fluid which is secreted by the pituitary gland. Sometimes, but rarely, we find within or on the surface of the pitui- tary gland, a solid and sandy substance (acervulus ccrebri.)(\) IV. ROOT AND DECUSSATION OF THE OPTIC NERVE. § 1760. The larger anterior and inferior part of the root of the optic nerve which is the largest, and the decussation of this pair of nerves, follow the two bodies described in the preceding paragraph ; these parts are situated outwardly on the anterior extremity of the cerebral peduncles, inwards and in the centre before the grayish plate which forms the inferior wall of the third ventricle, from which the optic nerve receives in the angle formed by the union of its anterior with its posterior half, filaments which may be regarded as its anterior root. When speaking of the optic nerve, we shall give a more detailed de- scription of the course and union of its roots. V. GRAY PLATE OF THE INFERIOR WALL OF THE THIRD VENTRICLE. § 1761. The gray plate (tuber cinereum) of the inferior wall of the third ventricle, is thicker in its posterior than in its anterior half, which is extremely thin, so that it tears very easily, merely from its weight, when the brain is turned over and all its sides are not well supported. It is continuous forward with the anterior extremity of the corpus cal- losum, where it forms on the surface of the anterior commissure a thin expansion, across which we perceive this cord. II. LATERAL REGIONS. § 1762. The two lateral regions of the lower face of the cerebrum, are much more extensive than the central. Their internal edges touch anteriorly and posteriorly where they are separated only by the falx cerebri, while in the centre, there is a space rilled by the parts we are about to describe. (1) Bichat, Anat. descript., vol. iii. p. 75. 440 DESCRIPTIVE ANATOMY This larger part of the lower face of the cerebrum, is formed by the lower face of the posterior and of the middle lobe. It presents a slight concavity posteriorly in all that part which corresponds to the posterior lobe, which is entirely covered by the cerebellum. Anteriorly it is shghtly convex, loose, and terminated by a rounded extremity. Its anterior part projects considerably, and forms the lowest region of the cerebrum. It extends to the small wings of the sphenoid bone, and passes about an inch beyond the central part, which terminates by the decussation of the optic nerves. This blunt anterior extremity of the middle lobe is loose, and covers the inferior extremity of the lateral part of the fissure of Sylvius. Be- hind it, the lower face of the middle lobe forms at first a large convex eminence, which rests outwardly on the base of the skull, and which covers within, the posterior part of the root of the optic nerve, with which it is united only by a short cellular tissue, and by the pia-mater. This eminence is the commencement of a conical projection, which contracts from before backward, and marks in this place the transition from the external to the internal face of the cerebrum, and forms the posterior part of the inner edge of the middle lobe. The upper part of the eminence, the hook, has a direction from within outward, and from before backward, and terminates in a blunt extremity, which is con- tinuous with the medullary semicircular band. The loose and con- cave edge of which is turned forward, while its attached and convex edge looks backward. This band called the corpus fimbriatum (tania, s. fimbria), enlarges inward and upward. When the cerebellum is turned downward and forward, we see very clearly that it blends with that of the opposite side, and forms the posterior part of the fornix. Below, it is a longitudinal band, which has the same direction, but is less prominent -f this is termed the fascia dentata. The latter extends forward a little farther than the preceding, and is covered by the external part of the base of the hook. It gradually enlarges from before backward, and presents numerous elevations and depressions situated longitu- dinally one after another. The lower part of the internal edge of the lower face of the emi- nence which has the same direction, but which projects more, extends backward, upward, and inward, and is continuous with the posterior part of the corpus callosum. Its most internal part, which presents a convexity upward and downward, is white and smooth. The gray substance is seen where this internal part is continuous with the lower face of the cerebrum, and there also its circumvolutions commence, at least, unless we consider the fascia dentata as a rudiment, which seems more correct, inasmuch as a layer of gray substance, which communi- cates with the rest of the cortical substance of the brain, passes from each side to the posterior extremity of the corpus callosum on the origin of this inferior medullary layer, and is continuous with the fascia dentata. The circumvolutions arise imperceptibly in this place from the white band which we last described ; and the most internal forms a OF THE NERVOUS SYSTEM. 441 consiierable longitudinal prominence, which is not interrupted by transverse striae, or at least by none which are very manifest. The lower face of the anterior lobe, which is slightly concave and the internal edge of which descends much lower than the external, are situated before the anterior extremity of the middle lobe. The in- ternal edges of the two lobes approach each other very much. The middle lobe and the anterior lobe are separated by the internal part of the entrance of the fissure of Sylvius. This entrance corresponds entirely to the lower face. Its most internal part is loose, and is con- tinuous with the thin plate situated before the decussation of the optic nerves; (§ 1761) it becomes broader from within outward, and is perforated with numerous considerable openings, which increase in dia- meter from within outward, and give passage to the vessels sent off by the. origin of the middle cerebral artery into the cerebral substance. This is termed by Vicq-d'Azyr the anterior perforated substance (sub- stantia perforata antica),(l) and by Reil, the cribriform plate (lamina cribrosa).(2) This cribriform plate is formed almost entirely of gray substance. It is, however, white internally in its centre, whence arise the lateral lon- gitudinal striae of the corpus callosum, which go upward and inward. It is continuous outward and backward at the inner part of the summit of the middle lobe, and farther forward, with a small smooth elevation, about half an inch broad, where the white substance is exposed, and where the anterior and posterior lobes unite, without being separated by a deep fissure. The olfactory nerve proceeds at a little distance in a deep groove, along the inner edge of the lower face of the anterior lobe ; its direction is from before backward, from above downward, and from without in- ward, and it is united to the lobe by the pia-mater, which extends like a bridge on its upper face. The extremity of this longitudinal groove, which is much deeper than the optic nerve is high, is bounded by a triangular tubercle, the olfactory tubercle (processus, s. caruncidus mammillaris), from whence the nerve partly arises. We also see a white band proceeding from it; this goes backward, upward, and outward, and terminates in the fissure of Sylvius, at the union of the anterior and posterior lobes, at the point where the white substance becomes visible externally. II. EXTERNAL FACE. § 1763. The external face is convex, and is most prominent in its centre on each side upward and downward. It is imperceptibly con- tinuous with the upper and lower faces, less however with the first than with the second. The fissure of Sylvius divides it into an anterior (1) Loc. cit., p. 545. (2) Archiv.fur diePhysiologie, vol. ix. p. 199. Vol. II. 56 442 DESCRIPTIVE ANATOMY. and a posterior half. At first view this fissure seems only an indenta- tion, the direction of which is obliquely from below upward, and from before backward, and is situated at about the centre of the lateral face, a httle nearer its anterior than its posterior extremity, the parietes of which are formed, the inferior by the upper face of the anterior part of the middle lobe ; the superior, on the contrary, by the lower face of the middle part of the anterior lobes, and we may consider its posterior ex- tremity as the upper limit of the external face. An attentive examina- tion, however, soon shows that it has much more extent. In fact, at the outer extremity of the anterior cribriform plate, (§ 1762) the com- mencement of the fissure of Sylvius, hitherto single, divides into an an- terior and a posterior groove. The posterior is that just described. The anterior is much shorter, goes directly upward, and communicates with the posterior extremity of the posterior, by a third groove, which pro- ceeds directly from before backward. These three grooves conse- quently include -a triangular space, the lower part^of which is seen where we separate the two parietes of the posterior groove; but we cannot see its whole extent until we have opened the superior horizon- tal groove, by raising, that part of the anterior lobe which forms it ante- riorly. We then observe that the central part of the anterior lobe, at first convex, goes from below upward into this middle portion of the fissure of Sylvius, and thus forms a triangular space called the island of the fissure of Sylvius, then immediately descends again before its larger up- per part, resting upon it, then describes a right angle to go directly out- ward for about an inch, and finally joins, also at a right angle, the ex- ternal face of the hemisphere, and particularly of the anterior lobe. The lower and horizontal face of this reflected portion of the anterior lobe, which may be called the roof of the fissure of Sylvius, is situated at the upper face of the anterior and inferior part of the middle lobe, so that it entirely conceals the island. The latter is about two inches long and an inch and a half high for- ward. It terminates backward in a blunt summit, and curves outward. We remark on its surface three or four flat circumvolutions, which di- verge and enlarge from below upward ; the anterior of these are shorter, but broader, perpendicular, and partly also go directly a little forward, while the posterior are longer, narrower, and proceed more obliquely backward. Both arise from the right portion, where the two lobes join and emanate as torn a common centre of irradiation. These circumvolutions are separated from those of the middle lobe by a smooth space about four lines broad ; but they are so intimately united anteriorly with those of the anterior lobe, that they seem to be the continuation of it. OF THE NERVOUS SYSTEM. 443 III. UPPER FACE. § 1764. The upper face is very convex from before backward, in which direction it curves uniformly. It is only slightly convex from without inward. It is the longest face of the brain. IV. INTERNAL FACE. § 1765. The upper face forms a right angle with the internal, which is perpendicular and straight. This latter face is placed against that of the opposite side, from which it is separated by the falx cerebri. When the two internal faces are separated, we see at their base, the upper part of the corpus callosum, which unites them in most of their length. Behind the posterior extremity of the corpus callosum, there is most generally, but not constantly,(l) a deep groove, almost perpendicular, which may more properly be regarded as the limit between the pos- terior and the middle lobe, inasmuch as it corresponds exactly to the commencement of the posterior horn of the large lateral ventricle, and lodges the posterior cerebral artery. V. CIRCUMVOLUTIONS AND ANFRACTUOSITIES. § 1766. The upper, the internal, the external, and most of the in- ferior face of the outer surface of the cerebrum, is uneven from nu- merous elevations and depressions there seen. The elevations called circumvolutions (gyri), from the curves they describe, are situated between the depressions termed anfractuosities (sulci), so that each is included between two grooves. They are covered in every part, outwardly by a layer of gray substance, which is at most but a line or a line and half thick. They are formed of medullary substance, and hence the latter alone determines the form of the surface of the brain. The external layer of gray substance is single in almost every part; and it is almost always divided, only in a slight extent in the posterior and inferior circumvolutions of the internal face of the hemispheres, by a band of white substance, into an external and an internal layer,(2) so that the structure of this part of the brain is more complex than the rest. The medullary band is infinitely thin- ner than the two gray layers, which together are not thicker than a single layer, and of which the internal is sometimes equal to that of the external, and sometimes also greater or less than it. However constant may be this arrangement in this place, we have never found it else where, except in the cornu Ammonis. (1) Scemmerring, De basi encephali, tab. iii. (2) Vicq. d'Azyr, in the Mem. de Paris, 1781, p. 506. 444 DESCRIPTIVE ANATOMY. The circumvolutions have a rounded surface, and are situated directly at the side of one another, so that the prominences of one corres- pond to the depressions of another, although where the angles are very re-entering, the prominent part of an adjacent circumvolution oe not perfectly fill them ; whence, in many places, particularly in those where large curves are observed, triangular spaces exist, which are included between two circumvolutions. But even in these places, the latter approach or touch at the bottom of the anftactuosities. These circumvolutions vary much in the manner in which they are continuous with one another. Their height and breadth are not uniform in every part; the latter generally, being some lines greater. They are usually a little more than an inch high, and a little less than an inch broad. We generally observe in the places where they are broadest, a greater or less depression, which has most commonlly, but not always, the direction of the length of the circumvolution, and the depth of which is usually proportioned to the breadth of the latter. This groove evi- dently marks the division of the circumvolution into two. It is more rare to see analogous depressions extending transversely from one edge to the other. These circumvolutions are not perfectly similar either in different subjects, or in the two hemispheres of the same cerebrum : they differ, on the contrary, very much, which circumstance may be considered as a character peculiar to the cerebrum of man, since as Vicq-d'Azyr has already remarked,(l) the cerebrum of the other mammalia is much more symmetrical. Those on the lower face are much more sym- metrical, and more constant than the lateral and the superior. The former are mostly longitudinal, the others have every direction. The anterior and the posterior are generally smaller than the middle. § 1767. After describing the parts of the surface of the cerebrum of the brain, which are observed without any derangement of this viscus, ari d which may consequently be called the external, we proceed to describe in the same order, those which are seen after partially or wholly raising the preceding, according to the situation which they occupy, without having any regard at present to their connections with each other, or with the whole cerebral mass. I. TUBERCULA QUADRIGEMINA. § 176S. The tubercula quadrigemina (eminentia quadrigemina, s. bigemina, s. nates et testes), form a square mass, situated forward and laterally between the posterior extremities of the optic beds, below the pineal gland and the posterior commissure, before the cerebellum, and above the cerebralpeduncles. This mass is oblique from abovedownward and from before backward; it is about nine lines long, and ten or twelve (1) Mem. de Paris, 1783, p. 512.