eR ue er me Tass SMCCRR ES 3 SN x ~ cae nies oe Ny a Ss Oy y t YU es & ”, i) 2 1869 THE LIBRARY 7 “ks oa 1 a i - e 7 7 “3? Ay OW REICH - 2 4 ef SO ert | w ore ad Pe, Be ji IE PONIMOre Sa = ay i= a we ¢ a @ > i ae a 7 date a OIA e € Des. ? ee i [Ginn Mites ee RS ] vn Tes &* ©€ Ghoti Antericat, Misum ie ON A OY Ore) Tie Aly he Gane ease BY JACOB: REIGHARD Professor of Zoology in the University of Michigan AND H. S. JENNINGS Instructor in Zoology in the University of Michigan WITH ONE HUNDRED AND SEVENTY-THREE ORIGINAL FIGURES DRAWN BY LOUISE BURRIDGE JENNINGS SECOND EDITION, REVISED This is a facsimile reproduction of the American Museum of Natural History Library’s copy. NEW YORK HENRY HOLT AND COMPANY 1902 aft ranottauborce silent a ‘Tome imnieyt Wey: iene | a ANATOMY OF THE CAT PQ aye hy BY JACOB REIGHARD Professor of Zoology in the University of Michigan AND H. S. JENNINGS Instructor in Zoology in the University of Michigan WITH ONE HUNDRED AND SEVENTY-THREE ORIGINAL FIGURES DRAWN BY LOUISE BURRIDGE JENNINGS SECOND EDITION, REVISED REOeEs NEW YORK HENRY HOLT AND COMPANY 1902 Copyright, rgor1, BY HENRY HOLT & CO. ROBERT DRUMMONT PRINTER, NEW YORK. PR Aees ALTHOUGH the cat has long been in common use for the practical study of mammalian anatomy, a clear, correct, not too voluminous account of its structure, such as should be in the hands of students in the laboratory, has remained a desideratum. A number of works have been published on the cat, some of them of much value, yet there is none which ‘ulfils exactly the conditions mentioned. The books which ‘ave appeared on this subject are the following: 1. Strauss-Durckheim, H. Anatomie descriptive et com- parative du Chat. 2 vols. Paris, 1845. 2. Mivart, St. George. The Cat: an Introduction to the Study of Back-boned Animals, especially Mammals. New Vor loolr 3. Wilder, Burt G., and Gage, Simon H. Anatomical Technology as applied to the Domestic Cat. New York, 1882. 4. Gorham, PF. P.; and) Tower, Ri» W!) A laboratory Guide for the Dissection of the Cat. New York, 1895. 5. Jayne, H. Mammalian Anatomy. Vol. I. Phila- delphia, 1898. The first of these works treats only of the muscles and bones, and is not available for American students. Its excel- lent plates (or Williams’s outline reproductions of the same) should be in every laboratory. The second book named is written in such general terms that its descriptions are not readily applicable to the actual structures found in the dissection of the cat, and experience has shown that it is not fitted for a laboratory handbook. It contains, in addition to a general account of the anatomy of the cat, also a discussion of its embryology, psychology, palzontology, and classification. lll iv PREFACE. The book by Wilder and Gage professedly uses the cat as a means of illustrating technical methods and a special system of nomenclature. While of much value in many ways, it does not undertake to give a complete account of the anatomy oi the animal. The fourth work is a brief laboratory guide. The elaborate treatise by Jayne, now in course of publica- tion, is a monumental work, which will be invaluable for refer- ence, but is too voluminous to place in the hands of students. At present only the volume on the bones has been published. As appears from the above brief characterization, none of these books gives a complete description of the anatomy of the cat in moderate volume and without extraneous matter. This is what the present work aims to do. In the year 1891-92, Professor Keighard prepared a partial account of the anatomy of the cat, which has since been in use, in typewritten form, in University of Michigan classes. It has been used also at the Universities of Illinois, Nebraska, and West Virginia, and in Dartmouth College, and has proven so useful for college work in Mammalian Anatomy that it was decided to complete it and prepare it for publication. This has been done by Dr. Jennings. The figures, which are throughout original, are direct re- productions of ink drawings, made under the direction of Dr. Jennings by Mrs. Jennings. The book is limited to a description of the normal anatomy of the cat. The direct linear action of each muscle taken alone has been given in the description of muscles; other matters belonging to the realm of physiology, as well as all histological matter, have been excluded. It was felt that the monumental work of Jayne on the anatomy of the cat, now in course of publication, forms the best repository for a description of varia- tions and abnormalities, so that these have been mentioned in the present volume only when they are so frequent as to be of much practical importance. Except where the contrary is stated, the descriptions are based throughout on our own dissections and observations and are in no sense a comrilation. For this reason we have not PREFACE. v thought it necessary to collect the scattered references to the anatomy of the cat that may occur in the literature. A collection of such references may be found in Wilder and Gage’s Anatomical Technology. In addition to the works already referred to, we have of course made use of the standard works on human and veterinary anatomy. Among these should be mentioned as especially useful the Axatomize des Hundes by Ellenberger and Baum. Other publications which have been of service in the preparation of the work are Windle and Parson’s paper Ox the Myology of the Terrestrial Carntv- ora, in the Proceedings of the Zoological Society of London for 1897 and 1898, T. B. Stowell’s papers on the nervous system of the cat in the Proceedings of the American Philo- sophical Society (1881, 1886, 1888) and in the Journal of Comparative Neurology (vol. I.), and F. Clasen’s Die Aluskelu und Nerven des proximalen Abschnitts der vorderen Extremt- tat der Katze, in Nova Acta der Ks]. Leop-Carol. Deutschen Akademie der Naturforscher, Bd. 64. Nomenclature.—TYhe question of nomenclature has been one of difficulty. What is desired is a wuzform set of anatomical names,—a system that shall be generally used by anatomists. At present the greatest diversity prevails as to the names to be applied to the different structures of the body. The only set of terms which at the present time seems to have any chance of general acceptance is that proposed by the German Anatomical Society at their meeting in Basel in 1895, and generally designated by the abbreviation BNA. This system has therefore been adopted, in its main features, for use in the present work. It seems impossible at the present time, however, to impose any one set of terms absolutely upon anatomists of all nations, and we have felt it necessary to use for certain familiar structures, in place of the BNA terms, names that have come to have a fixed place in English anatomy, and may almost be considered component parts of the English language. The German anatomists have expressly recognized the fact that this would be to a greater or less degree necessary among anatomists of different nations, and have characterized their list as for the present tentative, and vi PREFACE. capable of farther development. The only purpose of a name is that it shall furnish a key to a common understanding ; where the BNA name does not furnish such a key to English readers, and where there is a term in established English usage that does serve this purpose and seems unlikely to be sup- planted, we have used the latter. But we have endeavored to make the number of these exceptions as small as possible, and in such cases we have usually cited at the same time the term proposed by the German society, followed by the abbreviation BNA. When, on the other hand, we have adopted a BNA term for which there is also a commonly used English equiva- lent, the latter has likewise usually been cited in parenthesis. In deciding whether or not to use in a given case the BNA term many difficult cases arose. Will the common English name zzuominate bone (os innominatum) be replaced by the BNA term os cox@ or coxal bone? We have held this to be highly improbable, and have therefore used the term zxom- nate bone, merely citing os cor@ (BNA) as a synonym. In the same way we have used centrum as a designation of a part ofa vertebra, in place of corpus (BNA); premaxillary bone or pre- maxilla in place of os tncistvum (BNA); malar bone in place of os sygomaticum (BNA); trapezoid as a name of one of the bones of the carpus, in place of os multangulum minus (BNA), etc. In other cases where it has seemed probable that the BNA term would come into common use, though now un- familiar, this and the more common English expression are both used or used alternatively; such has been the case, for example, with the Gasserian ganglion or semilunar ganglion (BNA). In naming the cerebral sulci and gyri the system in use for man is not well fitted for bringing out the plan of those in the brain of the cat, so that it was necessary to reject the BNA names for these structures. As to the use of the Latin terms and their equivalents in English form, we have made a practice of employing in the text sometimes one, sometimes the other; this has the advan- tage of giving variety, and of impressing the interchangeability of the Latin and English forms on the mind of the student. Where a given structure is called by two equally well-known PREFACE. vii names, we have used both, holding that the student should become familiar with each and recognize their identity of meaning. In general we have maintained the principle that the primary purpose of such a work as the present is not to illus- trate or defend any particular system of nomenclature, but to aid in obtaining a knowledge of the structures themselves. With this end in view, we have used such terms as would in our judgment best subserve this purpose, making the BNA system, as the one most likely to prevail, our basis. In apply- ing the system we have had to keep in mind a number of sometimes conflicting principles. In some cases the judgment of other anatomists will doubtless differ from our own; but this we feel to be inevitable. The matter of an absolutely uniform nomenclature is not ripe for settlement at the present time. Some further explanation is needed in regard to the topo- graphical terms, or terms of direction, used in the present work. We have adopted the BNA terms in this matter also. The terms superior, inferior, anterior, and postertor have been avoided, as these terms do not convey the same meaning in the case of the cat as they do in man, owing to the difference in the posture of the body. In place of these terms are used dorsal and ventral, cranial and caudal. As terms of direction these, of course, must have an absolutely fixed meaning, sig- nifying always the same direction without necessary reference to any given structure. For example, cvamzal means not merely toward the cranzum, but refers to the direction which is indicated by movement along a line from the middle of the body, toward the cranium; after the head or cranium is reached, the term still continues in force for structures even beyond the cranium. Thus the tip of the nose is considered to be craniad of the cranium itself. Lateral signifies away from the middle plane; medzal toward it. Juner and outer or internal and external are used only with reference to the struc- ture of separate organs, not with reference to the median plane of the body. In describing the limbs the convexity of the joint (the elbow or knee) is considered as dorsal, the concavity being therefore Vili PREFACE. ventral. J/edial refers to that side of the limb which in the normal position is toward the middle of the body; /atera/ to the outer side. Terms of direction which are derived only from the structure of the limb itself are in some cases more conven- ient than the usual ones. In the fore limbs the terms radzal (referring to the side on which the radius lies) and w/nar (referring to the side on which the ulna lies) are used; in the hind limbs the terms 7z6za/ and fibular are used in a similar manner. JD/stal means toward the free end of a limb or other projecting structure; proximal, toward the attached end. For all these terms an adverbial form ending in -ad has been employed. Experience has shown this to be very useful in practice, and while not expressly recommended by the BNA, it is not condemned. Terms ending in -a/ are therefore adjectives; those ending in -ad are adverbs. In compounding these terms of direction, the hyphen has been omitted in accordance with the usage recommended by the Standard Dictionary. Thus dorsoventral is written in place of dorso-ventral, etc. The student will perhaps be assisted in understanding these compounds if he notes that the first component always ends in -o, so that the letter 0 prac- tically serves the purpose of a hyphen in determining how the word is to be divided. In one particular the BNA nomenclature is not entirely consistent. While recommending or at least permitting the use of the general terms dorsal and ventral in place of the human fosterior and anterzor, and crantal and caudal in place of superior and inferior, it retains the words anterior, posterior, superior, and inferior as parts of the names of definite organs. For example, we have the muscle serratus anterior in place of serratus ventralis; serratus posterior infertor in place of serratus dorsalis caudalis. This is very unfortunate, from a comparative standpoint, but we have felt it necessary to retain the BNA terms in order that the structures of the cat may receive the same names as the corresponding structures of man. In the matter of orthography we have endeavored to follow the best English anatomical usage, as exemplified in Gray’s PREFACE. ix Human Anatomy,—therefore writing peroneus in place of peroneus, pyriformis in place of piriformis, etc. The book is designed for use in the laboratory, to accom- pany the dissection and study of the structures themselves. Anatomy cannot be learned from a book alone, and no one should attempt to use the present work without at the same time carefully dissecting the cat. On the other hand, anatomy can scarcely be learned without descriptions and figures of the structures laid bare in dissection, so that this or some similar work should be in the hands of any one attempting to gain a knowledge of anatomy through the dissection of the cat. The figures have all been drawn from actual dissections, and have been carefully selected with a view to furnishing the most direct assistance to the dissector. It is hoped that no figures are lacking that are required for giving the students the necessary points of departure for an intelligent dissection of any part of the body. The fore limb is illustrated somewhat more fully than the hind limb, because it was thought that the fore limb would usually be dissected first; the hind limb will be easily dissected, with the aid of the figures given, after the experience gained in dissecting the fore limb. As the book is designed to accompany the dissection of the specimen in the laboratory, it was deemed best to give succinct specific directions for the dissection of the different systems of organs, together with suggestions as to methods of preserving and handling the material. These are included in an appen- dix. “ho: v Ay ’ ae 7 eel ; Di » i fy * 7 ij nies y i. tht Ay al LAP ; I : 7 ‘an ea a eh aa ° ; mtg i 4h 1d nel ae Ff Pike iaeg weer |) ee gh ~ hai was Pe ; i or aot oye ae ; F a yeti “ hi Pe be i Line | - al A vad - = } 4% : ¥ “ tes a) i) Pate Ans a aes 2 | Ry re! ae oe r i wn i 4 ri rt a 4, ; ny, en, at: 4 /i7a.%4 P = ao arf owe ml od we é t : = OS ee a " Lea | mh 400" hat 44 2 i Vir re i : an - io } doy ey 3 ee a w, Sire ' ‘e-., : j ; oe iy ms fs) “f= 4 i ne eeu seri thal ‘ P 1k a a — ‘ 1 ' a s P ay ay ; a). | ' roger: & 2. 1 Tea 41 , i 8 ¢_° j i" y 7% wr 6 = ai ia a be k Ate istZ ¢ (> Sega iy a _ 7 = q ire : ’ Vs 7 : = CONTENTS. PAGE HE SKELETONSOF) THE) CAD as ic7-sicis cicurcaniensrsssdatenereieotere clevevolefotare ehalanereroteate I i: he Viertebrald Column. jo Gia disaie wsvecleeue orsyerelorsreratototoaersiaietek a een ee I Shoracic: Vertebrae iss = <1 rsteis eveversys crore so acsiais oto Re a, Me Oe A I J Hino Woitotlasaoasocuodudu00 Gd0ddoG000dn hocuGoaspdooanoUeT 7 Sacral Viertebrecks SaGrumny.y.reteieuere eroreverarstareterrenst rene rekacle toner steic Ae) 1ke) CaudaluVertebrze) < yec.cre. le -.sceceusncreceiclaveb retorts stom cearteareretetete ae eioreerereyets II CervicaluiViertebree cy. .iicra e252 Eh roids Glam yarercrereresristoresctsieiel cicVen sie lercrsienoletete eke SGoon00¢ Seles 254! Atimpynntis Eien; ogqdaoucsdguognde beds couDobO RUE SOOnodOUGO0C 254 IVenUrogenttaluSystemeaaiteriec ete cvelorelsiels clelerooivelemiereitetelelrtelsttereiociersrel= 255 I. excretory Organs... ..« SHOGOdO BASSES CODD COO DOOD GOOD ORG 255 Ka dneyShaccwracisretneicee ail eleveiensicio/sisicieverereielsicveLolmclovelelerel Voie ores 255 MW rete aiersreraietekeloyenersicter nerafolel cratoreloveel skotereerstebelekelealelexctclveiereisteloiers 256 Bladder scree erereterelelrorcteraorereveroteteieverehers Bya ais elshans lolelictsfekeraienersioters 256 (SuprarenalUBodies) tjersiis cceictsmiee icra ciel sioieveleieleterercrsiseterers 257 2 GenitaluOrgansyarrelsrereteleln eteleichale eileen teveiieredeteeus forere re etetercleleiersts 257 Ame Malle srr teietershatetocieriele siete erick rioeter fs eletsyackeieerereterrers 257 féfy AKIUEVO Gosdo pols SUR ooo bau Seu nO DOC OOsOOOD DOUTO0D.ON ae 263 Muscles of the Urogenital Organs, Rectum, and Anus,.......... 268 a. Muscles Common to the Male and Female................ 268 6: Muscles; Peculiarto the) Malewaecsisiisciciscsisincieneciis cae 271 X1V CONTENTS. PAGE ¢, Muscles’ Peculiar’ to they Female! 222.5 azirine sis ste seis 272 THE CIRCULATORY: SYSTEM) «.. occ ccs stoveleletete ele oveteleteyerete/cte niclotsiereyeverseteiere 274 1 evel cart). ccc steteletevele le cteiciols @ clorelcretelenelersle ateleteleletetayeleeltel sfereheleteret terion 274 Ws AMhevArteries!sctv nos sieve oles ele = /aleloraketelat foie ie eleloieletelelerereteye tere tetretetee 280 Tr” Pulmonary Artery i.(c).0.icne siete ciate sein oie mv eiciels elerayeie Serer 280 P3had Novae Racine OOO slots ofoteholefelarste(o) aves siaie’ stots) efor tneeratoreetoters 281 A. Thoracic-Aorta and-its Branches... v2 4. aeite etree 281 GommoniCarotid “Artery. f:..7.7 sisie% s1ole de ral terete ene 283 SubclavianvArteny ice: creicieletoterer- ere adorelaleve stevens srolsielereielere 290 B. Abdominal Aorta ‘and its Branches. << 2c cers crete otaieletetetele 301 External Iliac Artery and its Branches ................ 309 MIB MUON GbE sosoosoncaeos Go OmoUb co UOndOGO Od oDo auNnOA000000 0000006 315 T., Veinssob the Peart 2 7n)vcin)<\orais = ole a1! oto)o\=Vole) stele! atelerereioierol teeters 315 2. Vena Cava Superior'and its Branches. . <:.%1..//0.0 e1e/cieicleleleiroeretete 316 Veins of the Brain:and Spinal! Cord... 62% <1: stereie sje sie jotereriee 324 3. Vena Cava Inferior and its’ Branches <2 .'0./2% 220 aie o sc 339 (1) Myelencephalon ooo ccc cet os ais os in ee sletols Sovaletsteyeteteey 344 (2) Metencephalon\ so ecirc ise «cir 22 18. ab CMD (oa Tofetole aloyerohs) < fetal Verotekel ote or eieso otovereratevelofetatel sieleretelotolorciefotere 22 LO se Unter parietal pevey soj-(ciettstabvoie cisioeiscisis siviats) « Qeieisiere cielo: « s006 1322 927) Rortal Vein testa ence seus ictal sis.sce stoisioe Gray cuateh oars loie SEA ciel coke tanevorniert ets ated 327 433. opinal’ Cord, cranial portionsem sac es.) seieec/< aren ec ce ce este Joon SEG 336 134. Section of spinal Cord ener cc ce ssiate waaiowss oho he Se sce yae co clatele aoe te 337 135. Origin of Spinal Nervésicieeisiri. cins ote oeps lee testes ToodoonD CO OCOO OE 337 136, \Canda, Equina, etc. ./. .)<:.,..45)...='s Ss sel sishe siepaietevsusier'e el elofetels, welavels toqstsiatetelate 338 XX FIG, 137s 138. 139. 140. I4I. 142. 143. 144. 145. 146. 147. 148. 149. 150. Ist. 152. 153. 154. 155; 156. 157. 158. 159. 160. 161. 162. 163. 164. 16s. 166. 167. 168, 169. 170. 171. 172. 173. LIST OF ILLUSTRATIONS. PAGE Brain, Dorsal Views 2s cieleisie.cle nicl eerie oi wisrsis s.0eisieie SIO AOU sedoonD Oo], Ye Brainsy Veritral Vive wis crcie sis s1-:eceseieraie oyeieieisloleo' sivie) sp clelelelerelefoleretehevore SEnGdO Buz Diagram Of Brains wsiers os oe 61+ « +0) 0°) s)icio i soto) ni es ole aloleretolelelstelelenerete e005 £13 GPE TMCS Was, ae hytcea es ov ehapotacs ecstasy ccegereieh a a etternestetene sve sess Sag Dorsal View of Midbrain and ’T'ween-brain................+20..-.00:> 350 Wentral <* «* ue ue COT | voi enesoxeleiny obatcbaveieraheVoiernetetencien 352 Longitudinal Section of Brain ...6 6 506.0. cere ccs she > «1 ohelseviels aielrevelelelateleye 356 Wateral: View of Brain .c 5.0 0.0.6; <,eloie)eceie, sleyersie) eye oe se) e cjerekn ee et eee ee 358 Wiagramiof Sulci and! Gyri ci... sce) $prody ‘9 *]DyAs ‘2 ‘LV dO NOLITEAS—'! “OTA THE VERTEBRAL COLUMN. 3 third of this ring is much thickened and forms the centrum or body (corpus) (4) of the vertebra. The centrum is a semi- cylinder, the plane face of which bounds the vertebral canal, while the curved surface is concave, longitudinally and is directed ventrad. The dorsal plane surface of the centrum is marked by a median longitudinal ridge on either side of which / Fic. 2,—Four?tH THORACIC VERTE- Fic. 3.—FourTH THORACIC VERTE- BRA, CRANIAL END. BRA, SIDE VIEW. a, vertebral foramen; 4, centrum; c, caudal, and d, cranial, costal demifacets; e, radix or pedicle; 7. lamina; g, transverse process; /, cranial articular facet; 7 caudal articular facet; 7, caudal articular process; 4, spinous process. 5} is an opening (nutrient foramen) for a blood-vessel. The ends are nearly plane, the caudal being slightly concave; they are harder and smoother than the other surfaces. They may be easily separated in a young specimen as thin plates of bone known as epiphyses. At the caudal end of the centrum, at its dorsolateral angle, is a smooth area on each side continuous with the surface of the epiphysis and bounded dorsolaterally by a sharp ridge of bone (c). Itis a costal demifacet. In corresponding positions at the cranial end of the centrum are two demifacets not limited by bony ridges (2). When the centra of two contiguous thoracic vertebra are placed together in the natural position the cranial costal demifacets of one together with the caudal demi- facets of the other form two costal facets (Fig. 4, ¢), one on each side, and each receives the head of a rib. The dorsal two-thirds of the vertebral ring forms the verte- bral arch which is continued dorsally into the long, bluntly pointed spinous process (Figs. 2 and 3, #) for attachment of muscles. 4 THE, SKELETON OF, THE GAT. The vertebral arch (each half of which is sometimes called a neurapophysis) rises on each side from the cranial two-thirds of the dorsolateral angle of the centrum, as a thickened por- tion, the radix or pedicle (Figs. 2 and 3, ¢), which forms the ventral half of the lateral boundary of the vertebral canal. From the dorsal end of each radix a flat plate of bone, the lamina (/f), extends caudomediad to join its fellow of the opposite side and form the vertebral arch. Owing to the fact that the radix rises from only the cranial two-thirds of the centrum there is left in the caudal border of the vertebral arch a notch bounded by the radix, the lamina, and the centrum. There is also a slight excavation of the cranial border of the radix. . When the vertebre are articulated in the natural posi- tion, these notches form the intervertebral foramina (lig. 4, d), for the exit of the spinal nerves. At the junction of radix and lamina the arch is produced craniolaterad into a short process, the transverse process (¢'), knobbed at the end. On the ventral face of its free end the transverse process bears a smooth facet, the transverse costal facet or tubercular facet (Fig. 4, ¢), for articulation with the tubercle of a rib. On the dorsal face of each lamina at its cranial border is a smooth oval area, the cranial articular facet (superior articular facet of human anatomy) (Figs. 2 and 3, #). Its long axis is oblique and it looks dorsolaterad. The slight projections of the cranial edge of the lamina on which the facets are situated are the inconspicuous cranial articular processes (prezyga- pophyses). On the ventral surface of each lamina at the caudal border, near the middle line is a similar area, the caudal articular facet (inferior articular facet of human anatomy) (7); these occupy the ventral surfaces of two projections which form the caudal (inferior) articular processes (postzygapophyses) (7). These are separated by a median notch. When the vertebra are in their natural position the caudal articular facets lie dorsad of the cranial facets and fit against them. They thus strengthen the joint between contiguous vertebre, while permitting slight rotary motion. THE VERTEBRAL COLUMN. 5 Differential Characters of the Thoracic Vertebre (Fig. 4). —Following the thoracic vertebrae caudad there is to be seen a gradual increase in the size of the centra brought about by an increase in their craniocaudal and transverse measurements. tal facets; d, intervertebral ; A, caudal articular pro- s g, mammillary processes 1 6) cranial articular processes; c, transverse co accessory processes: Fic. 4.—THorRACIC VERTEBRA, SIDE VIEW. ? a, spinous processes; 34, foramina; ¢, costal facets; /, cesses. The dorsoventral measurements remain nearly the same. The costal facets (Fig. 4, ¢) shift caudad so that on the eleventh, twelfth, and thirteenth thoracic vertebre each lies entirely on the cranial end of its centrum, while the caudal end 6 THE SKELETON OF THE CAT. of the centrum immediately preceding is not marked by any part of it. In the eleventh thoracic vertebra each costal facet is usually still confluent with the smooth cranial end of the centrum. In the twelfth vertebra the facets are separated by smooth ridges from the cranial end of the vertebra, while in the thirteenth vertebra they are separated by rough ridges. The spinous processes (a) of the first four are of about the same length. They then decrease in length to the twelfth, while the twelfth and thirteenth are slightly longer than the eleventh. The first ten slope more or less caudad, while the spinous process of the tenth vertebra is nearly vertical and those of the eleventh, twelfth, and thirteenth point craniad. Each of the transverse processes of the seventh thoracic vertebra shows a tendency to divide into three tubercles; one of these is directed craniad, the mammillary process (or meta- pophysis), one caudad, the accessory process (or anapophysis), while the third (transverse process proper) looks ventrad and bears the transverse costal facet. This division becomes more prominent in the succeeding vertebra, being most marked in the ninth and tenth. In the eleventh, twelfth, and thirteenth vertebrae the mammillary (g) and accessory (/) processes are very pronounced, while the transverse costal facet and that part of the transverse process which bears it have disappeared. The ribs of the eleventh, twelfth, and thirteenth vertebra are thus attached to their respective centra by their heads alone. The cranial articular processes (¢) are prominent on the first two thoracic vertebrae; back of these they are very small as far as the eleventh, so that the articular facets seem to be borne merely upon the dorsal surface of the cranial edge of the lamine. In the eleventh, twelfth, and thirteenth the cranial articular processes are large, bearing the articular facets on their medial surfaces, while the mammillary processes appear as tubercles on the lateral surfaces of the articular processes. The caudal articular processes (#) are prominent in the first thoracic, then smaller until the tenth is reached; in the tenth, eleventh, twelfth, and thirteenth they are large and their facets are borne laterally, so as to face the corresponding cranial THE VERTEBRAL COLUMN. facets. _Thus from the tenth to the thirteenth thoracic vertebra rotary motion is very limited, owing to the interlocking of the articular processes. Vertebre lumbales (Fig. 5).— The Lumbar Vertebre. The last thoracic vertebra form the transition to the typical ger than the thoracic vertebra. ar are | These lumbar vertebra. *sassao0id snoutds ‘f ‘sassaooid asraasuvy} ‘9 {sassao01d Arossaooe ‘p ‘sassadoid avpnoysze [epned ‘9 !sassadoid Areyprummeu ‘g fsassaooid aepnonie yerurso ‘v ‘WUIILUTA UvaWaAT—'S ‘org The centra are of the form of the centra of the thoracic vertebra, and increase in length to the sixth, but the seventh is about They increase in breadth to the last. the length of the first. 8 THE SKELETON OF THE CAT. The cranial articular processes (Vig. 5, @) are prominent and directed craniodorsad; they have the facets on their medial surfaces, while their dorsolateral surfaces bear the mammillary processes (6) as prominent tubercles. The caudal articular processes (c) are likewise large; their facets look laterad. When the vertebrz are articulated they are received between the medially glirected cranial processes. The accessory processes (@) are well developed on the first vertebra, diminish in size to the fifth or sixth, and are absent on the seventh and sometimes on the sixth. The transverse processes (more properly pscudo-transverse processes) (¢) arise from the lateral surface of the centra; are flat and are directed ventrocraniolaterad. The first is small, and they increase in length and breadth from the first to the sixth, those of the last being slightly smaller than in the sixth. The free ends of the last four are curved craniad. The spinous processes (f/f) are flat and directed cranio- dorsad. They increase in length to the fifth and then decrease. The first five are knobbed at the end. In a dorsal view the spinous process and cranial articular processes of each vertebra are seen to interlock with the caudal articular processes and accessory processes of the preceding vertebra in such a way as to prevent rotary motion, and this arrangement may be traced craniad as far as the eleventh thoracic vertebra. Sacral Vertebre. Vertebre sacrales (Figs. 6 and 7).— The three sacral vertebrae are united in the adult into a single bone, the os sacrum, or sacrum. Ina kitten the three verte- brae are separate, while in an animal almost mature the first two are united and the third is still separate. The sacrum lies between the last lumbar and the first caudal vertebrae and articulates laterally with the two innominate bones. It 1s pyramidal, with the base of the pyramid directed craniad, and is perforated by a depressed longitudinal canal, the sacral canal, which is a continuation of the vertebral canal, and by four large foramina dorsally and four ventrally. It may be described as having a cranial end or base and a caudal end or apex, a dorsal, a ventral, and two lateral surfaces. The base is slightly oblique and presents a smooth trans- THE VERTEBRAL COLUMN. 9 versely oval articular facet (the cranial end of the centrum of the first sacral vertebra), for articulation with the centrum of the last lumbar vertebra. Dorsad of this is the sacral canal, more depressed than the vertebral arch craniad of it. It sup- ports a spinous process (Fig. 6, a@) which is directed dorsad. At the junction of its lamina and radix is seen the prominent Fic. 6.—SAcRuM, DorsAL SURFACE. Fic. 7.—SACRUM, VENTRAL SURFACE, Fig. 6.—1, 2, 3, the three sacral vertebrae. a, a’, spinous processes; 4, cranial articular process of first sacral vertebra; c, expanded transverse process of first sacral vetebra; d@, caudal articular processes of third sacral vertebra; ¢, transverse processes of third sacral vertebra; /, tubercles formed by fused articular processes of the vertebrae; g, dorsal (or posterior) sacral foramina. Fig. 7.—1, 2, 3, the three sacral vertebra. a, the transverse ridges formed by the union of the centra; 4, cranial articular processes of first vertebra; c, transverse process of first vertebra; @, caudal articular processes of third vertebra; ¢, trans- verse processes of third sacral vertebra; /, /’, ventral (or anterior) sacral foramina; g, notch which helps to form third ventral sacral foramen. cranial articular process (4) with sometimes slight indications of a mammillary process on its lateral surface. Laterad of the articular facet is seen the cranial face of the expanded ‘‘ pseudo- transverse process’’ (c) of the first sacral vertebra. The ventral border of the base is concave ventrad, forming an arc of about 120 degrees. The apex shows the caudal end of the last sacral centrum. Dorsad of this are the vertebral arch with a very short spinous process (a’), and the caudal articular processes (@). Laterad of the centrum appears the laterally directed thin transverse process (e). The ventral or pelvic surface (Fig. 7) is smooth, concave craniad, convex caudad, and crossed by two transverse ridges (a) along which are seen the ossified remains of the interverte- bral fibro-cartilages. At the ends of the first ridge is a pair of nearly circular ventral (or anterior) sacral foramina (/) for 10 THE SKELETON OF THE, CAT, the passage of sacral nerves. At the end of the second ridge is a pair of ventral sacral foramina (/’), smaller than the first pair and continued laterocaudad into shallow grooves for the ventral rami of the sacral nerves. That portion of the bone lying laterad of a line joining the medial borders of these two pairs of foramina is known as the lateral mass of the sacrum and is composed of the fused transverse processes of the sacral vertebre. At the caudal margin of the ventral surface there is a notch between the lateral mass and the centrum (g). When the caudal vertebre are articulated, this notch helps to form a foramen for the third sacral nerve. The dorsal surface (Fig. 6) is narrower at its cranial end than is the ventral surface. Its cranial border bears laterally a pair of cranial articular processes (6) with their medially directed facets and between them it is concave, so that a large dorsal opening is left into the vertebral canal between the last lumbar vertebra and the sacrum. Caudad of the articular processes are two pairs of tubercles (/). These are the fused cranial and caudal articular processes of the sacral vertebrae. Caudad of them are the caudal articular processes of the last sacral vertebra (¢@). Craniolaterad of the middle and cranial tubercles are dorsal (posterior) sacral foramina ( ) for the transmission of the dorsal rami of the sacral nerves. Three spinous processes (@) appear between these rows of tubercles. They decrease in height caudad. That part of the surface in- cluded between the spinous process and the tubercles is made up of the fused lamina of the sacral vertebrae. That part between the tubercles and a line joining the lateral margins of the dorsal (posterior) sacral foramina is formed by the fused radices of the sacral vertebre. The lateral surface may be divided into two parts. Craniad is a large rough triangular area with equal sides and with one of its angles directed ventrocraniad. It is the lateral face of the pseudo-transverse process of the first sacral vertebra (Tig. 6, c). A smooth curved surface (the auricular facet) along its ventral edge articulates with the ilium, while the dorsal por- tion is rough for attachment of ligaments. Caudad is the narrow longitudinal triangular area of the lateral faces of THE VERTEBRAL COLUMN. II the fused transverse processes of the second and third sacral vertebre. Caudal Vertebre. Vertebre caudales (Fig. 1, y, and Figs. 8 and g).—The caudal vertebrae (21-23 in number) decrease gradually in size to the last one. Caudad they become longer and more slender and lose the character of verte- bra. They become finally re- duced to mere centra,—-slender rods of bone knobbed or enlarged at their two ends (Fig. 8). The re Oks. last one is more pointed than the Fig. 8. —Caudal Vertebra, from near others and bears at its caudal end nae aia fae Wericbee: a small separate conical piece, ventral view. a, transverse processes; the rudiment of an additional] % cranial articular processes; ¢, haemal processes; d, chevron bone. vertebra. The parts of a typical vertebra—vertebral arch, transverse processes, cranial and caudal articular processes—may be recognized in the vertebrae as far back as the eighth or ninth. The transverse processes (Fig. 9, a) are directed caudad and decrease rapidly in length. They are very small on the ninth vertebra, but may be recognized for a considerable distance back of this. The spinous process disappears at about the fourth caudal vertebra, and the vertebral canal becomes gradually smaller caudad, until on the eighth or ninth vertebra it becomes merely a groove open dorsad. Caudad of the third vertebra for a considerable distance, each centrum bears on each lateral face at its cranial end a short anterior transverse process, and on its ventral face at its cranial end a pair of rounded tubercles, hamal processes (c), which articulate with a small pyramidal chevron bone (d) so as to enclose acanal. These structures disappear caudad. Cervical Vertebre. Vertebre cervicales (Fig. 10).—The cervical vertebraee number seven. The first two of these are so peculiar as to require a separate description, so that the last five may be first considered. Passing craniad from the fourth thoracic vertebra to the third cervical there is a gradual transition. The centra of the 12 THE, SKELETON OF THE {GAT cervical vertebree are broader and thinner than those of the thoracic vertebre, while the vertebral arches and vertebral canal are larger (Fig. 11). The caudal end of each centrum is concave and looks dorsocaudad when the centrum is held with its long axis horizontal. The cranial end of the centrum is convex and looks ventrocraniad when the centrum is hori- zontal. These peculiarities are more marked in the third vertebra than in the seventh. The spinous processes grow "Up, S 1) EU Fic. 10.—CERVICAL VERTEBRA, SIDE VIEW. a, spinous processes; 4, cranial articular processes; ¢, caudal articular facet; d, intervertebral foramina; e, transverse process proper; /, processus costarius; g, wing of the atlas; 4, dorsal arch of the atlas; 7, atlantal foramen. rapidly shorter as we pass craniad; the fifth, sixth, and seventh are directed dorsocraniad, the third and fourth dorsad. The caudal articular processes are situated at the junction of the radices and laminz; their facets (Fig. 10, 2) look ventrocaudolaterad. The cranial articular processes also become more prominent than is the rule in the thoracic verte- bre; they are borne at the junction of radix and lamina and have their facets (Fig. 11, 6) directed dorsomediad. The cranial and caudal articular processes of each side are joined by a prominent ridge which is most pronounced in the third, fourth, and fifth vertebra. The characteristic feature of the cervical vertebra is their transverse process, so called. In each of them it arises by two roots, one from the centrum and one from the arch. THE VERTEBRAL COLUMN. 13 These two roots, which are broad and thin, converge and unite so as to enclose a canal or foramen, the foramen transver- sarium (Fig. 11, g), for the vertebral artery. Laterad of the foramen the two parts of the process are, in the third cervical, almost completely united, the dorsal part being, however, dis- tinguishable as a tubercle at the caudolateral angle of the thin plate formed by the process as a whole. This dorsal compo- nent is the transverse process proper (igs. 10 and II, e), while the ventral portion represents a rib, and is hence known as the processus costarius (7). The expanded plate formed by the union of these two processes is directed nearly ventrad and somewhat craniad in the third, fourth, and fifth vertebre. The two components of the process gradually separate as we Fic. 11.—SIXTH CERVICAL VERTE- Fic. 12,—ATLAS, VENTRAL VIEW. BRA, CRANIAL END. Fig. 11.—a, spinous process; 4, cranial articular facet; c, lamina; d, radix or pedicle; e, transverse process proper; /, 7’, processus costarius; g, foramen trans- versarium; #, centrum; 7, vertebral canal. Fig. 12.—a, ventral arch; 4, tuberculum anterius; c, lateral masses; d, trans- verse processes; ¢, cranial articular facets; /, groove connecting the foramen trans- versarium with the atlantal foramen; g, atlantal foramen; 4, caudal articular facets. pass caudad; in the fourth and fifth vertebrae the part which represents the transverse process proper forms a very prominent tubercle at the caudolateral angle of the plate formed by the processus costarius. In the sixth (Fig. 11) the two parts are almost completely separated ; the dorsal part forms (¢) a slender knobbed process, while the processus costarius is divided into two portions (f and /’) by a broad lateral notch. In the seventh the ventral part (processus costarius) is usually quite lacking, though sometimes represented by a slender spicule of bone. In the former case the foramen transversarium is of course likewise lacking. 14 TPHEVSKELE TON “OF PHE* GAT. The Atlas (Fig. 10, 1; Fig. 12).—The first cervical verte- bra or atlas has somewhat the form of a seal ring. The centrum is absent; it has united with the second vertebra to form the odontoid process or dens. Its place is taken in the atlas by a narrow flat arch of bone, narrower at the ends than in the middle, the ventral arch (Fig. 12, a) of the atlas. This connects the lateral, thicker portions of the ring ventrally and bears on its caudal margin a blunt tubercle (tuberculum anterius, Fig. 12, 6). Laterally the ring is thickened, forming thus the lateral masses (c) which are continued into the broad thin transverse processes (Fig. 10, g; Fig. 12;°¢@).) wach lateral mass bears at its cranial end on its medial surface a concave, pear-shaped facet, cranial (or superior) articular facet, (Fig. 12, e) for articulation with the condyles of the skull. These facets look craniomediad. Dorsad of each is a foramen, the atlantal foramen (Fig. 10, z; Fig. 12, g), which pierces the dorsal arch at its junction with the lateral mass. Caudal to the facet, on the medial face of each lateral mass, within the vertebral canal, is a tubercle. To the two tubercles are attached the transverse ligament (lig. 14, 6) which holds in place the odontoid process (dens) of the axis. That part of the lateral mass which bears the articular facet projects craniad of the dorsal arch and is separated by a deep triangular notch from the transverse process. Along the bottom of this notch runs a groove (Fig. 12, /), convex craniad, which connects the cranial end of the foramen trans- versarium and the atlantal foramen. The vertebral artery passes along it. The foramen transversarium is circular. It is bounded laterally by the lateral masses, and dorsally by the dorsal arch. The dorsal arch (Fig. 10, /) is two to three times as broad as the ventral, has a thick convex cranial border with a median notch, and a thin concave caudal border. The caudal articular facets (Fig. 12, %) are borne by the caudal ends of the lateral masses. They are slightly concave, triangular, and look caudomediad, so that their dorsal borders form with the caudal border of the dorsal arch nearly a semi- circle. The transverse processes are flat and directed laterad. THE VERTEBRAL COLUMN. 15 The attached margin of each is about two-thirds the length of the thinner free margin. The somewhat thicker caudal end of the transverse process projects further caudad than any other part of the vertebra and is separated by a slight notch from the caudal articular facet. From the bottom of this notch the foramen transversarium extends craniad and opens at the middle of the ventral face of the transverse process. Epistropheus or Axis (Fig. 10, 2; Fig. 13). —The second cervical vertebra (epistropheus or axis) is not so wide as the atlas but is much longer. Craniad the centrum is continued into a slender conical, toothlike projec- tion, the dens or odontoid process (I‘ig. 13, a) which represents the centrum of the atlas. The dens is smooth below for articulation with the ventral arch of the atlas. It is rougher above. Laterad of the dens the centrum bears a pair of large Fie. 13.—Axis or Epis- craniallLarticularfacetsy(2) swhich; look: 7.epueus, Sime View: ; a, odontoid process or craniolaterad. WThese'have each’ the form gens. 4. cranial articular of a right-angled triangle with rounded ea ana oe angles, one side of the triangle being ¢, transverse process; /, nearly horizontal. Each is separated from ‘!™« transversarium. the articular face of the dens by a roughened groove. The spinous process (c) runs the length of the vertebral arch. It extends craniad of the vertebral arch nearly as far as the dens, as a flat rounded projection. Caudad of the vertebral arch it projects for a short distance as a stout triangular spine. The caudal articular facets (@) are borne on thickenings of the caudolateral portions of the arch; they face almost directly ventrad. The transverse process (¢) is slender and triangular and directed nearly caudad. Its apex reaches no farther than the caudal or articular face of the centrum. Its base is traversed by the foramen transversarium (/). Differential Characters of the Cervical Vertebre.