—This subject has been more fully treated by Wenzel, loc. cit., p. 23. * J OF THE NERVOUS SYSTEM. 445 broad, and weighs half a drachm. It is composed of two pairs of rounded eminences, situated one after another from before backward. The anterior eminences are usually the largest, and about one line broad. They are called the nates, the posterior and the testes cerebri. The relation of the weight of the whole mass is to that of the whole cerebrum as 1:576. The four eminences are separated by a crucial depression. The anterior are usually more gray than the posterior; this difference of color is rarely as evident in the cerebrum of man, as in that of several animals, particularly the ruminantia. The eminences are of a grayish red internally, and are surrounded with a very thin medullary layer, so that the reddish tint they present, depends upon the color of the gray substance appearing through the external envelop. The layer on which they are placed, is of a much deeper gray, and is continuous with the gray substance of the cerebral peduncles. A considerable medullary band proceeds from the anterior extremity of the anterior eminences ; this goes forward towards the tubercle, which terminates posteriorly the inner face of the optic bed: a second band also extends either directly to the optic nerve, or to the internal corpus geniculatum, or even in part to the external. Another, which is still larger and longer, is detached from the posterior eminences : this goes to the rounded prominence of the lower extremity of the posterior face, that is, to the external corpus geniculatum. The tubercula quadrigemina, cover the upper part of the cerebral peduncles. They form an arch extended over a small space called the aqueduct of Sylvius (aquaductus Sylvii), which establishes a communi- cation between the fourth and the third ventricle. In the bottom and on the sides of this aqueduct, we remark longitu- dinal depressions, to which we shall return when describing the cere- bral ventricles. A narrow, prominent, medullary band, descends between the two posterior eminences from about their centre : this is situated exactly on the median line, and terminates in the large cerebral valve. 11. PINEAL GLAND. § 1769. The pineal gland, conarium, Ch. (Gl. pinealis, conarium), is an oblong rounded body, much broader from right to left than from before backward, solid, blunt at the extremity, of a very deep gray, sometimes of a reddish color, from three to four lines long, two to three broad, two thick, and weighing three grains, which always exists in the cerebrum, and which, probably, has not been found, owing to a super- ficial examination for it. This body is turned from before backward, and is attached anteriorly by its base by two thin medullary cords, which diverge from behind forward to the thalami optici, between which it is situated at their posterior part, but some lines distant from them on each side. It entirely covers the centre of the upper face of 446 DESCRIPTIVE ANATOMY. the anterior tubercula quadrigemina. Posteriorly, a medullary layer is detached from its base, which first goes forward, also blends with the upper face of the thalami optici, then immediately curves backward and goes to the point where the anterior pair of the tubercula quadri- gemina unite. This is termed the posterior small cerebral commissure, which is thinner at its anterior than at its posterior part, the first of which sometimes sends to the pineal gland, filaments similar to nerves, while the second always presents transverse grooves, which soon dis- appear on each side. The pineal gland always incloses at its posterior part, a small cavity, which varies in size ; its orifice is turned toward the middle cerebral ventricle, and the internal face of which is some- times very manifestly lined by a medullary layer. This cavity is rarely closed in all parts, and its parietes are also proportionally very thick. The variations in its capacity depend neither on the age nor on any other constant condition. It is more consistent than the gray substance generally. Before this gland, at its circumference, in its cavity, or finally in its substance, and sometimes in all these points at the same time, we find a yellowish substance, which is rarely abundant, but semitransparent, brilliant, hard, and formed of grains apparently irregular, but which are in fact rounded, and the diameter of which does not exceed half a line. (acervulus cerebri, s. glandula pineales).(1) With some rare exceptions,(2) this hard substance is constantly found after the seventh year according to Wenzel,(3) and sometimes at least after the sixth, according to our observations. Before this period we find in its place a more viscous mass, which is not more un- frequently found at an advanced age, and which then sometimes even coexists with the concretions. In young men the concretions of the pineal gland are usually found only around the organ and in its cavity, while in old men it also exists in its substance, or even only in the latter. Their color is not always perfectly the same ; generally they have a brighter tint in youth and in advanced age, than during the other periods of life. We however observe in this respect, differences which do not depend on the age. The larger calculi are usually darker than those which are small. In regard to the proportional quantity of these concretions, it is least in youth and in advanced age. In this respect, however, we observe differences which cannot be referred to a determinate cause. The num- ber of the concretions, also, has no direct ratio with the size of the pineal gland. (1) Sommerring, De [acervulo cerebri,' Mayence, 1785, ed. ii., in Ludwig-, Opp. neurol., vol. ii. p. 322. &* rr (2) We have never known it to be deficient. Wenzel has observed its absence only ■ix times in one hundred cases, (p. 156). (3) Loc. cit., p. 135. OF THE NERVOUS SYSTEM. 447 These concretions and the mass which they form, are united with each other, and with the adjacent parts, by a dense cellular tissue, and by an envelop like a sack. The mass is composed not only of a cer- tain number of smaller masses, but each of these latter are formed of several calculi, which are all perfectly round. Exposed to the air, these concretions become dry, opaque, and whitish. They seem entirely, or almost entirely, similar to the bones in their chemical composition.(1) The calculi of the pineal gland, are not a pathological appearance and the cause or the effect of the diseases of the mind,(2) as Morgag- ni, (3) Gum,(4) and Greding(5) assert, because they are found in very small quantity in four individuals who were fools.(6) Although they are not unfrequently less abundant than usual, when there is no de- rangement in the mind ; still the coincidence of their rarity with mental derangement, is curious, inasmuch as the fewness of these concretions in young and in old men, seems to lead to something analogous. III. CORPUS CALLOSUM. § 1770. The corpus callosum, mesolobe, Ch. (corpus callosum, trabs cerebri, commissura cerebri magna),(l) is situated between the two hemispheres and unites them. It is nearer their anterior than their posterior extremity, and occu- pies about the second and third anterior fifths of the length of the cere- brum, considering the length to be divided from before backward into five equal parts. It is, however, a little longer than two fifths. It is about three inches long and eight lines broad. It gradually enlarges from before backward, but again contracts a little nearer its posterior extremity. In most of its length, excepting the middle, it is covered by the lower part of the internal wall of the hemispheres, \ Inch advances on it, whence a deep depression in form of cul-de-sac, is formed on each side, somewhat analogous to the lateral cavities of the larynx. Its mean thickness is about three lines. It is uninterruptedly continuous on both sides, with the substance of the hemispheres, and there is no need of recurring to any artificial means to discover that it is formed of transverse medullary fibres, blended with grayish substance. (1) Gordon, loc. cit.. p. 135.—Pfaff, who has analyzed these concretions, found them composed of animal matter, and of much phosphate of lime, and a little of the carbonate. See Deutsches Archiv. fur die Physiologic, vol. iii. p. 170. (2) J. F. Meckel, Mem. de Berlin, 1754, p.J92.—Rcedercr, De cerebro, Gottingen, 1758.—Morgagni, De caus. et sed., ep. lxi. a. 3, 4.—Sommerring, loc. cit. (3) De caus. etsed., ep. v. 12. (4) De lapillis glandule pinealis in quinque mente alien., Leipsic, 1753. (5) Advers. med., vol. ii. p. 522. (6) Wenzel, loc. cit., p. 165. (7) Reil, Sur le systeme et I'organisation du corps calleux; in the Archiv. fur die Physiologie, vol. x. p. 171-175. 44S DESCRIPTIVE ANATOMY. The anterior extremity of its upper face is convex, and the posterior is concave, an arrangement which undoubtedly depends on the separa- tion of the two hemispheres from each other from before backward. The posterior edge is broailer than the anterior. On its upper face there is a superficial depression which extends through all its length, and corresponds exactly to the median line. Along this depression there is on each side a slight elevation, called the raphe, or the external suture of the corpus callosum (raphe, s. sutura externa corporis callosi). The raphe is not formed solely by the artery of the corpus callosum, but it is a sort of cicatrix, produced by the mutual adhesion of the two hemispheres. Independent, of this depression, we also remark on the upper face of the corpus callosum, two longitudinal striae, generally broader, which proceed on each side parallel to each other, although not perfectly sym- metrical ; these are called the lateral longitudinal stria (stria longitu- dinalis laterales). Reil terms them the covered bands, because- they are situated below the part of the hemispheres which projects inward, and which almost entirely covers the lateral part of the corpus cal- losum. Transverse fibres exist also on each side, on this upper face : they leave the median line, and are continuous with those of the hemis- pheres. We also observe transverse elevations on the lower face; but the latter resemble still more the fasciculi, separated from each other by superficial depressions. They arise from the inferior face of the corpus callosum, being concave and less extensive than the superior. In fact, the transverse fibres extend through all the thickness of the corpus callosum. These fibres are not transverse at the anterior and posterior extremi- ties of the corpus callosum: they there have a direction from before backward, and from without inward in the first, from behind forward and from without inward in the second, so that they converge. The corpus callosum is curved at each of its extremities. It is in- flected from before backward, and from above downward at its anterior extremity, from behind forward, and also from above downward at its posterior extremity. Reil termed the anterior curve the knee, and its extremity the beak, the posterior the glove. These two curves connect the upper and lower faces of the corpus callosum. The latter is much more complex than the other. After leaving the knee, it descends from before backward, extends to the anterior com- missure, reascends from behind forward, is parallel to the upper face, again proceeds forward, then a third time backward, and is finally con- tinuous with the upper face, after giving origin to the glove. This lower face is loose only at its anterior and its posterior part, forward from the knee to the anterior commissure, backward to its union with the arch; every where else it is uninterruptedly continuous with the septum lucidum. The commencement of the lower face from the knee to the anterior OF THE NERVOUS SYSTEM. 449 commissure, gradually becomes more and more narrow. From the knee to its centre, the upper raphe and the longitudinal lateral striae are very distinct. But the raphes disappear in this place, the striae approach each other still nearer from before backward, but do not touch ; and at the same time the lower face is grooved from the extremity of the su- perior raphe to the commissure, where it terminates by a small depression in form of cul-de-sac; consequently the two lateral halves of the corpus callosum are, in this place, less broad, and less flat, and have the form of a straight layer ; but their internal faces are inclined one towards another, whence comes the longitudinal groove which we have mentioned. Hence, also, the part of the corpus callosum, covered by the hemi- spheres, becomes narrower from before backward, after leaving the knee, so that the most posterior part is entirely disengaged, and it is directly continuous with the ascending internal face of the anterior lobes of the cerebrum. Hence, also, the lateral longitudinal striae are entirely loose in this place. They are directed backward, downward, and out- ward, and proceed below and before the anterior commissure, be- tween it and the decussation of the optic nerves. At the posterior ex- tremity of the lower face of the posterior lobe, they unite to the cribri- form plate or anterior perforated substance of the lower face of the cerebrum, so that in this place the corpus callosum is continuous, through them, with the lower face of the anterior and the middle lobes; although we cannot term the lateral longitudinal striae the peduncles of the corpus callosum, as has been done by Vicq-d'Azyr. Posteriorly the corpus callosum is also reflected on itself from above downward, and from behind forward. As the superior face of this reflected portion is adapted to the lower face of the straight portion, it forms what Reil has termed the glove. The septum lucidum is attached to all the rest of the lower face of the corpus callosum, which may be called its internal portion, in oppo- sition to the upper and loose part of the inferior, considering the latter as external. The corpus callosum is continuous at its posterior extremity in the posterior and descending horn of the lateral ventricles, partly with the roof of these cavities, partly with the medullary covering of the emi- nences they enclose, the pes hippocampi minor and the cornu ammonis, which will be described hereafter. IV. SEPTUM LUCIDUM. § 1771. The middle and anterior region of the part of the Cerebrum which extends from before backward on the median line, forms the septum lucidum,(l) septum median, Ch. (Septumpellucidum, s. lucidum). (2) This septum, which is extended vertically between the corpus (1) A very improper term, for the septum is but slightly, or even not at all trans- parent. (2) Meckel, Obs. sur la glandc pincale, sur la cloison transparente, etc., in the Mem. de Berlin, 1765, p. 91-102. Vol. II. 57 450 DESCRIPTIVE ANATOMY. callosum and the fornix is triangular. Its height and thickness are much greater anteriorly than posteriorly. It is continuous upward and forward with the anterior, horizontal, and reflected portion of the corpus callosum; posteriorly, but only to a slight extent, with the an- terior portion of the fornix, and forms the larger anterior part of the common internal wall of the lateral ventricles. It is composed of two layers, directly adapted one to the other, but they are not fused together. Each of these layers is formed in turn of an external thin and medullary stratum, and an internal thicker and gray stratum, the former of which is continuous with the medullary substance of the corpus callosum, and of the fornix. The medullary layer is lined by a very delicate membrane, which is demonstrated with peculiar facility, when there is an accumulation of serum in the space between the two layers.(l) The space between the two layers is the ventricle of the septum, called also the fossa of Sylvius, the sinus of the median septum, Ch. (ventriculus sepli), which is usually termed the fifth ventricle, and which Wenzel has called the first ventricle. This space does not every where present the same form or the same volume; but generally it is more spacious, and particularly broader in proportion, in the early periods of life, than afterward. Its breadth anteriorly is three or four twelfths of a line in the full grown fetus. It is usually about an inch and half long in the adult. It is always narrower in its centre, while at the anterior and the posterior extremity, it terminates in a triangular fossa, the angles of which are turned one towards the other. Opinions are divided on the question, whether this ventricle is entirely separated from the others, or if it communicates with them, whether the communication be constant or simply accidental. Opinions differ also in regard to the position of this opening. The ventricle of the septum is generally considered as a perfectly closed cavity. Our dissections have demonstrated that in the normal state it is always closed in subjects who are perfectly developed : it how- ever much exeeeds the limits generally assigned to it anteriorly ; for a canal which is at first rather broad, but which gradually contracts, and finally becomes very narrow, extends from its anterior part downward and backward, towards the third ventricle, to near the space between the anterior pillars of the fornix and the anterior commissure. We, however, cannot generally observe the orifice of this duct, although a communication between the third ventricle and that of the septum sometimes exists exactly in this place.(2) (1) Sabatier, loc. cit., p. 433.—Meckel, loc. cit., p. 96.—Wenzel, Prodr., p. 7.— Vingtrinier, Casremarquable d'kydropisie de la cavite du septum lucidum, oucavite de Sylvius, chez unejeunejille idiote; in the Revue medicate, vol. viii. p. 299 (2) Tarin, Anthropotomie, Paris, 1750, vol. i. p. 232. This septum sometimes opens by the small fissure which separates the two cords of the anterior pillar into the lateral ventricles. .'-»!" THE NI.KVOUS SYSTEM 451 V. FORNIX. § 1772. The fornix, trigone cerebral, Ch. (fornix) forms the lower part of the upper and anterior wall of the third ventricle. It is uninter- ruptedly continuous upward and backward with the corpus callosum, forward in most of its length with the septum. The upper and attached edge is convex; the lower is concave, and rests on the internal part of the upper face of the thalami optici, which it almost entirely covers, and is directed from behind forward, and from above downward. Pos- teriorly, the fornix is continuous by its posterior extremity with the corpus callosum. Externally, but first becoming broader, it joins unin- terruptedly, the manifestly fibrous envelop of the cornu ammonis, then unites directly forward with the corpus fimbriatum. The posterior part of the fornix presents oblique and transverse striae in its centre, and has been termed, very improperly, the lyre (lyra, s. psalterium), since, as Sabatier has already remarked, the Greek word -LaXKtg does not mean a lyre but an arch ; hence too the term xa/xa£iwv also applied to this part. The origin of the corpus fimbriatum, and the white envelop of the pes hippocampi, are called also the posterior pillars of the fornix. We may consider the centre of this latter as its body. Anteriorly, the fornix descends directly behind the anterior commissure, then turns backward, and penetrates before and below the optic thalamus of its side, in the floor of the fourth ventricle, where it seems to disappear. The portion of the fornix between its posterior extremity, and some lines beyond the anterior commissure, is flattened from above down- ward, and is single. After leaving this point, the fornix becomes cylindrical, and gradually divides into two lateral cords, which diverge from above downward, and are called its anterior pillars (crura fornicis anteriora), so that the anterior commissure which passes before them, is very evident in the interval between them. Each of these cords then glides below the optic bed of its side, in the floor of the fourth ventricle, directly above the decussation of the optic nerves. There, surrounded entirely by gray substance, it goes first outward, then again inward, so that it describes an arch very convex outwardly, whence opposite the union of the optic nerves, striae descend into the decussation, where they may be easily followed, and it finally termi- nates in the gray substance of the mammillary eminences. We may then consider these latter as making part of the fornix, and Santorini is perfectly right(l) in terming them the bulbs of the fornix (bulbi fornicis). The fornix, however, does not terminate in this,place; for a considerable medullary cord detaches itself from the mammillary emi- nences ; this proceeds within the optic bed, directly behind its internal face, covered in all parts by gray substance, enlarges above and ex- pands in a fan. The mammillary eminences also give off a third medul- lary cord, which proceeds, at least in great part, nearer the surface, on (1) Obs, anat., vol. iii. c. 2. 452 DESCRIPTIVE ANATOMY. the inner face of the optic bed, goes farther forward and divides into an anterior and a posterior fasciculus: the posterior follows from before back- ward the upper edge of the inner face of the optic bed, and is continu- ous with the peduncle of the pineal gland: the anterior goes outward, and is continuous with the semi-circular band, between the corpus striatum and the optic bed. Finally, the mammillary eminences also send backward and outward a third medullary cord, which is covered by the roof of the optic nerve, and goes to the optic bed. Thus the fornix represents a very complex chain, which unites the two hemispheres in several parts, and which also establishes a com- munication between the anterior and the posterior parts of each hemi- sphere. VI. THALAMI OPTICI. § 1773. The thalami optici, or the posterior cerebral ganglions, the optic beds (ganglia postica, Gall, corpora striata posteriora et superna, Vieussens ; thalami, s. colliculi nervorum opticorum), are two grayish, elongated, rounded bodies, which converge from behind forward, and from without inward, and are situated before the tubercula quadrigemina, envelop the anterior ends of the cerebral peduncles in most of their extent, especially upward and inward, so as to leave loose only a small part of them outward and downward, if we except the root of the optic nerve : but if we include this root, the cerebral peduncle is surrounded in this place by a complete ring, of which the optic bed is the commencement, and the union of the roots of the optic nerves the termination. These bodies are about an inch and a half long, nine or ten lines high, and from eight to ten broad. They weigh nearly four drachms, so that their weight is to that of the rest of the cerebrum, about as 1 : 36. Their upper face is convex. We there remark a longitudinal pro- jection, the direction of which is from before backward, and which is most prominent at its anterior part, and which imperceptibly disappears posteriorly. The most prominent part of this projection is the extremity of a large medullary fasciculus, which comes from the mammillary eminences, and expands superiorly like a fan. The internal face is slightly convex, and almost straight at its an- terior part, which is the most extensive. It is continuous with the upper at an almost right angle. At the anterior part of its union with this latter, we observe a white medullary band about one line and a half broad. The bands of the two sides which are inflected to go to meet each other, unite on the median line, where they become the peduncles of the pineal gland, then go backward to- wards the mammillary eminences, slightly concealed forward and down- ward by the inner face of the optic bed. Behind the posterior extremity of this medullary band, the internal wall is slightly convex, and terminates finally in a rounded promi- nence. OF THE NERVOUS SYSTEM. 453 The optic beds are not united by the nervous substance at their upper part, nor in those subjects which are perfectly developed, nor even at the early periods oflife,(l) although Vieussens,( 2) Santorini, (3-) Morgagni,(4) Winslow,(5) and Gunz,(6^ have asserted the contrary. They are connected in this place only by the pia-mater, which passes from one to the other. But their internal faces adhere anteriorly for the extent of three or four lines, by a small rounded cord, about a line broad, and formed of graj' substance, called the commissura mollis. Very rarely the commissura mollis,(7) does not exist ;(8) hitherto we have known it to be deficient only three times, nor is it common to find two situated one above the other.(9) Below there is no continuity of substance between the thalami optici. These two bodies are not united, except by the medium of the floor of the middle cerebral ventricle. The external face is convex, and intimately united to the corpus striatum, but in such a manner, however, that we every where observe between the two eminences, medullary substance, which is the con- tinuation of the cerebral peduncles. The posterior face is also convex, and always evidently divided into three rounded tubercles arranged in a triangle, and situated, one, the posterior (tuberculum ganglii postici posterius, s. posterius superius), upward and backward; the second, the internal corpus geniculatum (corpus geniculatum internum, s. tubercu- lum posticum medium), downward and inward: finally the third, the external corpus geniculatum (corpus geniculatum externum, s. tubercu- lum posticum inferius, s. externus), still lower and externally. The posterior tubercle is always larger than the two corpora geni- culata, but more connected than they with the substance of the pos terior cerebral ganglion. The two corpora geniculata are sometimes equal in size, but usually the internal is larger. Their form is rounded. Both are directly connected with the tubercula quadrigemina by medullary bands, which are sometimes blended, but are usually distinct and seperate from each other. The medullary band of the posterior tubercula quadrigemina, goes to the external corpus geniculatum, and that of the anterior to the internal corpus geniculatum. The first is much more constant and stronger than the second. (1) At least we have always observed this. Sabatier has made the same remark, (Anat., vol. iii. p. 437.) (2) Neurogr., 1. i. c. ii. (3) Obs. anat., c. iii. § 7. (4) Advers. anat., 1. vi. c. x. (5) Exp. anat., 1. iv. p. 163. (6) Prolusio de cerebro, ii. Leipsic, 1750, p. xi. (7) Morgagni and Gunz, claim the honor of its discovery. (8) Wenzel has known it to be deficient five times out of sixty-six, (De ccreb. p. 129). Gordon (p. 98) has always found it, and Sabatier almost always (p. 437.) (9) Vicq. d'Azyr, p. 527.—Wenzel, Prodr. p. 15.—We also have observed this anomaly. 