—It is possible to identify each of the cervical vertebre: The first by the absence of the centrum. The second by the dens or odontoid process. The third by the small spinous process and slightly marked 16 THE SKELETON OF (THE GAT. tubercle of the transverse process, and by a median tubercle on the cranial border of the vertebral arch. The fourth by the spinous process directed dorsad, and the short thick tubercle of the transverse process not trifid. The fifth by the spinous process directed craniad, and the more slender spine-like tubercle of the transverse process not trifid. The sixth by the trifid transverse process. The seventh by the long spinous process and the slender simple transverse process, and by the usual absence of the foramen transversarium. LIGAMENTS OF THE VERTEBRAL COLUMN. Fibro-cartilagines intervertebrales.—The separate verte- brae (except the atlas and axis) are united by the disk-shaped intervertebral fibro-cartilages, which are situated between the centra of the vertebra. Each consists of a central pulpy por- tion and a fibrous outer portion, covered by strong intercross- ing tendinous fibers which unite with the periosteum of the vertebra. : Ligamentum longitudinale anterius.—On the ventral face of the centra of the vertebrae, from the atlas to the sacrum, lies a longitudinal ligament, the anterior longitudinal ligament. It is very small, almost rudimentary, in the cervi- cal region: large and strong in the thoracic and lumbar regions. Ligamentum longitudinale posterius (Fig. 14, a).—A corresponding ligament (posterior longitudinal ligament) lies on the dorsal surface of the centra (therefore within the verte- bral canal). It is enlarged between each pair of vertebrae and closely united to the intervertebral fibro-cartilages. Ligamentum supraspinale.— Between the tips of the spinous processes of the thoracic and lumbar vertebrae extend ligamentous fibers. They are not united to form a distinct band, and can hardly be distinguished from the numerous tendinous fibers of the supraspinous muscles. Together they represent the supraspinous ligament. [rom the tip of the spinous process of the first thoracic vertebra to the caudal end of the spine of the axis extends a slender strand representing THE VERTEBRAL COLUMN. 17 the ligamentum nuche or cervical supraspinous ligament. It is imbedded in the superficial muscles of this region, some of which take origin from it. Ligamentous fibers are also present between the spinous processes of the vertebrae (ligamenta interspinalia): between the transverse processes (ligamenta intertransversaria), and between the vertebral arches (ligamenta flava). Capsule articulares.—The joints between the articular processes are furnished with articular capsules attached about the edges of the articular surfaces. These are larger and looser in the cervical region. Atlanto-occipital Articulation.—The joint between the atlas and the occipital condyles has a single articular capsule, which is attached about the borders of the articular surfaces of the two bones. This capsule is of course widest laterally, forming indeed two partially separated sacs, which are, how- ever, continuous by a narrow portion across the ventral middle line. This capsule communicates with that which covers the articular surface of the dens, and through this with the capsule between the atlas andaxis. That portion of the capsule which covers the space between the ventral arch of the atlas and the occipital bone represents the anterior atlanto-occipital mem- brane ; it is strengthened by a slender median ligamentous strand. The posterior atlanto-occipital membrane covers in the same way the space between the dorsal arch of the atlas and the dorsal edge of the foramen magnum. In it a number of different sets of fibers, with regard to direction and to degree of development, may be distinguished; these have sometimes been considered separate ligaments. The lateral ligaments of the atlas begin at the lateral angle of the cranial margin of the atlas, at about the junction of its dorsal and ventral arches, and pass cranioventrad to the jugular processes. Articulation between the Axis and Atlas.—The articular capsule is large and loose, being attached to dorsal and ventral borders of the atlas, about the articular surfaces of the axis, and to the cranial projection of the spine of the atlas. It also passes craniad along the ventral side of the dens and communi- 18 THE SKELETON OF THE GAT. cates here with the capsule of the atlanto-occipital articulation. In the dorsal part of the capsule a short strong ligamentous strand is developed, connecting the caudal border of the dorsal arch of the atlas with the tip of the cranial projection of the spinous process of the axis. The dens or odontoid process is held in place by the transverse liga- ment (Fig. 14, 4) of the atlas, which passes across the process as it lies with- in the vertebral canal of the atlas. The Fic. 14.—LIGAMENTS OF . . : a GonToPRocrs (hansverse ligament is attached at its or DENS. two ends to the medial surface of the First three cervical ver- .: ¢ hese ndibaccoreakall: sides of the atlas at about the region with dorsal surface re- where the dorsal and ventral arches of moved. a, ligamentum t] tl it longitudinale posterius; 4, pepe Uae UTE ; transverse ligament of the From the cranial end of the odontoid atlas; c, ligamenta alaria; 5 : : d, odontoid process; ¢, oc. Process the two ligamenta alaria (Fig. cipital condyles; 1, 2, 3, 14, ¢) diverge craniolaterad to the rough the first three cervical ver- ; tebrae; 4, basal portion of ventromedial angle of the condyles of USO SIE Vries tte: the occipital bone. II. RIBS. COSTA. (Figs. 1 and 15.) The cat has thirteen pairs of ribs. One of the fifth pair (Fig. 15) may be taken as typical. It is a curved flattened rod of bone attached at its dorsal end to the vertebral column, and at its ventral end to a cartilage (costal cartilage, Fig. 15, /) which serves to unite it to the sternum. The most convex portion of the bone is known as the angle (¢). Each rib presents a convex lateral and a con- cave medial surface, a cranial and a caudal border. The borders are broad dorsad and narrow ventrad, while the sur- faces are narrow dorsad and broad ventrad. The rib has thus the appearance of having been twisted. The rib ends dorsad in a globular head or capitulum (a), by which it articulates with the costal demifacets of two con- tiguous thoracic vertebre. Between the capitulum and angle RIBS. 19 on the lateral surface is an elevated area, the tubercle, marked by the smooth tubercular facet (c) for articulation with the transverse process of a_ vertebra. The constricted portion between the head and tubercle is known as the neck (collum) (7). The angle is marked by a projecting process (e) (angular process) on its lateral bor- der, for attachment of a ligament. The ribs increase in length to the ninth (the ninth and tenth are of the same length) and then de- crease to the last. They decrease | in breadth behind the fifth. The | first is nearly in a dorsoventral plane, while the others have their dorsal ends inclined slightly craniad. The tubercles become less promi- nent as we pass caudad and are absent on the last two or three ribs, which do not articulate with the transverse : Fic. 15.—FirrH Rip or LEFT process. SIpE, CRANIAL VIEW. The first nine ribs (true ribs or 4, head; 4, tubercle; ¢, tuber- cost vere) are attached separately eee bat le cae ay to the sternum by their costal carti- lage. lages. The last four (false ribs or coste spuria) are not attached separately to the sternum. The costal cartilages of the tenth, eleventh, and twelfth are united to one another at their sternal ends. They may be united also to the ninth costal cartilage or to the sternum by a common cartilage of insertion, or they may be quite free from the sternum. The thirteenth costal cartilages are free (floating ribs). Ligaments of the Ribs.—The articular surfaces between the head of the rib and the centra, and between the tubercle and the transverse process of the vertebra, have each an articular capsule. There are also a number of small liga- mentous bands from the tuberosity and the neck of the rib to the transverse process of the vertebra. 20 Fic. 16.—STER- NUM, VENTRAL VIEW. a, manubrium; 6, the separate pieces forming the body; c, bony part of the xi- phoid process (the expanded cartilaginous por- tion not being shown); d, facet for attachment of first rib. THE SKELETON : b) of the %, ramus of the ischium; 7, ramus of human ilium. The concavity of the pubis; 7, obturator foramen; 4, pubic tubercle; 7, iliopectineal line; the dorsal border (c) corresponds 2’, ilio-pectineal eminence; 77, anterior to thesereat selatic notch of the 7! am). | human ilium. At its caudal end is the short spine of the ischium (¢), which is nota part of the ilium. The ventral border of the ilium is broad caudad, becoming narrower craniad. The lateral margin of the ventral border is continued to a tuberosity at the edge of the acetabulum; its medial margin is called the 78 THE SKELETON OF THE CAT. iliopectineal line (/) and extends on the pubis to the symphysis. An eminence, the iliopectineal eminence (/’), on the iliopec- tineal line, lies opposite to the acetabulum at about the junction of the ilium and pubis. The cranial end of the bone is thick- ened, forming the crest (a) of the ilium. At the junction of the crest with the ventral border is a projection, the anterior superior process (7) of human anatomy. The pubis (///) (including the acetabular bone) enters into the formation of the acetabulum (d@) constituting about one- sixth the circumference, but less than one-sixth its area. It may be described as a flat, curved bone, contracted at the middle and expanded at the ends. The dorsal end enters into the acetabulum; the ventral end unites with the opposite bone at the symphysis pubis and sends caudad a projection, the ramus (2) of the pubis, which unites with the ramus of the opposite bone to form about two-thirds of the entire symphysis. At the sides of the symphysis a slightly marked angle projects craniad from each of the pubic bones; these two together con- stitute the pubic tubercle (4), for the origin of the rectus abdominis muscle. The surfaces of the ramus are smooth. One of its borders is concave and enters into the formation of the obturator foramen (7). Another of its borders is the ilio- pectineal line (/). Its third border is rough for the symphysis. The ischium (//) has the form of a triangular prism con- tracted at the middle. Its cranial end forms nearly two-thirds of the acetabulum. Its caudal end bears dorsad a rough thickening, the tuberosity of the ischium (g). From the caudal half of the ventral border of the bone a sickle-shaped process, the ramus (/) of the ischium, curves medioventrad and then craniad and joins the ramus of the pubis. Its medial border is rough and enters into the symphysis, forming the caudal one-third. The lateral angle of the bone is rounded. Its dorsal angle is marked near the cranial end by the spine (e) of the ischium. The concavity between this spine and the tuberosity corresponds to the lesser sciatic notch (/) of human anatomy. The acetabulum (@) is cup-shaped. The ventral one-sixth of its border is deficient and a broad groove extends from the PELVIC LIMBS. 79 deficiency to the bottom of the cup. The deficiency, incisura acetabuli, or acetabular notch (a’), is closed naturally by a ligament, and the groove gives origin to the ligament (liga- mentum teres) which attaches the head of the femur. Femur (Fig. 56).—The femur is the proximal bone of the posterior extremity. It consists of enlarged proximal and distal ends connected by a nearly cylin- drical shaft. The proximal end presents on its medial side a hemispherical head (a) which fits into the acetabulum. It is supported by a neck () which is con- tracted near the head and expanded dorso- ventrally where it joins the remainder of the bone. The medial surface of the head presents near its ventral border a depres- sion (c) for the insertion of the round liga- ment of the femur. Ventrad the articular surface of the head extends as an acute projection onto the shaft, so that the whole articular surface appears somewhat pear- On the lateral side of the proxi- mal end opposite the head is a_ projecting mass, the great trochanter (d), forming the end of the shaft. On the medial side of the great trochanter at its junction with the neck is a deep fossa, the trochanteric fossa or digital fossa (¢) for the insertion From the ventral surface of shaped. 56.—Lerr Femur, of muscles. VENTRAL SIDE. the great trochanter a ridge, the inter- trochanteric line (/), is continued distad, ending in a pyramidal projection, the lesser trochanter (g), which serves for the insertion of muscles. A second ridge is continued to the lesser trochanter from the neck. A slight but well-marked a, head; 64, neck; c, de- pression for round liga- ment; @, great trochanter; e, trochanteric fossa; /, intertrochanteric line; g, lesser trochanter; 7, linea aspera; 2, medial condyle; J, lateral condyle; &, inter- condyloid fossa; Z, lateral epicondyle. ridge, the spiral ridge or line, runs round two sides of the neck parallel to the second ridge. 80 THE SKELETON \OF\ THE CAT. The shaft is nearly straight and cylindrical. A rough line is continued along its ventral surface from the lesser trochanter, and a similar line along its lateral surface from the greater trochanter; these unite ventrad to form the linea aspera (Z). On its ventral surface is a nutrient foramen, directed proximad. The shaft gradually widens distad and ends in two condyles (¢ and 7) which are continuous dorsad but separated ventrad by a deep notch, the intercondyloid fossa (£). The distal surface of the shaft and condyles is articular. This articular surface is larger on the lateral condyle (7). The part of the articular surface on the end of the shaft (patellar surface) is for the patella; that part of it on the condyles and separated by the notch is for the tibia. On the lateral surface of the lateral condyle is a slight prominence, the lateral epicondyle (/), and on the medial sur- face of the medial condyle is another prominence, the medial epicondyle; both are for the attachment of ligaments. Patella (Fig. 1, ~).—The patella is a small flat bone with a pear-shaped outline, having its apex distad. It lies against the articular surface at the lower end of the shaft of the femur. It thus covers the knee-joint. The inner surface is smooth and convex from side to side, but concave in a proximodistal line. It fits against the lower end of the femur. Its outer surface is rough and concave. It is a sesamoid bone inserted in the tendon of the quadriceps femoris muscle. Three other sesamoid bones are found in the region of the knee (see Fig. 61, p. 89). Two are in the tendons’ef the gastrocnemius muscle, proximad of the two condyles of the femur. The third is in the tendon of the popliteus muscle, just laterad of the lateral condyle of the femur. Tibia (/, Fig. 57).—The tibia is the longer of the two bones of the leg between the knee and the ankle, and is the longest bone of the body. It has a triangular shaft and enlarged proximal and distal ends. The proximal end is curved ventrad and projects into two prominences, the tuberosities, on either side. Each tuberosity bears on its proximal end an articular facet for the condyles of the femur; these are known respectively as the lateral and PELVIC LIMBS. medial condyles (a and 4) of the tibia. The condyles are oval, convex dorsoventrad, and concave from side to side. The two con- dyles are separated at the middle of their contiguous margins by a bicuspid projection, the spine of the tibia (c). They are con- tinuous dorsad, but separated ventrad by a deep notch between the tuberosities, the popliteal notch. On the distal side of the lateral condyle is an elongated facet for the proximal end of the fibula. The shaft is triangular, smallest at about its middle and enlarged at both ends. It presents dorsal, medial, and lateral borders, and medial, lateral, and ventral surfaces. The lateral surface is concave proximad. The medial surface The two are continuous at the distal end. At their proximal ends the border separating them is raised into a prominent ridge, the crest (@) of the tibia, the proximal end of which contributes to increase the proximal sur- face of the bone, and presents an oblong tubercle (¢) for the insertion of the liga- mentum patelle (ligament of the quadri- ceps femoris muscle). The ventral surface is concave proximad where it abuts upon the tuberosities. Its proximal half is crossed by two rough parallel lines, the distal one of which crosses in a spiral course from the lateral to the medial border; near its begin- ning is a nutrient foramen. The distal end extends farther distad on its medial side. The extension is the medial malleolus (7). The malleolus presents two grooves on its medial surface for the tendons of muscles. On the lateral side of the distal is Convex. Fic. 57.—TIBIA AND FIBULA OF LEFT Lec, DorsaL VIEW- f, tibia; 77, fibula. a, medial condyle of the tibia; 4, lateral con- dyle; c, spine of the tibia; d, crest of the tibia; ¢, tubercle for at- tachment of the patellar ligament; 7, medial malleolus; g, projection of dorsal surface of the tibia; 4, head of fibula; 7, lateral malleolus. end is an oblique triangular facet for the distal end of the 82 THE SKELETON OF THE CAT. fibula. The ventral surface of the distal end presents an ob- lique border which passes from the apex of the malleolus proximolaterad. The dorsal surface extends into a V-shaped projection (g) between the malleolus and the fibular facet. The distal end presents an oblique ridge running from the apex of the V-shaped extension of the dorsal surface to near the base of the medial malleolus. The ridge and the con- cavities on either side of it, the medial one of which is deeper, fit against the proximal trochlear surface of the astragalus. Fibula (//, Fig. 57).—The fibula lies at the lateral side of the tibiain the shank. It is a slender triangular bone with enlarged proximal and distal ends. The proximal end or head (Z) is flattened. It bears a facet on its proximomedial surface for articulation with the tibia, and is longitudinally grooved on the outer surface. The shaft has a very sharp medial border. This border is turned toward the tibia and gives attachment to the interosseous membrane, which runs between the tibia and fibula. The distal end is expanded to form the lateral malleolus (z). This bears a facet on the proximal portion of its medial surface near its dorsal margin, for the tibia, and distad of this is a second facet for the astragalus. The ventral and lateral sur- faces are grooved for tendons. Tarsus (Fig. 58).—The tarsus consists of seven bones. The longest of these, lying on the lateral side of the foot and forming the support of the heel, is the calcaneus or Os calcis (a). It articulates distad with a bone, the cuboid (c), which bears the fourth and fifth metatarsals. Lying between the calcaneus and the tibia is the astragalus or talus (2), the distal end of which articulates with the boat-shaped navicular or scaphoid (d). The scaphoid bears on its distal surface the three cunei- form bones, lateral (e), medial (g), and intermediate, bearing the rudiment of the first metatarsal and the second and third metatarsals. Astragalus. (Talus BNA) (Fig. 58, 6).—The astragalus may be divided into body, neck, and head. The body is marked on its proximal surface by a deep pulley-like groove for the articulation with the distal end of the tibia, and on its META- AND PHALANGES oF LEFT Foor, VENTRAL VIEW. Fic. 58. — Tarsus, TARSUS, a, calcaneus; 4, astragalus; ¢, cuboid; d, scaphoid; e, lat- eral cuneiform; g, medial cuneiform; /, peroneal groove, for the tendon of the peroneus longus muscle; 7, proximal phalanges; 7, second row of phalanges; 4, distal phalanges; 7, sesamoid bones, 1, rudi- mentary first (medial) meta- tarsal; 2, 3, 4, 5, the other metatarsals. PELVIC LIMBS. 83 lateral and medial surfaces by curved facets for articulation with the malleoli of the tibia and fibula. This entire surface for articulation with the bones of the leg is known as the trochlea. The lower surface is marked by two facets separated by a groove; these are for articulation with corresponding facets on the calcaneus. Distally the bone contracts to form the neck and enlarges at the end, forming the head, which is smooth on its distal surface for articulation with the navicular or sca- phoid. Calcaneus (Fig. 58, a, and Fig. 59). —The calcaneus (0s calcis) is the largest bone of the foot and forms the heel. It is two or three times as long as broad and has six surfaces: dorsal, ventral, medial, lateral, proximal, and distal. The proximal one-half of the dorsal surface (Fig. 59) is smooth, while the distal half is broadened and bears two facets which are separated by a groove. These articulate with the corresponding facets on the astragalus. The medial Fic. 59. CALCANEUS OF RIGHT Foot, DorsAL VIEW. a, distal facet for cuboid; 4, proximal end with groove for tendon of Achilles; c, sustentacu- lum tali; ¢, peroneal tubercle. 84 THE SKELETON OP @UHE (CAT. facet is borne on a projection of the bone, the sustentaculum tali (c). Distad of the facets the surface is rough. The ventral surface is smooth. The proximal end (0) is grooved for the tendon of Achilles. The lateral surface is smooth and marked by a grooved tubercle, the peroneal tubercle (@), near the distal end. The medial surface is marked by part of the articular facet for the astragalus, and also by the grooved sustentaculum tali. The distal end (a) articulates with the cuboid. Cuboid. Os cubotdeum (Fig. 58, c).—The cuboid has somewhat the form of a cube and articulates by its proximal end with the calcaneus (a), and by its distal end with the fourth and fifth metatarsals. Its medial surface articulates with the scaphoid (@) and lateral cuneiform (¢). The ventral surface is marked near its distal end by an oblique ridge, distad of which is a deep groove, the peroneal groove (#), for the tendon of the peroneus longus muscle. Scaphoid. (Os naviculare pedis BNA) (Fig. 58, @).— The scaphoid is a boat-shaped bone. Its proximal surface is marked by a concave facet for the head of the astragalus (0), and its distal surface has three facets for the lateral (¢), inter- mediate and medial (.¢) cuneiform bones. At the junction of the ventral with the medial surface is a prominent tubercle. The lateral surface bears two linear facets for articulation with the calcaneus (a) and cuboid (c). Lateral Cunetform. Ectocunetform. Os cunetforme ter- tium BNA (Fig. 58, e).—The lateral cuneiform is a wedge- shaped bone with a hooked process extending from the ventral sharp angle of the bone. It articulates by its proximal end with the scaphoid (¢), and by its distal end with the third metatarsal. The medial surface bears near its distal end two facets for the second metatarsal, and on its proximal end a facet for the intermediate cuneiform. The caudal surface has a facet on its proximal end for the cuboid (c¢). Intermediate Cuneiform. Mesocuneiform. Os cunetforme secundum BNA.—The intermediate cuneiform is small and wedge-shaped, with the base of the wedge dorsad. It lies between the lateral cuneiform and the medial cuneiform, articu- lates by its proximal end with the middle facet of the scaphoid, PELVIC LIMBS. 85 and bears on its distal end the second metatarsal. It is not visible in ventral view. Medial Cunetform. Entocunetform. Os cunetforme primum BNA (Fig. 58, g).—The medial cuneiform lies on the medial side of the foot. It is a flat triangular bone about twice as long as broad, and broader at its proximal end than at the distal end. It bears on its distal end the rudimentary first meta- tarsal. The proximal end is oblique and bears a concave facet for the lateral distal facet of the scaphoid (@). The lateral surface has a concave facet at its proximal end for the inter- mediate cuneiform, while the distal portion is applied against the medial surface of the second metatarsal. Bones of the Foot or Pes (Fig. 58).—JMetatarsals. Meta- tarsus (Fig. 58, 1-5).—The metatarsals are five in number. They bear a close resemblance to the metacarpals, but they may be distinguished by their bases. The first metacarpal (1) is rudimentary and conical. Its base has a facet for the distal end of the medial cuneiform ( g), while the outer surface fits into a depression on the inner sur- face of the base of the second metatarsal. The second (2). The proximal surface of the base is tri- angular, corresponding to the distal end of the intermediate cuneiform. The medial surface is marked by two concavities, one along the proximal border for the distal end of the medial cuneiform, and one distad of this for the first metatarsal. The lateral surface bears on the proximal margin an oblique tri- angular facet dorsad and a similar facet ventrad, both for the lateral cuneiform (¢). Distad of these facets is a rough ridge. The ¢hird (3). The proximal end of its base is a triangular facet with the apex directed ventrad and the sides excavated. It is for the distal end of the lateral cuneiform (e). Its medial surface presents a depression which receives the ridge of the second metatarsal. On the lateral surface a short distance distad of the proximal border is a triangular concave facet, and near the proximal border ventrad a second concave facet. Both are for the fourth metatarsal. The fourth (4). The proximal end is convex, notched medially and facetted for the cuboid (c). Its medial surface 86 THE SKELETON “OF” THE CAT. bears dorsad, a short distance from its proximal end, a smooth tubercle, and ventrad a small convex facet. Both articulate with facets on the lateral surface of the third metatarsal. The lateral surface has a sinuous facet along its dorsal border, and ventrad of this a depression. There is a second facet along the ventral border. Both facets are for the fifth metatarsal, and the depression is for ligaments. The fifth (5) has its base flattened and expanded so as to be wedge-shaped, with the apex of the wedge directed proxi- mad. Its dorsal end extends into atubercle. It thus presents only lateral and medial surfaces. The medial surface shows two tubercles, one distad of the other. The distal tubercle and the distal half of the proximal tubercle are facetted and fit into the sinuous facet on the fourth metatarsal. A narrow facet on the ventral border of the surface articulates with the facet on the ventral border of the lateral surface of the fourth metatarsal. The proximal half of the distal tubercle is facetted for the cuboid (c). The lateral surface is smooth, non-articular, and obliquely grooved. Phalanges (Fig. 58, 2, 7, #).—There are three phalanges in each of the four digits, and these are almost identical with those described for the manus. Sesamotd Bones. Ossa sesamotdea (Fig. 58, /).—The sesamoid bones are found at the joints between the metatarsals and phalanges, and are in all respects like those of the manus. JOINTS AND LIGAMENTS OF THE PELVIC LIMBS. Ligaments of the Pelvis.—The ilium and sacrum are articu- lated at the auricular facet of the ilium and the corresponding rough surface ofthe sacrum. The joint is an amphiarthrosis, per- mitting very little movement. A capsular ligament surrounds the articular surface, being attached to the bones about its circum- ference; itis short and strong. Craniad of the capsule is a thick very short ligament, composed of very strong transverse fibres passing from the rough surface of the sacrum to the correspond- ing rough surface of the ilium. This forms the lateral iliosacral ligament, which is united at its caudal border to the capsule. A strong, wide ligamentous band passes from the dorsal PELVIC LIMBS. 37 border of the ilium to the sides of the sacrum. This is indis- tinctly subdivided into several bands, which together represent the long and short posterior iliosacral ligaments of man. Synphysis pelvis.—The medial borders of the pubis and ilium meet in the middle line ventrad of the pelvis and are here united by cartilage. The joint is strengthened by numerous small bands which pass across the line of junction from one side to the other; these occur on both surfaces. The Hip-joint.—The hip-joint is an enarthrosis, or ball- and-socket joint in which more than half the spherical head of the femur is received into the acetabulum. The depth of the acetabulum is increased by a rim of fibrocartilage about its margin, forming the labrum glenoidale. This passes across the acetabular notch, forming the transverse ligament of the acetabulum; beneath it blood-vessels and nerves pass into the acetabular cavity. The capsule of the joint is large and loose. It is attached about the margin of the acetabulum, and passes over the head of the femur, to be attached to the bone several millimeters distad of the head. It thus encloses both the head and the neck of the femur. The ligamentum teres, or round ligament, is a very strong, short ligament which passes from the depression in the head of the femur to the bottom of the acetabulum. The Knee-joint (Figs. 60 and 61).-—The joint between the femur and the tibia is very complex. The surfaces of the con- dyles of the femur do not correspond to those of the condyles of the tibia. Between the ends of the two bones are placed two disks of cartilage, the menisci, or semilunar cartilages (Fig. 60, c and d; Fig. 61, a and 4), of such a form that the congruity of articular surfaces is restored. Each meniscus has a proximal surface corresponding to the form of one of the condyles of the femur, and a distal surface’ corresponding to a condyle of the tibia. The menisci are held in position by liga- ments. The knee-joint permits not only backward and forward movement, but also a small amount of rotary motion. The joint has two capsules, one on the dorsal (convex) side, the other on the ventral side. The two communicate 88 THE SKELETON OF THE CAT. only by a small passageway lying within the joint between the ends of the bones. The dorsal one is attached to the femur several millimeters proximad of the patellar surface and some distance on each side of the latter. The patella is imbedded in its outer wall, and it is attached to the tibia on the edges of the articular surface of the latter, from the crest to the tuber- osities. The capsule is also attached laterally and medially to the sides of the menisci, and is closely united to the patellar ligaments. Its cavity contains a mass of yellow fat. The ventral capsule is attached to the borders of the articu- lar surfaces of the femur and tibia on their ventral sides, to the menisci, and to the epicondyles of the femur and the tuberosi- ties of the tibia. Its walls are stronger and its cavity smaller than those of the dorsal capsule. The ligaments of the knee-joint (Figs. 60 and 61), aside from the capsules, may be classified into: (1) those which are connected with the patella; (2) collateral ligaments (Fig. 60, z and 7), which pass from the epicondyles directly distad along the sides of the joint to the tibia or fibula; (3) crucial ligaments (Fig. 60, gand/; Fig. 61, cand @), which cross within the joint from one side of the femur to the opposite side of the tibia; (4) ligaments which hold the menisci in place (Fig. 60, e and /; Pies O1, cand 7): (1) LIGAMENTS OF THE PATELLA.—The patella is im- bedded in the dorsal wall of the dorsal capsule of the joint. From its distal end a strong tendon or ligament passes distad to the crest of the tibia. This is known as the ligamentum patelle: it may be considered a part of the tendon of M. quad- riceps femoris. On the lateral side the capsule of the joint is strengthened by the transverse fibres of the tendon of M. plan- taris, which aid in holding the patella in place. (2) COLLATERAL LIGAMENTS.—Of these there are two. The ligamentum collaterale fibulare (Fig. 60, 7) is attached to the lateral epicondyle of the femur and passes distad across the tendon of the plantaris muscle to the head of the fibula. Dorsad of the fibular ligament and parallel with it passes the tendon of origin of the extensor longus digitorum. The liga- mentum collaterale tibiale (Fig. 60, 7; Fig. 61, g) begins on PELVIC LIMBS. 89 the medial epicondyle of the femur and passes distad to the lateral tuberosity of the tibia; part of it passes one to one and a half centimeters distad of the tuberosity to be attached to a rough ridge on the side of the tibia. (3) CRUCIAL LIGAMENTS.—There are two of these also. The ligamentum cruciatum anterius, or anterior crucial liga- ment (Fig. 60, g; Fig. 61, c), isa thick, strong ligament which begins on the dorsal part of the proximal end of the tibia nearer the medial side (Fig. 60, g), and passes ventrad and proxi- Fic. 60.—KNEE-JOINT, FROM THE Fic. 61. — KNEE-JOINT, FROM THE DORSAL OR PATELLAR SIDE. VENTRAL OR FLEXOR SIDE. Fig. 60.—The patella has been removed. 1, femur; 2, tibia; 3, fibula. a, patellar surface of femur; 4, tubercle for attachment of ligamentum patella; c, medial meniscus; d, lateral meniscus; ¢, /, ligaments of the menisci; g, ligamentum crucia- tum anterius; 4, ligamentum cruciatum posterius; 7, ligamentum collaterale tibiale; J, ligamentum collaterale fibulare. Fig. 61.—The capsule of the joint has been opened. 1, femur; 2, tibia (fibula not shown); 3, sesamoid bone in lateral head of M. gastrocnemius; 4, sesamoid in medial head of M. gastrocnemius; 5, tendon of M. popliteus, with sesamoid bone; 6, 7, lateral and medial condyles of the femur, with the intercondyloid notch between them; 8, 9, lateral and medial condyles of the tibia, with the popliteal notch between them; a, 4, medial and lateral menisci; ¢, ligamentum cruciatum anterius; d, liga- mentum cruciatum posterius; ¢, /, ligaments of the lateral meniscus; g, ligamentum collaterale tibiale. mad, between the ends of the two bones forming the joint, into the intercondyloid fossa of the femur, and becomes attached to the medial surface of the lateral condyle of the femur (Fig. 61, c). It is composed of two partially separated bands, form- ing a slight angle with one another. It is crossed near its dorsal and ventral ends by two of the ligaments of the menisci. The ligamentum cruciatum posterius, or posterior crucial liga- go THE SKELETON OF (THE “CAT. ment (Fig. 60, %; Fig. 61, @), begins on the tibia at the edge of the popliteal notch (Fig. 61, @), nearer the medial side, and passes dorsad and proximad to be attached to the ventral edge of the patellar surface of the femur, in the intercondyloid fossa (Eig. 00; 2). (4) LIGAMENTS OF THE MENIScI.—There are five of these, connecting the menisci with the femur or tibia. One (Fig. 60, ¢) passes from the dorsal edge of the medial menis- cus (c) transversely across the anterior crucial ligament (g) to the proximal end of the tibia nearer the lateral side. A second (Fig. 60, 7) passes from the dorsal margin of the lateral meniscus (@) transversely beneath the anterior crucial ligament (g) to the proximal end of the tibia nearer the ventral side and medial border. = == ee bdominis. ey LES SHOWN IN FIG. 73. e, cut end of M. longissimus capitis i, Mm. intercostales externi; £, Mm. intercostales interni; 7, M. transversus a or Bopy, EXPOSED AFTER REMOVAL OF THE Musc M obliquus capitis superior; d, M. longus atlantis; h, M. iliocostalis; 7 Fic. 69.—DEEP MUSCLES a, M. biventer cervicis; b, M. complexus; ¢ M. longissimus dorsi; g; M. spinalis dorsi, 125 126 THE MUSCLES. (a) Muscles of the Lumbar and Thoracic Regions.—The muscles of the lumbar and thoracic regions are mostly covered by a strong fascia, known as the lumbodorsal fascia (Fig. 68, v). This consists of two sheets, the superficial sheet being applied directly to the outer surface of the inner sheet, or sepa- rated from it by a mass of fat. The superficial sheet (Fig. 68, v) overlies the lumbar region and the caudal half of the thoracic region. On the medial side it is attached to the spinous processes of the vertebrae and is united closely to the deeper layer. Laterally this fascia is continuous with the latissimus dorsi (#7) and obliquus abdominis externus (f). Caudad it is attached to the spine of the ilium and becomes continuous with the fascia covering the gluteus muscles. The deeper sheet (Fig. 70, c) is of a tendinous character, forming the external tendinous layer of the longissimus dorsi, many of whose fibres take origin from its under surface. It is described more fully in the account of this muscle. M. longissimus. dorsi (Fig: 69, 7, 7’, 73) Misa yomea and 6).—A very large muscle, filling most of the region between the spinous processes and transverse processes of the lumbar and thoracic vertebra, and extending into the cervical region. The muscle is largest in the lumbar region (Fig. 69, /; Fig. 70), where it is divided into a narrow medial (Fig. 70, a) and a thick lateral portion (Fig. 70, 6), the latter being again partially subdivided by the fascia. The two parts unite farther craniad. The medial division (Fig. 70, a) consists of muscular bundles connecting the spinous processes of the vertebrae with the accessory and mammillary processes of other vertebrae; it is continuous caudad with the extensor caude lateralis (Fig. 70, f). The muscle-fibres take origin in the sacral region by small round tendons from the spinous processes of the last two sacral and the caudal vertebrae. They curve cranioventrad, forming a large belly, and are inserted into the accessory and mammillary processes of the lumbar vertebra. In the thoracic region this division unites with that portion of the lateral divi- MUSCLES OF sion in which the fibres coming from the fascia of origin are in- serted into the lamine and trans- verse processes of the thoracic vertebre. The lateral division (Fig. 70, 6) is much larger than the medial one, forming in the lumbar region a nearly cylin- drical mass. Origin from the crest of the ilium (Fig. 70, 1) and the medial surface of the ilium as far caudad as the auricular impression; also from the deep layer of the lum- bodorsal fascia (c). This fascia is connected with the crest of the ilium and with the tips of the spinous processes of the vertebre in the lumbar and thoracic regions, and from it a large proportion of the fibres of the longissimus take origin. In the lumbar region it dips into the muscle as an intermediate longitudinal sheet (c), partially dividing it lengthwise into two parts. Fibres taking origin from the lateral surface of this inter- mediate sheet curve cranioven- trad, and are inserted on the transverse processes of the lum- bar vertebre. Fibres taking origin from the medial surface of the sheet pass mediocraniad and are inserted into the acces- sory processes and the surfaces’ of the vertebral arches. THE BODY. 127 = : = SSS SSS SS Zia “ ca MAES ‘ 4 Se Se S=== SB 89—-7-ZZA BZ —SSSS== — LLL Z = = Ss —. vie Fic. 70.—MUuUSCLES ON THE DORSAL SIDE OF THE VERTEBRAL COLUMN IN THE LUMBAR, SACRAL, AND CAU- DAL REGIONS. Both sheets of the lumbodorsal fascia have been removed, the deep layer (c) being cut where it passes into the longis- simus dorsi. I, crest of ilium; 4-7, tips of spinous processes of the fourth to seventh lumbar vertebrae, J, Z/, tips of spinous processes of first two sacral ver- tebree. a, 6, M. longissimi dorsi (a, medial portion; 4, lateral portion; 2’, portion taking origin from the lumbo- dorsal fascia); c, cut edge of deep layer of lumbodorsal fascia; d, M. multifidus spine; e, M. extensor caudz medialis; J, M. extensor caudz lateralis. g, M. abductor caudz externus, "Lh? Saero-¢ ‘ hee ov r a bit peated dpm. ‘ (ili peneeeh| In the thoracic region (Fig. GOV7-s) | 128 THE MUSCLES most of the fibres are inserted in separate bundles by small tendons on the transverse processes of the vertebrae, while some of the medial fibres unite with tendinous strands which become attached to the lamine and articular processes of the vertebre. At the region of the eighth or ninth thoracic verte- bra the spinalis dorsi (Fig. 69, ¢) begins to be separated off on the medial side, the separation becoming complete only some distance farther craniad; the longissimus dorsi then con- tinues into the cervical region (/’’). Bundles of fibres become attached in the manner above described to transverse processes of all the thoracic vertebrz. In the cervical region (/”’) the muscle spreads out and becomes thinner, and bundles of fibres become attached to the transverse processes of the cervical vertebree as far forward as the second. In the more cranial portion of its extent the muscle receives fibres having origin on the articular processes and lamina of the cervical and a few of the more cranial thoracic vertebra. The portion of the muscle which is inserted on the cervical transverse processes (/”’) is sometimes distinguished ‘as the longissimus cervicis; it is not well separated from the rest of the muscle in the cat. The longissimus capitis (Fig. 60, e; Fig. 73, g) is to be considered a differentiated cranial portion of this muscle. . Relations. —Outer surface with the following, beginning with the caudal end: the sartorius (Fig. 68, g), the latissimus dorsi (Fig. 68, 7), the lumbodorsal fascia (Fig. 68, y), the serratus posterior inferior (Fig. 73, 2) and superior (Fig. 73, 2), and the levator scapule (Fig. 73, %). Lateral margin with the abdominal muscles, the iliocostal (Fig. 69, ), and the levator scapule (Fig. 73, %). Medial side with the multi- fidus spine (Fig. 70, @), the spinous processes of the thoracic vertebrz, the spinalis dorsi (Fig. 69, ¢), the complexus (Fig. 69, 4), the biventer cervicis (Fig. 69, a), and the longissimus capitis (Fig. 69, ¢@). Action.—Extends the vertebral column. M. iliocostalis (Fig. 69, %).—This is a muscle about 14 to 2 centimeters wide, lying on the dorsal portion of the ribs, laterad of the longissimus dorsi (/’). It is composed of many MUSCLES OF THE BODY. 129 partly separated bundles, each with an oblique tendon. The muscle begins at the last or next to the last rib, where it is connected with the longissimus by a rather small bundle of fibres. The rest of the muscle-fibres take origin in bundles from the lateral surface of the ribs, at about the angles, or from thin tendons connecting the angles, of the ribs; they pass -obliquely craniad and are inserted, usually by tendons, on the lateral surface of the third or fourth rib craniad of the one on which the given bundle has origin. The insertions on any given rib lie ventrad of the origins on the same rib. In the cat this muscle is confined to the thoracic region. Relations.—Outer surface with the serratus posterior inferior (Fig. 73, 2) and superior (Fig. 73, 7), and the levator scapula (I*ig. 73, #). Inner surface with the dorsal surface of the ribs, the external intercostals (Fig. 69, 7), and craniad with the levatores costarum. Medial edge in contact with the longissi- mus dorsi (Fig. 69, /’). Action.—Draws the ribs together. M. spinalis dorsi (I'ig. 69, ¢).—A muscle interconnecting the spinous processes of vertebrae some distance apart, in the thoracic and cervical regions. It lies on the medial side of the longissimus dorsi (/’). Origin by strong tendons from the tips of the spinous pro- cesses of the tenth to the thirteenth thoracic vertebrae. These tendons represent the cranial portion of the deep layer of the lumbodorsal fascia, and give origin also to many fibres of the longissimus dorsi, so that the two muscles are completely united at the origin of the spinalis. They become separated at: about the level of the sixth thoracic vertebra, the spinalis form- ing a strong separate bundle passing into the neck region close against the sides of the spinous processes. The insertion is by fleshy bundles into the sides of the spinous processes of the first nine or ten thoracic vertebre and of the cervical vertebrz as far forward as the second. Some of the fibres of this muscle pass craniad into the biventer cervicis (Fig. 69, a). Relations. —Outer surface with the tendons of the serratus posterior inferior (Fig. 73, 7) and serratus posterior superior (Fig. 73, 7), and with the splenius (Fig. 73, 4), biventer 130 THE MUSCLES. cervicis (Fig. 69, a), and complexus (Fig. 69, 6). | Lateral and ventral surface with the longissimus dorsi (/’); medial surface with the spinous processes and the multifidus spine. Action.—Extensor of the vertebral column. M. multifidus spine.—This consists of bundles of fibres which have origin on the transverse processes or neighboring parts, pass craniodorsad across one or more vertebre, and are inserted into the spinous processes of vertebra lying some dis- tance craniad of the origin. They lie deeper than the muscles previously described. The muscle is most strongly developed in the lumbar region (Fig. 70, @), where it forms a thick inter- woven mass in which it is difficult to distinguish separate bundles. The fibres in this region have origin on the accessory or mammillary processes and usually pass over more than one vertebra between origin and insertion; their insertions reach the dorsal ends of the spinous processes, so that part of the muscle lies immediately beneath the lumbar fascia. In other regions the multifidus is covered by other muscles. In the thoracic region the separate bands are more distinct, and usually pass in their course over but one intervening vertebra. In the cervical region the bands are interconnected, forming a fairly distinct single muscle, which is described separately below as the semispinalis cervicis (ig. 71, c). The portion of this muscle attached to the head (semispinalis capitis) forms the biventer cervicis (Fig. 69, a) and complexus (4). Caudad this muscle passes onto the tail as the extensor caude medialis (hig. 470, 2). Relations.