454 DESCRIPTIVE ANATOMY The two corpora geniculata are composed only of medullary sub- stance externally. Internally they are formed by a mixture of white and of gray substance. They are continuous downward with the root of the optic nerve. The upper and posterior face of the optic bed, is covered with with a thin layer of white substance ; the internal of gray. Internally they present a mixture of white and of gray substance. Beside the medullary fasciculi from the tubercula quadrigemina, and which partly remain in the substance of the ganglion, partly also blend in its surface with the pineal gland, this body is formed of several superimposed layers, the rays of which are directed from within outward, unite in the substance of the cerebral peduncle, and intimately interlace with it. VII. CORPORA STRIATA. § 1774. The striated bodies, beds of the ethmoidal nerves, Ch., an- terior cerebral ganglions, Gall, (corpora striata, corpora striata antica inferiora, ganglia cerebri magna antica),(\) are two elongated, rounded, and flat bodies, formed almost entirely of a substance very gray externally, which occupy most of the lateral ventricles and the lower part of the anterior lobes. They are usually about two inches and a half long, and their greatest height is about one half of it. They are from eight to nine lines thick, and are highest and thickest anteriorly ; they gradually become thinner and lower posteriorly. The mean weight of each is about five drachms, and is to that of the optic bed as 5:4. The weight and proportional size of these two eminences are, however, not always the same, as has been determined by Vicq- d'Azyr and Gordon, with whose observations our own agree. Their weight is to that of the whole cerebrum as 1 :29. Their greatest diameter is from before backward, and from within outward. They are nearly four lines distant from each other forward, and about two inches posteriorly; because posteriorly the thalami optici and the tubercula quadrigemina exist between them, while anteriorly they are separated only by the septum, and the anterior part of the fornix. Their upper and their internal portions are loose and unattached to a considerable extent; this forms the floor, and the outer wall of the an- terior horn of the large cerebral ventricle, has a conical form, is gradu- ally elongated from before backward, where it is pointed, and de- scribes in its centre a considerable curve, the direction of which is from before backward. After leaving the external edge of this loose part, the medullary substance is reflected from below upward at an acute angle, and forms the lateral and upper walls of the large cerebral ven- tricle. When cut from within outward, proceeding from this edge, we arrive only into the medullary substance of the hemispheres, but if the incision is made downward and a little outward, we come to the (1) Magendie, Note sur les fonctions des corps slries et des tubercules quddrija- meaux ; in the Journ. de phys., vol. iii. p. 376. OF THE NERVOUS SYSTEM! 455 outer face of the corpus striatum, which makes an obtuse angle with the superior. This external face extends to near the entrance and the island of the fissure of Sylvius, from which it is only a few fines dis- tant. Its upper part is straight, and formed from behind forward by a layer of medullary substance about four lines broad. The lower is convex in almost all its extent, composed of gray substance, and but loosely connected with the medullary substance of the posterior part of the anterior lobe, in the midst of which it is imbedded, so that the cor- pus striatum can easily be detached from this latter. Only the pos- terior part of the lower half of the external face is also straight and medullary, because the white band we have mentioned is reflected downward and forward: but at its most posterior part it again becomes gray, and here the gray substance, which is visible externally above, forms a tail which is inflected downward and forward in the same direction as the medullary substance, but does not however extend to the anterior large half of the external gray face. The gray substance of the corpus striatum, seems then to be divided externally by a considerable layer of medullary substance, into an in- ternal and upper half, and an external and lower. The inferior face of this body is narrow and rounded. It is imper- ceptibly continuous with the internal and the external. Below it is blended with the medullary substance of the hemispheres, which gives it a whitish gray tint. The lower part of the internal face is convex, and closely envelops the external face of the optic bed. Horizontal, vertical, and oblique incisions, make us acquainted with the essential characters of the structure of the corpora striata. They demonstrate that these bodies are composed of three substances, one a deep gray, the second a light gray, and a third medullary, which form several alternate layers. All these layers describe arches, the convex edges of which are turned upward, and the concave edges downward. The medullary substance proceeds from behind forward, and from below upward, from the cerebral peduncle and the optic bed to the middle of the gray substance. At its entrance, which corresponds to the posterior extremity of the lower face of the corpus striatum, it ex- tends its whole height; but it soon divides into several fissures and superimposed layers, which are generally three in number, which go forward; the lower two of these are much narrower and shorter than the upper. The latter, which also extends farther forward than the other two, does not proceed except to the upper and posterior part of the loose face of the corpus striatum, while forward and downward it is entirely enveloped by the gray substance which forms its anterior extremity. At the same time its breadth diminishes forward and down- ward, and it is interrupted by some gray substance both from before backward and from above downward, so that it is divided below into several layers of small white rays, some of which occur also between 456 DESCRIPTIVE ANATOMY. the third and second layer. This white substance, however, pene- trates from behind forward, and from below upward, through the gray, and is continuous in every direction with the medullary substance of the hemispheres. The light gray substance forms the middle and lower part of the corpus striatum : it is situated between the inferior and the first medul- lary layers, and likewise between this and the second, which it much exceeds in thickness. It occupies the smallest part of the corpus striatum. Most of this body is formed of a deep gray substance, which is abun- dant particularly above, where it occupies the space between the second and third medullary layer, and forms the loose part of the corpus striatum, situated above and before this space. The corpus striatum is then formed by alternate layers of white and gray substance ; all these layers are conical. Those of gray substance bulge forward, and those of white substance backward. All terminate in a point at the opposite extremity, and interlace with each other. The light gray substance which forms the middle and lower part seems to be formed by an imperfect separation of white and gray sub- stance ; for the two lower layers of white substance are not so pure a white as the upper, which are contrasted with a deep gray sub- stance. The best method of becoming acquainted with the structure of the corpus striatum, is to cut and scrape its posterior and inferior part, and follow the medullary substance of the cerebral peduncle within it. The cerebral peduncle enters it from below upward, and from behind forward, and the medullary substance with which it is continuous is enveloped directly downward, inward, and outward, by the gray sub- stance ; the corpus striatum is interrupted by this only in a small por- tion of its posterior extremity. The medullaiy substance of the cerebral peduncle disappears at the posterior extremity of the corpus striatum, like the branches of a fan, in the form of fascicuh, which penetrate the gray substance in all parts, enlarge from before backward, and become thin from within outward. It sends outward and inward numerous radiating and pointed prolonga- tions which expand in the gray substance, but do not extend to the circumference. The gray substance of the corpus striatum is then divided in its whole extent by the white, which is continuous with the cerebral pe- duncle, into two parts, an external and an internal, which are blended together below, but not above. The white band of its upper face is the anterior edge of the medullary expansion which passes through it; and the commencement of the medullary substance of the hemisphere formed by the white substance which passes through the middle of the corpus striatum. As the medullary substance gives off in its course expansions which radiate in every direction, the corpus striatum ought necessarily to OF THE NERVOUS SYSTEM. 457 present internally the appearance described above, when cut trans- versely and longitudinally ; so that it much resembles the cerebellum, from which also the medullary substance disappears in thin layers, only there the gray substance which covers the latter, instead of having the same form, merely appears as a layer which is expanded uniformly over its surface. VIII. T(ENIA SEMICIRCULARIS. § 1775. In the groove between the upper faces of the corpus striatum and the optic bed, is a narrow and prominent band, called the tania semicircularis (stria cornea, s. terminalis, s. tania striata, s. geminum centrum semicirculare). This band is a little more than a hne broad and is slightly prominent; it commences before the foramen of Monro, near the anterior pillar of the fornix, with which it is always connected. It rarely terminates at the posterior extremity of the corpus striatum: it generally curves downward and outward, and disappears near the end of the roof of the descending horn of the lateral ventricle, where it communicates with the summit of the corpus fimbriatum in the descending horn of the great ventricle, and the most external fibres of the corpus fimbriatum and of the anterior commissure. This band projects but shghtly in the early periods of hfe : is whitish, and formed of longitudinal fibres, which raise in this place the inner membrane of the ventricle. It afterwards becomes, particularly on its inside, more prominent and brownish, and there is deposited on the sur- face of the medullary fibres primarily existing and which alone form it at the commencement, a more or less brownish layer, which is hard and solid, whence it is called the lamina cornea. This change ensues as the subject grows older, or cephalic affections exist; so that it is not essential to the organization of the band. Tarin considers this substance as of a peculiar nature.(1) Vicq-d'Azyr regards it as the common gray substance.(2) Wenzel has attended particularly to its formation, and considers it as formed by an effusion of fibrin, and as it is developed, the adjacent membrane of the ventricles also thickens, and the number of the glands of Pacchioni increase.(3) IX. ANTERIOR COMMISSURE. § 1776. The anterior commissure (commissura anterior, s. mag- na,)(4) is a transvere, rounded, medullary fasciculus, which is slightly flattened from above downward, and is a little thicker than the optic nerve : it is inclosed in a sheathe formed from the pia-mater, and is situated directly in front of the anterior peduncles of the fornix. Its anterior part is loose and exposed, but on the right and left the cord (1) Advcrs. anat., 1750, p. 2. (2) Loc. cit., p. 430. (3) Loc. cit., p. 82. (4) Reil, Archiv. fur die Physiologie, vol. xi., p. 89. Vol. II. 58 458 DESCRIPTIVE ANATOMY. penetrates into the lower and anterior part of the corpus striatum ; is a little broader, becoming also gradually thinner ; goes outward, then backward, and a httle downward, and thus describes an arch which is convex forward. This arch passes through the substance of the cor- pus striatum, but does not blend with it, and is situated in a special canal from which it is grooved. After leaving this transverse canal, it va- nishes in rays, and terminates in the lower region of the fissure of Sylvius, and of the descending horn of the lateral ventricle, where it blends with the most external fibres of the corpus fimbriatum and tcenia semicircularis. Only the middle part of the anterior commissure is then perceptible,, and even this to a very slight extent without, if none of the cerebral substance be removed. This cord unites the anterior and inferior parts of the posterior lobe of the two hemispheres, and forms the anterior part of a ring which is closed posteriorly by the fornix, its appendages, and the tcenia semi- circularis. It is, however, very probably connected with the origin of the olfac- tory nerve, since it passes above the anterior cribriform plate, at a little distance from its roots, especially the external, and an undoubted rela- tion between the development of these roots and that of the commis- sure, may be demonstrated in animals. Hence the origin of the optic and olfactory nerves very much resemble each other. The structure of the anterior commissure is extremely curious, since it resembles a nerve, not only being surrounded externally by a thin neurilemmatic envelop, but is also formed internally by fasciculi of a very minute cellular tissue. The external and internal envelops do not disappear, except at the place where the commissure vanishes on leaving the corpus striatum. X. CEREBRAL VENTRICLES. § 1777. The substance of the cerebrum is not perfectly solid. It incloses a considerable space, which corresponds generally in form to that of the external face, because it proceeds into all parts of this viscus, but its extent is much less. We may term this space generally the cerebral ventricle (ventriculus cerebri), or the central fissure (fissura centralis). The floor of this cavity is formed by that part of the cerebrum which corresponds to the anterior cords of the spinal marrow, and of which it is properly only a development. Its sides and roof are formed by the parts superadded to these cords. It begins at the posterior extremity of the upper face of the medulla elongata in the place where the posterior cords of the spinal marrow separate, and is here called the rhomboidal sinus, or the calamus scrip- torius; it continues then under the cerebellum, where it gives rise to the fourth ventricle, dilating in every direction: thence it contracts and OF THE NERVOUS SYSTEM. 