—Outer and lateral surface in the lumbar region with the longissimus dorsi (lig. 69, 7) and the lumbodorsal fascia (Fig. 68, 7); in the thoracic region with the longissimus dorsi (Fig. 69, /’) and spinalis dorsi (g). Inner surface with the arches, articular processes, and spinous processes of the ‘vertebre. Action.—I\ ©): Action.—Pulls the humerus inward (mediad). M. teres major (lig. 75, @; Fig. 77, c).—A thick muscle, triangular in cross-section, lying parallel with the glenoid border of the scapula. Origin (Fig. 76,7; Fig. 78, 6) from the vertebral one-third of the glenoid border of the scapula, and from fascia covering the subscapularis (Fig. 77, @) and the infraspinatus (Tig. 75, ¢) over a small area near the gleno- vertebral angle of the scapula. It may touch the insertion of the rhomboideus. Insertion (F"-82, fy by a tendon common to it and the latissimus dorsi (Fig. 79, @’), as already described. Relations. — Outer — surface with the caput longum (Fig. 75, g) and the long portion (Fig. 80, f) of the caput mediale of the triceps, the latissimus dorsi (Fig. 77, e), and the cutaneus maximus. Inner surface with the serratus anterior (I*ig. 73, 2), the scalenus (Pig! +73, 7), the transversus costarum (Tig. 73,7), and) «the, biceps (Mies 77,"2)); Dorsal border with the subscapu- laris (Fig. 77, a) and infraspina- tus: (Pic3755"c): Fic. 78.—MEDIAL SURFACE OF THE SCAPULA WITH THE AREAS OF ATTACHMENT OF MUSCLES. a, M subscapularis; 4, M. teres major; c, M. serratus anterior; @, M. levator scapule; ¢, M. rhomboideus; /, M. oc- cipitoscapularis; g, M. biceps; 4, M. coracobrachialis; z, caput longum of M. triceps. Action.—Rotates the humerus inward and flexes it in oppo- sition to the infraspinatus, teres minor, and the deltoidei. 164 THE MUSCLES 2. Muscles of the Brachium or Upper Arm. M. clavobrachialis and the pectoralis group (Fig. 65, page 109) lie partly in this region; they have been described. M. coracobrachialis (Fig. 77, 7; Fig. 79, c).—A very short muscle covering the inner (medial) surface of the capsule of the shoulder-joint. It extends from the coracoid process to the proximal end of the humerus. Origin (Fig. 78, 2).—By a round tendon from the tip of the coracoid process. Insertion (Fig. 82, e) usually by fleshy fibres on an area five to eight millimeters long and about half as wide, which lies on the medial side of the humerus parallel with the ridge which runs from the dorsal end of the lesser tuberosity to the shaft and close to it. The proximal end of the area is about one centimeter from the proximal end of the head of the humerus. Relations. —Medial surface with the biceps (Fig. 77, xg), pectoralis minor (Fig. 65, 0), and teres major (Mig. 77, ¢). Lateral surface with the capsule of the shoulder-joint. Dorsal border with the subscapularis (Fig. 77, a) and the long portion of the caput mediale of the triceps (Fig. 77,7). Action.—Adducts the humerus. The part of the coracobrachialis just described is known as the short head. A Jong head is sometimes found. It is a conical bundle of fibres of varying size, which arises from the tendon of origin of the short head. It passes distad into a long and extremely slender tendon, the insertion of which varies greatly in different individuals. It is commonly on the humerus in the region of the supracondyloid foramen. _ M. epitrochlearis or extensor antibrachii longus (Fig. 65, +).—A thin, flat muscle on the inner or medial side of the brachium, from the lateral surface of the latissimus dorsi (Fig. 65, g) to the olecranon process of the ulna. Origin from the lateral or outer surface of the ventral border of the latissimus dorsi (Fig. 65, g) near the insertion of the cutaneus maximus. Fibres are often attached to the teres major and the pectoralis minor. Insertion by a flat tendon which is closely connected with MUSCLES ‘OF THE THORACIC LIMBS: 165 that of the pectoantibrachialis (Fig. 65, 7) and is continuous with the general antibrachial fascia, into the caudal border of the cutaneous (dorsal) surface of the olecranon process of the ulna. Relations.—Outer (medial) surface with the integument, the latissimus dorsi (Fig. 65, g), and the cutaneus maximus. Inner (lateral) surface with the biceps (Fig. 65, 7), caput longum (Fig. 65, s), and caput mediale (Fig. 77, 7, &) of the triceps. Action.—Extends the antibrachium and tends to supinate the hand by rotating the ulna. M. biceps brachii (Fig. 77, ¢; Fig. 65, 2).—A thick, fusi- form muscle lying on the front (ventral) surface of the humerus. Origin (Fig. 76, c) by a strong, round tendon from the bicipital tubercle of the glenoid angle of the scapula, at its coracoid margin. (In man there is a second head—coracoid head—from the coracoid process.) The tendon passes through the capsule of the joint and then along the bicipital groove, which is converted into a canal by a strong ligament. Insertion by a rounded tendon (Fig. 87, 4) on the bicipital tuberosity of the radius (Fig. 86, £). Relations. —The tendon of origin passes through the capsule of the joint, which is covered by a part of the pectoralis minor. The muscle is then spanned for the middle part of its course by the bicipital arch (lig. 65, ¢’), a description of which is given below. Farther distad it is covered by the clavobrachial (Fig. 65, &) and epitrochlearis (Fig. 65, 7). At its distal end (Fig. 79, 7’) the muscle passes between the pronator teres on the radial side and the conjoined tendon of the brachialis and clavobrachial (Fig. 79, z’) on the other. The biceps lies throughout most of its length on the ventral surface of the humerus, and touches along the medial border of its inner sur- face the coracobrachialis (Fig. 77, f), the teres major (Fig. 77, ¢), the intermediate portion of the caput mediale of the triceps (Fig. 77, &), and the short portion (Fig. 77, 2) of the same. Its lateral border touches the pectoralis minor (Fig. 65, 0) and the brachialis (Fig. 79, 2). Action.—Flexes the forearm, and tends to supinate the hand. 166 THE MUSCLES. The bicipital arch (Fig. 65, ¢’) is a tendinous arch formed over the biceps muscle. Its outer or lateral pillar is formed by the tendon of the pectoralis minor (0), to which may be added part of the latissimus (g) tendon. Its inner or medial pillar is formed by the conjoined tendon of the teres major and latissimus dorsi (Fig. 79, @’), while the xiphihumeralis (Fig. 65, £), cutaneus maximus (Fig. 62, 4), and epitrochlearis (Fig. 65, ~) are connected with one or the other pillar or with the muscles composing them. The caudal portion of the deep layer of the pectoralis major (Fig. 65, 7) may be connected with the inner pillar. M. brachialis (Fig. 79, 7; Fig. 75, 2).—From the lateral surface of the humerus to the ulna. Origin (Fig. 83, g, g’) from a long V-shaped line two to four millimeters wide on the lateral surface of the humerus. The apex of the V is just distad of the teres minor tubercle (¢). Its dorsal limb (g’) extends along the lateral supracondyloid ridge to a point opposite the proximal margin of the supra- condyloid foramen; its ventral limb (g) extends in the direc- tion of the deltoid ridge to the middle of the bone. No muscle-fibres take origin between the two limbs. The fibres converge and end ina flat tendon which joins the tendon of the clavobrachial (Fig. 79, 2). Insertion (Fig. 87, c).—The dorsal portion of the depressed rough area on the lateral surface of the ulna just distad of the semilunar notch. Relations.—Outer surface with the acromiodeltoid (lig. 75, /), the caput laterale of the triceps (Fig. 75,0/2),@ne brachioradialis (Fig. 75, #), and the proximal end of the ex- tensor carpi radialis longus (Fig. 75, 7). Inner surface with the humerus. Medial edge with the pectoralis major (Fig. 65, 2) and the biceps (Fig. 77, g). Action.—F lexor of the antibrachium. M. triceps brachii.—The triceps muscle of the cat, like that of man, is divisible (as its name indicates) into three main portions. These are a lateral portion (caput laterale), an intermediate or long portion (caput longum), and a medial por- tion (caput mediale). The first two correspond to the simi- MUSCLES OF THE THORACIC LIMBS. 167 larly named heads in man; the medial portion falls into a number of subdivisions whose homologues are uncertain. Fic. 79.—DEEP MUSCLES ON THE MEDIAL SIDE OF THE HUMERUS. a, M. supraspinatus; 4, M. subscapularis; c, M. coracobrachialis; ad, M. teres major (@’, its tendon); ¢, part of M. latissimus dorsi joining the teres major; f, cut end of M, pectoralis minor; g, long part of caput mediale of M. triceps brachii; 4, in- termediate part of caput mediale of M. triceps; 7, M. brachialis (2’, its tendon); 7, short part of caput mediale of M. triceps; 4, cut end of M. clavobrachialis; /, 2’, cut ends of M. biceps; 7, M. brachioradialis; 7, M. extensor carpi radialis longus; 0, M. ex- tensor carpi radialis brevis; /, fifth head of M. flexor profundus digitorum; g, first head of M. flexor profundus digitorum. 1, humerus; 2, olecranon; 3, medial epi- condyle of humerus. Caput laterale (anconeus lateralis) (Fig. 75, 7; Fig. 68, 7). —The lateral portion is a flat muscle (most of it subcutaneous) on the lateral side of the brachium, connecting the proximal end of the humerus with the olecranon process of the ulna. 168 THEASMUSCLES: Origin (Fig. 81, 4’).—By a flat tendon trom the proximal portion of the deltoid ridge and the distal border of the teres minor tubercle. Insertion (Fig. 86, c) by a thin, flat tendon into the lateral border of the dorsal surface of the ulna between a point oppo- site the dista] margin of the semilunar notch and the proximal end of the olecranon. Relations.—Lateral surface with the integument, and at the proximal end with the spinodeltoid and acromiodeltoid (Fig. 75, eand /). Medial surface with the brachialis (Fig. 75, 2), the caput longum (xg), the caput mediale, the brachioradialis (4), the anconeus (I*ig. 80, 7), and the origins of the extensor carpi radialis longus (lig. 75, 7), the extensor communis digitorum (wm), and the extensor digitorum lateralis (v). Caput longum (anconeus longus) (I"ig. 75, ¢; Fig. 68, 2; Fig. 77, z).—A prismatic, fusiform mass connecting the scapula with the olecranon. Origin (Fig. 78, 2) by a thick, flat tendon from a triangular area one or two centimeters long at the glenoid end of the scapula on the glenoid border. The base of the area is about one millimeter from the margin of the glenoid fossa. Insertion (Fig. 86, 6).—The muscle ends in a thick tendon which passes over the bifurcated ventral end of the olecranon and is inserted upon the rounded tuberosity which forms the dorsal angle of the olecranon. Relations.—Lateral surface with the caput laterale (Fi ig. 75, 4), a portion of the caput mediale (Fig. 77, 7 and 4), the spinodeltoid (Fig. 75, e), the infraspinatus (Fig. 75, c), and the integument. Medial surface with the epitrochlearis (Fig. 65, “) and the conjoined portions of the latissimus dorsi and teres major (Fig. 79, @’). Ventral border with the caput mediale (Fig. 77, 7 and &). Caput mediale.—The medial head consists of three portions Giga 7.9,, 7). (1) The long portion (anconeus posterior) (Fig. 77, 7; Fig. 79, &; Fig. 80, /). Origin (Fig. 83, e) from a triangular area on the dorsal sur- face of the humeral shaft. The base of the area is against the MUSCLES OF THE THORACIC LIMBS. 169 articular head, and its apex about one-sixth the length of the humerus from the head. It is between the coracobrachialis and the lateral head of the triceps. Fic. 80.—DEEP MuSCLES ON THE LATERAL SURFACE OF THE Humerus, a, part of M. supraspinatus; 4, part of M. infraspinatus; c, M. teres minor; @, M. teres major; ¢, part of M. latissimus dorsi joining M. teres major; /, long part of caput mediale of M. triceps brachii; g, cut insertion of M. acromiodeltoideus; ”, M. brachi- alis; 2, M. brachioradialis; 7, intermediate part of caput mediale of M. triceps brachii; &, M. extensor carpi radialis longus; 7, M. anconeus; 7, M. extensor communis digi- torum. I, great tuberosity of humerus; 2, 3, superficial radial and dorsal interos- seous branches, respectively. of the radial nerve. Insertion (Fig. 86, @).—The muscle ends in a long, slen- der tendon which passes through the furrow on the ventral 170 THE MUSCLES. angle of the olecranon and is inserted into an oblique ridge which forms the dorsal limit of the furrow. The tendon is separated from the floor of the furrow by a synovial bursa. (2) The intermediate portion (anconeus internus) (Fig. 77, ec 1S%: 70, i ioe OOn 7a). Origin (Fig. 82, g) by fleshy fibres from a triangular area proximad of the middle of the dorsomedial surface of the humerus. The length of the area equals about one-fourth the length of the bone. Its apex points proximad and is almost continuous with the apex of the area of origin of the long por- tion. Insertion (Fig. 87,7) by short tendon-fibres into the medial border of the ventral and proximal surfaces of the olecranon. It is connected with the tendon of the long portion. (3) Short portion (Fig. 70.074 is-b770e)- Origin (Fig. 82, 4) from the outer surface of the bony bar which encloses the supracondyloid foramen of the humerus, as far as the medial epicondyle. oe Insertion (Fig. 87, e) by fleshy fibres into the medial border of the olecranon distad of the tuberosity for the insertion of the caput longum. Relations of the caput mediale.—Lateral surface with the caput laterale (Fig. 75, %), the humerus, and the anconeus (Fig. 80, 7). -Dorsal surface with the caput longum (Fig. 77, 2), the epitrochlearis (Fig. 65, 7), and the teres major (Fig. 79, @). Ventral surface with the biceps (Fig. 77, g). Action of the Triceps.—The entire triceps group forms a powerful extensor of the forearm. The short portion of the medial head tends also to rotate the arm outward, so as to supinate the hand. M. anconeus (Fig. 80, /).—A triangular muscle on the outside of the elbow-joint from the humerus to the ulna. Origin (Fig. 83, 2).—An irregularly triangular area at the distal end of the dorsal surface of the humerus. The area of origin is limited laterally by the sharp lateral supracondyloid ridge. It sometimes extends onto the lateral epicondyle. Insertion (Fig. 86, @).—The lateral surface of the ulna from the distal margin of the semilunar notch to the proximal end MUSCLES OF THE THORACIC LIMBS 171 t- i} | P Le UTA EMERY | q Kili il "| ww AN Co ait TL Ki : — Ly ,) AN Fic. 81.—VENTRAL Sur- Fic. 82.—MEDIAL SIpE_ Fic, 83.—DoRSAL SURFACE FACE OF HUMERUS, OF HUMERUS, WITH OF THE LEFT HuUMERUS, WITH THE AREAS OF THE AREAS OF AT- WITH TIE AREAS OF ATTACHMENT OF MuS- TACHMENT OF MUusS- ATTACHMENT OF Mus- CLES. CLES. CLES. Fig. 81.—a, M. subscapularis; 4, M. supraspinatus; c, Mm. teres major and latis- simus dorsi; d, M. pectoralis minor; ¢, deep layer of M. pectoralis major, 7, super- ficial layer of M. pectoralis major; g, M. acromiodeltoideus; 4, M. spinodeltoideus; h’, caput laterale of M. triceps; 7, M. brachialis; 7, second portion of M. brachialis; ~ k, M. extensor carpi radialis longus; 7, M. extensor carpi radialis brevis; 7, M. ex- tensor communis digitorym; 7, M. extensor lateralis digitorum; 9, M. extensor carpi pene: short portion of caput mediale of M. triceps; 7, M. pronator teres; 7, M. palmari§ longus; s, third and fourth parts of M. flexor profundus digitorum; 7, M. flexor carpi radialis; 2, second héad of M. flexor profundus digitorum. Fig. 82.—a, M. supraspinatus; 4, M. subscapularis; c, M. pectoralis minor; d, long portion of caput mediale of M. triceps; e, M. coracobrachialis; /, Mm. teres ;-major and latissimus dorsi; g, intermediate portion of caput mediale of M. triceps; 4, deep layer of M. pectoralis major; 7, superficial layer of M. pectoralis major; 7, M. anconeus; 4, short portion of caput mediale of M. triceps; 4 M. pronator teres; my M, flexor carpi radialis; 7, second head of M. flexor profundus digitorum; a, third and fourth heads of M. flexor profundus digitorum; /, M. palmaris longus; g, M. :flexor carpi ulnaris. Fig. 83.—a, M. supraspinatus; 4, M. subscapularis; c, M. infraspinatus; d, M. teres minor; ¢, long portion of caput mediale of M. triceps; /, M. coracobrachialis; & &, M. brachialis; 4, intermediate portion of caput mediale of M, triceps; 7, M. anconeus; 7, short portion of medial head of M. triceps; 2, M. pronator teres; 4 second and third heads of M. flexor profundus digitorum; 7, M. palmaris longus; n, M. extensor carpi ulnaris. 172 THE MUSCLES: of the olecranon. The muscle covers the capsule of the joint and is closely adherent to it. Relations.—Outer (dorsal) surface with the caput laterale (Fig. 75, 2) and the intermediate portion (Fig, 80; 7)) of the caput mediale. Inner surface with the bones and the capsule of the joint. Action.—Keeps the capsule tense and probably rotates the ulna slightly so as to pronate the hand. 3. Muscles of the Antibrachium or Forearm. Fascia of the Forearm.—The muscles of the forearm are not in contact with the skin, but are covered by the strong antibrachial fascia. This consists of two layers. The super- ficial one is a continuation of the general subcutaneous fascia of the arm; it covers the forearm as a continuous sheet which becomes thinner distad, and is finally lost near the wrist. The deep layer forms a dense, tendinous sheet which is closely applied to the muscles. It begins partly as a continuation of the general fascia of the arm, partly from the tendons of the triceps and epitrochlearis muscles. The sheet is attached to the dorsal surface of the ulna, between the extensor carpi ulnaris and the first head of the flexor profundus digitorum. It surrounds the forearm as a continuous sheath. On the lateral surface it dips between the extensor muscles, becoming closely attached to them and forming a partial sheath for each; it is attached with special firmness to their tendons. On the medial side of the arm the fascia passes smoothly over the flexors without dipping between them; it is continuous, however, with the border of the pronator teres, and distad of this muscle it is firmly attached to the radius. At the wrist the fascia becomes attached to the longitudinal ridges on the dorsal surface of the head of the radius, bridging thus the intervening grooves and holding the tendons in place between the ridges. The fascia then continues to form the dorsal fascia of the hand. On the ventral side of the wrist the fascia becomes thickened to form a strong transverse ligament (Fig. 77, 1), which is attached at its radial and ulnar ends to the carpus, and which holds in place the tendons of the MUSCLES OF THE THORACIC LIMBS. 73 flexor muscles. Distad of the transverse ligament the fascia spreads out in the palm of the hand, and becomes united with the fibrous pad which is situated here. On the fingers the fascia becomes attached to the phalanges, forming tendinous sheaths, the so-called vaginal ligaments, for the flexor muscles. Near the base and the head of the first phalanx strong, narrow, ring-like bands, the annular ligaments (Fig. 88, 2), are formed in these sheaths; these surround and bind down the tendons of the flexor muscles. A. MUSCLES ON THE ULNAR AND DORSAL SIDE OF THE FOREARM (extensors and supinators) (Fig. 75, p. 158). M. brachioradialis or supinator longus (Fig. 75, £; Fig. 77, n).—This is a ribbon-like muscle lying on the lateral side of the brachium and the ventrolateral border. of the antibra- chium just beneath the superficial fascia. It connects the humerus and the radius. Origin.—By a thin tendon from about the middle fifth of the dorsal border of the humerus, or sometimes proximad of the middle. The muscle curves over the outer surface of the brachialis (Fig. 75, 2), to which it is closely applied, and runs along the lateral border of the antibrachium to its insertion. Lnsertion by a short tendon into the ridge which forms the ventral limit of the groove on the outer surface of the styloid process of the radius and upon the adjacent ligaments. Relations. —Outer surface with the integument, and at the proximal end with the caput laterale of the triceps (Fig. 75, %). Inner surface with the brachialis (2), the extensor carpi radialis longus (7) and brevis, and the extensor communis digitorum (vz). A ctton,—Supinator of the hand. M. extensor carpi radialis longus (Fig. 75, /; Fig. 77, 0).—This lies along the radial side of the forearm, and con- nects the humerus and the second metacarpal. Origin (Fig. 81, &) from the middle portion of the lateral supracondyloid ridge between the origin of the brachialis (7) and the anconeus. About the middle of the forearm the muscle ends in a slender tendon (Fig. 84, ¢) which passes through the groove on the radial side of the dorsal surface of the distal end of the radius. 174 THE MUSCLES. Insertion (Vig. 84, e¢).—The tendon passes across the car- pus and is inserted onto the dorsal surface of the base of the second metacarpal on the radial side just distad of the groove for the radial artery. Relations.—Outer surface at the proximal end with the caput laterale of the triceps (Fig. 75, %), farther distad with the integument and the brachioradialis (4#); the distal tendon with the extensor pollicis brevis (Fig. 84, d). Radial surface with the brachialis (Fig. 75, z) and the integument. Ulnar surface with the extensor carpi radialis brevis (Fig. 77, f), and near the proximal end with the extensor communis digitorum (Fig. 75, 22). Action.—¥xtensor of the hand. M. extensor carpi radialis brevis (Fig. 77, ~).—A slender muscle from the humerus to the third metacarpal. Origin (Tig. 81, 7) from the distal part of the lateral supra- condyloid ridge distad of the extensor longus. Near the carpus the muscle ends in a slender tendon which passes through the groove with the extensor longus tendon. The tendon then diverges from the extensor longus and has its Insertion (Vig. 84, f) into the radial side of the dorsal sur- face of the base of the third metacarpal. Relations.—Outer surface with the extensor longus (Fig. 77, 0), the integument, and distad with the extensor pollicis brevis (Fig. 84, 7). Radial surface with the extensor longus. Ulnar surface with the extensor communis digitorum (Fig. 75, m)-and the extensor brevis pollicis. Inner surface with the pronator teres (Fig. 77, 7), supinator (Fig. 85, 4), and extensor brevis pollicis (Fig. 85, @). Action. —¥xtensor of the hand. M. extensor digitorum communis (Fig. 75, #).—A slen- der muscle from the lateral supracondyloid ridge of the humerus to the phalanges of the second, third, fourth, and fifth digits. Origin (lig. 81, m).—The distal surface of the lateral supracondyloid ridge dorsad of the origin of the extensor carpi radialis brevis. At the junction ofthe middle and distal thirds ofthe radius the muscle passes into a large, flat tendon (Fig. 75, 7’) which passes MUSCLES OF THE THORACIC LIMBS. 175 through the groove on the middle of the dorsal surface of the distal end of the radius. The groove is converted into a canal by a strong transverse ligament. The tendon divides near the groove into four portions (Fig. 84, a) which diverge and pass to the four ulnar digits. Insertions. —YVéach division of the tendon as it passes over the dorsal sur- face of the first phalanx has its border connected by strong fascia to the dorsal surface of the phalanx. It finally passes through the groove at the distal end of the first phalanx and is inserted mostly into the base of the second phalanx; a portion continues distad to be inserted into the third phalanx. Relations. —Outer surface with the integument and at the origin with the caput laterale (Fig. 75, /) of the triceps. Radial surface with the extensor longus (7) and extensor brevis. Ulnar surface with the extensor digitorum lateralis (7). Inner surface with the supinator (Fig. 85, 6) and the extensor pollicis brevis (Fig. o> a): e Fic. 84.—ARRANGEMENT OF Action.—Extensor of the four ulnar rue Tenpoxs on THE digits BACK OF THE HAND. ate ; a, M. extensor communis M. extensor digitorum lateralis digitorum; b, M, extensor late- Fig. z). (This corresponds in posi- ‘is digitorum; c, M. exten- ( 8-75) ) ( P I sor indicis; d, M. extensor tion to the extensor digiti quinti proprius brevis pollicis; e, M. extensor of man.) carpi radialis longus; 7, M. extensor carpi radialis brevis; Origin (Fig. 81, 2) from the lateral g, M. extensor carpi ulnaris; supracondyloid ridge of the humerus Me ES ate distad of the origin of the extensor wrist. communis. The muscle passes along the ulnar border and dorsal surface of the forearm between the extensor communis (Fig. 75, 7) and the extensor carpiulnaris(0). Near the carpus it ends ina tendon 176 THE MUSCLES. (x), which divides immediately into three or four (Fig. 84, 4). These pass through the groove on the ulnar side of the dorsal surface of the radius and diverge to the digits lying beneath the extensor communis tendon. Insertion (Fig. 84, 6).—The three tendons on the ulnar side join the ulnar sides of the tendons of the extensor com- munis (a) at their insertions. The radial of the four tendons (not always present) joins the tendon of the extensor indicis (c) and may also give a branch to the radial side of the base of the first phalanx of the third digit. Relations. —Outer surface with the integument. Radial border with the extensor communis digitorum (7); ulnar border with the extensor carpi ulnaris (0). Inner surface with the supinator (Fig. 85, 4) and the extensor brevis pollicis (Fig. 85, a); distad with the extensor indicis (ig. 85, ¢). Action.—Extensor of the four ulnar digits. M. extensor carpi ulnaris (lig. 75, 0). Origin.—(1) By a short, broad tendon from the distal por- tion of the lateral epicondyle of the humerus (Fig. 81, 0) distad of the origin of the extensor lateralis, and (2) by a smaller tendon from the ulna at the dorsal tip of the semilunar notch (Fig. 86, 2). The muscle passes along the ulnar side of the forearm dorsad of the extensor digitorum lateralis (vz). It ends near the junction of the middle and distal thirds of the forearm in a large, flat tendon (0’) which is closely adherent to the ligaments of the wrist and which passes over the distal end of the ulna to its Insertion into the tubercle on the ulnar side of the base of the fifth metacarpal (Fig. 84, ¢). Relations.—Outer surface with the integument. Radial (or ventral) border with the extensor digitorum lateralis (Irig. 75, 2); ulnar (or dorsal) border with the flexor profundus digi- torum (g). Inner surface with the radius, the extensor indicis Fig. 85, c), and the extensor pollicis brevis (Fig. 85, a). Action.—Indicated by its name. M. extensor indicis (proprius) (Fig. 85, c; Fig. 75, p) (in- cludes extensor pollicis longus also). MUSCLES OF THE THORACIC LIMBS. D7 Origin (Fig. 86, f) by short, fleshy fibres from the lateral surface of the ulna between the semilunar notch and the junce. tion of the third and fourth (distal) fourths. The muscle-fibres pass obliquely distad and toward the radial side and join the tendon (Mig. 85, ¢’), which runs nearly the whole length of the radial surface. Insertion (Fig. 84, c).—The tendon passes through the groove on the ulnar side of the dorsal surface of the base of the radius and divides into two. Both of these usually go to the base of the second phalanx of the second digit, but one may pass to the pollex, or there may be three divisions going to the first three digits. hic, 85.—Drrre MuscLes ON THE EXTENSOR SURFACE OF THE RADIUS AND ULNA. a, M. extensor brevis pollicis (a’, its tendon); 4, M. supinator; c, M. extensor in- dicis (c’, its tendon); @, tendon of M. extensor carpi radialis brevis; e, tendon of M. extensor carpi radialis longus. I, humerus; 2, olecranon; 3, styloid process of ulna; 4, distal end of radius; 5, head of radius. Relations.—Outer surface with the integument, the extensor carpi ulnaris (ig. 75, 0), and the extensor digitorum lateralis (Fig. 75, 2). Dorsal border with the flexor profundus digi- torum (Fig. 75, 7). Inner surface with the extensor brevis pollicis (Fig. 85, a). Action as indicated by the name. M. supinator (Fig. 85, 4).—A flat muscle wrapped spirally about the proximal end of the radius. Origin by a short, strong tendon from the lateral side of the annular ligament of the radius and by tendinous fibres from the ' radial collateral ligament passing from the humerus to the radius. From the tendon of origin the fibres diverge, passing toward the radial side and distad. Insertion (Fig. 86, g).—The dorsal and part of the ventral surface of the proximal two-fifths of the radius to within 178 Fic. 86. — LATERAL OR EXTENSOR SUR- FACE OF RADIUS AND ULNA, WITH THE AREAS OF ATTACH- MENT OF MUSCLES. a, long portion of caput mediale of M. triceps; 4, caput lon- gum of M. triceps; ¢, caput laterale of M. tri- ceps; @, M. anconeus; e, M. extensor carpi ulnaris; /, M. extensor indicis; g, M. supina- tor; 4, M. extensor brevis pollicis; 7, M. pronator teres; 7, M. flexor profundus digi- torum; %, M. biceps. THE MUSCLES five millimeters of the articular face of the head. Relations.—Outer surface with the ex- tensor carpi radialis brevis, extensor com- munis digitorum (Fig. 75, #z), and extensor lateralis digitorum (Fig. 75, 2). Radial border with the pronator teres (Fig. 77, 9). Inner surface with the radius. Action.—Supinator of the hand. M. extensor brevis pollicis or extensor ossis metacarpi pollicis (Fig. 85, @) (includes M. abductor longus pollicis of man). Origin (Fig. 86, %) by fleshy fibres from the ventral half of the lateral surface of the shaft of the ulna from the semilunar notch to the styloid process; from the ulnar half of the dorsal surface of the radius from the bicipital tubercle to a short distance distad of the middle of the bone;-and from the interosseous membrane between these two areas. The fibres converge to form a strong, flat tendon (Fig. 84, @) which passes obliquely over the tendons of the extensor carpi radialis longus (e) and brevis (/) to its Insertion into the radial side of the base of the first metacarpal. The radial sesamoid bone of the wrist is imbedded in the tendon at its insertion. Relations. —Outer surface with the ex- tensor carpi radialis brevis, the extensor communis digitorum (Fig. 75, 2), extensor lateralis digitorum (Fig. 75, 7), and extensor indicis (Fig. 85, ¢). Inner surface with the radius and ulna, and distad with the tendons of the two extensores carpi radiales (Fig. 84, e and /). Action.—Extends and abducts the pol- lex. MUSCLES OF THE THORACIC LIMBS. 179 B. MUSCLES ON THE RADIAL AND VENTRAL SIDE OF THE FOREARM (flexors and pronators). M. pronator teres (Fig. 77, ¢@). Origin (Fig. 82, 7) by a short strong tendon from the extremity of the medial epicondyle of the humerus. Insertion (Fig. 86, z) by fleshy fibres and short tendinous fibres along the medial border of the radius, at its middle. The radial edge of the muscle is continuous with the strong deep layer of the antibrachial fascia. Relations.—Outer surface with the superficial fascia. Radial border with the tendon of the biceps (Fig. 79, 2’), with the extensor carpi radialis brevis (Fig. 77, ), and the supinator (Fig. 85, 6). Ulnar border with the flexor carpi radialis (Fig. 77, r) and part of the flexor profundus digitorum (Fig. 77, 7). A ction.—Pronates the hand by rotating the radius. M. flexor carpi radialis (Fig. 77, v).—A slender fusiform muscle. ~ Origin (Fig. 82, m) from the tip of the medial epicondyle of the humerus. Insertion.—The slender tendon passes through a deep groove between the os magnum and the first metacarpal. The groove is converted into a canal by the overlying tendons and muscles. The tendon is finally inserted into the bases of the second and third metacarpals. Relations.—Outer surface with the pronator teres (Fig. 77, q), the superficial fascia, and the third head of the flexor profundus (w). Radial border with the pronator teres (@). Ulnar border with the third and fourth heads of the flexor pro- fundus. Inner surface with the ulna proximad and the fifth head of the flexor profundus (z’) distad. Action indicated by the name. M. palmaris longus (Fig. 77, s).—A flat fusiform muscle beneath the fascia on the medial border of the forearm. Origin (Fig. 82, £) by a short flat tendon from the distal part of the medial surface of the medial epicondyle of the humerus. About one centimeter from the wrist the muscle ends in a flat tendon which passes through the transverse ligament and divides on the hand into four or five (or sometimes only three) 180 THE MUSCLES. ~—— tendons (Fig. 77, s’) which diverge to the insertions. The ulnar portion of the flexor sublimis digitorum (Fig. 77, 2) takes origin from the common tendon before its division. Insertion.—\ach tendon except the first gives off a branch which spreads out in the trilobed pad in the palm. The middle two of these may be traced to the integument covering the pad. The tendon is then inserted (Fig. 88, a) near the base of the first phalanx onto the outer surface of the perforated portion of the flexor sublimis tendon (4, 6’) at its side, except that to the thumb, which divides near its distal end into two which are inserted into the sesamoid bones at the base of the first phalanx. The tendons of insertion are closely united to the fibrous pulley- ring at the base of the first phalanx, and each may send a slip to the base of the phalanx at either side of the ring. Relations. —Outer surface with the superficial fascia and one head of the flexor sublimis (Fig. 77, x). Radial border with the flexor carpi radialis. Ulnar border with the flexor carpi ulnaris and a part of the flexor profundus digitorum. Inner surface with the flexor carpi radialis (7), the flexor carpi ulnaris (4), the flexor profundus digitorum (7), and the radial head of the flexor sublimis digitorum. Action.—F¥ \exor of the first phalanx of each of the digits. M. flexor carpi ulnaris (Fig. 77, ¢, 7’). Origin.—There are two heads. The first or humeral head (¢’) takes origin in common with the second part of the flexor profundus from the median surface of the distal end of the humerus just distad of the medial epicondyle (Fig. 82, g). The second or ulnar head () takes origin by fleshy fibres from the lateral surface of the olecranon and from the dorsal border of the ulna from the olecranon to a point distad of the semilunar notch (Fig 87, f). The two heads join proximad of the middle of the forearm. The muscle passes obliquely across the ven- tral surface of the forearm to its Insertion by fleshy and tendinous fibres into the proximal surface of the pisiform bone. Relations. —Outer surface with the integument and the palmaris longus (Fig. 77, s). Inner surface and ulnar border with the flexor profundus digitorum. MUSCLES OF THE THORACIC LIMBS. 181 Action indicated by the name. M. flexor sublimis digitorum (or perforatus).--This muscle is in two parts, which are given a common name only because of the similar structure and insertions of their tendons. The ulnar part (Fig. 77, +) is a conical muscle taking origin from the outer surface of the tendon and muscle of the palmaris longus and from the adjacent ligament. It gives rise to two or three tendons (Iig. 88, 6) which arise from distinct slips of the muscle; these pass to the ulnar two or three digits. That passing to the fourth or fifth digit receives an accessory slip from a small mass of fibres attached to the transverse liga- ment on the radial side of the palmaris tendon. The radial part is a small flat triangular muscle which takes origin from the outer surface of the tendon formed by the junction of the tendons of the first and second parts of the flexor profundus. It divides into two slips, each giving rise to a tendon. These tendons (Fig. 88, 6’) pass to the second and third digits. That to the third digit may divide into two, one of which goes to the fourth digit. Hach of the four tendons (Fig. 88, 6 and 0’) is perforated by a tendon of the flexor profundus (Fig. 88, c) as it passes through the fibrous pulley-ring at the base of the first phalanx. It then continues beneath the flexor profundus tendon through the second pulley-ring (2) and is inserted into the base of the second phalanx. Relations. —Outer surface of the ulnar part with the integu- ment; inner surface with the palmaris longus (Fig. 77, s). Outer surface of the radial part with the palmaris longus; inner surface with the flexor profundus. Action.—Flexor of the second phalanx of digits 2-5. M. flexor profundus digitorum (or perforans).—This arises by five heads, the tendons of which join one another at the wrist to make the strongest and deepest of the flexor tendons. The frst or ulnar head has origin (Fig. 87, ¢) from the dor- sal half of the medial (radial) surface of the ulna from the proximal lip of the semilunar notch to within a centimeter of the styloid process. Its fibres converge to a large flat tendon which forms the lateral (ulnar) and superficial part of the common tendon. 182 Fic. 87.—RabIUuS AND ULNA, Medial or Flexor Side, with M. pronator quadratus and the Areas of Attachment of Other Muscles. a, M. pronator quadratus; 4, tendon of M. biceps; ¢, conjoined tendon of M. brachialis and M. clavobrachialis; @, insertion of caput longum of M. triceps; ¢, insertion of short portion of caput mediale of M, triceps; /, origin of M. flexor carpi ulnaris; g, origin of first head of M., flexor profundus digitorum; 4, origin of fifth head of M. flexor profun- dus digitorum; z, intermediate portion of caput mediale of M. triceps. THE MUSCLES. The second head has origin (Fig. 82, 2) from the distal end of the medial epicondyle of the humerus between the flexor ulnaris and the third and fourth heads of the profun- dus. It may be very closely attached to these muscles at their origins. Its tendon joins the radial border of the tendon of the first head. From this junction the radial part of the flexor sublimis arises. The third head (Fig. 77, u) has origin (Fig. 82, 0) by astrong tendon from the medial epicondyle of the humerus, between the palmaris (/) and flexor radialis (#). Its tendon forms the radial part of the common tendon. The fourth head has origin by a strong tendon from the medial epicon- dyle of the humerus just ventrad of the origin of the second head and the flexor ulnaris, to which many of its fibres are attached. Its tendon forms the middle and superficial part of the common tendon. — The fifth or radial head (Fig. 75, qg; Fig. 77, wv’) has origin (Fig. 87, ) from the middle third of the ventral surface of the shaft of the radius over an area limited by two oblique bony ridges; from the adjacent parts of the interosseous membrane; and from the ventral part of the medial surface of the shaft of the ulna between a point about two centimeters distad of the semi- lunar notch and the junction of the middle and distal thirds of the shaft. MUSCLES OF THE THORACIC LIMBS. 183 Its very thick tendon forms the middle and deep part of the common tendon. The common tendon (Fig. 88, c’) covers the carpus and metacarpus ven- It divides into five tendons (c) which pass to the five digits and are z7- trally. serted into the bases of the terminal phalanges. Those of the first four digits perforate the tendon of the flexor sublimis (6) at the base of the first phalanx of each digit. At the same place each passes through a fibrous pulley-ring attached to the base of the phalanx. Each then passes through a second pulley-ring (2) near the head of the phalanx and is finally inserted into the base of the terminal phalanx. Relations. — Outer surface with the pronator teres (ig. 77, ¢), flexor carpi radialis (lig. 77, 7), palmaris longus (s), flexor carpi ulnaris (2), integument, and extensor carpi ulnaris (Fig. 75, @). surface with the radius, ulna, interosseous Inner membrane and pronator quadratus (Fig. 37. a). Action.—F lexor of all the digits. M. pronator quadratus (Fig. 87, a). —A thick quadrangular muscle whose fibres run obliquely between the distal ends of the ulna and radius. Origin by fleshy fibres from about the distal half of the ventral (flexor) surface or border of the ulna and from the interos- seous membrane adjacent to the area. The fibres pass obliquely distad toward the radial side to their Insertion by fleshy fibres into the ven- Fic, 88.— ARRANGEMENT OF THE TENDONS of M. palmaris longus, M, flexor sublimis digito- rum, and M. flexor pro- fundus digitorum, with Mm. lumbricales. The integument, fibrous pads, and the _ palmaris longus (except the ends of its tendons) have been re- moved; the flexor sublimis has been cut. a, cut ends of tendons of M. palmaris longus; 4, tendons of M. flexor sublimis digitorum, ulnar division; 6’, radial part of M. flexor sublimis digitorum; ¢, tendons of M. flexor profundus digi- torum (c’, the common ten- don); d, M. abductor digi- ti quinti; e, M. flexor brevis digiti quinti; -74, Mm. lum- bricales (/’, their tendons). I, transverse ligament of tral (flexor) surface of the radius distad of wrist: 2, annular ligaments. the area of origin of the fifth head of the profundus. 184 THE MUSCLES. Relations.—Outer surface with the flexor profundus. Inner surface with the radius, ulna, and interosseous membrane. Action as indicated by the name. 4. Muscles of the Hand. A. BETWEEN THE TENDONS.—Mm. lumbricales (Fig. 88, f, /').—Four small muscle in the palm of the hand. Origin by fleshy fibres from the outer (palmar) surface of the tendon common to the ulnar four parts of the profundus (c’). Insertion (f').—The four slips are flat at their origin. Ikach becomes cylindrical and curves about the base of one of the four ulnar digits and is inserted into the radial side of the base of the first phalanx close to its ventral border. Action.—Bend the digits toward the radial side. B. MUSCLES OF THE THUMB.—M. abductor brevis pollicis (lig. 77, w) (in- cludes also the opponens pollicis of man). —A very minute, probably rudimentary muscle. Jrigin from the transverse ligament Fic. 89.—DrErr Musc Les O11 oS oF THE PaLm or THE (1) which connects the prominent fibrous, ITAND. ; _ hairless projection that lies over the pisi- a, M. flexor brevis polli- ; : ‘ cis; 6, M. adductor pollicis; form bone with the radial border of the cy My interossens of second ihead of the radius. Mhe muscle passes digit (M. flexor brevis digiti Te 3 secundi); d, M. adductor radiodistad and ends in a very slender digiti secundi; e, M. in- : 5 5 BG erosscue! OPtbind diate tendon, the insertion of which is into the M. interosseus of fourth base of the first phalanx of the thumb. digit; g, M. opponens digiti : ac > quinti; h, M. interosseus of M. flexor brevis pollicis (Fig. 89, a). fifth digit (M. flexor brevis Origin by fleshy fibres from the ad- digiti quinti); z, M. ab- . ductor digiti quinti. 1-5, Jacent borders of the os magnum and sca- ithe digits inorder. pholunar bones and from the fascia which bridges the intervening groove for the flexor carpi radialis. Insertion by a short tendon into the base of the first phalanx of the pollex. Action. —F lexor of the thumb. MUSCLES OF THE THORACIC LIMBS. 185 M. adductor pollicis (Fig. 89, 2). Origin by fleshy fibres from the ventral border of the os magnum. It curves about the base of the first metacarpal on its ulnar side to its insertion. Insertion by fleshy fibres into the base of the first phalanx of the pollex on its ulnar side. C. MuscLes LYING BETWEEN THE METACARPALS.— Mm. interossei (Fig. 89).—Small stout muscles lying on the palmar surfaces of the metacarpals of the second, third, fourth, and fifth digits. : Origin by fleshy fibres from the ventral or lateral surfaces of the bases of the metacarpals. Near the distal end of the metacarpal each divides into two masses which pass onto the lateral surfaces of the metacarpal, so as to leave the ventral surface of the distal end exposed. Insertion partly onto the lateral surfaces of the base of the first phalanx and its sesamoids, and partly by a slender tendon (Fig. 84, 2) which is continued dorsad to join the extensor tendon of the digit. D. SPECIAL MUSCLES OF THE SEGOND DIGIT (THE INDEX).—M. flexor brevis digiti secundi (or indicis).—This name may be applied to M. interosseus of the second digit (Eig. 80; xc): M. abductor digiti secundi.—This name might be applied to a portion of the interosseus of the second digit which is sometimes differentiated from the remainder. Origin from the radial and ventral surfaces of the base of the second metacarpal, and from the ventral surface of the trapezium. Insertion into the radial side of the base of the first phalanx of the second digit and into its sesamoid. M. adductor digiti secundi (Fig. 89, @). Origin from the ventral surface of the os magnum. Insertion into the ulnar side of the base of the first phalanx of the second digit. E. SPECIAL MUSCLES OF THE FIFTH DiGiT.—M. ab- ductor digiti quinti (Fig. 89, z).—A thick, small, conical bundle. 186 THE MUOSELES. Origin from the distal surface of the pisiform bone and from the transverse ligament on the ulnar side of the pisiform. It ends in a slender tendon which runs along the ulnar side of the fifth metacarpal to its Insertion into the ulnar side of the base of the first phalanx of the fifth digit. M. flexor brevis digiti quinti (Fig. 89, %; Fig. 88, ¢).—: This covers the ventral surface of the fifth metacarpal, and is really the interosseus of this digit. Origin by fleshy fibres from the ventral surface of the base of the fifth metacarpal; from the ventral process of the unci- form bone, and from the transverse ligament proximad of the fifth metacarpal. Insertion by fleshy fibres into the ventral border of the proximal end of the first phalanx of the fifth digit. M. opponens (adductor) digiti quinti (lig. 89, g). Origin by a flat tendon from the ventral surface of the os magnum on the ulnar side of the adductor pollicis (4). It passes toward the ulnar side and distad, the fibres diverging to their Insertion (1) into nearly the whole of the radial surface of the fifth metacarpal, (2) into the base of its first phalanx. V. MUSCLES OF THE PELVIC LIMBS. 