459 passes under the tubercula quadrigemina, and forms the aqueduct of Sylvius; it then again enlarges in every direction, principally, how- ever, from above downward, between the thalami optici, where it forms the third ventricle, terminates anteriorly in this place in a cul-de-sac, but extends much to the right and left, and thus forms on each side the lateral ventricle. The cerebral ventricle considered as a whole has the form of a cross, the anterior longitudinal arm of which is considerably shortened, while each of the lateral ones is divided into three arms. All the different compartments communicate uninterruptedly with each other. This cavity is not entirely closed. Its internal face, and conse- quently that of the cerebrum, communicates with the external in many parts, viz. backward, between the cerebellum and the medulla oblongata by the small transverse fissure (fissura cerebri transversa parva); and forward, between the corpus callosum, the corpus fim- briatum, the tubercula quadrigemina, and the thalami optici, by the large transverse fissure (fissura cerebri transversa magna). These spaces, however, which are caused by the interruption of the cerebral substance, are filled by the arachnoid membrane and the pia-mater. The parietes of these different cavities are smooth, and moistened with serum. Many anatomists(l) admit here only the choroid plexus, and no special membrane. Bichat(2) and Wenzel,(3) on the con- trary, whose opinion is more correct, have there found a special mem- brane, which is, according to the former, a continuation of the arach- noid membrane, while the latter regards it as a membrane of a parti- cular character. The internal membrane of the first, second, third, and fourth ventricles is evidently continuous with the arachnoid; but that which lines the fifth forms a closed sac. This circumstance, however, proves nothing against Bichat's opinion, since the ventricle of the sep- tum probably communicates with the others at first. The inner membrane of the cerebral fissure- is demonstrated with peculiar facility in youth, when the medullary substance above the lateral ventricles is carefully removed. It may be easily demonstrated also(4) in the ventricle of the septum or the corpora striata, in the posterior horn of the large ventricles, and on the floor of the fourth. It usually becomes thicker in hydrocephalus internus. Sometimes also it is very evident when serum accumulates between it and the cerebral substance. It can rarely, however, be separated completely, and some cerebral substance almost always adheres to its external face. Hence why many anatomists have termed it the mcdidlary layer (lamina medullaris). Very recently, also, Reil has applied the term epithelium (1) As Scemmerring, loc. cit., p. 48, § 59. (2) Tr. des membranes, p. 216. (3) Prodromus, § 8, p. 8. De cerebro, cap. viii. Integumentum vcntriculorum cerebri et par Hum in iis si/arum, p. 80. (4) Wenzel, loc. cit., p. 81. 460 DESCRIPTIVE ANATOMY. to the union of this membrane with the shapeless substance which covers the parts of the cerebrum below it.(l) Its thickness also varies in ihe normal state in the different regions where it is considered. Of the divisions comprised by the cerebral ventricle, we have already described the rhomboidal sinus (§ 1729) : we have then only to exa- mine the others. a. Ventricle of the cerebellum. § 1778. The ventricle of the cerebellum, the fourth ventricle, the fifth ventricle (ventriculus cerebelli, ven. quartus, s. quinlus, Wenzel),(2) is triangular: its base looks downward and backward, and its summit upward and forward. It is continuous downward and backward with the rhomboidal sinus of the medulla oblongata. It penetrates back- ward and upward between the anterior and posterior extremities of the vermiform process in the substance of the cerebellum, and terminates there in a point. Anteriorly it passes under the posterior edge of the tubercula quadrigemina, and is continnous with the aqueduct of Syl- vius. Its floor, which in the natural position of the cerebrum, consti- tutes the anterior wall, is formed by the upper face of the annular pro- tuberance. Along the median fine is a longitudinal groove about one hne deep; on each side of this rises a prominence which turns over from within outward. From the anterior to the posterior extremity of this floor a narrow and elongated blue place extends, which probably exists only in man ; this is formed of numerous minute blood-vessels, and is apparently connected with the origin of the auditory nerve(3). The posterior and inferior wall is formed by trie anterior and internal face of the posterior half of the vermiform process, and laterally by the posterior valve. The lateral walls are composed of the anterior and middle prolongations of the cerebellum. Finally, the superior is formed posteriorly by the posterior face of the anterior half of the vermiform process, and anteriorly by the anterior cerebral valve. The fourth ventricle is open posteriorly, so that in this place the inner face of the cerebellum is continuous with the external by the small cerebral fissure. (1) Archiv.fur die Physiologic vol. ix. p. 143. (2) Desmoulins, Memoire sur le rapport qui unit le diveloppement du nerf pneu- mogastrique a cehii des parois du quatrieme ventricule ; in the Journ. de phys. exp., vol. iii. p. 362. (3) Loculi cerulei in basi ventriculi quinti; in Wenzel, loc. cit. vol. xvii. p. 168-169.—This blue place has already been described by Vicq-d'Azyr, in the Mtm. de Paris, 1781, p. 585. OF THE NERVOUS SYSTEM 461 b. Aqueduct of Sylvius. § 1779. Theaqueduct of'Sylvius(aqaductusSylvii,s. canalis eminentia quadrigemina), is a very narrow channel which establishes a commu- nication between the ventricles of the cerebrum and cerebellum. It is formed below by the upper and convex face of the cerebral peduncles, on the sides and above by the tubercula quadrigemina, and anteriorly by the posterior commissure and the pineal gland. It is continuous posteriorly with the fourth ventricle, anteriorly with the third, and also communi- cates in the latter place with the external face of the cerebrum. The parietes of this canal present four longitudinal depressions, an inferior, two lateral, and a superior.(l) The inferior is the most posterior, and is situated in the median line: it terminates the longitudinal groove in the floor of the fourth ventricle. The lateral are situated farther forward, become deeper towards the centre, and converge from behind forward. The superior, which corresponds exactly to the inferior, and which passes through the centre of the upper face, is the deepest: it is broader an- teriorly and still deeper posteriorly. We do not consider these depressions as particularly important, as Wenzel thinks them. We regard them only as the remains of the large ventricle covered in the fetus by the tubercula quadrigemina. c. Third ventricle. § 1780. The third ventricle (vent, tertius, s. processus fissura me- diana perpendicularis, Gordon), commences at the anterior extremity of the aqueduct of Sylvius, and descends obliquely from behind for- ward. It is much larger than the fourth ventricle in man, while in animals the reverse is true.(2) Its form is very irregular, resembling an oblong square. Its length is much greater than its height, and it is only a few lines broad. Its floor is formed by the gray substance situated before the cerebral peduncles by the mammillary eminences, finally between and before the latter, by the decussation of the optic nerves. Its anterior face is co- vered by the thin layer of gray substance situated before the decussa- tion of the optic nerves, by the anterior peduncles of the fornix, and by the anterior commissure. Its upper wall or roof is covered by the body and the posterior peduncles of the fornix, and also by the posterior fold of the corpus callosum. Finally, its lateral walls are formed below by the internal, and above by the external faces of the thalami optici. Its lower face is the most irregular : considered generally, it descends from behind forward; but we remark in it two culs-de-sac, the posterior of (1) Wenzel, Scrobiculi in canali corporum quadrigeminorum. Loc. cit., vol xvi p. 166-167. (1) Wenzel, loc. cit., cap. 21-22. 462 DESCRIPTIVE ANATOMY: which is the commencement of the infundibulum, and the anterior is situated before the decussation of the optic nerves. Both of these depressions terminate in a point. The fourth ventricle is imperfectly divided near its centre, posteriorly into an upper and a lower half by the commissura mollis of the tha- lamic optici. The anterior, superior, and inferior walls are perfect, but the lateral presents a space, or rather the anterior and the superior lateral walls are not united by cerebral substance. The middle and lateral ventricles of the cerebrum communicate by this space between the optic beds and the fornix. When the pia-mater and arachnoid membrane to which it gives passage are removed, it is quite large, but when these two membranes continue in place it is very small, and forms a very narrow opening between the lower anterior extremity of the thalamic optici and the anterior pillars of the fornix. This opening is called the foramen of Monro (foramen JVEonroi). It is constant, except in certain pathological states. The impossi- bility of passing air from one of the lateral ventricles into the other, the permanent fullness of one of these cavities after the Other has been opened and the fluid removed from it, and finally the difference some- times remarked between the liquids accumulated in the two lateral ventricles,(l) have been adduced as arguments against its existence. But most of these phenomena may be explained by the falhng of the vascular plexus across the opening, and also by the morbid adhesion with the edges of this latter, or of the edges themselves. (2) This latter cause is more probable, as most of the observations on which the above mentioned arguments rest have been made in circumstances favorable to a morbid adhesion. (3) We must not confound with the foramen of Monro an opening ad- mitted by incorrect anatomists in the septum lucidum, which does not exist; when this is seen, it depends on the awkwardness of the ana- tomist, the bad condition of the cerebrum, or a morbid laceration. In fact the third ventricle is continuous upward and backward with the aqueduct of Sylvius ; but it also communicates with the external under the posterior extremity of the corpus callosum, above and before the pineal gland, through a broad opening of which the pia-mater and the arachnoid membrane which penetrate into the cerebrum, contract the diameter, and which forms the central part of the large cerebral ventricle. There is consequently in this place, about the centre of the ence- phalon between the cerebrum and cerebellum, a point where the ex- ternal face of the cerebrum is continuous anteriorly and posteriorly (1) Portal, Sur une hydropsie particuliere des ventricules lateraux du cerveau et sur lacloison qui les separe; in the Mem., de Paris, 1770, p. 240. (2) Monro, Onthe brain, Edinburgh, 1793, ch. 1. (3) Vicq-dAzyr, in the Mem. de Paris, p. 539. OF THE NERVOUS SYSTEM. 463 with the internal by means of the third ventricle, and from before back- ward by the aqueduct of Sylvius. d. Lateral ventricles. § 1781. The lateral, anterior, or large ventricles (ven. cerebri late- rales, s. anteriores, s. magni, s. tricornes),(l) are situated in each hemisphere, on the sides of the corpus callosum, the fornix and the septum. They have an irregular are generally oblong form, being arranged so that their greatest length extends from before backward. Above they do not pass beyond the corpus callosum, and that part of the hemispheres into which the body extends. They form their roof, which must not be described as a separate and distinct part from the rest of the cerebral substance. We may distinguish in it a middle part, and horns or curves (cornua). The middle part proceeds directly from behind forward, and from above downward. It is continued inward by the septum lucidum and the corpus callosum, outward by the corpus striatum. Its floor forms most of the fornix. 1. Anterior horn. § 1782. The anterior horn is the smallest. It goes outward and downward. It is convex forward, and concave backward. It is situated between the anterior wall of the ventricle, and the anterior extremity of the corpus striatum. 2. Posterior horn. § 1783. The posterior horn, and the inferior or descending horn, are detached from the posterior extremity of the central part. _ The posterior horn, the digital depression (fovea digitata), termi- nates imperceptibly in a blunt point, goes rather directly backward, although it inclines also a little outward, and extends almost to about an inch from the posterior extremity of the hemisphere: its length, however, varies much. The internal wall, and always that alone, presents in its inside a considerable eminence, called the digital eminence, the spur, the nail, the pes hippocampi minor (eminentia digitalis, calcar, unguis).(2) This eminence is very.constant. We have always found it in the numerous brains we have dissected. Wenzel, out of fifty-one subjects (1) Haase, De ventriculis cerebri tricornibus, Leipsic, 1789.—Rudolphi, De ven- triculis cerebri Gripswald, 1796. (2) Morand, Obs. anat. sur quelques parties du cerveau; in the Mem. de 1 aris, 1744, p. 430. 464 DESCRIPTIVE ANATOMY. dissected for this purpose, found only three in whom it was deficient on both sides, and two where it appeared on one side only.(l) This part bulges a little at its centre, and terminates posteriorly in a rounded extremity, which gradually becomes thinner. It is very con- stant in respect to its existence and situation: but its form and volume differ considerably, even in the two hemispheres of the same cerebrum. Its form is sometimes narrow and elongated, and sometimes broader. It is generally smooth; but it sometimes presents several transverse grooves, especially posteriorly, or is divided by a longitudinal groove into two halves, the upper of which is generally the larger. Its size is usually in direct ratio with the development of the poste- rior horn. But there are exceptions to this rule, for a very small horn often incloses a very large eminence, while another which is very large may contain one which is hardly perceptible. The structure of this eminence. is generally homogeneous. It is composed of one circumvolution and a half: a small triangular groove arises from the bottom of one of the cavities between two adjacent hemispheres, on the inner face of the posterior cerebral lobe ; its summit is turned upwards, and its medullary substance is conti- nuous with that of the inner face of the posterior horn. Its gray sub- stance is blended with a layer of cortical substance, situated directly below the white substance which covers the internal face of the poste- rior horn, and forms with this latter the inner layer of the pes hippo- campi minor. The medullary layer of this eminence is continuous upward with the white substance of the circumvolution above, as the gray substance also is continuous with the gray substance of the cir- cumvolution which follows it. This arrangement is easily recognized when we cut the pes hippo- campi minor transversely. There is then a resemblance in regard to form between the external circumvolutions and the pes hippocampi minor: this disappears or at least becomes smaller when the pia-mater is removed.(2) 3. Descending horn. § 1784. The descending or lateral horn, the largest of the three horns of the lateral ventricle, is convex outward and concave inward. It goes downward and forward in the external face of the cerebral peduncle, and occupies the lower, inner and anterior part of the middle lobe ; but it does not extend to its extremity, for it terminates half an inch behind it. On its lower face are two large eminences, the cornu Ammonis and the corpus fimbriatum. (1) Loc. cit., p. 144-145. (2) Wenzel, loc. cit., p. 146. OF THE NERVOUS SYSTEM. 465 The cornu Ammonis or pes hippocampi (cornu Ammonis, s. arietis, s. pes hippocampi, protubcrantia cylindrica, Ch.) is convex externally and concave internally, and rests on the lower face of the descending horn. It gradually becomes broader and higher backward than for- ward. Its anterior extremity, which is also that of-the descending horn of the lateral ventricle and is considerably broad, curves inward and usually but not always presents from two to five longitudinal notches. The loose face of the cornu Ammonis is medullary, and longitudinal fibres are often very distinct in this layer of white sub- stance, which is otherwise so thin that the gray substance which forms most of the protuberance is easily distinguished. Sometimes, but rarely, we find a second eminence, which varies in length, at the side of and behind the cornu Ammonis so that it seems divided into two parts situated one above the other. This eminence is termed the collateral eminence of Meckel (eminentia collateralis Meckelii), and seems to arise from suspended development. On the inner and concave side of the cornu Ammonis is a narrow falciform medullary projection, which is perfectly parallel to this side, but less broad than it, and terminates in an inner loose and sharp edge on which the large choroid plexus rests. This is termed the corpus fimbriatum (tania, s. fimbria). This body ceases about an inch before the large cornu Ammonis, and terminates imperceptibly in a circum- volution of the cerebrum. At the side of the corpus fimbriatum, but farther inward and back- ward, consequently a little covered by it, but situated out of the de- scending horn, is another analogous and shorter body of gray substance which exists in the depression between it and the inner descending edge of the large lateral horn : this is the fascia dentata. The loose edge of this small eminence is divided from above down- ward by numerous transverse incisions or folds into about twelve or fourteen small segments, which give it a waved appearance; these disappear on removing the pia-mater. A transverse.incision across the parts within the descending horn shows that the cornu Ammonis is covered on its upper and lower faces by a medullary layer, which terminates above in the corpus fimbria- tum, and which penetrates farther inward below and is reflected in the medullary substance of the lower face of the horn. Next to this medullary layer comes another of gray substance which is much thicker, being as thick as that on the surface of the cerebrum ; this exactly covers the preceding, and is continuous with the cortical en- velop of the encephalon. The upper face, which is farther from the median line, and consequently forms the outer part of this gray layer, is the fascia dentata. The internal is continuous with the gray sub- stance of the inner face of the lower part of the posterior lobe of the cerebrum. Vol. II. 59 466 DESCRIPTIVE ANATOMY. Between this internal and this external part a thinner medullary layer is interwoven ; this enlarges above where it is loose and unat- tached. These parts are then evidently similar to the corresponding halves of two adjacent circumvolutions, between which a medullary layer penetrates instead of the pia-mater alone, and which is covered inter- nally only by a very thin medullary layer. The thin medullary layer which covers the gray substance is con- tinuous in all parts with the rest of the white substance, but that which exists before the lower face of the cornu Ammonis is always separated in every part from that opposite, which covers the upper face of the eminence and is inflected only at the upper part to go and meet it. If these adhered, this lower layer and this inner layer of gray substance of the cornu Ammonis united to the floor of the descending horn of the lateral ventricle and to the substance below, would form a complete circumvolution. The medullary envelop of the cornu Ammonis is continuous with the posterior part of the corpus callosum, and partly also with the pos- terior pillar of the fornix. The whole corpus fimbriatum passes into the latter. The lateral ventricles are inclosed and enveloped by cerebral sub- stance in most of their extent, which is uninterrupted. This is true particularly of the anterior horn and the posterior horn. On the contrary, the middle region and the lower horn are interrupted in a considerable part of their extent, since the fornix and the corpus fimbriatum are not united to the adjacent parts. From this arrange- ment it follows that the middle region communicates from above down- ward and from without inward with the third ventricle: that the descending horn is in relation with the external face of the posterior cerebral lobe, and consequently that there is between the corpus fimbri- atum and the posterior part of the optic beds, a space which forms the two sides of the large cerebral fissure, with the central part of which it is blended internally. If we then separate the edges of this space which is filled by the arachnoid membrane, and also by the pia-mater and the cellular tissue, we arrive at the descending horn of the lateral ventricle and the third ventricle without cutting the cerebral substance ; thus by slitting the roof of the descending horn from within outward, we can reflect from behind forward all the posterior part of the hemi- spheres with the corpus callosum and the fornix. II. TEXTURE. § 1785. The cerebrum is the developed and expanded anterior part of the spinal marrow. OF THE NERVOUS SYSTEM. 467 The two lateral cords of this anterior part intercross and form above the decussation, the pyramids, which project very distinctly on the lower face of the medulla oblongata. At their sides is a narrower fasciculus, the fibres of which divide below the olivary bodies into an anterior and a posterior layer, which surround these eminences, above which they again unite to enter the annular protuberance. The third fasciculus is the largest. It is situated inward and back- ward at the side of the preceding. It forms the floor of the calamus scriptorius and of the fourth ventricle, where it is covered by the gray substance. These three fasciculi, situated one above another, and separated by the gray substance and also by the transverse fibrous layers which arise from the lateral prolongations of the cerebellum, pass through the annular protuberance. They unite in front of this protuberance, and form the cerebral pe- duncle, of which the pyramids form the outer and lower side, and the two other cords the inner and upper side. The formation of the cerebral peduncle by longitudinal layers, the edges of which converge from without inward, is more evident in the lower face than in the upper, the lower and convex face of which rests on the upper and concave face of the former. We may then oppose the upper and the lower parts to each other, and call the former the base and the latter the cap (Haube), of the cerebral peduncle.(l) The three fasciculi produced by the division of each lateral anterior cord in the medulla oblongata, still continue separate in the cerebral peduncle and the cerebrum. It is most convenient to describe the middle fasciculus first, because it terminates the soonest. This fasciculus proceeds from within outward, and divides in the posterior part of the pons Variolii into two fasciculi: one. proceeds below the black substance of the cerebral peduncle ; the other, termed the knot,(2) goes upward, is seen externally between the anterior and middle prolongations of the cerebellum, and proceeding along the outer face of the former, goes obliquely to the posterior tubercula quadrige- mina. It divides at the outside of the latter into two arms; one goes forward upon the external corpus geniculatum, and into the optic bed: the other proceeds transversely inward, disappears below the tubercula quadrigemina, forms the roof of the aqueduct of Sylvius, and blends forward with the posterior commissure, backward with the middle cord which goes from the posterior tubercula quadrigemina to the large cerebral valve. The lower anterior fasciculi of the anterior cord of the spinal marrow, which correspond to the pyramids in the medulla oblongata, and (1) Reil, Archiv. fur die Physiologic, vol. ix. p. 150. (2) Reil, Archiv. fur die Physiologic, vol. ix. p. 50', 468 DESCRIPTIVE ANATOMY. which are the direct continuation of them, form the lower part of the cerebral peduncle, and go from below upward and from within outward below the optici thalami. The upper and posterior, which are larger, proceed directly towards the posterior part of the optic beds. Both unite, leave the optic bed outward and the fibres of the layer forward, which proceed from within outward, and pass above them ; at the anterior and externalside of the protuberance, these cords and fibres interlace and give rise to a kind of suture, expanding in every direction. The-external layers are reflected backward, and do not pass through the optic bed. Hence it follows, that in each of the cerebral hemispheres there is a semicircle, the concavity of which is turned toward that of the opposite side, while it is convex externally, and which like the cerebral pe- duncle is composed of layers or rings which are directed from above downward. These rings expand in every direction like the sticks of a fan. Reil terms this the corona radiata. The posterior and middle rings, which are fewer, soon go outward and backward, and form most of the posterior and middle cerebral lobes. The anterior are more numerous, first pass through the corpus striatum, and then form the larger anterior lobe of the cerebrum. The circumvolutions are formed of two strata of layers which are fitted to each other; they are united by serum effused in the ventri- cles, and may be more or less easily detached in the cadaver by com- pression, or by hardening the brain in different modes. III. WEIGHT. § 1786. The cerebrum generally weighs three pounds, apothecaries' weight. Its proportion then to the cerebellum is as 8 : 1, and to the medulla oblongata as 72 : 2, IV. CONSISTENCE. § 1787. In regard to consistence, it differs only from the annular protuberance, which is much harder. CHAPTER III. ENVELOPS OP THE CENTRAL PART OF THE NERVOUS SYSTEM. § 1788. The central part of the nervous system is, as we have already stated, (§ 176) surrounded by several superimposed mem- branes. For a long time three have been admitted, an internal, the OF THE NERVOUS SYSTEM. 469" pia-mater, a middle, the arachnoid, and an external, the dura-mater. But the ancient anatomists, and Lieutaud, Sabatier, and Chaussier among the moderns, considered the internal and middle as forming but one, called the meningeal (meningina), which is composed of two layers distinct in the vertebral column, on-the cerebellum and lower face of the cerebrum, but intimately blended in all other parts. We must admit as correct, that the two inner membranes are very intimately connected in several parts, that they must be considered as forming only one : for we cannot demonstrate in the upper and lateral parts of the surface of the cerebrum, the two layers mentioned by Chaussier, and which he says are united by a very short cellular tissue. The pia-mater is alone visible in these parts. In fact it is asserted that the arachnoid membrane extends like a bridge on the circumvolutions, while the pia-mater penetrates into these cavi- ties, and that the former membrane may be easily separated by inflation: but we have always observed in repeating this and similar experiments, that the pia-mater was raised, and not a membrane distinct and separate from it. It does not follow, however, that we must admit that the two inner meningeal membranes are the same. On the contrary, the following arguments exist against this opinion: 1st. Difference of structure. The arachnoid membrane is whitish, semitransparent, and destitute of vessels ; the pia-mater is transparent and formed entirely of blood-vessels united by cellular tissue. 2d. Difference in the arrangemement. The two membranes are entirely distinct in several parts, and the arachnoid membrane is never found except on the surface, while the pia-mater penetrates deeply, and every, where attends the surface of the cerebrum and spinal mar- row. 3d. The structure of the fetus. In the cerebrum we can easily sepa- parate the arachnoid membrane from all the encephalon. 4th. Difference of pathological changes. The arachnoid membrane becomes harder and thicker: false membranes are formed by exudation from it. The pia-mater generally only receives more blood, and con- sequently assumes a redder tint. We must admit, however, that the pia-mater in several parts, particularly internally, sometimes expert ences those changes regarded as belonging exclusively to the arach- noid membrane. As the latter blends in a single membrane with the pia-mater within the skull, so too it unites with the dura-mater in the skull and vertebral canal so intimately, that it is very difficult and almost impossible to separate them. 470 DESCRIPTIVE ANATOMY. ARTICLE FIRST. OF THE PIA-MATER. § 1789. The pia-mater (tunica cerebri vasculosa, s. propria, s. pia- mater) is a thin membrane formed of mucous tissue, in which the large vessels which go to or return from the central part of the nervous sys- tem expand. • Its unattached upper face is smooth and moistened with serum. The internal, on the contrary, presents inequalities which arise from numerous villosities, greater or less branches of vessels, which at- tach it to the surface of the brain and spinal marrow. It not only lines the external face of the central portion of the nervous system, but also penetrates in several parts within it, where it conducts those vessels which carry the blood; and receives those which take it up again. We may then divide it into external and internal. These two sections of the membrane present considerable and constant differences in dif- ferent regions of the central portion of the nervous system. I. PIA-MATER OF THE SPINAL MARROW. § 1790. The pia-mater of the spinal marrow increases very much from above downward in thickness, hardness, and solidity. It exactly envelops the spinal cord in all its extent, so that when cut across, the medullary substance rises above the surface of the incision. Its color is yellowish white. Its external face is smooth and entirely loose: it is in contact with the arachnoid membrane, from which it may be easily separated by blowing air between the two membranes. At the lower extremity of the spinal marrow, the pia-mater becomes a simple filament, which descends between the nerves of the cauda equina to the lower extremity of the spinal dura-mater, with which at is blended at its termination. Its internal part is formed by an anterior and a posterior prolonga- tion, of which -the former is larger and more apparent. These two prolongations extend from before backward and from behind forward, into the two middle fissures, and are arranged like the neurilemma as "we have already remarked (§ 160). II. PIA-MATER OF THE ENCEPHALON. § 1791. The pia-mater of the encephalon should necessarily be dis- tinguished into internal and external, from the manifest differences in its form, presented within or on the outside of the organ. OF THE NERVOUS SYSTEM. 