1. Muscles of the Hip. A. ON THE LATERAL SURFACE OF THE HIP. Fascia of the Thigh.—After the removal of the superficial fascia with its fat and blood-vessels, there is seen a strong glistening fascia, the fascia lata (Fig. 68, z, page 117), cover- ing the vastus lateralis muscle over the dorsal half of the thigh. Ventrally it dips between the vastus lateralis and the biceps femoris and, becoming gradually thinner, is lost on the surface of the former muscle. Passing over the dorsal border of the thigh, it extends beneath the sartorius and is attached to the dorsal border of the vastus medialis. Toward its distal end the fascia is continuous with the tendon of the biceps femoris and dorsad with the border of the sartorius muscle, while MUSCLES OF THE PELVIC LIMBS. 187 between these points it is united with the tendon of the vastus lateralis; it thus gains insertion into the patella. At its proxi- mal end the fascia receives the insertion of the tensor fascie late (Tig. 68, 7). M. tensor fascia late (Fig. 68, 7, page 117; Fig. 92, a). —The tensor fasciz late is a thick triangular muscle which may be recognized by its insertion into the proximal end of the fascia lata (Fig. 68, 2; Fig. 92, a’). Origin by fleshy fibres as a thick triangular prism from the outer margin of the ventral border of the ilium craniad of the auricular impression and from the fascia covering the ventral border of the gluteus medius (lig. 90, 4) over its cranial half. The caudal border of the muscle may be continuous with the cranial border of the gluteus, maximus. The muscle spreads out in a fan-like manner, covering the proximal third of the dorsal surface of the thigh. The cranial fibres pass farther distad than the others. Insertion into the fascia lata (Fig. 68, z) along an irregular line which begins caudad at the base of the great trochanter and ends on the cranial side of the thigh at the junction of the first and second thirds. Relations.—Outer surface with the cutaneus maximus (Fig. 62, 6, page 94) and craniad with the sartorius (Fig. 68, g). Cranial border with the sartorius (g); caudodorsal border with the gluteus medius (Fig. 90, ). Inner surface with the gluteus medius, the rectus femoris (Fig. 92, 6), and the vastus lateralis (Fig. 90, @). Action indicated by the name. It also assists the quad- riceps femoris in extending the leg. M. gluteus maximus.—The gluteus maximus is a rather small quadrangular muscle in the angle between the gluteus medius (Fig. 90, 4) and the caudal vertebre. . Origin (Fig. 163, 3, page 401) by fleshy fibres from the tips of the transverse processes of the last sacral and the first caudal vertebre, from the fascia covering the spinous muscles dorsad of the transverse processes of these vertebra, and from the fascia covering the gluteus medius. The muscle passes laterad and slightly caudad to its 188 THE MUSCLES. Insertion by tendon and muscle-fibres into a tubercle on the caudal side of the great trochanter at the middle of its distal end, and for a few millimeters into the ridge which continues distad from this tubercle. . Relations.—Outer surface with the caudofemoralis (Fig. 68, s, page 117), the superficial fascia, and a few fibres of the cutaneus maximus. Inner surface with the abductor caudz internus, the tenuissimus (Fig. 90, ¢), the great sciatic nerve (Fig. 163, a), the obturator internus (Fig. go, ¢), the gluteus medius (Fig. 90, 6), the gemellus superior, and the pyriformis (Fig. 163, 7). Cranial border with the gluteus medius and the tensor fascia lata. Caudal border with the caudofemoralis (Big; 68;.s); Action. —Abducts the thigh. M. gluteus medius (lig. 90, 4).—The gluteus medius is a very large triangular muscle which connects the ilium and the sacrum with the great trochanter (1). Origin by fleshy fibres (1) from the superficial sacral fascia; (2) from the lateral surface of the fascia which covers the sur- face of the supraspinous extensor muscles of the tail; (3) from the fascia intervening between it and the tensor fascia late; (4) by tendon fibres from the dorsal half of the crest of the ilium and its dorsal border, and the dorsal half of the lateral surface craniad of the auricular impression; and (5) from the tips of the transverse processes of the last sacral and the first caudal vertebra. The fibres converge to a strong internal tendon. [nsertion into the proximal end of the great trochanter. Relations. —Outer surface with the gluteus maximus and tensor fascize lata, and between these with the strong fascia lying beneath the cutaneus maximus muscle. Inner surface with the gluteus minimus, the pyriformis, and the gemellus superior. Cranial border with the tensor fascia lata. Caudal border with the gluteus maximus. Action.—Abducts the thigh. M. pyriformis (Fig. 163, 7).—The pyriformis is a triangu- lar muscle covered by the gluteus maximus and the gluteus medius (Fig. 90, 6) and overlying the gemellus superior (Fig. 163, 6). MUSCLES OF THE PELVIC LIMBS. 189 Origin by fleshy fibres from the tips of the transverse processes of the last two sacral and the first caudal vertebra. The muscle passes laterad through the great sciatic notch to its Insertion by a flat tendon into an elongated area on the proximal border of the great trochanter just outside (caudad) of the insertion of the gemellus superior. Relations.—Outer surface with the gluteus medius (Fig. go, 6) and the gluteus maximus. Inner surface with the gemellus superior (Fig. 163, 6), the great sciatic nerve (Fig. 163, a), and the flexor caude longus (Iig. 68, x). Action.—Abductor of the thigh. M. gemellus superior (lig. 163, 6).—The gemellus superior is a triangular muscle lying beneath the pyriformis (Fig. 163, 7). It is broader than the pyriformis, so that it projects beyond its borders both caudad and craniad. It is closely united craniad with the gluteus minimus, so that the limits of the two are definable only with difficulty. Its caudal border is closely united to the gemellus inferior. Origin by fleshy fibres from an elongated area on the dorsal border of the ilium and ischium. The area is narrowed craniad. It does not quite reach the posterior inferior iliac spine in the one direction nor the spine of the ischium in the other direction. The fibres converge to a strong tendon the Insertion of which is into a triangular area dorsad of the tip of the great trochanter. Relations. —Outer surface with the gluteus medius (Fig. 90, 4), the pyriformis (Fig. 163, 7), the great sciatic nerve (Fig. 163, a), and the gluteus maximus. Inner surface with the ilium, ischium, the capsularis, the caudal edge of the gluteus minimus (lig. 163, 5), and the cranial edge of the obturator internus (Fig. go, e). Action.—Rotates the femur and abducts it so as to carry the foot outward. M. gluteus minimus (Fig. 163, 5).—The gluteus minimus is a long triangular muscle beneath the middle of the gluteus medius (Fig. 90, 6) and with its caudal border against or. covering the cranial border of the gemellus superior (Fig. 163, 6), to which it is frequently closely united. 190 THE MUSCLES. Origin from the ventral half of the ilium, from near its cranial end to a point midway between the posterior iliac spine and the spine of the ischium. The muscle ends in a strong flat tendon. Insertion into an oval facet at the base of the dorsal surface of the great trochanter on its lateral side. Relations.—Outer surface with the gluteus medius (Fig. 90, 6) and at the caudal border with the gemellus superior (Fig. 163, 6). Inner surface with the capsularis and rectus femoris (Fig. 92, 6). ; Action.—Rotates the femur so as to carry the foot out. M. capsularis (gluteus quartus, or epimeralis).—The cap- sularis is a small flat bundle of muscle-fibres which lies obliquely beneath the gluteus minimus (Fig. 163, 5) and gemellus superior (6) on the lateral or outer surface of the ilium. Origin by fleshy fibres from the surface of the ilium over a triangular area between the origin of the rectus femoris (Fig. 92, 6) ventrad, the gemellus superior (Fig. 163, 6) dorsad, and of the gluteus minimus (Fig. 163, 5) craniad and the aceta- bulum caudad. The muscle passes over the smooth surface of the ilium and the pubis ventrad of the acetabulum and then over the capsule of the joint. Insertion by fleshy fibres for about one centimeter in the middle line on the dorsal surface of the femur distad of the great trochanter. Relations. —Outer surface with the gluteus minimus (Fig. * 163, 5), the gemellus superior (6), and the vastus lateralis (Fig. 90, @). Inner surface with the ilium, the rectus femoris (Fig. 2, 6), the capsule of the joint, and the vastus medialis (Fig. 2,76). A ction.—Rotates the thigh so as to carry the foot inward, hence antagonizes the iliopsoas. M. gemellus inferior.—The gemellus inferior is a flat tri- angular muscle situated just caudad of the gemellus superior and beneath the obturator internus (Fig. 90, ¢), so that it is seen on reflecting the latter Origin from the dorsal one-half of the whole lateral surface of the ischium between the ischial spine and the ischial tuber- MUSCLES SOF ATHE (PEEVIG “LIMBS. IgI dsity. The fibres converge toward its insertion. The inner surface of the muscle is covered by a strong tendon. Insertion into the inner surface of the tendon of the obturator internus (Fig. 90, ¢) by tendon- and muscle-fibres. Some of the muscle-fibres are inserted into the capsule of the joint. Relations.—Outer surface with the obturator internus (Fig. 96, ¢). Medial surface with the ischium. Caudal border with the quadratus femoris (Fig. 90, 7). Cranial border with the gemellus superior. Action.—Abductor of the thigh. The muscle may be con- sidered as a separate head of the obturator internus (Fig. 90, @). M. quadratus femoris (Fig. 90, /).—The quadratus femoris is a short thick muscle connecting the ischial tuberosity (2) and the proximal end of the femur. It lies just caudad of the obturator internus (¢) beneath the proximal end of the biceps femoris (Fig. 68, 7). The orzgzz is by fleshy fibres from a considerable triangular area on the lateral surface of the ischium near the tuberosity. The area lies between the origin areas of the gemellus inferior, biceps, semimembranosus, and the obturator externus. Insertion into the distal two-thirds of the ventral border of the great trochanter and about half the adjacent surface of the lesser trochanter. Relations. —Outer surface with the tenuissimus (Fig. 90, ¢), the biceps (Fig. 68, 7), the semitendinosus (Fig. 90, 7), and the great sciatic nerve (Fig. 163, a). Caudal border with the semimembranosus (Fig. 90, 7). Ventral border with the adductor femoris (Fig. 90, 7); dorsal border with the obturator internus (Fig. 90, ¢) and gemellus- inferior. Action.—Extensor of the thigh and rotator of the femur so as to carry the foot inward. M. obturator externus.—The obturator externus is a flat triangular muscle beneath the adductor femoris (Fig. 92, ¢). Origin by fleshy fibres from the median lip of the obturator foramen and from both dorsal and ventral surfaces of the rami of the pubis and ischium adjacent to the lip. Also from the { a ew] 192 THE MUSCLES. outer surface of the ramus of the ischium as far as the area for the quadratus femoris (Fig. 90, /). The fibres converge to a strong flat tendon. Insertion into the proximal por- tion of the bottom of the tro- chanteric fossa. Relations. —Ventral sur- face with the adductor fem- oris (Fig. 92, g). Dorsal surface with the pubis and ischium. Caudal border with the quad- ratus femoris (Tig. 90, /). Action. — Assists the iliopsoas. B. MUSCLES ON THE MEDIAL SuR- FACE OF THE HIp.— M. obturator internus (Fig. 90, e¢).—The obtura- tor internus appears as a tri- angular muscle caudad of the ge- mellus superior. Fic. 90.—MuscLes ON THE LATERAL SIDE OF THE LEG, AFTER REMOVAL OF THE MUSCLES SHOWN IN Fic. 68 (Biceps, TENSOR FASCI@ LATA, Caupo- FEMORALIS, AND GLUTEUS MAXIMUS). a, M. sartorius; 4, M. gluteus medius; c, M. rectus femoris; ¢@, M. vastus lateralis; e, M. obturator internus; J, M. quadratus femoris; g, M. tenuissimus; 2, M. ad- ductor femoris; 7, M. semimembranosus; 7, M. semi- tendinosus; %, M. vastus intermedius; 7, M. plantaris; m, m’, n’’, M. gastrocnemius, outer head (7, part from the external sesamoid bone; 7’, from the plantaris; 72”, from the superficial fascia); 7, M. tibialis anterior; 0, M. soleus; ~, M. extensor longus digitorum; g, M. peroneus longus; 7, M. peroneus tertius (7’ its tendon); s, M. peroneus brevis; ¢, tendon of Achilles; a, M. extensor brevis digitorum, I, great trochanter of femur; 2, tuberosity of ischium, with cut origin of M. biceps femoris; 3, patella; 4, calcaneus; 5, transverse liga- ments; 6, lateral malleolus. MUSCLES OF THE PELVIC LIMBS. 193 Origin by numerous small separate heads from the dorsal surface of the ramus of the ischium along its symphysis and following its medial border from the symphysis nearly to the tuberosity. The fibres form a flat muscle which narrows and passes through the lesser: sciatic notch, turns ventrad and ends in a strong flat tendon whose Lnsertion is into the bottom of the trochanteric fossa of the femur. The tendon is continued proximad on the inner surface of the muscle and forms a smooth firm surface by which the muscle glides over the dorsal border of the ischium. Into the inner surface of this tendon near its insertion the tendon of the gemellus inferior is inserted. Relations.—Medial surface within the pelvis with a mass of fat separating it from the pelvic organs. Dorsal or outer sur- face with the biceps femoris, the tenuissimus, the caudofemora- lis, and the great sciatic nerve. Inner surface with the ischium and the great sciatic nerve. Caudal (or ventral) border with the quadratus femoris. Action.—Abductor of the thigh. M. iliopsoas (Fig. 162, 8; Fig. 91, c).—The iliopsoas (equivalent to the human psoas and iliacus) is a conical muscle emerging from the abdominal cavity onto the medial surface of the femur. Origin.—(a) The portion corresponding to the human psoas (Fig. 162, 8) arises by ten vertebral heads. The first five of these come from the five cranial tendons of origin of the psoas minor (Fig. 162, 9); the sixth from a tendinous expansion which passes from the tendon of the first head over the ventral longitudinal muscles to the transverse process of the fifth lumbar vertebra. The seventh, eighth, ninth, and tenth heads arise by fleshy fibres from the ventral surfaces of the centra of the last four lumbar vertebrz. : (6) The portion corresponding to the human iliacus arises y fleshy fibres from the ventral border of the ilium, from ., osite the auricular impression to the iliopectineal eminence. he portions of the muscle all converge to form a conical ° ss which ends in a strong tendon lying on its outer sur- L 194 THE MUSCLES. Insertion by tendon and fleshy fibres into the apex of the lesser trochanter of the femur. Relations.—Dorsal surface with the quadratus lumborum (with which this muscle is partly united), the rectus femoris (Fig. 91, @), and, by the iliac head, with the gluteus minimus. Ventral and medial surface with the psoas minor (Fig. 162, 9) and the peritoneum. Lateral edge with the transversus abdominis (Fig. 162, 4). Action.—Kotates the thigh so as to carry the foot out; also flexes the thigh. 2. Muscles of the Thigh. M. biceps femoris (Fig. 68, ¢, page 117).—A very large flat muscle covering about two-thirds of the lateral side of the thigh. Origin (Fig. 90, 2).—From the ventral surface of the tuberosity of the ischium by tendon- and muscle-fibres. The fibres diverge, and near the knee the mass has spread out, end- ing in a fascia. The dorsal border of the muscle and the common fascia are continuous dorsad with the superficial fascia of the thigh and with the tendon of the caudofemoralis (lig. 68, s). Ventrad it is continuous with the superficial fascia of the shank. Insertion into rather more than the proximal one-third of the dorsal border of the tibia along its lateral margin and into the lateral margin of the patella. In passing over the knee- joint it is closely united to the underlying ligaments and tendons. . Relations.—Outer surface with the superficial fascia and with a few of the most caudal fibres of the cutaneus maximus (Fig. 62, 6, page 94). Cranial (or dorsal) edge with the pando morals (Fig. 68, s) and the vastus lateralis (Fig. go, @). Caudal border with the semitendinosus (Fig. 68, 2) and a mass of fat. Inner surface with the caudofemoralis (Fig. 68, s), the tenuissimus (lig. 90, g), the obturator internus (Fig. go, e) the quadratus femoris (Fig. 90, /), the semitendinosus (Fi 68, 2), the semimembranosus (Fig. 90, z), the adductor fem (Fig. 90, %), the great sciatic nerve (Fig. 163, a), and d’ MUSCLES OF THE PELVIC LIMBS. 195 with the following muscles of the lower leg: the tibialis anterior (Fig. 90, 2), the extensor longus digitorum (Fig. 90, f), the peroneus longus (lig. 90, g), and the lateral head of the gastrocnemius (I*ig. 90, 7). Action.—Abductor of the thigh, and flexor of the shank. M. tenuissimus or M. abductor cruris (Fig. 90, ¢).—A very slender muscle, only three or four millimeters wide. Origin from the tip of the transverse process of the second caudal vertebra, in common with the caudofemoralis (Fig. 68, s) or gluteus maximus. It passes. obliquely beneath the biceps femoris (lig. 68, 7) distad and ventrad, to the distal end of the ventral border of that muscle. Here it becomes con- tinuous with the ventral border of the biceps, ending in a con- tinuation of the same fascia into which the biceps is inserted. Relations.—Outer surface with the caudofemoralis (Fig. 68, s) and the biceps femoris (Fig. 68, 7); distad with the integument. Inner surface with the obturator internus (Tig. go, ¢), quadratus femoris (/), semitendinosus (7), adductor femoris (), semimembranosus (z), and distad with the muscles of the lower leg. M. caudofemoralis (parameralis, Strauss-Durckheim) (Fig. 05,55, page. tL7). Origin by a flat tendon from the transverse processes of the second and third caudal vertebrae. The muscle forms a flat band which passes distad along the middle of the lateral side of the thigh over the pelvis and caudad of the great trochanter. At the middle of the thigh it ends in a very thin tendon. The tendon passes distad along the medial surface of the biceps femoris (Fig. 68, ¢), pierces the fascia lata near the knee, and passes to its Insertion into the middle of the lateral border of the patella. Relations. —Outer surface with the superficial fascia and a few fibres of the cutaneus maximus ; distad with the biceps femoris (Fig. 68, 7). Cranial border with the gluteus maxi- mus; caudal border with the biceps femoris. Inner surface with the tenuissimus (Fig. 90, ¢), the gluteus maximus, the abductor caude internus, and with the obturator internus (Fig. 90, ¢); distad with the vastus lateralis. 196 THE MUSCLES. Action.—Abducts the thigh and helps to extend the shank. M. semitendinosus (lig. 90, 7).—A long slender muscle on the ventral (caudal) border of the thigh, between the semi- membranosus (7) and the biceps femoris (Fig. 68, 7). Origin from the apex of the tuberosity of the ischium beneath the origin of the biceps femoris. The muscle passes to the medial side of the shank and ends in a thin but strong tendon (Fig. 92, 2’) about five millimeters broad. The tendon curves proximad and passes beneath the gracilis tendon (Fig. gI, 0) to its Tisertion into the crest (dorsal border) of the tibia one or two centimeters from its proximal end. Relations. —Lateral surface with the biceps femoris (Fig. 68, 2), the integument, a mass of fat, and distad with the gas- trocnemius (Fig. 92, 7) and popliteus (Fig. 92, #). Caudal surface with the integument. Medial surface with the semi- membranosus (Fig. 90, 7) and distad with the integument of the lower leg. Action.—F lexor of the shank. M. semimembranosus (Figs. 90 and 91, z; Fig. 92, 4).— A thick prismatic muscle lying along the ventral (or caudal) side of the thigh between the semitendinosus (7) and the gracilis (Fig. 91, 6). Origin by short tendon-fibres from the caudal border of the tuberosity and the ramus of the ischium. The muscle mass is divided throughout most of its length into two portions (Fig. 92, # and #’), one of which (%’) lies laterad and caudad of the other. The two portions pass to the medial side of the knee. The caudal portion (%’) ends in a strong flat tendon five milli- meters broad, the Insertion of which is into the medial surface of the femur on the medial epicondyle, at the middle of its distal border and into the adjacent medial surface of the tibia behind the lateral ligament. The dorsal part has its zzsertzon into the distal one and one-half to two centimeters of the ridge which is continued from the medial epicondyle of the femur onto the shaft; and nto the sesamoid bone of the medial epicondyle. MUSCLES OF THE PELVIC; LIMBS. 197 Relations.—Lateral surface with the semitendinosus (Fig. 90, 7), the biceps femoris (Fig. 68, 7), and distad with a small part of the adductor femoris (Fig. 92, ¢), and with the gas- trocnemius (Iig. 92, 7). Medial ? surface with the gracilis (Fig. gt, 6) and distad with the sartorius (Fig. 91, a). Cra- nial (or dorsal) border at the origin with the quad- ratus femoris (Fig. 90, J); for the remainder of its length with the adductor femoris (lig. go, /). Caudal bor- der with the integu- ment proximad. Action. — Extensor of the thigh. M. sartorius (lig. 91, a; Vig. 68, g).—A large flat muscle along the medial side of the thigh near its cranial (dorsal) border. Origin from the ventral half of the crest of the ilium and from the medial half of its ventral border craniad of the auricular impression. The caudal third of the origin is by a thin tendon, the rest by fleshy fibres. Fic. 91.—MuscLes ON THE MEDIAL SIDE OF THE LEG. a, M. sartorius; 4. M. gracilis; ¢c, M. iliopsoas; d, M. rectus femoris; e, M. vastus medialis; 7, M. pectineus; g, M. adductor longus; 7, M. adductor femoris; 7, M. semimembranosus; 7, M. semitendinosus; 4, medial head of M. gastrocnemius; 7, M. plantaris; 7, M. flexor longus hallucis (72, its tendon); 7, M. flexor longus digitorum; (7’, its tendon); 0, M. tibialis posterior; /, M. tibialis anterior; g, M. interosseus of second digit. I, patella; 2, calcaneus; 3, medial malleolus; 4, second _ metatarsal; 5,. transverse ligament of the lower leg. 198 THE MUSCLES. Insertion on a long S-shaped line which begins on the dorsal border of the tibial shaft about two centimeters from its proximal end, passes thence to the middle of the proximal end of the medial surface of the tibia, thence across the ligaments of the knee-joint and the medial surface of the medial epicondyle to the patella, crosses the patella obliquely to the middle of its proximal end, and may be continued for some distance proximad along the middle line on the fascia. Relations. —Medial surface with the integument and proxi- mad with the internal oblique muscle (Fig. 68, f). Lateral (inner) surface with the tensor fascie late (Fig. 68, 7), the vastus lateralis (Fig. 90, @), the superficial fascia, the vastus medialis (Fig. 92, c), the rectus femoris (Fig. 92, 6), and the distal end of the semimembranosus (Fig. 92, 4’). Action.