471 a. BXTEKNAL PIA-MATEB. § 1792 .The external pia-mater of the cerebrum, the cerebellum, and spinal marrow, is intimately adapted to the surface of these three sec- tions of the central part of the nervous system, and penetrates into the greatest as well as into the smallest cavities to their bases, so that it represents exactly the external form of the parts. It does not leave the surface of the brain except in a few points. Thus in the calamus scriptorius, it passes from side to side, forming a transverse bridge sustained by a small medullary prominence, which is continuous forward at an acute angle with the pia-mater which covers the pos- terior face of the cerebellum. So too the thin layer which closes the third ventricle forward and downward before the decussation of the optic nerves, is often replaced by the pia-mater only, which extends like a bridge from one hemisphere to the other. These prolongations which penetrate into, the superficial cavities, particularly into the grooves of the cerebellum and the anfractuosities of the cerebrum, are real folds,(l) since each is composed of two layers, which are united more intimately at the entrance of the anfractuosities than in their course and at their base, which must be attributed partly to the large vessels which pass in this place to the surface of the encephalon, so that they are easily insulated from each other when these vessels are destroyed. The external pia-mater is continuous with the internal, wherever the external face of the encephalon is itself continuous with the internal, that is with that which forms the parietes of the ventricles. Thus these two membranes unite in the fourth ventricle, through the pos- terior cerebral fissure, and in the aqueduct of Sylvius, and also in the lateral ventricles by the anterior cerebral fissure. We frequently observe on the external pia-mater, rounded and gene- rally soft corpuscles, which are yellowish white, and collected in seve- ral masses; these are generally termed.the glands of Pacchioni (Gl. Pacchioniana)(2) but Bichat terms them the cerebral granulations (granulationes cerebrates). These corpuscles are situated principally along the centre of the superior longitudinal groove, especially at the orifice of the veins which enter into it. Placed on the external face of the pia-mater, they pass through the dura-mater, and even enter into the cavity of the sinus, where they are covered by the inner membrane of the venous system. They are generally arranged in several groups, but so that the different corpuscles of one must rest on a common base. They vary much in number and size ; their structure is entirely homo- geneous. As they are found particularly in the latter periods of life, as they never exist before, as they are not numerous except in per- (1) Soemmcrring, De cerebri administrationibus anatomicis, vasorumque ejus habitu; in Munchner Denkschriften for1808, p. 66, 67. (2) Pacchioni, Epist. phys. anat.; in Opp. omn., Rome, 1741, p. 125. 472 DESCRIPTIVE ANATOMY. sons often afflicted with diseases of the head, and as they are not ob- served particularly in any animal, we have reason to think them mere morbid formations resulting from the frequent rush of blood towards the brain.(l) Still in no case do they deserve to be called glands. They have no excretory canals which carry a fluid secreted by them between the dura-mater and the pia-mater, or between this latter and the encepha- lon, or even within the cerebral ventricles, as Pacchioni asserts. B. INTERNAL PIA-MATER. § 1793. The internal pia-mater differs from the external in its tex- ture and form. In fact it is thinner and of a more delicate tissue. It adheres more intimately to the parts which it lines, and is, in fact, blended with them, as are the serous membranes with the articular cartilages upon which they pass. The portion which does not cover the surface of the ventricles, gives rise to the choroid plexuses (plexus choroidei). These latter are composed essentially only of that portion of the internal pia-mater which is loose and entirely unattached in the ventricle. They form an immense number of folds which inter- cross, and are arranged in several parallel longitudinal series. They are situated on the internal pia-mater, very near its union with the external, and on the edges of the fissures by which the external and the internal faces of the brain communicate. We find them in every section of the cerebral fissure, or of the cavity of the ventricle generally. Are not the folds there observed so many marks of the prolongations of the external pia-mater, which enter into the grooves of the external face, or rather do they not result from the collapse of the choroid plex- uses after the early periods of life, when they are larger and are situ- ated in the cavities of the encephalon, whioh are much more exten- sive ?(2) The branches of the veins from the inner face of the cerebral sub- stance, unite in the choroid plexuses^ and the arteries which penetrate into this same substance ramify in them. (1) Wenzel, loc. cit., cap. i. Corpusculain exteriori meninge et infra eamabs utro- que falcis latere.—Portal (Coim-sd'anat. med., vol. ii.) has already doubted the glan- dular nature of these corpuscles, and maintained they were only cellular tissue filled with adipose substance (p. 10). In regard to similar bodies found in the choroid plexuses, he says, " (p. 44) as these glandular bodies appear only in disease, are they not concretions which are formed in the cellular tissue of the pia-mater, varying in size and hardness'?" (2) Desmoulins thinks (Journal de physique, Feb. 1821) the choroid plexuses and teke arise, from the fact that the internal pia-mater, after deposing concentric layers of white fibres, finally contracts. From this contraction or obliteration, result the concave internal surfaces of the folded membrane of the hemispheres, and the for- mation of the white and solid nucleus known as the oval centre. Tiedemann has already expressed, with slight modifications, the same opinion as Meckel. Desmou- lins thinks that the membrane of the hemispheres gradually folds to produce the circumvolutions, and that the pia-mater contracts proportionally in the cavity of the ventricles. He admits, consequently, the correctness of Gall's process for unfolding OF THE NERVOUS SYSTEM. 473 We also find there some corpuscles corresponding to the glands of Pacchioni of the external pia-mater, in the same cases as the latter, and most generally at the same time as they. Another very common pathological change of the choroid plexuses, is the occurrence of serous cysts, which are there accidentally deve- loped. I. CHOROID PLEXUS OF THE FOURTH VENTRICLE. § 1794. The choroidplexus of the fourth ventricle (plexus choroideus ventriculi quarti) begins on each side at the side and on the lower face of the root of the fourth lobe of the cerebellum, and is situated between it, the anterior edge of the monticule, the facial, the auditory, the glosso-pharyngeal, the pneumo-gastric, and the accessory nerves. Thence itgoes transversely on the anterior partof the calamus scriptorius directly below the monticule, between it and the restiform body, and approaches that of the opposite side. The two plexuses united by a narrow band of the pia-mater then divide each into an anterior and a posterior branch. The posterior branches ascend in the posterior groove of the cerebellum, along the anterior part of the internal face of the monticule, become pointed, blend together, and terminate at the upper extremity of the uvula. The anterior, which are shorter, approach each other from be/ore backward, and are blended together on the nodule of Malacarne. This plexus receives from below upward the ramifications of the basilar and vertebral arteries and from above downward, and also on the sides those of the veins which arise from the inner face of the cere- bellum. The glands of Pacchioni are perhaps more common in this part than in the choroid plexuses of the cerebrum. II. CHOROID PLEXUSES OF THE CEREBRUM. § 1795. The internal pia-mater of the cerebrum begins at the large cerebral fissure. It forms a layer which is much broader in the centre than on the sides, but more folded, on the contrary, on the sides than in the centre, the brain, and thus explains the nature of what the latter terms the mucous neuri- lemma of agglutination of the internal surfaces, saying that it is the residuum of the pia-mater, which sometimes becoming permeable to the blood, can re-establish in greater or less portions, the primitive liberty of the internal surfaces. We only men- tion this assertion, without disputing it, as it seems easy to do with advantage. It is connected with another opinion of Dcsmoulins, that the development of the intellec- tual faculties is in direct ratio with that presented by the surface of the folded mem- brane of the hemispheres, consequently in a ratio with the number and depth of the circumvolutions. (Sur le rapport le plus probable entre V organization du cerveau et ses fonctions, in the Journ. compl, desde mid. vol. xiii. p. 206). F. T. Vol. II. 60 474 DESCRIPTIVE ANATOMY. It goes inward and forward from the posterior edge of the corpus callosum, the internal face of the posterior lobes, the cerebral peduncles, the tubercula quadrigemina, and from the middle anterior portion of the cerebellum, is continuous on one side with the external pia-mater which covers these parts, and envelops on the other the pineal gland, and proceeds forward and inward under the posterior edge of the corpus callosum and of the fornix. It thus forms a triangular layer, the base of which looks backward and the summit forward. The internal face of this layer is united by its lower part with the upper face of the optic bed, and by its upper with the lower face of the fornix. Hence these faces are connected so intimately, except at the lower part, for the space of about two lines deep and one high, that the third ventricle is perfectly closed at its upper part, and is separated outward from the two lateral ventricles. This portion of the internal pia-mater may be termed the choroid web (tela choroidea, Vicq-d'Azyr.) It is continuous outward and backward with the choroid plexuses of the lateral ventricles. These plexuses which arise from the opening through which the two lateral ventricles communicate, proceed from behind forward and from within outward on the lower face of the centre of each ventricle, and afterward descend from behind forward in the lateral horn, on the corpus fimbriatum and the cornu Ammonis. A slight fold attaches them in all their course to the lateral edges and the anterior edge of the fornix and the corpus fimbriatum which is detached from it. Their form then exactly represents that of the descending horn, into which they penetrate to its anterior extremity, and the lower face of which they cover in great part. At their anterior extremity, that is, at their origin, in the communication open between the two lateral ventricles they are very narrow, but they gradually enlarge from before back- ward, and finally become considerably broad. Their breadth, however, does not increase from their origin to the lower extremity of the lateral horn. Their broadest and thickest part corresponds to about their centre, that is, where instead of internal they become external. There, in fact, they form a kind of button, which has been remarked by Vicq-d'Azyr,(l) and has been admitted by Wenzel.(2) The vessels, particularly the veins, are there much larger and also more tortuous than in the rest of the plexus: the internal pia- mater which unites them also forms there more numerous folds. (1) Loc. cit. p. 541. " The region in which the plexus is thickest, is that where it curves backward, at the level of the posterior prolongations of the lateral ventricles." Vicq. d'Azyr has also described the structure of the choroid plexus, and this figure of it resembles that given by Wenzel. (2) Loc. cit. n. ix. Animadv. peculiarem quand. proprietatem plexus choroidei, etc. Proprietas quedam ratione morborum, ut nobis videtur, notatu digna ab aucto- ribus pratervisa. OF THE NERVOUS SYSTEM. 475 The choroid plexus also, when otherwise perfectly healthy, is rather more disposed in this place to morbid changes, such as thickening, opacity, and more or less abundant granulations which vary in form and size, and which probably arise, at least in part, in the folds of the plexus, but which are also developed on the surface of these folds.(l) The greater development of the choroid plexus in this place depends particularly, and even solely, on the origin at that part of the pos- terior horn, which receives no special choroid plexus. Besides this common choroid plexus, we sometimes find in the lateral ventricles a smaller and anterior plexus, which is situated on the corpora striata. This communicates with the veins which proceed between the anterior and posterior cerebral ganglions, and with those which arise from these eminences.(2) On the contrary, we constantly find two small choroid plexuses, those of the third ventricle, which extend from before backward, from the anterior extremity of the lateral choroid flexus to the circum- ference of the pineal gland, separate from each other in this course, are attached to the lower face of the tela choroidea, gradually increase in size and receive the vessels of the third and fourth ventricle. All the sections of the general ventricle of the encephalon include then the choroid plexuses which communicate by the internal pia- mater and the cerebral vessels, and which are most generally found more or less precisely in the same state in the same subject. ARTICLE SECOND. OF THE ARACHNOID MEMBRANE. § 1796. The arachnoid membrane (mem. arachnoidea, s. mucosa), the second envelop of the spinal marrow and encephalon, is delicate, thin, semitransparent, whitish, and perfectly homogenous in structure. We have not as yet been able to discover in it either vessels or nerves. It is very distant from the preceding in the vertebral column and in the lower part of the skull. It surrounds the spinal marrow, like a sac which is much larger than this cord, which is attached to it only by some distinct filaments of cellular tissue. It begins at the lower extremity of the vertebral co- lumn, and gives a general envelop which covers the origin of all the nerves in the spinal canal until they leave this cavity. We may then separate it very much from the spinal marrow by blowing in air, or by any analogous process. (1) Vicq-d'Azyr has also made this remark: he expresses himself very strongly against the glandular nature of this body. (2) Vicq. oVAzyr, p. 540. 476 DESCRIPTIVE ANATOMY It is also intimately united with the dura-mater in the place where this membrane forms narrow canals which receive the nerves before they leave the vertebral canal, and where the shps of the ligamentum dentatum are attached to its surface. It proceeds from the spinal marrow to the encephalon, enlarging very much. It adheres to the lower and middle portions of the cere- brum, and also to the posterior part of the cerebellum- and to the lower face of the medulla oblongata very loosely and by long distinct bands of cellular substance, passes like a bridge from the spinal marrow to the posterior part of the cerebellum, and from one lobe of the latter organ to another, consequently fills the space between them, closes the common cerebral fissure posteriorly, below and on the sides, is re- flected from the annular protuberance on the floor of the third ventricle towards the decussation of the optic nerves, with which it is intimately united, as also with the nerve itself; then arrives at the lower face of the anterior lobes, and connects both these two lobes and also the central part of the posterior, on which it extends on each side on leaving the annular protuberance. It also forms a bridge which proceeds on the fissure of Sylvius, between the posterior and anterior lobes. All the veins and nerves which come from the encephalon, and also the arteries which go to it, are covered by prolongations of the arach- noid membrane until they emerge from, or enter the cranium. But the places we have mentioned are the only ones where it is so slightly attached to the subjacent pia-mater that it may be considered a separate and distinct membrane. In every other part, even where it passes from one circumvolution to another, proceeding over the anfrac- tuosities, it is so intimately united with the pia-mater that, however carefully we may attempt to raise it, particularly by the common mode, that of insufflation, this membrane is always detached with it from the surface of the cerebrum. § 1797. From the idea generally formed of it, the arachnoid mem- brane forms only a single layer, which covers the outer face of the spinal marrow and encephalon; but it rarely extends farther, and has a more complex course. In fact, it is reflected from all the places through which the nerves and vessels pass upon the dura-mater, the internal face of which it covers, and also penetrates within the ence- phalon through the large cerebral fissure. The first proposition is perfectly demonstrated either by dissecting the arachnoid membrane and the dura-mater in the normal and abnor- mal state, or by analogy. The brilliant and smooth appearance of the inner face of the dura-mater favors it, since the parietes of the pectoral cavity, the abdominal cavity, and the pericardium, depend for this character on the presence of serous membranes, which after directly covering the surfaces of the organs,leave them to be reflected externally. This external layer of the arachnoid membrane is fitted to the inner face of a fibrous membrane like the serous tunic of the pericardium, the peritoneum and the two pleura in many places, the synovial OF THE NERVOUS SYSTEM. 477 membranes, &c. That the shining appearance of the inner face of the dura-mater does not depend on this membrane is proved by the fact that the interior of the canals it furnishes to the nerves out of the arachnoid sac is very uneven. When we examine the dura-mater either from without inward or from within outward, although all the external layers seem formed of fibres and of a very complex texture, we may always detach to a greater or less extent an internal layer, which, is thinner than the others, and has not a fibrous appearance : this may be easily proved in the early periods of fife. This internal layer is sometimes separated from the others by a congestion of pus .between it and the dura- mater it lines. (1) The arachnoid membrane not only covers the surface of the cere- brum, but also penetrates within this organ. The place where it enters is between the anterior extremity of the upper face of the cerebellum and the corpus callosum, in the place where the portion of this mem- brane which covers the cerebrum unites to that of the cerebellum, without forming however a simple sac. The connection seems on the contrary to be interrupted by a rounded opening in this place, in the circumference of which the glands of Pacchioni are generally situated in old persons, and which give passage to the veins which arise from the ventricles of the cerebrum : but this opening is the commencement of the inner part of the arachnoid membrane, for it leads to a canal which passes on the pineal gland and extends from behind forward on and between the anterior edges of the optic beds, and below the fornix to the anterior extremity of the third ventricle. This canal surrounds the venous trunks which return from the middle and lateral ventricles. It is every where perforated for the branches which go to it. Its external face is connected with the adjacent parts of the cerebrum only by slight adhesions, and is also attached to the veins by distinct fila- ments. It terminates at the foramen of Monro. Thence it continues, uniting intimately to the pia-mater, with the internal membrane of the ventricles, which in the normal state is much thinner than it, but. which in the pathological state, in inflammation and hydrocephalus, thickens, becomes opaque, whitish,.so that then it is still nearer to it and to the outer part of the arachnoid membrane. The arachnoid membrane most resembles the serous membranes in its form, texture, secretions, its anatomical relations with the encepha- lon and spinal marrow and with the dura-mater, and in its diseases, as thickening, increase of its secretory power, whence result congestions of serum, adhesions between contiguous surfaces or the formation of accidental membranes. It is almost exactly like them. Gordon then is wrong in supposing that the analogy between its texture and that of the serous membranes is not proved, and that we must consider it as a separate organic tissue different from all others. (1) Vicq-d'Azyr, in the Mim.de Paris, 1781, p. 497, 478 DESCRIPTIVE ANATOMY. All the facts we have adduced authorize us to arrange the arachnoid membrane and the dura-mater in the class of sero-fibrous membranes. It however is important to remark, that these two membranes are very intimately united with each other, and that the difference observed between them in the adult does not exist in the fetus, where we find, instead of the dura-mater, only a single thin transparent membrane destitute of fibres, and having all the characters of a serous membrane. But there we evidently have a new fact in support of our opinion in regard to the nature of the arachnoid membrane. At first only the inner layer of the dura-mater is formed; afterward it is changed exter- nally into a fibrous tissue, or this tissue is developed between it and the bones. ARTICLE THIRD. OF THE DURA-MATER. § 1798. The dura-mater (dura meninx), a fibrous membrane, is the most external envelop of the spinal marrow and encephalon. It forms a sac closed in every part, which has the form of these two organs. Its external face looks to the inner face of the spinal canal and the skull; the internal is turned towards the outer face of the arachnoid membrane. This latter is smooth in every part. The vessels of the spinal portion of the dura-mater arise from the vertebral, the intercostal, the lumbar, and the sacral arteries: those of the cranial portion from the internal maxillary artery. I. SPINAL DURA-MATER. § 1799. The spinal portion of the dura-mater differs in several res- pects from the cephalic. It forms a very long canal, terminated at its lower part in a cul-de-sac, which occupies the whole spinal canal, gradually enlarges from above downward, but terminates in a blunt summit at the lower extremity of the sacrum. This sac is narrower than the spinal canal, to which it adheres, principally on the sides and posteriorly, only by a very loose cellular tissue, which contains, espe- cially at its lower part, an abundance of substance similar to fat, of a reddish yellow color. It is united anteriorly to the posterior ligamen- tous envelop of the vertebral column much more intimately. The two faces of the spinal dura-mater are smooth. It is not only longer, but much broader than the spinal marrow. Outwardly it gives to each spinal nerve a sheath which accompanies it to beyond the in- tervertebral foramen, enlarges a little in this place on account of the OF THE NERVOUS SYSTEM. 479 ganglion of the posterior root, and gradually terminates in the external cellular tunic of the nerve. It is very evidently formed of longitudinal fibres which are more re- gular but less distinct than those of the cranial portion, and it is thinner than the cerebral dura-mater. II. CEREBRAL DURA-MATER. § 1800. The portion of the dura-mater which corresponds to the encephalon, is attached to the internal face of the skull by numerous small ramifications of vessels which extend from it to the bones : its external face is corrugated. It adheres very strongly to the skull at its lower part: its lateral and upper faces are connected with the su- tures more intimately than with the other parts of the cranium. The arteries and veins proceed on its external face in the slight de- pressions which they exactly fill, and also project above its surface. There are but few fibres visible on its external face. The centre of its upper part presents some which are irregular, flat, have a transverse direction, and intercross. We distinguish through the dura-mater the vessels of the pia-mater, and also the elevations and depressions of the external face of the en- cephalon. The inner part of its upper face presents at intervals along the large longitudinal sinus, and some fines from this venous canal, some broad and some narrow openings which are seen principally in the region of the sinciput. Internally it presents in all its extent a fibrous texture much more distinct than that of the spinal portion. We may divide the fibres seen there into two layers. The external follow a longitudinal direction for all the extent of the membrane, and are arranged very compactly; the internal are placed on the preceding, to which they generally adhere but slightly, and are much more separated from each other ; they are particularly apparent and very numerous at the upper part, while they gradually disappear at the lower. Although the dura-mater is usually considered as divided into seve- ral layers, between which the venous sinuses proceed, and is composed of two folds, and although we can in fact divide it into two layers, still this separation is purely artificial, always excepting the serous layer ; we can never form them except by destroying the tissue, and we may at pleasure diminish or increase the number of the layers. The cerebral dura-mater principally differs in its arrangement from the spinal by the following characters : 1st. It does not form a single sac but a cavity which is divided into several partitions by different prolongations which it sends inward. These prolongations are in direct ratio with the development of the encephalon, as they divide the cavity of the skull into compartments 480 DESCRIPTIVE ANATOMY destined to receive the principal portions of this organ. We number three of them, a transverse and two longitudinal. They have this in common, that at their external edge, which is connected with the in- ternal face of the skull, they divide into three layers, the external of which continues to follow the direction of the common sac of the dura- mater, while the two internal converge inward and are soon blended in a single layer which terminates in a loose internal edge. Besides the external, edges, the internal edges, and the faces of these prolonga- tions, are continuous with each other, and they may be described under the common name of the crucial prolongation of the dura-mater (pro- cessus dura matris cruciatus), the branches of which extend to the right and left, upward and downward, and forward and backward. The transverse prolongation is the tentorium of the cerebellum, the transverse septum (tentorium cerebelli). Its form is nearly semicir- cular. Its posterior,convex, and internal edge, which is thelongest,arises from the transverse branches of the cruciform ridge of the occipital bone, and from the upper edge of the petrous portion of the temporal bone. The anterior which is much smaller and concave, is loose : it forms the posterior and lateral parts of an opening which is closed anteriorly by the basilar portion of the spheno-occipital bone, and is attached on each side by two separate points to the anterior and posterior clinoid pro- cesses, between which it covers on both sides the-sella turcica. The cerebellum and the medulla oblongata are situated under this tentorium, which- completely separates from the rest of the skull, excepting only from the anterior opening, the posterior and inferior part destined to receive it. The central portion of the tentorium is continuous upward and downward with the two longitudinal prolongations, the falx of the ce- rebrum, and the falx of the cerebellum, both of which are c. Third ventricle, d. Lateral ventricles, 1. Anterior horn, 2. Posterior horn, 3. Descending horn, H. Texture, III. Weight,* IV. Consistence, Chap. III. Envelops of the brain Art. i. Pia-mater, I. Of the spinal marrow, II. Of the encephalon, a. External pia-mater, &. Internal pia-mater, i. Choroid plexus of the fourth ventricle, ii. Choroid plexuses of the cerebrum, Art. ii. Arachnoid membrane, Art. hi. Dura-mater, I. Spinal dura-mater, II. Cerebral dura-mater, III. Ligamentum denticulatum, Chap. IV. Periodical differences of the nervous system I. Substance, i. Spinal marrow, n. Medulla oblongata, hi. Cerebellum, iv. Cerebrum, v. Envelops, Chap. V. Motions of the centre of the nervous system, Chap. VI. 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