—Adducts and rotates the femur and extends the tibia. M. gracilis (Fig. 91, 4).—The gracilis is a flat, thin, sub- cutaneous muscle occupying the ventral half of the medial sur- face of the thigh. Origin by a strong tendon from the caudal three-fourths of the symphysis of the ischium and pubis. The tendon may extend caudad of the symphysis in the middle line to the level of the tuberosity of the ischium. For about its first centimeter the tendon is common to the two muscles of opposite sides and gives origin on two sides to the fibres of the adductor femoris. The common tendon divides into two which pass laterad, each ending in a convex border from which the muscle-fibres . spring. Insertion.—It ends ina thin aponeurosis, part of which is continuous with that of the sartorius. The aponeurosis is finally inserted into the medial surface of the tibia near its proximal end, while distally it is continuous with the fascia. Relations.—Outer (medial) surface with the integument. Inner (lateral) surface with the semimembranosus (Fig. 91, 7) and the adductor femoris (Fig. 91, “). Action.—Adducts the leg and draws it caudad. M. adductor femoris (magnus et brevis) (Fig. 92, ¢; Fig. 90, #).—The adductor femoris lies between the semimembrano- MUSCLES OF THE PELVIC LIMBS, 199 sus (Fig. 92, #) and the femur. Its proximal part is covered by the semimembranosus, while its distal part lies outside of it. Origin by muscle-fibres from the rami of the pubis and the ischium along the whole of the length of the symphysis; from the ramus of the ischium between the symphysis and the tuberosity, and from the tendon of origin common to the two gracilis muscles. Insertion into nearly the whole of the ventral surface of the shaft of the femur. The area begins at the base of the great trochanter opposite the proximal end and the insertion area of the gluteus maximus. It extends thence distad along the caudal border of the surface as an area about one millimeter wide. At the junction of the first and second thirds of the shaft the area expands and occupies the whole of the ventral surface of the bone, ending at the intercondyloid fossa. Relations. —Lateral surface with the biceps (Fig. 68, 2), the great sciatic nerve (lig. 163, a), the tenuissimus (Fig. go, ), and the semimembranosus (Fig. 92, #); dorsolateral border in contact with the vastus lateralis (Fig. 92, c). Dorsal surface with the quadratus femoris (Fig. 90, /) and obturator externus (Fig. 90, e). Caudal surface with the semimembranosus (Fig. 92, 4). Medial surface with the gracilis (Fig. 91, 4), adductor longus (Fig. 92, /), pectineus (Fig. 92, ¢), vastus medialis (Fig. 92, c), and distad with the medial head of the gastroc- nemius (Fig. 92,17).74, .). Action.—An Se Saar of the thigh. ° M. adductor longus (Fig. 91, g; Fig. 92, f).—A thin muscle which covers the dorsal half of the medial surface of the adductor femoris (Fig. 92, g). Origin by muscle-fibres from the median three-fourths of the cranial border of the pubis, the line of origin forming a medial continuation of that of the pectineus (Fig. 92, ¢). Insertion by a thin aponeurosis into the external linea aspera of the femur along the second and third fifths of the bone. Relations. —With its medial or cranial surface the adductor longus forms part of the boundary of a depression among the muscles at the proximal end of the medial side of the leg. 200 THE MUSCLES. This depression is called the iliopectineal fossa; it contains the femoral vein and artery and saphenous nerve imbedded in fat (Fig. 127). The medial edge of the adductor longus is in relation with the integument; the lateral edge with the pec- Fic. 92.—SECOND LAYER OF MUSCLES ON THE MEDIAL SIDE OF THE THIGH, a, M. tensor fascize latee; a’, fascia lata; 4, M. rectus femoris; ¢, M. vastus medi- alis; @, M. iliopsoas (cut); e, M. pectineus; 7, M. adductor longus; g, M. adductor femoris; 4, 2’, M. semimembranosus; 7, M. semitendinosus (2’, its tendon); 7, medial head of M. gastrocnemius; 4, M, popliteus; ¢, M. flexor longus digitorum. 1, patellar ligament; 2, ligamentum collaterale tibiale. tineus (Fig. 92, ¢). Inner or caudal surface with the adductor femoris (Fig. 92, ¢). Action.—Adductor of the thigh. M. pectineus (Fig. 92, ¢).—A flat band -of fibres closely united with the adductor longus (/), of which it appears to be a lateral continuation. Origin by fleshy fibres from the lateral one-fourth of the cranial border of the pubis. The muscle passes over the smooth outer surface of the pubis between its origin area anc MUSCLES OF THE PELVIC LIMBS. 201 the acetabulum, crosses the iliopsoas (2) obliquely and has its Insertion by muscle-fibres into an elongated area (five milli- meters in length) on the shaft of the femur just distad of the lesser trochanter and between the insertion of the adductor femoris (g) and that of the vastus medialis (c). Relations. —TVhe cranial edge forms part of the floor of the iliopectineal fossa. Lateral surface in relation with the iliopsoas (2) and vastus medialis (c); medial surface with the adductor longus (/) and adductor femoris (¢). Action.—Adductor of the thigh. M. quadriceps femoris.—The quadriceps femoris is a very powerful extensor muscle on the front of the thigh. It consists of four muscles which unite to form the great extensor of the shank. It is inserted into the patella and through it, by the ligamentum patella, into the tibia. It may be compared to the triceps brachii. The parts are: (1) M. rectus femoris (Fig. 92, 4; Fig. go, c). Origin by strong tendon from an elongated triangular area which has its base at the acetabulum and its apex about five to seven millimeters craniad of the acetabulum, along the ven- tral border of the illum. The area is between that for the capsularis and that for the iliopsoas. The muscle is flat near its origin, but soon becomes a triangular prismatic mass which is united to the dorsal border of the vastus lateralis (Fig. 90, @) at the junction of the middle and last thirds of the thigh. Insertion into the oblique area on the outer surface of the patella near its proximal border in connection with the vastus lateralis. Relations. —Outer or lateral surface at the origin with the gluteus minimus, the edge of the capsularis, the gluteus medius (Fig. 90, 6), and farther distad with the vastus lateralis (Fig. 90, 7). Medial surface with the tensor fascia lata: (I'ig. 92, a), sartorius (ig. 90, @), and vastus medialis (I"ig. 92, c). Inner (caudal) surface with the vastus intermedius. (2) M. vastus lateralis (lig. 90, ¢7).—A flat triangular prismatic mass Joined distally to the preceding. It covers the dorsal part of the lateral surface of the thigh. Origin from a triangular area on the dorsal and lateral sur- 202 THE MUSCLES. faces of the shaft and the great trochanter of the femur. The base of the area is at the great trochanter, and its apex is at the junction of the second and third fifths of the shaft on the linea aspera. The linea aspera forms the ventral boundary of the triangle, while its dorsal boundary is formed by a line drawn from its apex to the dorsomedial angle of the great trochanter. The mass unites with the rectus femoris (c) by its dorsal border at the junction of the middle and distal thirds of the thigh. Insertion into the oblique area on the outer surface of the patella near its lateral border in connection with the rectus femoris. (3) M. vastus medialis (Fig. 92, c) lies on the medial side ' of the thigh. Origin by fleshy fibres over a diamond-shaped area on the shaft of the femur lying between the medial branch of the linea aspera and the area for the vastus lateralis. Proximad the area is bounded by the spiral line, and distad it is bounded by a line parallel to the spiral line and having its proximal end at about the junction of the first and second thirds of the bone. The muscle forms a triangular, prismatic mass. It ends ina thin aponeurosis which is continuous dorsad with the border of the rectus femoris (Fig. 92, 4), and ventrad sometimes with the tendon of the gracilis (Fig. 91, 9). Insertion into the medial border of the patella and the liga- mentum patella. The insertion may extend onto the head of the tibia. The adjacent surfaces of the vastus lateralis and the vastus medialis are connected over their distal thirds by an aponeuro- sis which passes transversely beneath the rectus femoris. The distal end of the aponeurosis is inserted into the proximal border of the patella. Its proximal end receives the insertion of some muscle-fibres which form a part of the vastus médialis as here described. This mass of fibres is described by Strauss- Durckheim as the crural muscle. Sometimes the transverse aponeurosis is continuous with only one of the two vasti and sometimes with neither, so that the insertion of the crural of Strauss-Durckheim becomes more or less independent. Relations of the vastus medialis. Outer (medial) surface MUSCLESSOF FTHESPELVIC LIMBS. 203 with the sartorius (Fig. 91, a) and the structures in the ilio- pectineal fossa. Cranial (or dorsal) surface with the rectus femoris (Fig. 92, 4) and vastus intermedius. Caudal (ventral) surface with the pectineus (Fig. 92, ¢), adductor longus (Fig. 92, /), adductor femoris (lig. 92, g), and semimembranosus (Figy92, 2)! (4) M. vastus intermedius.—A flat mass of muscle which lies beneath the rectus femoris. Origin from nearly the whole of the dorsal surface of the ae shaft of the femur between the areas for the vastus medialis and vastus lateralis. The area of origin extends distad to an oblique line the middle of which is about one and one-half centimeters from the patellar surface, the lateral border of the area being longer than the medial border. Insertion by muscle-fibres into the capsule of the joint. The central fibres are inserted about one centimeter proximad of the patella, while the lateral mass passes to the level of the proximal end. Relations. —Outer surface with the rectus femoris (Fig. 92, 6); borders with the vastus medialis (Fig. 92, c) and vastus lateralis (Fig. 90, @); inner surface with the femur. Action.—The quadriceps extensor is an extensor of the shank. The vastus intermedius acting separately is a tensor of the capsule of the knee-joint. 3. Muscles of the Lower Leg (Crus). A. ON THE VENTRAL SIDE.—M. gastrocnemius.—This is the great muscular mass of the calf. It arises by two heads, the caput laterale or lateral head (Fig. 90, mz), and the caput mediale or medial head (Fig. 91, £), of the gastrocnemius. Caput laterale (Fig. 90, m2, m', m’’).—The origin of the lateral head is in four portions: (1) From the tendon of origin of the plantaris which comes from the middle of the lateral border of the patella. The ten- don ends in a small conical mass of fibres (v’) which joins the ventral part of the common head. (2) By a slender flat tendon, distad of the first, from the i &2.>.er “ » Te ey Oe ee ee Tes DE ET 204 THE MUSCLES. superficial fascia of the shank (s’’), The tendon ends in a conical mass which joins the dorsal border of the common head. (3) By a strong tendon and by muscle-fibres from the distal border of the lateral sesamoid bone (Fig. 61, 3) of the femur. These fibres (7) form the middle and outer part of the common head. (4) By muscle-fibres from the middle of the outer surface of the aponeurosis covering the plantaris (ig. 90, 7) along rather more than the proximal half of the tibia. The lateral head thus formed is flat and fusiform in section. Caput mediale (Fig. 91, 4; Fig. 92, 7).—The medial head resembles the lateral head closely. Origin by a strong tendon from the medial sesamoid bone of the femur (Trig. 61, 4) and by muscle-fibres from the surface of the shaft for a short distance proximad of this. The two heads unite by their contiguous borders at the junction of the first and second thirds of the tibia. The common muscle narrows rapidly and ends in a flat tendon which joins the tendon of the soleus to form the so-called ten- don of Achilles (tendo calcaneus) (I*ig. 90, 7). This has its Insertion into the proximal end of the calcaneus (Fig. go, 4) near its ventral border. This tendon together with that of the soleus (Fig. 90, 0) and the fascia of the shank forms a tubular sheath for the tendon of the plantaris. Relations. —(1) Of the lateral head. Lateral (outer) surface with the biceps femoris (Fig. 68, 7) and the superficial fascia. Medial (inner) surface with the popliteus (Fig. 92, £), the plantaris (Fig. 90, 7) (to which it is closely united), the medial head of the gastrocnemius (Fig. 91, #), the soleus (Fig. go, 0), and the peroneus longus (Fig. 90, g). (2) Of the medial head. Medial (outer) surface with the superficial fascia and the tendons of the gracilis (Fig. 91, 4), semimembranosus (Fig. 92, %’), and semitendinosus (Fig. 92, 7). Lateral (inner) surface at the origin with the adductor femoris (Fig. 92, ¢), then with the plantaris (Fig. 91, 7), the popliteus (Fig. 92, #), flexor longus digitorum (Fig. 91, 7), and the lateral head of the gastroc- nemius (Fig. 90, 77). Action.— Extensor of the foot. (It is to be noted that what MUSCLES OF THE PELVIC LIMBS. 205 is called extension in the foot is analogous to what is called flexion in the hand, so that the extensors of the foot are most readily to be compared with the flexors of the hand.) M. plantaris (lig. 90, 7; Fig. 91, /).—A fusiform muscle covered distally by the gastrocnemius, but appearing between the two heads of the gastrocnemius at their proximal ends (Pig90) 2): Origin by a strong tendon from the middle of the lateral border of the patella and by fleshy fibres from the ventral border of the lateral sesamoid. The patellar tendon ends in a flattened head which passes ventrad over the lateral epicondyle of the femur and then curves distad; it is closely united with the lateral head of the gastrocnemius. The muscle ends in a thick tendon which passes through a sheath formed by the tendons of the gastroc- nemius and soleus, and the fascia of the shank. The tendon passes over the grooved proximal end of the calcaneus onto its ventral surface. It is held in place against the groove by two sheets of aponeurosis, which leave the tendon on either side for a distance of more than a centimeter and are attached to the lateral surfaces of the calcaneus at its proximal end. Lateral motion is thus hindered, while longitudinal motion is permitted. Between this tendon and the tendon of Achilles is a synovial bursa which aids the gliding movement of the tendon. In the sole of the foot opposite the distal end of the calcaneus the tendon broadens and ends in the flexor brevis digitorum (pedis perforatus) muscle, which might also be considered as a second part of the plantaris. In man the plantaris is inserted into the calcaneus along with the gastrocnemius. Relations.—The muscle is covered throughout by the two heads of the gastrocnemius (Fig. 90, #; Fig. 91, #), except at the proximal end (Fig. go, 7), where it is in contact with the integument. Inner surface in relation with the popliteus (Fig. 92, &), the soleus (ig. 90, 0), the flexor longus digitorum (Fig. 91, 2), and flexor longus hallucis (Fig. 91, 7). M. soleus (Fig. 90, 0).—A flat fusiform muscle lying beneath the plantaris. Origin by muscle-fibres from the lateral surface of the head 206 THE MUSCLES. of the fibula, and by tendon-fibres from the proximal two-fifths of its ventral border. Insertion.—TYhe muscle ends in a slender tendon which joins the lateral border of the gastrocnemius tendon to form the tendon of Achilles (Fig. 90, 7), which forms the sheath of the plantaris tendon. Relations. —Outer surface with the gastrocnemius (Fig. 90, m) and plantaris (Fig. 90, 7). Inner surface with the peroneus longus (Fig. 90, 7), peroneus tertius (Fig. 90, 7), and flexor hallucis (Fig. 91, 72). Action.—Assists the gastrocnemius to extend the foot. M. triceps sure.—The gastrocnemius and the soleus are sometimes considered as forming a single muscle, with three heads, under the name triceps sure. : M. popliteus (Fig. 92, #).—A triangular muscle passing from the femur obliquely toward the medial side over the ven- tral surface of the proximal end of the tibia. Origin by a strong tendon from the popliteal groove on the surface of the lateral epicondyle of the femur. In the tendon is a sesamoid bone, the popliteal bone (lig. 61, 5, page 89), which glides over the ventral part of the lateral articular facet on the proximal end of the tibia. As the muscle passes over the joint it is closely attached to the joint capsule. From the popliteal bone, which with the tendon lies within the capsule of the knee-joint, the muscle-fibres diverge to their Insertion into the proximal end of the ventral surface of the tibial shaft on the medial side of the medial oblique ridge. The area of insertion extends slightly onto the medial surface of the bone. Relations.—Outer surface with the gastrocnemius (Fig. 92, 7) and plantaris (Fig. 91, 7), and with the tendon of the semitendinosus (Fig. 92, 2). Distal border with the origins of the soleus and flexor longus digitorum. Inner surface with the capsule of the knee-joint and the tibia. Action.—Rotates the thigh so as to turn the toes inward. The three following deep muscles on the ventral surface of the shank are covered by a deep fascia (the deep crural fascia) MUSCLES OF THE PELVIC LIMBS. 207 which separates them from the overlying muscles. This fascia stretches from the dorsal border of the tibia about the ventral side of the shank to the medial border of the tibia. It sends a slip beneath the border of the fibula. M. flexor longus digitorum (Fig. 91, # and ).—Owing to the reduction of the first digit in the cat the tendon of the flexor longus hallucis (7) has become united to that of the flexor longus digitorum (7), so that the two might be considered separate heads of a single muscle. The head corresponding to the flexor longus hallucis (wv) is much larger than that corre- sponding to the flexor longus digitorum (7). The two heads will be described separately. (1) M. flexor longus hallucis (Fig. 91, #).—This lies against the ventral surface of the tibia and fibula beneath the popliteus (Fig. 92, &) and soleus (Fig. 90, @). Origin by fleshy fibres, (1) from the sheet of deep crural fascia which dips between it and the tibialis posterior (Fig. 91, 0) and the flexor longus digitorum (7). (2) From the ven- tral surface of the tibia distad of the lateral oblique line to within one to three centimeters of the distal end of the shaft. (3) From the medial surface of the shaft and head of the fibula and from the whole interosseous ligament. On the fibular side the origin may extend onto the tendon of the popliteus and the fascia of the peroneus longus. The fibres form a flat fusiform mass ending one centimeter from the heel in a strong flat tendon (#') which passes over the groove on the distal surface of the astragalus and over the groove on the sustentaculum tali. The two grooves are converted into a continuous canal by strong transverse ligaments, and the canal is lined by an extension of the synovial bursa of the ankle-joint. Emerging from the canal the tendon broadens and receives on its medial side the insertion of the tendon of the flexor longus digitorum (). The tendon gives origin on its outer surface to the lumbricales and to the common plantar ligament. The tendon continues to broaden until it reaches the middle of the length of the meta- carpals; here it divides into four tendons which pass to the terminal phalanges of the digits. Insertion.—The relations of the four tendons and their 203 THE MUSCLES. insertions are identical with those of the flexor profundus digi- torum of the hand. Relations.—Outer surface with the soleus (Fig. 90, 0) and * plantaris (Fig. 91, 7). Lateral border with the soleus, the peroneus tertius (I*ig. 90, 7), and peroneus brevis (Fig. 90, 5s). Medial border with the tibialis posterior (Fig. 91, 0) and flexor longus digitorum (Fig. 91, 7). Action.—F lexor of the phalanges. (2) M. flexor longus digitorum (lig. 91, 7). Origin by muscle- and tendon-fibres from thé ventral sur- face of the tibia over its proximal half between the oblique ridges; by fleshy fibres from an aponeurosis between it and the tibialis posterior (Fig. 91, 2), and by tendon from the medial surface of the head of the fibula. At the junction of the middle and distal thirds of the bone the muscle ends in a slender ten- don which passes through the ventral groove on the medial surface of the tibia and, curving onto the sole of the foot, becomes attached to the medial border of the common tendon described under the last. Relations. —Outer surface with the medial head of the gas- trocnemius (Fig. 91, #) and with the superficial fascia. Inner surface with the tibialis posterior (Fig. 91, 0). Medial border at the proximal end with the popliteus (Fig. 92, #), lateral border with the tibialis posterior (Fig. 91, 0), and flexor longus hallucis (Fig. 91, #2). Action.—¥ lexor of the phalanges. M. tibialis posterior (Fig. 91, 0).—A slender flat fusiform muscle beneath the flexor longus digitorum and between it and the flexor longus hallucis. Origin by fleshy fibres from nearly the whole medial surface of the head of the fibula, from the inner surface of the apo- neurosis between it and the flexor longus digitorum (7), and by a few fleshy fibres from the ventral surface of the tibia between the oblique ridges. Some fibres may also arise from the outer surface of the aponeurosis covering the flexor longus hallucis (m). The muscle ends at about the middle of the tibia in a slender flat tendon which passes parallel to the tendon of the flexor longus digitorum () through the dorsal groove on the MUSCLES OF THE PELVIC LIMBS. 209 medial surface of the distal end of the tibia. This groove is converted into a canal by a transverse ligament. Beyond the canal the tendon turns onto the plantar surface of the foot and passes through a groove on the ventral surface of the scaphoid bone. It then divides. Insertion into the outer tuberosity on the surface of the scaphoid, and onto the proximal end of the ventral surface of the medial c: