COLUMBIA LIBRARIES Ol-l-illt HEALTH SCIENCES STANDARD HX64061671 QM23 T65 1 898 Descriptive anatomy RECAP Columbia ^Bnitier^ftp THE LIBRARIES Mthital Hiiivavv Digitized by the Internet Archive in 2010 with funding from Columbia University Libraries http://www.archive.org/details/descriptiveanatoOOtowl DESCRIPTIVE ANATOMY WM. B. TOWLES, FORMER Professor of Anatomy in the University of Virginia AND IN THE University of Vermont. REVISED AND ENLARGED BY W. G. CHRISTIAN, present Professor of Anatomy in the University of Virginia. ANDKRSON BROS., PUBLISHERS, University of Virginia. 1898. u COPYRIGHT, 1898, BY ANDERSON BROS. i\VVE_P/?^V7. PREFACE. Towles' Notes on Anatomy, which forms the basis of the present work was not the work of a single man, but the out- growth of a school. This school, founded here, probably, by Prof. Robley Dunghson, who brought the Edinburgh tradi- tions into his teaching, was perfected by Prof. John Staige JJavis, who, in his turn, instructed Prof. Towles, from whom the present writer acquired what knowledge of anatomy he possesses The effort of all of the teachers in this school has been to make the instruction clear, simple, and practical ; and these have been the characteristics of the Notes While endeavoring to increase the amount of information contained m the work and to make it more representative of the lectures the writer has tried to preserve those characteristics which have alw^a3^s distinguished the School of Anatomy at the Uni- versity of Virginia. At this late day it is impossible for any one towrite an original work on such a subject as anatomy, and originality is not claimed for this work. It has simply been the writer's purpose to adopt the best, in his opinion trom all of the other writers he has been able to read ; but at the same time, no statement has been made in this book which has not been verfied by dissection. The effort has been made to make this a student's book • it IS not intended to imitate those works which are designed for practitioners and students alike. In the opinion of the writer a successful work of the kind last mentioned is a manifest impossibility, the needs of the student and the needs of the practitioner being entirely dissimilar. It has been the inten- tion in this work to give to the student a clear, complete state- ment of the positive truths of anatomy, leaving embrvology and histology, so largely treated in other works, to the care of the professors of these subjects. The writer has discussed neither surgery nor practice of medicine, but descriptive anatomy, pure and simple, in such a way as the needs ..f the student demand. Universily of Virgima. W. G. Christian. Aiig^ist, i8g8. DESCRIPTIVE ANATOMY. OSTEOLOGY. fj^- d'"^/ °n *' ^"'' '"^'"^ ^° '° f"^™ the human skele- ton md.vxdually and ,n relation to one another, with re<.ard to the appearaiices which they present to the unaided eve and he uses for wh.ch they are intended, constitutes Osteo o " as perta,n,n^ to Descriptive Anatomy. The chief uses of tissues. 2d. To form receptacles for important organs. 3d To form uny.eld.n^ points of attachment for the muscles: n!ayb?utni7ed.^^ ''''''' '''°'''' -''''' "--- -tion In order to fulfill these functions, bones present manydiffer- mto. 1st. Long Bones, when the extension in one direction Srreatly exceeds that in the other. 2d. Plat Bones, when he extension ,n two directions greatly e.xceeds that i^ the olher relation to other Jnes. 2d. Th^e^'cTass tf wl^ch^ ifb:!::^ 3d. &,veadescr,pt,on of the appearances on the bone: whethe here be surfaces, borders, extremities, shaft, depressions or elevafons, and especially note any articular surface thalis a nect.on ,t ,s proper to explain two technicalities of frequent use -Internal and External-these terms should be used w.th reference to the middle line or plane of the body, that is ne object >s ,„ternal to another because it is nearer th' midd cav^'tv . ''• "" f "" "'"' '"-■-■•ectly with reference to a The' bo ^", T""' """^ '"' '^™^ '" "e here emoloyed. The bones are d,v,ded into those of the vertebral column o e Thorax: of the Upper Extremity: of the Lower Extremity of the skull; the Os Hyoides; the Ossicula Auditus DESCRIPTIVE ANATONY. The Vertebral Column. The vertebral column or spine, consists of a series of sep- arate bones, classed as irregular, called vertebra, and extends from the base of the skull to the lower termination of the TDelvis It is flexuous in direction and of unequal size at dit- ferent places, smallest in the neck, it gradually enlarges to below its middle and then suddenly tapers to a point it transmits the weight of the head to the lower extremities, o-ivino- support on each side to the bones which enclose the thoracic cavitv, and indirectly to those of the upper extremities. Towards its lower termination it has expanding from it on either side the bones which form the pelvis. It forms the re- ceptacle for the spinal marrow and its envelopes. In the adult it consists of twenty-six pieces, called vertabras, which are divided into four classes; in the neck they are called cervical vertebrae, and are seven in number: In the Thoracic region— Dorsal— twelve in number. In the Abdominal region— Lumbar— five in number. In the Pelvic region— Pelvic— two in number. The last are known as sacrum and coccyx, and before adult life are composed of nine pieces-the sacrum having five and the coccyx four. The vertebra of the different regions have characteristics which distinguish them from those of other reo-igns, and each vertebra certain less noticeable ones which designate its position in its own region. Kach region, how- ever, possesses one or more bones so widely different from the typical vertebra of that region as to deserve the appellation of "Peculiar." Since there are appearances common to the vertebrae ot all regions, these must be first noted. Vertebra. Kach vertebra consists of the following parts : 1st, Body ; 2i, Foramen for the spinal cord;. 3d, Lamina (2); 4th, Pedicles (2)'; 5th, Spinous process ; 6th, Transverse Processes (2) ; 7th, Articular Processes (4); 8th, Intervertebral Notches (4). OSTEOLOGY. 3 ]st. The Body is the front, thick, massive portion of the bone, flattened above and below to articulate with adjoining- bones, indirectly by the intervention of cartilag-e ; it is more or less circular in outline and slig-htly flattened behind ; the edg-es project somewhat in front and laterally, so as to produce a furrow on the front ; its posterior aspect forms the anterior boundary of the spinal foramen. 2d. The Spinal Foramen lies between the body in front and the spinous process behind, and is bounded laterally by the lamina. It is a large opening-, varying- in form and size in the different regions. 3d. The Lamina spring-s, one each side, from the postero- lateral aspect of the body, throug^h the medium of the pedicle, and arches back to meet its fellow to form the spinous process thus inclosing the spinal foramen. It is flattened from side to side, and presents an upper and a lower border. 4th. The pedicle is the more or less rounded commencement of the lamina. 5th. The Spinous Process juts backward from the union of the two laminae. 6th. The Transverse Process projects laterally from near the anterior extremity of the lamina on either side. 7th. The Articular Processes are four, two superior and two inferior. They extend upward and downward from the lamina. 8th. The Intervertebral Notches are four, two superior and two inferior ; they are furrows on the upper and lower aspects of the pedicles. Cervical Vertebra. The discrimination of a Cervical Vertebra involves the fol- lowing- points: it is the smallest; its body is smallest, having- its transverse diameter g-reater than the antero-posterior ; on its upper aspect the lateral edges are raised into ridg-es. The spinal foramen is larg-est and is triangfular. The lamina is narrow and long-. The spinous process is triang-ular and bifid at the extremity, g-enerally. The transverse process is perforated at its base by an opening- called the vertebral fora- 4 DESCRIPTIVE ANATOMY. men, is grooved above and bifid at its extremity, forming- two nodules which are called the anterior and posterior tubercles of the transverse processes. The Articular processes are oblique ; the superior face upward, inward and backward, the inferior downward, forward and outward. Dorsal Vertebra. To discriminate a typical Dorsal Vertebra the following- appearances must be noted: The body is intermediate in size betw-een that of a cervical and a lumbar vertebra ; there is no g"reat preponderance of the one diameter over the other ; althoug-h in the upper part of the reg"ion the transverse is slig-htly g-reater, and in the middle portion the antero-posterior. The most characteristic feature is the appearance, on the postero-lateral aspect of the body, of articular half-facets, situated, two on each side, at the upper and lower borders : these are for the reception of the heads of the ribs. The spinal foramen is smaller than in the other re- g-ions, and is nearly round. The lamina is short, slopes obliquely from behind, upward and forward, and is almost entirely covered by the orig-in of the processes which spring- from it. The pedicle is deeply notched inferiorly. The spinous process is triang-ular, and is disting-uished from that of a cervical vertebra by not being- bifid, it extends downward and slig-htly backward. The transverse process is peculiarly well marked, being- large, long- and extending- outward and backw^ard, increasing- in size as it removes from its orig-in so as to present an enlarg-ement at its termination ; that is, it is "clubbed." It bears on its anterior face, near its termination, an articular facet. The superior articular processes are ver- tical and look from each other, outward and backward ; the inferior are opposite. A Lumbar Vertebra. In the lumbar reg-ion the whole bone is more massive than in the cervical and dorsal reg-ions. The body is larg-e, its transverse diameter g-reater than the antero-posterior. Its anterior surface is concave from above downward, convex from OSTEOLOGt". 5 side to side, slightly lipped above and below. The superior and inferior faces present a concave central portion with an elevated circumference. The posterior face althoug-h nearly flat, presents a slig^ht concavity from above downward and from side to side with larg-e opening's for the veins. No lateral articular facets are seen on the body. The spinal foramen is obscurely triangular and is intermediate in size between the larg-e cervical and small dorsal. The pedicles are short and thick, project nearly backward with but a slight inclination outward and are marked below by deep and wide intervertebral notches. The superior notches are narrow and shallow. The laminae, short and massive, pass downward backward and inward to join the spinous process, and are partly hidden by processes. The spinous process is nearly quadrilateral, strong and thick. It projects straight back- ward and terminates in a blunt, rough almost clubbed extremity. The transverse processes spring from the junction of the body and pedicles. They are long narrow, thin and curved, resem- bling a rib in shape. They pass backward and outward with a slight inclination upward. The superior articular processes are cut nearly vertically, as in the dorsal region, but, unlike the latter, face toward each other so that their direction is backward and inward. They are concave from before back- ward to receive the inferior processes, and are situated at the junction of the pedicles and laminae. The inferior processes, situated entirely on the laminae, are vertical, convex from be- fore backward and face outward and forward so as to be received between the inverted superior processes. Peculiar Vertebrae. The foregoing description of a vertebra in each region is, as stated, of one typical of that region ; and this typical vertebra is one from about the middle of that region. Toward the con- fines of each region the vertebrae partake more or less of the characters of vertebrae in the adjoining regions, and so far depart from the type as to deserve the appellation "Peculiar" — thus demanding a special description. The departure from 6 DESCRIPTIVE ANATOMY. the typical vertebra is so g-reat in some instances that the bones have received special names. In the cervical region there are three peculiar vertebrae — ■ the first, second and seventh. The First Cervical Vertebra, or Atlas. This vertebra is known as the Atlas because it supports the weig-ht of the head ; it resembles only in a slig-ht deg-ree a ty- pical vertebra, having no body and being- scarcely more than a ring- of bone. It is described as consisting- of four parts — two arches and two lateral masses — surrounding- a spinal fora- men of remarkable size — much larg-er than in any other verte- bra. The lateral masses stand one on each side, being- connected before and behind by the anterior and posterior arch. The anterior arch is much shorter than the posterior, and forms one-fifth of the circumference of the bone ; it presents on the middle of its front an elevation, called the anterior tubercle of the Atlas and opposite this, on the posterior face of the anterior arch, is a circular, concave articular facet for the o^Ojitpid process of the next vertebra. The ppsterior arch forms about two-fifths of the circumfer- ence of the bone. It is convex and rough behind, presenting in the mid line a slig-ht rough eminence called the posterior tubercle of the Atlas, a rudimentary spinous process. The upper bordler of the posterior arch presents, jjist behind the lateral mass, a deep groove or notch, the superior intervertebral notch and below, behind the inferior articular process, a similar but slighter groove, the inferior intervertebral notch. It will be seen that the intervertebral notches are behind the articular processes in this vertebra instead of being in front as in a typical vertebra. Kach lateral mass forms about one-fifth of the bony circle, and sustains, above and below, the articular processes. The superior are oval, concave, oblique, articular pits, whose long diameter is directed from in front backward and outward ap- proaching each other more nearly in front than behind, ^d looking upward, inward, and forward. About their middle OSTEOLOGY. 7 they are frequenty slig-htly encroached upon by the non-articu- lar portion of the bone so as to g-ive them something- of a kid- ney shape. The inferior processes are smaller, circular, slightly concave or"Hat and directed downward, inwar3 and slightly backward. The inner face of each lateral mass is marked, just below the superior articular process, by a slight tu'Bercle intended for ligamentous attachment. The trans- yerse processes project outward and a little downward. They are large and prominent, perforated at the base but not marked by either groove or tubercle as in the typical vertebra. The Second Cervical Vertebra, or Axis. The body of the Atlas becomes ossified to the Axis and ap- pears on that bone as the odontoid process. This process occu- pies the whole of the upper surface of the Axis, springing by a slightly constricted portion called the neck, ascending* and enlarg-ing" for a short distance to again decrease and finally ter-^T' minate as a blunt point. On either side, just below the termi-^ nation, there is a rough depression for ligamentous attach- ment. Below this and on its anterior face, is a smooth circu- la'f, convex articular facet tcLplay oji a similar surface on the rfffteriof arch of the Atlas. Ju-st opposite to this, on the pos- terior surface, is a second smooth surface fgir the play of the transverse ligament. "T^he tjody is marked in front by a verti- cal ridge and on either side of this by deep depression. The superior articular facets appear to be seated on the junction of the pedicles and body. They are circular in form, nearly flat and face upward and outward, possibly slightly forward. The transervse processes, less prominent than those of the Atlas, are not bifid and pass downward and outward. The}'' are pierced by the vertebral foramen, which runs from below upward toward the superior articular facet and then turns ab- ruptly outward, forming nearly a right angle. The laminae are thick and strong- ; the spinous process, strong- and thick, projects straight backward, is deeply g-rooved on its under sur- face and frequently bifurcated at the extremity. There is barely a trace of a superior intervertebral notch, which, when present, lies behind the articular process. The lower portion 8 DESCRIPTIVE ANATOMY. of the bone presents the characteristics of a typical cervical vertebra, but is more massive. Vertebra Prominens, or Seventh Cervical Vertebra. This vertebra derives its sobriquet of prominens from its possession of a remarkably long-, thick, uon bifid, spinous process, which disting-uishes it from the other cervical verte- brae. It is also larg-er than the other vertebrae of this region, its spinal foramen is smaller and the lower surface of the body is more like that of a dorsal vertebra. Peculiar Dorsal Vertebrae. The peculiar dorsal vetebrae are the first, ninth, tenth, eleventh and twelfth. The /i}'st presents on each side of its body, above andpostero- laterally, a whole facet for the head of a rib ; below, in corresponding position, a half facet on each side. The ninth has but one demi-facet on each side, which is on the upper border. The /^;z//^ has one whole facet on each side above. The eleventh has one whole facet on each side', but its transverse process has no articular facet. The tzvelfth has one whole facet on each side ; its transverse process has no articular facet and its inferior articular processes are everted. The Pelvic Vertebrae. The pelvic vertebrae, specifically known as sacrum and coccyx, form the lower part of the vertebral column, and derive the appellation of pelvic from the fact that they form the posterior wall of the pelvis in the articulated skeleton. They are described separately. Sacrum (Sacer-Sacred.) The sacrum lies between the fifth lumbar vetebra above and the coccyx below, and between the two ossa innominata. It is triangular in outline, its base being- upward and its trun- cated apex below and backward and tipped by the coccyx. Its anterior face is concave, both from above downward and from side to side, more so in men than in women, this being- one means of disting-uishing- the sex to which the pelvis OSTEOLOGY. 9 belonofed. It is described as consisting- of an anterior and posterior face, two lateral borders, a base and an apex. The anterior face is concave and presents two vertical rows of foramina, of four each, one row on each side of the middle line, called the anterior sacral foramina ; the upper two in each row, are considerably larg-er than the lower two. Con- necting- each foramen with the corresponding- one in the opposite row is a ridge ; these ridg-es marking- the line of union of the five separate vertebra? of which the sacrun con- sisted in the 3'oung- subject. Passing- outward from each foramen is a groove for a sacral nerve. The posterior face of the sacrum is narrower than the ante- rior, is convex both from above downward and from side to side and is rough. Above, in the mid line, is seen the trian- gular opening- of the spinal canal ; below this is a row of roug-h projections, the rudimentary spinous processes. The upper two of these are usually distinct, while tlje two lower coalesce. • The lower spine is wanting- and here the spinal canal is exposed. External to the sacral supines is seen a row of slig-ht projections, the rudimentary articular processes, and between these and the spines is a vertical g-roove, the sacral, continuous with the vertebral g-roove above. Exter- nal to the articular tubercles is a row of foramina, less reg-u- lar in outline and smaller in size than those on the front, the posterior sacral foramina, four in number like those on the anterior face. External to these again, and nearly on the lateral border, is another row of roug-h tubercles, the rudimen- tary transverse processes. The lateral borders, broad and thick above, narrow, thin and roug-h below, present superiorly and anteriorly a long-, ear-shaped articular facet for the os innominatum, behind this a deep rough depression for ligamentous attachment. The base, or upper extremity, presents in the mid line an oval articular surface, corresponding in shape and size to the lower surface of the last lumbar vertebra, with which it arti- culates. On either side of this is a broad, smooth expanded surface, called the wing of the sacrum. Behind the articular 10 DESCRIPTIVE ANATOMY. surface is seen the triangular upper opening- into the sacral canal, a continuation of the spinal canal. This canal passes through the sacrum, decreasing in size as it descends, and is open posteriorly below on account of the absence of the last spinous tubercle of the sacrum. On either side of the opening is an articular process. These processes, like the superior articular processes of a lumbar vertebra, face toward each other. In front of the articular processes on either side is a groove corresponding to the intervertebral notch of other ver- tebra. The apex, or lower extremity of the sacrum, presents an oval surface for articulation with the coccvx, and on either side of this an articular nodule, called the cornu. Behind the oval surface is the opening of the sacral canal which terminates the spinal canal. Coccyx. The coccyx forms the lower extremitv of the vertebral column; it originally consists of four pieces or verte- brae united, in the adult, into one bone, which is sometimes ossified to the sacrum. It is triangular in shape; its base is above, presenting an oval articular facet for the truncated apex of the sacrum; its apex is below and forward the bone con- tinuing the curve of the sacrum and frequently deviating to one side. The Vertebral Column as a Whole. Viewed as a whole the vertebral column presents two pyra- mids with their bases opposed, the superior pyramid being com- posed of all the vertebra from the second cervical to the last lumbar, the inferior consisting of the nine pelvic vertebra. On more careful examination it will be found that the supe- rior pyramid may itself be divided into three, one extending from the second cervical to the first dorsal, the second from the first to the fourth dorsal, base upward, and the last con- sisting of the remaining vertebra with the base at the fifth lumbar. These smaller pyramids are comparatively unimpor- tant. Although the general direction of the vertebral column is vertical, it does not present a straight line. In the cervical OSTEOLOGY. 11 reg"ion, and including* the first and second dorsal vertebras, it is convex forward, in the dorsal concave forward, in the lumbar, convex and in the pelvic ag-ain concave forward. Thus it will be seen to consist of alternate compensatory antero-posterior curves, an increase in the curvature of one reg-ion always causing- a corresponding* compensation in the reg^ion below. Viewed from the front we see the convex bodies of the vertebrse, marked by their transverse g^rooves and separated by the intervertebral disks, the whole presenting- the curvatures above described. Posteriorly, in the mid line, will be seen the spi- nous processes, rudimentary in the first cervical, prominent in the second, decreasing- in size until the sixth is reached, well marked and prominent in the seventh and even more prominent in the first dorsal. From this point the spines become long-er in the dorsal region until the ninth is reached, but, owing- to their downward inclination, less prominent. Ag-ain prominent and projecting- backwards in the lumbar, they become indis- tinct in the upper sacral and disappear entirely in the lower sacral reg-ion. Sometimes there are normal deviations from the mid line even in health, so that the spines do not form a straig-ht line down the back. On either side of the spines is seen a g-roove which is broad and shallow in the cervical, deep in the dorsal and, becoming- less marked in the lumbar, finally disappears in the lower pelvic reg-ion. Laterally may be seen the sides of the bodies of the vertebrae, presenting- in the cervical reg-ion the transverse processes, g-rooved by the intervertebral foramina ; intervertebral foraminaand transverse processes with articular facets for ribs, in the dorsal ; and similar foramina and spine-like transverse processes in the lumbar reg-ion. The pelvic reg-ion shows the lateral border of the sacrum and coccyx. The length of the vertebral column varies at different periods of life and in different individuals. In the adult it is from twenty-four to twenty-eig-ht inches long-. Sternum. The sternum or breast bone, forms the middle portion of the tho.racic wall in front, the dorsal vertebras occupying- the 12 DESCRIPTIVE ANATOMY. mid-line behind; connecting* these on each side are the ribs, which are prolong-ed by the costal cartilages. Kxtending- out- ward from the upper end of the sternum on each side is the clavicle. The direction of the long* axis of the sternum is downward and forward. Originally consisting of six parts, these in the adult become united into three — the upper or Manubrium, the middle, or Gladiolus, and the lower, E)nsi- form or Xiphoid cartilage. These are united by cartilage, but later in life may become ossified together, the ensiform cartilage frequently becoming ossified and firmly united to the gladiolus. The Manubrium or first piece of the sternum has an anterior and posterior surface, upper and lower extrem- ity and two lateral borders. The anterior surface is slightly convex from Side to side, usually a little concave from above downward, and roughened for muscular attachment. The posterior is concave from side to side and smooth. The upper extremity is marked in the mid-line by a notch known as the inter-clavicular. E^xternal to this and located at the junction of the upper extremity and lateral border, is a smooth con- cavo-convex articular facet for the inner end of the clavicle. This facet is concave from above downward and outward and convex from before backward. The inferior extremity is marked by an oval, oblong articular surface for the upper end of the Gladiolus. The lateral borders present above a pit for the reception of the cartilage of the first rib ; below a half pit for the second costal cartilage, converted into a whole pit by articulation with the Gladiolus. Between these the border is rough, narrow and non-articular. The Gladiolus or second piece of the sternum, pre- sents an anterior surface, slightly convex from above downward and marked by three transverse ridges which indicate the junction of the four bones of which it was originally composed. The posterior surface is concave and smooth. The upper extremity shows an oval articular facet to correspond with the one on the lower extremity of the Manubrium. The lower extremity shows a similar, but OSTEOLOGY. 13 smaller facet for the Knsiform cartilag-e. The lateral borders are marked by a demifacet at the upper and lower ang-les re- spectively and four whole pits between these two. The upper demifacet is for the second costal cartilag-e, the lower, for the seventh and those between for the cartilag-es of the inter- vening" ribs. Between these pits are narrow, roug-h non- articular portions of bone. Occasionally the Gladiolus shows a foramen near its lower end. The E^asiform cartilag-e presents many varieties in shape and position. Above it has a small oval facet for the Gladio- lus, and on its lateral marg-in a half facet for the cartilag-e of the seventh rib. It is frequently deflected to one or the other side, and may be turned backward or forward. Viewed as a whole the Sternum is convex and roug-h ante- riorly, concave and smooth posteriorly, larg-e and broad above, presenting- the articular facets for the clavicles and the inter- clavicular notch, narrow and pointed inferiorl}^ Laterally it is marked by pits for the reception of the cartilag-es of the seven true ribs. The Ribs. The ribs are twelve pairs of long- bones situated on the side and front of the chest and forming- the g-reater part of the bony wall of the thorax. They are known by numbers from above downward. In describing- them a rib from the middle is taken and the characteristics common to all the ribs are described. This is called a typical rib. The peculiar ribs are then described. Of course all the ribs, from any given individual, may be disting-uished, but not from different persons. A Typical Rib. A typical rib, being- a long- bone, has a shaft and two extremities. The posterior or vertebral extremity is some- times improperly called the head. It consists of a head, neck and tubercle. The posterior, or vertebral extremity has a head which presents two articular facets separated by an antero-posterior ridg-e. The facets look the one upward and backward, the other downward and backward, are oval in form and articular for the demi-facets found on the bodies of the 14 DESCRIPTIVE ANATOMY. dorsal vertebrse above and below. The ridg-e is received in the interval between the two vertebra and is attached to the intervertebral disk. The neck extends outward and slig-htly backward from the head and terminates at the tubercle. It has an upper and a lower border, anterior and posterior sur- faces. The posterior surface is irreg-ular and roug-h for lio-amentous attachment; the anterior, smooth, concave, slopes obliquely from above downward and enters into the formation of the posterior wall of the thorax. The lower border is twice as thick as the upper, is long-er and roughened for the attachment of a ligament. The superior border is marked by a prominent crest which extends from the head to near the tubercle. In the lower ribs it rises from behind forward and terminates rather abruptly before reaching the tubercle ; in the upper it is less prominent and might be described as a simple ridge marking* the upper border. The anterior, or sternal, extremity, is flattened from before backwards, slig-htly larg-er than the shaft and is surmounted bv a pit for the reception of the corresponding- costal cartilag-e. The shaft slopes obliquely from above downward and for- ward, the degree of obliquity varying with the different ribs. It presents two surfaces, internal and external, and two bor- ders, inferior and superior. The posterior part of the shaft is nearly round and extends from the tubercle to the ang-le of the rib. Its surfaces look forward and backward. Prom the angle the ribs slope and the surfaces become internal and ex- ternal. The external surface is convex from before backward, flat or slightly convex from above downward and is marked at the angle of the bone by an oblique ridge. The internal sur- face is concave from before backward, convex from above downward and smooth. Near the lower border is seen a long- g-roove which, starting near the angle passes forward to the anterior third where it gradually loses itself on the inferior border. The superior border is twice as thick as the inferior and is slig-htly roug-hened for muscular attachment. The in- ferior border, thin and sharp, overhangs the g-roove on the inner surface and is itself marked by the same g-roove near its anterior extremit}'. OSTEOLOGY. 15 Peculiar Ribs. The peculiar ribs are the first, second, tenth, eleventh, and twelfth. The First Rib departs more widely from the t3'pical rib than any other. Its surfaces look one upward and forward, the other downward and backw^ard, its borders inward and outward. The superior surface, broad and fiat, presents near the middle an oblique ridg-e which separates two g^rooves, the in- ternal for the subclavian vein, the external for the subclavian artery. The external border, convex and roug-h and thicker than the internal border, is not marked by either ang-le or ridge as is the case with a typical rib. The posterior extrem- ity presents a head with only one articular facet, as this rib articulates with but one vertebra. The neck is flattened from above downward and has no crest. The anterior ex- tremity is thick and roug-h, being* marked on its upper sur- face by a roug-h elevation for the attachment of a lig-ament. The inferior surface is smooth. The second rib, long-er than the first, approaches more nearly the typical rib. It is marked by a crest on its neck and an ang-le and ridg-e on the shaft, but both are less distinct than in the typical rib. The tenth, eleventh, and twelfth each have a whole facet, articu- lating- with but a single vertebra. The tenth has a pit at its chondral extremity for the reception of a cartilage which binds it to the cartilag-e of the ninth and, throug-h it, to the seventh. The eleventh and twelfth are merely tipped at their extrem- ity with cartilag-e and are called floating- ribs, because they are not attached to any other rib. These ribs have no artic- ular facet on the tuberosity for the transverse process. The Costal Cartilages. The costal cartilag-es are flat pieces of hyaline cartilag-e attached by one extremity to the ribs and by the other to the pits on the lateral aspect of the sternum. Their surfaces are anterior and posterior and the borders superior and inferior. 16 DESCRIPTIVE ANATOMY. They increase in leng"th from the first to the seventh and each has its separate pit on the sternum down to and includino- the seventh. From the seventh the cartilages are attached to the cartilag-e of the seventh rib and through it to the ster- num. It is from this arrangement of the cartilages that the upper seven ribs are called vertebro-sternal, the next three, vertebro-chondral and the last two vertebral. The first three cartilages are horizontal, the next seven inclined ob- liquely upward, the obliquity increasing from the fourth to the tenth, while the last two are horizontal or inclined slightly downward. The Clavicle. The Clavicle or, collar-bone, extends nearly horizon-- tally outward but inclined slightly upward, from the upper end of the sternum on' either side. It is a long bone ; and like other long bones, is divided for study into a shaft and two extremities. The inner extremity is thick, the bone grad- ually diminishing in size as it passes from the inner to the outer end. The bone is round or triangular ; and bears on its inner extremity a concavo-convex articular surface, convex from above downward and outward, concave from before back- ward. This surface is intended for articulation with a simi- lar saddle-shaped surface on the upper outer aspect of the first piece of the sternum. Generally, just below this, is found another articular facet to play upon the cartilage of the first rib. The outer extremity is flattened from above downward, rough and subcutaneous on its upper surface, slightly rough- ened on its lower surface, and presents at its tip a small articu- lar facet, oval in outline, the long diameter directed from be- fore backward, and looking downward and outward. This is for articulation with the the acromion process of the scapula. The body of the bone presents two surfaces, superior and inferior ; and two borders, anterior and posterior. The inferior surface presents a long shallow groove, the subclavian, terminated internally by the roughened surface which is sometimes a process and sometimes a depression, called the rhomboid impression. Following the groove OSTEOLOGY. 17 outward, we reach, near the posterior border of the bone, a prominent tubercle, called the conoid ; and extending* outward and forward from this is a roug-hened ridg-e, called the trapezoid ridg-c. The superior surface is round, convex, smooth except at its inner and outer ends, where it is roughened for muscular attachment, and is subcutaneous. The aulerior border is convex for its inner two-thirds, thick and round; concave for its outer one-third, thin and sharp. The posterior border is concave for its inner four-fifths, and is smooth ; it is convex for its outer one-fifth, and is rough, thicker than the outer part of the anterior bor- der, but not so thick as the inner extremity of the posterior border itself. The upper surface and anterior border are subcutaneous. The Scapula. The scapula, or shoulder blade, is a flat triangular bone, situated on the upper postero-lateral aspect of the chest, extending" over the upper eig-ht ribs with the exception of the first. It consists of a body having- two surfaces and three borders, three angles and two processes. The anterior face, or venter, is concave, has ridg-es run- ning- upward and outward, and presents a deep depression towards its upper outer part, which is called the subscapular angle. This face of the scapula is in the main occupied by the subscapular fossa; but it must be remembered that there is a smooth surface at the superior and inferior angles of the bone and along the posterior border, which while belonging- to the'venter of the scapula, does not belong- to the subscapular fossa. The posterior face, or dorsum, is convex from above downward, presenting- a prominent ridg-e, the spine, which commences at the posterior border and runs upward and out- ward towards the head, dividing- the dorsum into two unequal parts : the smaller above called the supraspinous fossa, and the three-fold larger below called the infraspinous fossa. The supraspinous fossa is triangular in outline, the apex of the triang-le being- directed outward, is concave from above downward and from before backward, and smooth. 18 DESCRIPTIVE ANATOMY. The iufraspinous fossa occupies nearly all of the remaining- portion of the dorsum of the scapula ; but there is a strip along" the anterior, or axillary, border, and a triang-ular space at the inferior angle which do not belong to the infraspinous fossa, thoug^h they belong- to the dorsum of the scapula. The fossa, which is triangular in outline, the apex directed downward and the base upward, presents near its center a prominent bulg-e, and external to this a broad vertical g-roove. External to this groove is a prominent ridg-e which extends as far as the axillary border of the scapula. It is useless to say that the spine furnishes a portion of both supra and infraspinous fossse. The sj^ine is triang-ular and presents three borders, two of which are free, one looking- backward and the other outward and forward. The one which looks directly forward, the so-' called "attached border," is simply the attachment of the spine to the remaining- portion of the bone. The spine itself presents a superior surface which is concave, and enters into the for- mation of the supraspinous fossa, and an inferior surface which is slig-htly convex from without inward, slightly concave from above downward, smooth, and forms part of the infra- spinous fossa. Its posterior border is roug-h, commences as a smooth triang-ular surface near the vertebral border of the bone, rises as it passes forward becomes thicker and rougher, and terminates near the upper outer angle by becoming- a roughened projection of bone, known as the acromion process. This posterior border presents a superior lip, an inferior lip, and an intermediate space intended for muscular attach- ments. The external border of the spine is smooth, round, and con- cave, and is the inner limit of the g-roove which extends around it and forms the means of communication between the supra and infraspinous fossae. The superior border of the scapula is thin, and is the shortest of the borders. Near its outer ex- tremity it is deeply notched, the notch being known as the suprascapular notch. It terminates in the superior ang-le of the bone by joining with the posterior or vertebral border. OSTEOLOGY. 19 The posertior or vertebral border, commencing- at the supe- rior angle passes downward and inward to the point at which the spine spring-s from the posterior border. Prom this point downward it chang-es its direction, and is nearly vertical, with a slig-ht inclination outward. This border of the scapula, like the posterior border of the spine, is composed of two lips and a roug"h intervening* space. It is intermediate in thickness be- tween the superior and the axillary borders. The a?iterior, or axillary, or outer border is thick. Just be- low the external ang-leof the bone it presents a roug-h impress- ion from one-half to three-quarters of an inch in leng-th, which is intended for muscular attachment. Below this point is seen a vertical g-roove, which passing- downward upon the axillary border winds g-radually to the posterior surface of the bone, which it reaches at the junction of the lower third with the upper two-thirds of the axillary border. Starting from the rough impression is a vertical ridg-e, which is the posterior boundary of the above-mentioned groove. Crossing this ridge at the middle of the axillary border of the scapula is a trans- verse groove which transmits an artery from the anterior to the posterior surface of the scapula. Below the termination of the vertical groove the axillary border of the scapula becomes thinner, and is roughened for muscular attachment. Of the angles of the bone the superior is situated at the junction of the superior and posterior borders, and is about a right angle. It is usually deflected slightly backward ; and presents anteriorly a smooth surface, belonging to the venter of the scapula, but not entering into the subscapular fossa. The inferior angle at the junction of the posterior and axil- lary borders is acute, having a roughened surface anteriorly and posteriorly. The anterior angle is expanded, and is the thickest portion of the bone. It is frequently called the "head" of the bone ; and bears upon its extremity a hollow, oblong, vertical concavity, known as the glenoid cavity. This cavity has its long diameter directed from above downward. It is oval in outline, with the large end below and the small end above. It is supported upon the bone by 20 DESCRIPTIVE ANATOMY. the narrow constricted portion, which is called the "neck" of the scapula. This neck is distinct anteriorly and posteriorly ; but above is obscured by the orig-in of the coracoid process of the bone, and below by the impression for the attachment of the triceps muscle. The processes are two : the coracoid process, which spring's from the bone just above the glenoid cavity. Its direc- tion is at first upward and slig^htly forward, but after pass- ing a short distance, about half-an-inch, it abruptly changes its course, and runs nearly outward, with a slight inclination forward. At its origin one surface looks upward and back- ward and the other downward and forward ; but after the change in its direction one surface looks upward and forward and the other one downward and backward. The upper surface is roughened for muscular attachment, while the lower is smooth and concave. The tip is marked by a smooth impression for muscular attachment. The Acromion Process, is the termination of the spine. It presents one surface which looks upward and back- ward, one which looks downward and forward, an external border, an internal border, and an apex. The superior sur- face is rough, irregular and subcutaneous ; the inferior surface is rather smooth, is concave, and is pierced by numerous nutrient foramina. The external border is convex and roug'h for muscular attachment. The internal border is concave ; and is marked near its outer extremity by a smooth, oblong- articular facet, the long- diameter of which extends from be- fore backward ; and the surface itself is oblique, looking* slightly upward and inward. The apex is roughened for muscular attachment. The upper surface of this process ap- pears to be a continuation of the posterior border of the spine, whose superior lip corresponds to the inner border of the process, the low^er lip to the outer border, while the rough intermediate lip expands into the upper surface. The Humerus. The Humerus, (L. Humerus) or skeleton of the upper ex- tremity, is a long- bone having a shaft and two extremities. OSTEOLOGY. 21 The Head, or Upper Extremity, presents for examina- tion a smooth, rounded portion the head proper, form- ing- something- less than half a sphere, which looks up- ward, inward and backward and is articular for the glenoid cavity of the Scapula. E^xternal to this is a constricted part of the bone, separating- the head from the next appearances, called the anatomical neck. It is narrow and well marked above but becomes indistinct below and be- hind. External to the anatomical neck there is a largfe projec- tion called the g^reater tuberosity. It is prominent and bulg-- ing, looks outward and forward and has on its summit three smooth impressions for the attachment of three of the muscles of the scapular g-roup. Internal to the greater is a smaller projection called the lesser tuberosity. It is sharper and more prominent than the greater tuberosity and has on its summit but one muscular impression. Between the two tuber- osities is a deep groove, the bicipital, bounded on either side by two prominent ridges, the internal and external bicipital ridges of the humerus. Below the tuberosities the bone is constricted and round, forming the surgical neck. The Louver Extremity is flattened from before backward, is bent forward, and presents a3light curve of torsion from with- out inward. On either side is a rough prominence called, im- properly, the condyle, internal and external, the internal being the larger of the two. From either condyle there passes up to the shaft of the bone a large ridge of which the external is much more prominent and curved than the internal. Proceed- ing now from the external condyle inward, we next see a rounded articular surface, the eminentia capitata, whose articular surface extends higher up anteriorly than posteriorly. It is for articulation with the cup-like cavity on the upper ex- tremity of the radius. Internal to this is a shallow articular groove for the play of the rim around the head of the radius. Internal to this we encounter two antero-posterior articular ridges, separated by an antero-posterior articular groove the three forming a trochlear surface for the reception of the greater Sigmoid cavity of the Ulna. The internal ridge is 22 DESCRIPTIVE ANATOMY. larger and its articular surface extends higher up in front than the external. Above the trochlea, both before and be- hind, is a deep pit-like depression. The one in front is for the reception of the coronoid process of the Ulna, the one be- hind for the Olecranon. The olecranon fossa is deeper and larger than the coronoid. In some bones, the thin septum separating the two cavities is absent and then there is a fora- men between the two fossae. Between the inner condyle and the internal surface of the trochlea, is a deep depression for the passage of an important nerve. The Shaft of the bone, cylindrical above, prismoid in the middle and below, presents three surfaces and three borders. The borders are anterior and two lateral; the surfaces, poste- rior and two lateral. The anterior border begins at the greater tuberosity as the external, or anterior bicipital ridge. Prominent and well marked above, it passes down the mid-line of the bone to termi- ate at the coronoid fossa, separating the internal from the external surface. The internal border begins above as the inner bicipital ridge. It passes at first downward and back- ward, then vertically downward to terminate as the internal condyloid ridge. It is prominent above and below, less dis- tinct in the middle of its course. The external border com- mences at the back of the greater tuberosity and passes straight down to the outer condyle where it becomes the external condy- loid ridge. "Very sharp and prominent below, rough and well marked above, it is obliterated in the middle by the passage of the musculo-spiral groove. The internal surface begins as the bottom of the bicipital groove. It passes downward and backward at first and then vertically downward. It is narrow above, wider in the mid- dle and smooth and looking forward and inward below. This surface is usually marked about its middle by the nutrient foramen, though this appearance is often found on the inner border. The external surface begins at the base of the greater tuberosity, passes straight downward to the middle of the OSTEOLOGY. 23 bone and then curves forward until it is almost anterior. About the middle of this surface there is a larg-e roug-h surface, with the apex downward, called the deltoid impression from its supposed resemblance to the Greek "Delta" inverted. Be- low the apex of the impression the musculo-spiral groove crosses to the front, smoothing the outer face, which remains smooth and without appearances throughout. The posterior face is round and smooth above, but becomes broad and flat below. Commencing on the posterior surface and winding downward and outward, is a broad shallow groove, the musculo- spiral. This groove is indistinct on the posterior face, obliter- ates about two inches of the outer border and is finally lost on the external face. The Ulna. The Ulna is a long bone, consisting of a shaft and two ex- tremities, distinguished as upper and lower. It is the inner and more massive of the bones of the fore-arm. The Upper Extremity is composed of two processes called olecranon and coronoid. The olecranon process is found oc- cupying the summit of the bone and may itself be divided for study into a superior, posterior and anterior surface and two lateral borders. The upper surface, indistinctly quadrilateral in outline, terminates anteriorly in a bluntly pointed projection called the beak, and is marked by a rough surface posteriorly for the attachment of a muscle, while in front is found a transverse groove extending backward to become continuous with grooves which mark the lateral borders. The posterior surface is triangular in form, the large end of the triangle directed upward, rough and subcutaneous. The anterior sur- face is concave from above downward, convex from side to side, articular and enters into the formation of the greater sigmoid cavity. The Coronoid process juts forward from the front of the bone. It is triangular in form, the base of the triangle being attached to the bone while the apex points forward. It pre- sents a superior and an inferior surface and two lateral margins. The superior surface is smooth and articular, convex from 24 DESCRIPTIVE ANATOMY. side to side, concave from before backward, and is continuous with tHe similar surface on the olecranon process. The infe- rior surface is very irregular. It is marked near its middle by a rough impression for the attachment of a muscle, the brachialis anticus ; at its junction with the shaft, usually, by a slight projection, the tubercle of the ulna, and at its junc- tion with the internal margin by a roughened elevation, also for muscular attachment. The inner margin is roughened for muscular attachment ; the external presents a concave, oval, articular facet, the long diameter from before backward, which receives the rim around the head of the radius. It is called the Lesser Sigmoid cavity of the ulna. The Greater Sigmoid cavity is formed by the two processes, is concave from above downward, convex from side to side and might be described as consisting of four depressions, two on either process, to receive the articular ridges on the Humerus, separated by a vertical ridge and a transverse groove. The outer side of this cavity is continuous with the Lesser Sigmoid cavity. The Lozver Extrejnity of the ulna is much smaller than the upper, and consists of two projections separated by a notch, the inner on the postero-internal aspect of the bone is the smaller and longer, and terminates in a blunt point. It is called th.e. styloid ■p7'ocess of the ulna. The outer process is called the capitiiliim 2el?2ce(Dim.. of Latin caf>i{t, head) and is artfcular upon its summit and around the greater portion of its circumference. The notch which separates the two processes is narrow, and is intended for the attachment of the fibro- cartilage which enters into the formation of the wrist joint. The articular surface upon the summit is smooth, slightly concave, and does not directly articulate with the carpus but only through the interposition of the fibro-cartilage. The articular rim which surrounds three-fourths of its circumfer- ence is smooth and convex, and intended to play in the cavity which is found upon the lower extremity of the radius. The Shaft of the ulna is distinctly three-sided ; and hence presents three borders and three surfaces. The surfaces are anterior, internal and posterior ; the borders are anterior, OSTEOLOGY. 25 posterior and external, or interosseous. The anterior surface is broad above, narrow and round below. For the upper three-fourths of its course it is usually concave from side to side, presenting- a shallow groove. The subcutaneous inter- nal surface is broadband flattened above, convex and slightly flattened in the middle, round and narrow below. The poste- rior surface is widest about its middle and presents usually a vertical ridge, which divides it into two unequal portions, of which the inner part is the broader. The upper portion of this surface presents a small triang'ular space ; below it is rounded like the remaining surfaces. Of the borders, the anterior begins above at the inner side of the base of the coro- noid process. Prominent and well-marked above, it passes downward to the front of the styloid process, becoming rounder and more indistinct in the lower one-third of its course. The posteterior border commences above at the apex of the triangle of the posterior surface of the oelcranon process. Prominent, well-marked, and sub-cutaneous above, it becomes round and smooth below, and terminates at the back of the styloid pro- cess. The external or interosseous border commences by the convergence of two lines, one from either side of the lesser sigmoid cavity. It is sharp, thin, and well-marked for the middle two-fourths of its course. Below it becomes indistinct or imperceptible, and terminates at the front of the capitulum ulnai. The Radius. The Radius (L. radius, a ray, or spoke of a wheel) is the outer of the two bones of the fore-arm ; and like other long bones it is divided into a shaft and two extremities. Its Ufiper Extremity, unlike the ulna, is much smaller than its lower ; and presents for examination a head upon whose summit is an articular, cup-shaped depression for articulation with the eminentia capitata of the humerus. This depression is surrounded by an articular rim ; and is supported upon a constricted portion called the "neck," which terminates below on its inner aspect in a prominent projection, called the tuber- cle or bicipital tuberosity of the radius. This tuberosity 26 DESCRIPTIVE ANATONY. presents posteriorly a prominent roug-h elevation, for mus- cular attachment while anteriorly it has a smooth surface for the play of a bursa. On the large Lozuer Extrejuity we find the summit present- ing- a triangular articular cavity, the carpal, with its apex directed outward, and terminating- in a point or projection, called the styloid process. The base is directed inward, and is continuous with the articular facet found on the inner aspect of the lower extremity. The carpal cavity is divided into two portions by a slig"ht antero-posterior ridge. The external portion is continued from the summit of the bone on to the inner face of the styloid process ; and is triang*ular in form. The internal portion, quadrilateral in form, is continuous with the smooth oval, oblong* articular facet, whose long* diameter is directed from before backward, found on the inner face of the lower extremity, and called the sig'moid cavity of the radius. Between these two, the sigmoid and carpal cavities, is found a non-articular strip, intended for the attachment of the fibro-cartilage. The anterior face of the lower ex- tremity is roug-h, and projects forward. The posterior face is rough and irregular. It is marked by ^ five vertical grooves with intervening ridges. Two of these grooves are found upon the styloid process, while of the remaining three, one, very narrow, is separated from the styloid process, b}'' a very prominent projection of the bone, while the other is broad and shallow, and is found near the inner end of the posterior face. The Styloid Process itself presents an internal and an exter- nal face : the internal being articular, and continuous with the 8 articular surface of the carpal cavity ; the external rough for ligamentous attachment, and marked by the grooves above mentioned. Its anterior and posterior borders are roughened, while its tip has a blunt point. The Shaft of the radius has three surfaces and three bor- ders. The surfaces are anterior, posterior, and external ; the borders anterior, posterior, and internal or interosseous. The anterior face is narrow above, slightly convex, becomes OSTEOLOGY. 27 broader as It approaches the lower extremity of the bone, is slig-htly concave in the middle and is flat at the lower end. It is marked b}^ an oblique ridg-e, which will be mentioned later. The -posterior face is convex in the upper and lower portions of its course, slightly concave in the middle. The external face is convex throughout its extent, so that the bone appears to be bowed outward. The anterior border begins at the front of the bicipital tuber- osity ; it passes downward and outward, crossing- the upper one-third of the bone until it reaches its middle third, in which situation it is known as the oblique line of the radius mentioned above. From this point it continues vertically downward to the front of the styloid process of the radius, where it terminates. The posterior border beg"ins at the back of the neck of the radius, and running- vertically downward, more prominent in the middle than elsewhere, terminates at the back of the sty- loid process. The internal border or interosseous ridg-e, beg-ins also at the tuberosity near its posterior portion, passes downward, sharp and prominent about its middle, more indis- tinct below, and terminates at the lower extremity of the bone, by dividing- into two lines which enclose the sigmoid cavity of the radius. The Hand. The skeleton of the hand consists of the skeleton of the Carpus, the Metacarpus, and Phalanges. The Carpus. The skeleton of the carpus or wrist, consists of seven small, irregular bones, arranged in two rows one above the other ; in the upper row are three bones, arranged in the following order from without inward: 1st, the Scaphoid; 2nd, the Semilnnar ; 3d, the Cuneiform, on the front of which plays a sesamoid bone, called the Pisiform. In the lower row in the same order are : 1st, the Tra-pcziiim ; 2nd, the Trapezoid \ 3d, the Os Magnum ; 4th, the Unciform. The Bones of the Upper Row. The bones of the upper row articulate laterally with one 28 DESCRIPTIVE ANATOMY. another ; the bones on the inner and outer side respectively have no bones on the inner side of the one and the outer side of the other, and hence there is no articular surface on that aspect of the bones. It must be further noted that viewed from the back there appear to be but three bones in the upper row, placed laterally, the scaphoid, semilunar and cueniform ; but viewed from the front the pisiform is seen perched upon the cuneiform, so that the latter bone has no articular facet on its inner side. The Scaphoid. This bone has a su-perior surface, which is rounded, convex, and articular for lower end of Radius; an inferior surface, which is concave and articular for the upper extremity of the os magnum; an outer extremity, which looks downward and outward and is articular for the trapezium and trapezoid; an inner extremity with an oval articular facet, whose long diameter is directed from before backward, for articulation with a similar facet upon the semilunar. Ivike all the bones of the carpus, the anterior and posterior surfaces are non-articular; but unlike most carpal bones, the anterior sur- face is broader than the posterior. The Semilunar, the second bone in the first row, has a superior sinface, convex, smooth, and articular for lower end of Radius; an inferior surface having- two articular facets, one concave, oval, with its long- diameter antero-posterior, articular for the head of the os mag-num,the other long* and narrow for the unci- form; an outer edg-e, articular for the scaphoid; and an inner ^ triang-ular in shape, larg-er in size than the outer one, and ar- ticular for the cuneiform; anterior and f>osterior surfaces, roug-hened and non-articular. The anterior surface is broader than the posterior, as is the case with the scaphoid. The Cuneiform presents an inferior surface, concavo- convex for articulation with the unciform; an external sur- face, flat, slightly triang-ular, articular for the semilunar ; an antero-external surface, which is articular for the pisiform, while internally it terminates in a blunt projection which is not articular. Tho. postei'ior surface is broad and roug-h, the anterior surface is rough and narrow. It is usually said that OSTEOLOGY. 29 this bone is articular upon its anterior face ; but the surface which receives the pisiform bone looks upward more than forward, and is also directed slig-htly outward. The Pisiform is a rounded bone ; and is in reality only a sesamoid bone, embraced by the tendon of the flexor carpi ulnaris. It is articular upon only one surface, the surface which looks downward and backward. It is g-enerally de- scribed as being- the only bone of the carpus which is articular upon its posterior surface. The Bones of the Lower Row. The Trapezium, the first bone of the second row, is easily disting-uished by the possession of a concavo-convex, or saddle- shaped articular surface, which is directed downward and outward. This is its inferior surface. Its superior surface is marked by a smooth, concave articular surface for the re- ception of the outer end of the scaphoid. The outer surface is roug-h, prominent and non-articnlar. The inner face is marked above by a smooth concave articular surface for the outer face of the trapezoid, while below this, separated from it by a rough groove, is a flat surface, looking- downward and inward for the second metacarpal. Its f>osterior surface, broader than its anterior, is roug-h and prominent, while the anterior surface is easily disting-uished by an oblique g-roove, which runs from above downward and inward. The Trapezoid can be most easily disting-uished by exclusion, having- none of the characteristics of the other bones. It has a broad, somewhat quadrilateral posterior surface ; a narrow and roug-hened aiiterior surface. Its superior surface is con- cave, and articular for the held of the scaphoid. Its external surface is slig-htly convex above for articulation with the trape- zium. The inferior surface is concave from before backward, and articular for the head of the second metacarpal bone; while the internal surface is also concave from before backward, and articular for the lateral aspect of the os magnum. The Os Magnum presents superiorly a rounded articular head to be received in the cavity which is furnished by the scaphoid and semilunar bones, the articular surface extending 30 DESCRIPTIVE ANATOMY. further on its posterior than on its anterior aspect. Inferiorly it presents a quadrilateral, oblique articular facet, which artic- ulates with the upper extremity of the third metacarpal bone, and which is continuous with the articular facet found upon its, inferior and external lateral aspect for the inner edg-e of the upper extremity of the second metacarpal bone. The outer surface presents an articular facet, at the anterior infe- rior angle, convex from before backward, for articulation with the inner face of the trapezoid. The internal surface presents near its posterior marg-in an articular facet, broader above than below and somewhat L-shaped, the large end of the L directed upward. This is for articulation with the outer face of the unciform. The -posterior surface is broad, rough, and marked by a depression just below the articular head ; the anterior face ^ narrower, than the posterior, is bulging and prominent, and roughened for ligamentous attachment. The Unciform is more easily distinguished than any bone of the hand. Its upper face looks upward and inward; and is frequently described as its internal face. This face is in- tended for articulation with the cuneiform ; and presents like that bone a concavo-convex articular surface, which is contin- uous with the upper extremity of the bone, also convex for articulation with the os magnum. Its outer face looks outward and slightly downward ; and is marked near the posterior surface by an Iv-shaped facet, similar to the one found on the inner surface of the os magnum, and intended for articulation with that bone. Its inferior surface is marked by two articu- lar facets, separated by a slight ridge, these facets articulating with the fourth and fifth metacarpal bones. Its posterior face, much broader than the anterior, is roughened for ligamentous attachment. ^\i^ anterior face will be at once distinguished by a very prominent projection found on the lower inner face of the bone. This projection, named the unciform p7'ocess, looks forward and slightly outward, being a little curved in its course. It is one of the prominent land-marks of the hand. The remainder of the anterior face is roughened for ligamentous attachment. OSTEOLOGY. 31 The Carpus as a xcholc presents us with four separate sets of articulations ; vi2. The articulation betxveen the upper rozu of the carpus and the zurist, the articulation between the first and second rows, the articulation between the second row and the metacarpal bones, and the articulations between the individual bones of the carpus. When examined in the articulated skel- eton, it is seen that the superior row presents a condyle, oblong-, oval and articular. The long- diameter of this condyle is transverse ; the bones which form it are from without in- ward : the scaphoid, the semilunar, and the cuneiform, the pisiform not entering- into its formation. The articulation Ijctzjeoi the tzuo 7'ozus of carpal bo)ies is sinuous in outline, or concavo-convex, the trapezium and trapezoid tog-ether forming- a cavity for the reception of the head of the scaphoid, while the head of the os mag-num and the upper end of the unciform form tog-ether a convex articular surface received into a con- cavity which is contributed to by the scaphoid, the semilunar, and the cuneiform bones. The articulation betzveen the bo?ies of the second roz'j and the metacarpal bones consists first of a saddle-shaped articulation, the trapezo-metacarpal ; while the remaining- articulations vary in form with the varying- surfaces found upon the extremities of the metacarpal bones and the corresponding- surfaces on the carpal. TJie articulations be- izveen the carpal bones themselves have been mentioned in the description of those bones. It will be noticed that none of these bones are articular on their posterior and anterior aspects, thoug-h it is said that the cuneiform is articular ante- riorly and the pisiform posteriorly, but these surfaces do not look directly forward and backward. When viewed from its posterior aspect, the first row presents a set of but three bones, the pisiform not being- seen from the posterior face. It will be noticed that the carpal bones taken as a whole form an arch whose concavity is directed to the front, and whose convexitv is directed backward. Hence it can be readily seen that all of the bones of the carpus, with the two exceptions mentioned, are broader upon their posterior than upon their anterior aspect. This arch of course g-ives streng-th to the hand, while at the same time permitting the necessary flexibility. 32 DESCRIPTIVE ANATOMY. Metacarpus. The metacarpus is formed by five bones classed as long- bones ; four of these, for the four fiug-ers, being- nearly paral- lel, while the fifth — for the thumb — recedes from the others as it descends. The metacarpal bones articulate above with the lower row of the carpus ; below with the upper extremity of the first phalanges. At their upper ends they articulate laterally with one another, except the metacarpal bone of the thumb ; but at the lower end they do not articulate with one another. The metacarpus, like the carpus, is arched trans- versely, the convexity being posterior. One of its constitu- ents may be thus described : A Typical Metacarpal Bone. The Metacarpal Bones are long- bones, presenting- a shaft and two extremities, the upper extremity called the base and the lower called the head. The upper extremity is quadri- lateral ; and it presents anterior and posterior surfaces, of which the posterior surface is the broader, these two surfaces being- roughened for ligamentous attachment; two lateral surfaces, which are marked by articular facets, intended for articulation with the adjoining metacarpal bones. The Summit of the bone is marked by a quadrilateral articular facet, for articulation with one of the carpal bones of the second row. The Lozver Extremity, or head, terminates in an articular surface, oblong antero-posteriorly, and articular higher up in front than behind. On either side of this surface is a depres- sion, and behind this depression is a well-marked tubercle. Posteriorly the lower extremity is flattened and rough, while anteriorly it presents a slight groove, caused by the passag-e of the tendons of the flexor muscles. The Shaft is triangular and arched, with the convexity of the arch directed backward. It presents a posterior and two lateral faces, an anterior and two lateral borders. The posterior face at its upper end presents a median Ion- OSTEOLOGY. 33 g-itudimal ridgfe, with a slig-ht depression upon either side of it. This ridg-e, as it passes downward, divides about the middle of the bone into two, each, graduall}'- sepa- ratinor, descends to reach the tubercle above the lateral de- pression on the lower extremity. The triang-ular space between these diverg-ing- ridg-es is flattened. The lateral faces are concave and smooth from above downward, so that each pair of bones would leave between them a space for the attachment of muscles. These are known as the interosseous spaces. The bone is concave towards its anterior aspect, and marked by the anterior border, which is a rather indistinct vertical ridg^e separating" the lateral faces from one another. This description applies more or less closely to all the metacarpal bones; but each possesses appearances character- istic of itsell, by which it may be discriminated. E^ach bone is known by the name of the fing"er which it supports; but the metacarpal bones are also known by numbers from without inward. The Metacarpal Bone of the Thumb is the shortest and larg"est. Its posterior surface is broader and flatter than the remaining- bones, and its lateral borders are more distinctly marked w^hile upon its summit it bears a saddle-shaped or concavo-convex articular surface, concave from before back- ward, and convex from side to side. This with the absence of any lateral articular facet will disting-uish it from the other bones of the metacarpus. The Metacarpal Bone of the Index Fing-er is the long-est, is next in size to that of the thumb, while its base presents three articular facets, two of which are upon the summit, one flattened for articulation with the trapezium, one concave for articulation with the trapezoid, and one upon the internal lateral aspect for articulation wnth the metacarpal bone of the second fing^er. The Metacarpal Bone of the Second Finger is next in size and in length. On its base it presents an articular facet for the OS magnum; on its outer lateral aspect an articular facet for the metacarpal bone of the index finger; on its inner lateral Des Anat — 3 34 DESCRIPTIVE ANATOMY. aspect an articular facet for the metacarpal bone of the ring- fing-er, while its upper outer posterior aspect is prolong-ed into a styloid process, projecting- upward between the trape- zoid and the os mag-num. On its inner lateral aspect the articular facet is divided into two by a g-roove. The Metacarpal Bone of the Ring- Finger, next in size and length, is the typical metacarpal bone. On its external lateral aspect a groove divides the articular facet into two for the two corresponding- facets on the inner lateral aspect of the metacarpal bone of the middle fing-er. The Metacarpal Bone of the Little Fing-er is the smallest. Its base presents a superior articular facet for the unciform, and a lateral facet on its outer aspect for the corresponding- facet on the metacarpal bone of the middle fing-er. On the inside of the base is a rough and prominent tuberosity with no lateral articular facet, which in itself disting-uishes it from the other metacarpal bones. The Phalanges. The Phalang-es consist of three rows of long- bones, extend- ing from the heads of the metacarpal bones to the tips of the fingers. The rows are numbered from the metacarpal bones, first, second, and third, the third row being- usually called ungual. The Thumb has but two phalang-es, the second phalanx taking- the place of the characteristic ung-ual or third. The first phalanx is the long-er, and its shaft is semi-cylin- drical. The posterior surface is convex both from above down- ward and from side to side and is smooth. The ante- rior surface is slightly curved longitudinally, and is broader above than below. The two lateral borders, well-marked above, terminate in slight tubercles at the lower aspect of the bone. The Base or Upper Extremity presents a smooth round shallow articular facet, whose transverse diameter is slig-htly g-reater than the antero-posterior, and it is almost cup- shaped. This is for articulation with the head of the meta- carpal bone. The Head or Lozuer Extremity presents an antero-posterior g-roove, surmounted on either side by an artic- OSTEOLOGY. 35 ular ridg-e, constituting- a trochlear surface. On either side of the head is a slig-ht depression, marked in front and behind by- trifling' elevations or tubercles. The second phalanx presents on its base a receiving- surface for the trochlea ; that is, a central ridg-e with lateral depres- sions to receive the corresponding- elevations. Like the first phalanx it is broad and expanded above, narrower below. Its lower extremity presents a trochlea for articulation with the third, or ung-ual phalanx. The second phalanx with the exception of the head is like the first, only it is shorter and less massive. The Third, or Ung-ual Phalanx (Z. Ung-nis, a nail) presents on its base an articular surface to receive the trochlea of the second. It then becomes rapidly narrow ; but just before it terminates, it expands into a broadened surface. The bone is smooth on its posterior, but roug-h, prominent and flat on its anterior surface. The posterior aspect of this phalanx supports the nail, while the anterior surface supports the tis- sues which form the pulp of the corresponding- fing-ers. There being- but two phalang-eal bones for the thumb, the second phalanx for the thumb corresponds to the ung-ual phalanx for the other fing-ers. The Skeleton of the Lower Extremity. The skeleton of the lower extremity consists of the skeleton of the hip, thig-h, leg- and foot. Os Innominatum. The Os Innominatum (L. Theun-named bone) haunch bone, is the most important bone in forming- the pelvic cavity, and corresponds to the Scapula in the upper extremity. In the foetus it consists of three bones — Ilium, Ischium and Pubis, and, since the bone is very irreg-ular in outline, this division has been retained in describing- the bone in the adult. The Ilium (Deriv. uncertain) or flank bone, is the larg-e, expanded, upper j)ortion of the bone. It is divided for study into and internal and external surface, anterior, posterior, and superior borders, the latter being- known as the crest. 36 DESCRIPTIVE ANATOMY. The crest of the ilium is sinuous in outline. Viewed from in front it is seen to be convex for its anterior four fifths, con- cave for its posterior one fifth. In front and behind it termin- ates in roug^h projections, known as the anterior and posterior superior spinous processes. The crest consists of two lips, external and internal, and a roug-h intervening- space or middle lip. The anterior border consists of two projections, anterior superior and anterior inferior spinous processes, with a notch between. The superior is more prominent but less massive than the inferior. Below the inferior is a slig^ht g^roove separating* it from the margin of the acetabulum. The posterior border is less reg-ular in form than the anterior and like it, is marked by two projections with an intervening- notch. These are called the posterior superior and posterior inferior spinous processes. They are sharper and less distinctly marked than those on the anterior border, and the notch between is not so deep. Below the posterior inferior spinous process is a deep notch, part of which is found on the ilium and the remainder on the ischium, called the g"reater sacro-sciatic. The external surface is curved in outline being- concave for the posterior four fifths, convex for the anterior one fifth. On the posterior border is a deep notch, called g-reat sciatic, and commencing- in this notch, and curving- forward and upward from it, are three lines disting-uished as superior, inferior and middle. The superior curved line, the shortest and most distinct of the three, beg-ins near the upper marg-in of the sciatic notch and passes upward and slig-htly forward until it reaches the crest near its posterior one filth. The middle, which is the long-est, beg-ins at the middle of the sciatic notch and passes upward and forward, markedly curved, to terminate just above the anterior superior spinous process. The inferior, the least distinct, starts at the lower portion of the notch and, passing- forward and slig-htly upward, reaches the anterior border of the bone a little above the anterior inferior spinous process. The whole surface is roug-hened for the attachment of muscles and presents the orifices of numerous foramina for the transmission of blood vessels, the larg-estof which is found near the middle of the bone just below the middle curved line. OSTEOIvOGY. 37 The internal surface, much smoother than the external, is concave for its anterior two thirds both from above downward and from before backward, forming* the iliac fossa. Just be- fore the bone unites with the ischium it is crossed by a smooth, elevated ridge which forms a part of the ilio-pectineal line. The portion of bone below this is smooth, nearly flat, continu- ous with the inclined plane of the ischium, and enters into the formation of the true pelvis. The posterior one third of the internal surface is very irregular in outline. In front this sur- face is occupied by a roug-h, ear shaped articular surface which articulates with a similar surface on the sacrum. Behind this is a roug-h surface, made up of intervening- elevations and depressions for the attachment of lig-amentous fibres. The Ischium is the lower, massive portion of the bone. It is divided for study into a body, tuberosity and ramus. The body is triang-ular and presents for examination three surfaces and three borders. The surfaces are internal, external and posterior; the borders, anterior, posterior and external. Nearly the whole of the external surface is occupied by the articular surface furnished by the ischium to the acetabulum; but a small portion below the rim of the acetabulum is occupied by a g-roove, the lower border of which is the mark of division between the outer surface and the tuberosity. The internal surface slopes obliquely from above downward and inward, facing- inward and backward. It is smooth and concave from before backward and continuous above with a similar surface on the inner face of the ilium. The posterior surface is quadrilateral, forms the posterior wall of the acetabulum and is roug-hened for muscular attachment. The anterior border is thin and sharp, slopes upward and forward to join the pubes and forms the posterior boundary of the thyroid foramen. The external border is thick and rounded and forms the posterior part of the rim of the acetabulum. The posterior border is long- and sharp, nearl}' vertical in direction and is interrupted a little below the middle by a prominent projection of bone called the spine of the ischium. Above the spine a deep notch is found which enters into the formation of the 38 DESCRIPTIVE ANATOMY. great sacro-sciatic notch; below the spine, a similar, but shallower notch forms the lesser sacro-sciatic notch. The tuberosity is the rough lower end of the bone on ^vhicli the body rests w-'hen in the sitting- posture. It has an inferior surface w^hich is roug-h and triang-ular, and just above this, a smooth portion, divided into two bv an oblique ridge, the parts above and below the ridge being intended for muscular attachment. Internally it presents a rough, prominent ridge which separates the lower surface from the internal, and above this ridge a smooth g-roove. The Ramus passes forward, inw^ard and slightly up- ward. One surface looks outward and forward, the other inward and backward. One border looks outw^ard and forms the anterior boundary of the obturator foramen, the other looks inward and forms, with the ramus of the pubis, the outer boundary- of the pubic arch. This internal border is thick and divided into two lips and an inter- vening space. The two lips pass downw^ard to become con- tinuous with similar lips on the lower surface of the tuberos- ity. The internal border is averted, its upper part looking nearl}" forward. At the junction of the ramus of the ischium with that of the pubes there is sometimes seen a rough line. The Os Pubis iL. Pubes, hair, or down) is divided for stud}^ into a body and a ramus. The body is the horizontal portion of the bone, and is divided into two surfaces, anterior and posterior, two borders, upper and lower, and tw^o extremi- ties, internal and external. The posterior surface is concave from before backward, convex from above downward and smooth. The anterior surface is convex from before backward, slightly concave from above downward, broad at its inner and narrow at its outer extremity, and rough for muscular attachments. The superior border is marked at its junction with the internal extremity by the angle of the pubis; external to this and run- ning outward and forward is a rough ridge called the crest. The crest terminates after a course of about three fourths of an inch in a prominent projection of bone called the spine. OSTEOLOGY. 39 Runningf outward and backward from the spine and separating- the superior border from the posterior surface, is a sharp ridg-e of bone called the pectineal line; in front of which is a triang"ular surface, limited in front by the anterior surface of the pubis, the pectineal triang-le. The base of the triangle, which is directed outward, terminates in a rough prominence known as the pectineal eminence. The inferior border forms the superior boundary of the thyroid foramen and is marked by an oblique g-roove, which, from within the pelvis, extends forward and inward. The internal extremity, called the symphysis pubis, is an oval, roug^h articular surface, the long- diameter of which is directed from above downward and back- ward. It is covered by a series of nipple shaped projections and in the recent state is lined with cartilag-e. The external extremity is in part attached to the ilium, while the remainder is free and enters into the formation of the acetabulum. The ramus of the pubes is short and extends downward and slightly outward. Its surfaces look backward and for- ward, its borders inward and outward. The inner border presents two lips and an intervening- space, the two lips being continuous with those found on the ramus of the ischium. The acetabulum (L. a vessel for holding- vinegar, from a supposed resemblance) is a nearly circular, cup-shaped cavity, one-fifth of which is contributed by the pubes, a little less than two-fifths by the ilium and a little more than two-iifths by the ischium. It is articular around the whole of its cir- cumference except a small portion at the lower and inner part, where a deep notch interrupts the prominent rim which else- where surrounds the cavity. This notch, called the cotyloid, leads to a deep non-articular depression in the bottom of the cavity, which in the recent state lodg-es amass of fat and, with its margins, g-ives attachment to the ligamentum teres. The thyroid or obturator foramen is found below and in front of the acetabulum. It is irregularly oval in outline and its boundaries are formed as follows : Behind by the anterior border of the body of the ischium, in front bv the outer border of the ischilo-pubic rami, above by the lower border of the body 40 DliSCRIPTlVE ANATOMY. of the pubes, the groove on that bone furnishing- nearly the whole of the upper boundary. Pelvis. The Pelvis (L. a basin or laver, from a resemblance to an ancient basin.) The pelvic g"irdle is far more powerful than the shoulder g-irdle, the individual bones being more massive and bound more firmly to one another. The cavity has been divided by the ilio-pectineal line, into the true and the false pelvis, thoug-h the latter term should not be used, since the false pelvis is simply a part of the abdominal cavity. The pelvis is the cavity circumscribed by the sacrum, coc- cyx and two ossa innominata, containing- in the living- subject some of the small intestine, a part of the larg-e intestine, and the genito urinary apparatus, in part. It is bounded behind by the sacrum and coccyx and throug-hout the rest of its ex- tent by the ossa innominata. It is divided into two portions, the false pelvis and the true. The false pelvis is that por- tion between the two iliac fossae bounded behind by the junction of 5th lumbar and sacrum, while in front it has no bony wall. It extends from the crest of the ilium above to the pectineal line below. This pectineal line, also called linea ilio-pectinea, is a prominent ridg-e extend- ing around the os innominatum from the symphysis pubis to the sacro-iliac symphysis. At the linea ilio-pectinea the pelvis is suddenly contracted and the true pelvis beg-ins. The plane circumscribed by the ilio-pectineal line is called, the brim or inlet of the pelvis, or superior strait of the pelvis. The true pelvis thus extends from this brim downward to what is called the outlet, or inferior strait of the pelvis. The outlet is limited in front by the lower end of the symphysis pubis; the arch formed by the diverg-ence of the pubic rami being called the pubic, or sub-pupic arch. Behind, the outlet is limited by the tip of the coccyx. Laterally the outlet is bounded by the tuber ischii. The pelvis is so attached to the vertebral column as to render the plane of the inlet oblique, from behind downward and forward, and so g-reat is this obli- quity that the top of the symphysis pubis is about four inches OSTEOLOGY. 41 below the level of the promontory of the sacrum. The so- called axis of the superior strait is an imag-inary line, perpen- dicular to the plane of the brim and cutting- it at its centre. The true pelvis is much deeper behind than in front, measuring" posteriorly five inches, latterally three and one-half inches, and at the pubes one and one-half inches. Besides these meas- urements, obstetricians employ others, as of the outlet and inlet, called diameters. The diameters usually g-iven are for the inlet, antero-posterior and transverse. The objects observable on the exterior of the pelvis are as follows: in front the symphysis pubis and below this the pubic arch; on either side the obturator foramen, farther out the acetabulum; behind this the g-reater and lesser sciatic notches, separated by the ischiatic spine; on the centre behind are the sacral spines. The pelvis differs in the two sexes; the characteristic points in the female are as follows: 1st, the thyroid foramen is more distinctly triang-ular; 2d, the pelvis is more capacious — meas- uring" more transversely and antero-posteriorly, but less ver- tically; 3d, the ang-le of the pubic arch is g-reater by 10°, measuring- from90° to 100°. The pelvis in the neg-ro is observably smaller than in the Caucasian. The Femur. The Femur (Z. Femur, the thig-h) is the long-est and most powerful bone in the body. It is divided for study into a shaft and two extremities. The upper extremity presents a head, neck and two tuberosities called trochanters. The Upper Extremily consists of the head, neck and two trochanters. The Head, smooth and g-lobular, projects upward, inward and forward from the neck, and forms about two thirds of a sphere. It is marked a little below and behind its centre by a deep pit which in the recent state lodg-es the outer end of the lig-imentum teres. The neck slopes downward, outward and backward from the head, is flattened from before back- ward and is divided into an anterior, and posterior surf ice, an 42 DESCRIPTIVE ANATONY. Upper and a lower border. The anterior surface is flat and slightly roughened ; the ^posterior, convex from above down- ward, concave from within outward, is smooth and rounded. The upper border, only one half the length of the lower, is broad, round, thicker than the lower and marked at its outer extremity by a deep pit called the digital. It is nearly straight. The lower border is thinner, longer and more oblique than the upper. B2I0W and behind it terminates at the lesser trochanter while the upper terminates at the greater trochanter. The great trochanter is a quadrilateral piece of bone which projects upward from the junction of the neck and shaft. Its outer surface is marked by an oblique ridge; a di- agonal, running from the postero-superior angle to the antero- inferior angle. The surface in front of the diagonal is rough, that behind it is smooth. The inner surface is taken up almost entirely by the digital pit. The anterior border is thick and rough, the posterior, thinner and rounded, the upper thin and rather sharp, terminating posteriorly in a blunt pro- jection which overhangs the digital pit. The lesser trochan- ter is much smaller than the greater, projects from the inner posterior aspect of the bone, is round in form, bluntly pointed at its apax and marked by a single muscular impression for the attachment of the biceps flexor femoris. Extending from the base of the great trochanter downward and inward to the lesser is a roughened ridge of bone known as the posterior inter-trochan- teric line. On the anterior aspect, and starting from the base of the great trochanter, there is a more prominent line which winds around the bone, pissing downward and inward until it reaches the inner face of the bone when it turns and runs outward, called the spiral line of the femur. This line is sometimes incorrectly called the anterior inter-trochanteric line. It passes about half an inch below the lesser trochanter. The Lozuer Extremity of the femur is flattened from before backward, so that the lateral diameter exceeds the antero- posterior. It consists of two round or oval articular surfaces, called condyles, two rough projections, one on either side, called tuberosities, and an intervening notch. If the bone is OSTEOLOGY. 43 held vertically it will be seen that the inner condyle is pro- lonored downward considerably below the outer to compensate for the obliquity of the bone caused by the width of the pelvis, which separates the heads of v the bone, while the lower extremities approach each other. The long- diameter of the articular surface of each condyle is from before backward ; but it will be seen upon careful examination that the inner condyle is long-er and narrower than the outer, that its articular surface extends hig-her up behind and not so hig-h in front. The outer condyle is more oval, is shorter than the inner, its articular surface extending- hig-her up in front than behind. The two condvles are separated behind by a deep and roug-hened notch, called the intercondyloid notch. This notch is marked on either side by a depression for the attachment of the corresponding crucial lig^aments of the knee- joint. In front this notch is continuous with a smooth articu- lar surface, concave from side to side, convex from above downward, and forms a trochlea for the opposite surface of the patella. Each condyle presents an internal and an external surface. The external surface of the external condyle is marked by a prominent roug-h tuberosity, called the outer tuberosity of the femur; and below this is an antero-posterior g"roove for muscular attachments. The internal surface of the external condyle is the outer boundary of the intercondy- loid notch. The internal surface Q>i the internal condyle is likewise marked by a roug-h projection, called the internal tuberosity oj the femur; while the outer surface of the inter- nal condyle is the inner boundary of the intercondyloid notch. The inner surface of the inner and the outer surface of the outer condyles are each marked by nutrient foramina. Above each condyle is seen a slig^ht depression on the posterior aspect of the bone, which is intended for the attachment of the g"as- trocnemius muscle. Leading- upward from either condyle is a ridge. These ridg-es approach each other above to reach the linea aspera. They are known as the condyloid ridges, and more properly belong- to the shaft of the bone. Between these ridg-es is a triangular roughened space called the Popliteal Triangle. 44 DESCRIPTIVE ANATOMY. The Shaft of the Femur. Like most long- bones the femur is triangular upon cross-section ; and therefore presents for study three surfaces and three borders. The surfaces are anterior and two lateral ; while the borders are posterior and two lateral. The anterior surface is round, convex from above down- w^ard, so that the bone is bowed in outline, with its convexity forward, convex from side to side, and broader above and below than in the middle. Of the two lateral surfaces, the external is slig-htly concave fromabove downward, and smooth; the inter)ial also slightly concave from above downward, broader than the external, and smooth. The lateral borders are indistinctly marked. The external lateral, commencing- at the base of the trochanter major, extends, indistinctlv marked, down to the outer tuberosity of the femur. The internal lateral^ commencing- at the spiral line of the femur, passes downward to the inner tuberosity. The -posterior border, called linea as-pera is the most distinct of the three. It may be considered as con- sisting- of a central portion, called the "body ;" and an upper and a lower portion. The central portion, or body, occupies about the middle two-fourths of the bone. It presents an internal and an external lip, and a roug-h intervening- space, which are intended for muscular attachments. Above it divides into three lines : one winds around about a quarter of an inch below the lesser trochanter to become continuous wnth the spiral line of the femur ; one passes upward to the base of the lesser trochanter ; while the vertical passes upward and outward to join the posterior border of the g-reater trochanter. Below it subdivides into two ridges, which are known as the two condyloid ridges. These two ridges diverge from each other, enclosing the -popliteal space, a smooth triangular space found at the lower extremity of the shaft, the base of which is directed downward to the condyles and the apex up- w^ard to the linea aspera. Of these two lines the external is the more distinct, the internal being obliterated near its middle by the groove which transmits the femoral artery. About the middle of the shaft of the bone, and rising either in OSTEOLOGY. 45 the linea aspera or upon its external surface close to the linea aspera, is found a larg-e nutrient foramen, which is directed obliquely upward and outward. The Patella. The Patella (Iv. Patella, a small pan), or knee-pan, is a sesamoid bone situated on the front of the knee joint, devel- oped in the tendon of the triceps extensor cruris. It presents for examination two surfaces, anterior and posterior, two extremities, superior and inferior, and two borders, internal and external. The aiiterior surface is rough, marked by a number of vertical lines and a number of nutrient fora- mina. The posterior surface is smooth and articular. Near its middle it presents a prominent vertical ridg-e ; and on either side of this a depression, also articular, in- tended for the reception of the condyles of the femur. The posterior face forms the receiving- surface for the trochlea. These depressions are dissimilar in size and shape ; and cor- respond to the dissimilarity of the condyles of the femur, the outer depression being larger and more nearly circular, while the inner is smaller and more oval in outline. The upper extremity of the bone is blunt, rough, and marked by a trans- verse ridge ; the lower extremity, smaller and more pointed, is roughened. Of the borders, the external is thinner and sharper than the iutcrnal. Both are roughened for the attach- ment of the tendinous fibres of the triceps. The Tibia. The Tibia (Z. Tibia, a flute or pipe) is a long bone, con- sisting of a shaft and two extremities. It is the larger of the two bones making up the skeleton of the leg. The Upper Extremity is expanded so that its transverse diameter is much greater than its antero-posterior. It pre- sents upon its summit two shallow articular cavities, called glenoid cavities, intended to receive the condyles of the femur, and in correspondence with them are dissimilar in shape, the outer being circular and the inner oval. The inner cavity has its long diameter antero-posterior ; the outer cavity is shal- 46 DESCRIPTIVE ANATOMY. lower, as well as being- circular in outline. These cavities are separated from one another by a prominent projection, which is called the spine of the tibia. This spine is bifurca- ted ; and is situated nearer to the posterior than to the anterior surface of the extremity. In front and behind the spine is seen a roug-hened, non-articular space, which is intended for lig-amentous attachment. On the front of the bone, about an inch below the articular cavities, is a roug^h triang-ular space, below which is seen a projection, called the anterior tubercle of the tibia. This tubercle is smooth above and roug-h below, the rougfhened lower portion being intended for muscular at- tachment. That expanded portion of the bone upon which the g-lenoid cavities rest is known as the tuberosity of the ti- bia, internal and external. The internal tuberosity, somewhat more prominent than the external, is roug-h, and marked near its posterior portion by a deep transverse, or antero-posterior groove. The external tuberosity is roug-hened, as is the inter- nal, and posteriorly is marked by a flat, circular, articular facet, which is directed downward, outward, and backward, and is intended for articulation with the upper extremity of the fibular. Behind, the tuberosities are both roug-hened for ligamentous attachment. The Lozver Extremity is four-sided ; and is about half the size of the upper. On its inner side there extends downward a rough projection of bone, called the internal malleolus (L. A small mallet). It corresponds nearly to a styloid process. This internal malleoeus presents two surfaces, two borders, and an extremity. Of the sur- faces, the internal is rough, and subcutaneous, while the external is smooth triangular and articular, entering into the formation of a cavity found upon the extremity of the tibia for articulation with one of the bones of the tarsus. The anterior border of the malleolus is shorter than the posterior, and is vertical in its direction, while the longer posterior border is oblique, extending downward and forward, and has upon it a well-marked groove for the transmission of a tendon. The extremity is blunt ; and is marked behind by a pit-like depres- OSTEOLOGY. 47 siou. On the outer surface of the lower extremity is a trans- verse depression, sometimes articular, more g-enerally roug-h- ened, which receives the lower extremity of the fibula. The lono- diameter of this depression is directed from before back- ward ; and leading- upward from it are two lines, which shortly converg-e, enclosing* between them a roug-h triang-ular space for the attachment of interosseous lig-aments. The anterior aspect of the lower extremity is roug"hened for lig'a- mentous attachment, while the posterior, also roug-hened, is marked by a vertical groove. The summit presents an artic- ular facet, continuous with the one on the outer face of the internal malleolus, and intended for articulation with the upper surface of the astrag-alus. This facet is broader externallj'" than internally, and broader in front than behind. It is con- cave from before backward, and nearly flat from side to side. The Shujt of the bone is three-sided, presenting- an internal, an external, and a posterior surface, and an anterior and two lateral borders. The bone is g-enerally somewhat twisted, particularly in the neg-ro race; and is bowed, convex internally and concave externally. The internal surface is broad above, becoming- slig-htly narrow below; is convex both from above downward, and from before backward; and is subcutaneous. The external face, which is concave from above downward, is marked by a vertical g-roove close to the external border of the bone. This face in the lower third curves g-radually forward to the anterior face of the bone. The posterior face is broad and flat for the upper one-fifth of the bone, becoming- more rounded in the middle and flatter and broader in the lower portion. At its upper part it is marked by an oblique ridg-e, called the Popliteal Line, which extends downward and in- ward from the external tuberosity of the bone. Below this ridg-e the posterior surface is marked about its middle by a ■vertical ridg'e, which exists only for about the middle of the bone, disappearing- in the lower portion. Near the commence- ment of the vertical ridg-e, g-enerally on the posterior surface, is found a larg-e nutrient foramen, being- in fact the larg-est in the body, which conveys the blood to the interior of the bone. 4S DESCRIPTIVE AXATOLIY. Of the borders the anterior, or shin, is very sharp and very prominent. It is sinuous in outline, more distinct in the upper two-thirds of the bone, while in the lower third it passes to the front of the internal malleolus, and blends with the ante- rior border of this projection. The internal border, separating- the internal from the posterior surface, begins as an indistinct line at the inner tuberosity, becomes more prominent about the middle of the bone, and finally passes to the posterior border of the internal malleolus. The external border com- mences above at the outer malleoeus. in :r : nr of the articular facet for the Qbnla. It is the inter :s-r j.s : r i-r, It is indis- tinct above, well marked in the riiiir r:: n of the bone, and at the low^er extremity divides iiit t v linci, ^rhich form the boundaries of the triangular 5p3.cc rnrnrioned as being- on the loTver extremity of the bone. The Fibula, The Fibula (ILr. Fibiilc. ?- cli-.; is the outer and more sienirr : tiie two bones formina; the skeleton of the leg. It is 1 i : ::^ ;: : ne, having" of course a shaft and two extremities. The Upper Extremity, or head, is club-like in outline, and presents :n it- upper inner aspect an articular facet, the con- : :ur :: v hi :: n.ries in different bones. It is circular in form usually sliofhtly concave, but it may be flat and looks upward, forward and inward. It is intended for articulation \^ith a similar facet on the outer tuberosity of the tibia. The outer aspect of this extremity is roug^hened for muscular and ligamentous att2.c"nrnent, and terminates above in a blunt projection, called the styloid proce \ ^bula. The Loixer Extremity is usually spinen :f as the External Malleolus. It i- iir^cr ir : n: r- pointed than the upper and is indistinctiip trimgiilar. It may be described as consisting of internal and external surfaces, anterior and posterior borders, and an apex. The outer surface is prominent, convex, rough and subcutaneous. The internal surface is articular through a part of its extent : mi both above and below the articular surface is found 2. rinpitrned space — that above for the inter- osseous ligaments v, nich. i::nch it to the fibula, that below for OSTEOLOGY. 49 lig-amentous fibres binding- it to the foot. The articular space is intended for the lateral aspect of the astragalus, and occa- sionally extends upward to the fibula. The posterior border is nearh' straig-ht, is much thicker than the anterior border, and is marked by a shallow g-roove for the passag-e of tendons. The (Ditcrior border is narrow and convex, and slopes obliquely from above downward and backward. The apex is a blunt, roug"hened point. The Shaft of the bone is twisted, presenting" what is known as the curve of torsion, so that its faces and borders chang-e their relative positions in the diiTerent portions of the bone. The faces ma}- be described as external, internal, and posterior. The external face, narrow and convex above, becomes broader about the middle of the bone, and owing- to the twisting- of the bone becomes posterior at its lower one-third. The internal face, slig-htly curved above, marked by a ridg-e over the central portion of the bone, twists at the lower third to become anterior. The posterior face, narrow and convex above, broader and still convex at the centre, be- comes flat and internal at the lower one-third of the bone. Of the borders, the anterior is slig-htly marked above, prominent in the middle of the bone, divides into two lines at the lower one-third, one of which becomes external and passes to the posterior border of the external malleolus, while the other, more slig-htly marked, passes to the anterior border of the external malleolus, leaving- between them a triangular spaca, which is a continuation of the internal surface. The external border, commencing- at the head of the bone, much more slightly marked than the internal border, becomes posteri- or in the lower third of its course, and passes to the back of the external malleolus. The /;//6'r;/«/Z'('>r(^/rr commences at the back of the head of the fibula, becomes the interosseous ridge in the middle of the bone, running down upon the internal face, and twists to the front of the bone in the lower portion of its course. The Foot. The Foot bears a strong resemblance to the hand: differing essentially from it however in that it is at right angles to the Deji Anat— 4 50 DESCRIPTIVE ANATOMY. leg-; and consequently its surfaces are superior and inferior, instead of anterior and posterior. It consists of an irregular set of bones forming- the Tarsus, a set of long- bones forming- the Metatarsus, and the Phalang-es. The Tarsus. The Taisiis consists of seven bones: The Os Calcis, Astra- g-alus. Scaphoid, Cuboid, and three Cuneiform bones, known as E^xternal, Middle, and Internal, sometimes as First, Second, and Third. These bones are arrang-ed in two rows: the first row, or posterior row, consisting- of the os calcis and astrag-alus the remaining- five bones forming- the second row. The Bones of the First Row. The Os Calcis (Iv. Calx, the lieel) forms the posterior abutment of the arch of the foot, and is known as the heel bone. It pre- sents for examination two extremities, anterior and posterior, and four surfaces, superior, inferior, and two lateral. The upper sicr/ace consists of two portions, one behind the other. The posterior one-half of the upper surface is roughened, marked by the presence of a few nutrient foramina, and is non-articular. It is convex from side to side. The anterior portion presents two articular surfaces, separated by an oblique g-roove. Of these surfaces, the larg-er and more posterior is convex in outline, and oblique in direction. Its long diameter is directed from before downward and outward; and it corresponds to the concave receiving- cavity on the infe- rior surface of the astragalus. The anterior is an oblong articular facet, concave from above downward and outward, the direction of its long diameter ; and intended for the recep- tion of the convex articular facet on the lower surface of the astragalus. The groove which separates the two surfaces is called the Sulcus Calcanei (Iv. THe furrow of the heel), and is directed like the surfaces : that is, downward and outward. The inferior surface is rough, narrow, and non-articular; and presents near its posterior extremity two tuberosities, of which the internal is the larger. The anterior part of the inferior surface is hardly more than a rough and rounded border. The OSTEOLOGY. 51 external surface is convex througfhout its course, is very roug^h for the attachment of ligaments; and is marked by two gfrooves, one above the other, separated by a slig-ht roug-hened ridg^e. These g-oooves are intended for the transmission of tendons. The internal surface is deeply concave ; and is overhung- in its anterior portion by a projection of bone, which is called the sustentaculum tali (L. A support for the ankle), or lesser ■process of the os calcis. The deep concavity on the internal surface is caused mainly by this projection of bone, which is grooved on its under surface for the transmission of a tendon, and which bears on its upper surface the g-reater portion of the anterior one of the two facets on the superior face of the bone. The posterior extremity is quadrilateral in outline, roug-h at its lower portion, smooth above for the play of the bursa between itself and the tendon Achillis. The aiiterior extremity is concavo-convex, forming- a saddle-shaped articula- tion between this bone and the cuboid. This surface is con- cave from above downward and outward, convex in opposite direction. The Astrag-ulus, the second bone of the first row, lies between the tibia above, the two malleoli at the sides, and the OS calcis below. It presents like the os calcis four sur- faces and two extremities, the surfaces, as is the case with the OS calcis, being- superior, inferior, and two lateral, while the extremities are anterior and posterior. The superior surface is divided into two portions, a posterior articular portion, and an anterior, frequently called the "neck" of the bone, which is non-articular. The articular portion is narrow behind and broad in front, a fact which g-overns some of the movements of the ankle-joint. It is composed of a central depression with two elevated ridg-es, one upon either side, or, in other words, it is a trochlear surface. The inferior surface is in the main artic- ular, consisting- of two facets. The posterior facet is quadri- lateral and concave, its long- diameter directed downward and outward ; and corresponds to the posterior of the two facets on the upper surface of the os calcis. The anterior articular facet is convex. Its long- diameter likewise is directed down- ward and outward ; and it corresponds to the concave facet on 52 DESCRIPTIVE ANATONY. the OS calcls. Between these two articular surfaces is a deep oblique g-roove, running" downward and outward, which is called the Sulcus Tali. This sulcus corresponds in position to the sulcus calcanei ; and when the two bones are articula- ted, the junction of the two sulci forms a canal, which is known as the Sinus Tarsi. The internal face is articular to a small extent ; that is, at the junction of the internal and superior faces is found an oblong- articular facet, its long- diameter di- rected from before backward, continuous with the articular surface on the superior face of the bone, and intended for ar- ticulation with the internal malleolus. Below^ this articular facet is a rough depression for ligamentous attachment ; and the remainder of the internal surface is likewise roug-hened. The external surface is triang-ular or pyriform, the base up- ward and apex downward. It is concave from above down- ward, sHg-htly convex from before backward, and is continu- ous with the articular facet on the superior surface of the bone. It is intended for articulation with the external mal- leolus. Below the articular surface is a slight roug-hness for ligamentous attachment. The anterior extremity, or head of the bone, is oval, convex, and articular ; the long diameter of the head, slightly oblique in direction, is from above down- ward and inward, and is intended for articulation with the cavity found upon the scaphoid. This head is supported upon a constricted portion of the bone, sometimes called the "neck", a part of which has been already seen as a roughened surface, in front of the articular facet. The remaining portion of the neck is rough and thick. The -posterior extremity is hardly more than a narrow border. It is marked by a slight transverse groove just behind the superior articular surface ; and by an oblique groove, which extends downward and in- ward, and is continuous in the articulated foot with the concave inner face of the os calcis. The Bones of the Second Row. The Cuboid lies between the os calcis behind, the scaphoid and external cuneiform to its inner side, and the fourth and fifth metatarsal bones in front. It presents four surfaces, OSTEOLOGY. 53 superior, inferior, external, and internal, and an anterior and a posterior extremity. The upper surface looks upward and outward, and is roug-h and irregular for the attachment of ligaments. The inferior surface is very irregular in outline. A little in front of the middle- it is divided by a prominent ridge, called the peroneal ridg-e, into an anterior portion, which is occupied almost entirely by a groove, also called peroneal, and a larger posterior portion, which is roughened for ligamentous attachment. The peroneal ridge terminates externally in the tuberosity, a somewhat rounded blunt projection of bone, which constitutes one of the landmarks of the foot. The in- ternal face near the junction of the inner and superior faces is marked by an oblong articular facet, which is intended for articulation with the external cuneiform bone. Occasionally behind this facet is another smaller facet for articulation with the scaphoid, though usually these bones do not articulate with one another. Below the articular facet the bone is rough for the attachment of the interosseous ligaments. The external face is in reality only a border. It is narrow and rough- ened, presenting the projection of the peroneal ridge and the commencement of the peroneal groove. The anterior extrem- ity is divided into two articular facets by a vertical ridge. The inner of these facets is quadrilateral in outline; the external, triangular. They are intended for articulation with the fourth and fifth metatarsal bones respectively. The posterior ex- tremity is concavo-convex, being concave from above downward and inward and convex from within outward, to correspond with a similar articular surface on the anterior extremity of the os calcis. At the junction of the inferior and internal surfaces tl.is extremity is prolonged backward and inward, so that the OS calcis apparently rests partly upon a prolongation of the cuboid. The Scaphoid, the second bone of this row, presents an anterior posterior, superior, and inferior surface ; and in- ternal and external extremities. The posterior surface is entirely occupied by a concave smooth articular facet, whose transverse diameter is greater than its vertical, and is intended 54 DESCRIPTIVE ANATOMY. for articulation with the head of the astragalus. The anterior surface has three articular facets, separated by two slig-htly- marked vertical ridg-es. These facets articulate with the three cuneiform bones. The most internal, which approaches the nearest to the inferior surface of the bone, is large and slight- ly triangular; the central, quadrilateral; and the external, also nearly quadrilateral in outline, is oblique in its direction. Thtszcj)e7'ior surface \^ convex from side to side; and roughened for ligamentous attachment. The inferior surface, narrower than the superior, is also roughened for ligamentous attach- ment. The inner extremity of the bone is a blunt projection, the tuberosity of the Scaphoid which, with the tuberosity of the internal cuneiform, furnishes another of the landmarks of the foot. The(9«/er extremity is usually roughened; but occasion- ally presents a small facet for articulation with the cuboid. The Internal Cuneiform, like the other two, is irregularly wedge-shaped ; and lies on the inner side of the tarsus, between the first metatarsal in front, the scaphoid behind, and the middle cuneiform and second matatarsal to the outer side. It is the largest of the cuneiform bones; and unlike all of the others, is broader below than above. Its internal face is rough and convex. The external face is marked along the junction of the superior, external and posterior faces by a reversed L-shaped facet, intended for articutation with the middle cuneiform. In front of this facet is a smaller articular surface for the second metatarsal bone. The ■posterior face is concave, slightly triangular in outline, corresponding to the internal one of the facets upon the scaphoid. The anterior face is articular throughout, slightly convex, and is said to be kidney-shaped. The inferior face, or base of the bone, is very rough ; and terminates pos- teriorly in the blunt elevation or tuberosity of the internal cuneiform. The superior face is scarcely more than a rough narrow border. The Middle Cuneiform lies between the internal cunei- form on its inner, and the external cuneiform on its outer side, the scaphoid bone and the second metatarsal in front. OSTEOLOGY. 55 Its superior surface, much broader than its inferior, is roug-h and irreg"ular for the attachment of lio-aments. The inferior surface, scarcely more than a border, is also roug^hened. The iuterual surface presents a reversed Iv-shaped facet similar to the one found upon the internal cuneiform. The exter- nal surface has an articular facet upon its posterior portion ; but is non-articular in front, being- roug-hened for the attach- ment of the interosseojus ligament. The posterior surface is smooth, slightly quadrilateral in outline for articulation with the middle facet upon the scaphoid. The anterior surface is articular, convex slig"htly from side to side for articulation with the base of the second metatarsal bone. This bone is more distinctly wedg-e-shaped than the other two cuneiform bones. The External Cuneiform is intermediate in size between the internal and the middle. It lies with the middle cunei- form to its inner, and the cuboid to its outer side, the scaphoid behind and the third metatarsal bone in front. The bone appears to be slig"htly bent upon itself, so as to be concave internally and convex externally. Its superior sur- face is roughened like the preceding* tarsal bones ; its infe- rior surface, narrower than the superior, is likewise rough for lig-amentous attachment. The internal surface is slightly concave from before backward ; and presents an articular facet near its posterior end for articulation with the middle cuneiform. In front of this facet it is roughened for the interosseous ligfament. Near the anterior extremity is a very slight facet for articulation with the lateral aspect of the second metatarsal b^ne. The exteriial surface has an oblong facet near its upper posterior portion, corresponding" to the slight facet which is found on the inner face of the cuboid. In front of this the external surface is roug-hened for lig*amentous attachment. Posteriorly it presents a smooth, nearly flat ar- ticular facet, which is cut ol>li(]uelyv,u as to face backward and inward, thus disting-ui.shing- it from the other cuneiform bones, whose posterior extremities are cut squarely. The anterior surface, or extremity, presents a smooth quadrilateral articu- lar facet for articulation with the third metatarsal bone. 56 DESCRIPTIVE ANATOMY. The Metatarsal Bones. The Metatarsal Bones present the same g-eneral charac- teristics as the metacarpal. They are long- bones, pre- senting" a shaft and two extremities. Like the metacarpal bones they are five in number ; but are numbered from within outward . A Typical Metatarsal Bone. A Typical Metatarsal Bone presents a posterior extremity, or base, an anterior extremity, or head, and a shaft. The posterior extremity is quadrilateral in outline, marked by an articular facet upon its summit, and an articular facet upon each lateral aspects, its superior and inferior surfaces being- roug-h and square. Its head, much smaller than its base, presents on its summit an articular facet, which is convex, with its long- diameter vertical. Behind the head is a slightly constricted portion, which is surmounted on each side, near the dorsal aspect of the bone, by a well-marked tubercle, while a smaller tubercle is found near the plantar aspect. Near the plantar aspect the head is grooved for the transmission of tendons. The shaft of the bone is narrow ; and presents a dorsal sur- face marked by an indistinct ridge, bifurcating below to extend to the two dorsal tubercles. The lateral surfaces are concave, so as to leave an interosseous space between the adjoining metatarsal bones ; and the inferior border is rounded and indistinctly marked. The First metatarsal bone is very massive. Its poste- rior extremity presents a concavo-convex articular surface ; and its anterior extremity, presenting a rounded head, is, un- like the other metatarsal bones, nearly as larg-e as the posterior extremity. The Second metatarsal, the longest of the metatarsal bones, presents an articular facet on its summit for the middle cuneiform, on its inner side an articular facet for the internal cuneiform, and on its outer side a well-marked articular facet for the third metatarsal, and a somewhat slightly marked facet for the external cuneiform. OSTEOLOGY. 57 The Third metatarsal bone presents an articular facet on either side, that on the inner side being- divided into two by an antero-posterior g-roove. On its summit is an articular facet for the external cuneiform bone. The Fourth metatarsal is the typical metatarsal bone ; and need be no further described. The Fifth metatarsal bone has as its peculiar character- istic a blunt projection on the outer side of its base, this projection being- subcutaneous, and one of the most important landmarks of the foot. It has only one lateral articular facet. Certain g-eneral characteristics enable us to distinguish between the metatarsal and metacarpal Ijones. The most im- portant is that the metatarsal bones are all about the same length, but are slenderer than the metacarpal ; and whereas in the metacarpal bones the head is always of nearly the same or greater size than the base, in the metatarsal bones the base more than doubles the size of the head, with the sing-le excep- tion of the first metatarsal, which is disting-uished by other marks. The Phalanges. The Phalang-es of the toes, like those of the fingers, are arrang-ed in three rows, except that the great toe has, like the thumb, but two phalang-es, the place of the second being- taken by the ungual. They resemble those of the hand soclosely that a separate description is not necessary. They are smaller and shorter than those of the hand, the second phalanx partic- ularly being scarcely more than a neck of bone separating- two articular extremities, while the ungual phalanx is frequently scarcely distinguishable, except that for the first toe. In the fifth, or little toe the ungual and second phalanges are some- times found ossified together. The Skeleton of the Head. The skeleton of the head, or skull, consists of two'portions, the bones of the cranium and those of the face. Cranium. The cranium is the upper posterior division of the skull, and is formed by the union of eight bones — occipital, frontal, sphe- 58 DESCRIPTIVE ANATOMY. noid, ethmoid, two parietal and two temporal. These become securely ossified tog-ether in mature life, and can be separated only in the young- subject. Occipital. The occipital bone, sometimes called the first cranial vertebra, is situated at the posterior part of the cranium, and presents for examination two surfaces, four ang-les and four borders. The posterior surface, frequently erroneously called exter- nal, is convex, and presents above its centre an eminence called the posterior occipital protuberance ; curving outward from this on either side is a roug-h ridg-e called the superior curved line ; passing- downward from the protuberance to a large aperture — the foramen magnum — is a sharp ridge, the occipital crest ; arching outward on either side from the middle of the crest, and concentric with the superior curved line is the infe- rior curved line. The portion between the curved lines is slightly depressed and rough. At the lower termination of the crest is seen the foramen magnum, a large oval opening, whose antero-posterior diameter is the longer and whose larger end is behind. On either side of the front half of the foramen magnum is seen the condyle for articulation with the superior articular process of the atlas ; it is oval, convex, articular, and directed obliquely forward and inward. Just behind the condyle is a depression, the posterior condyloid fossa, with occasionally a foramen opening into it — the poste- rior condyloid foramen. In front of the condyle is the anterior condyloid foramen. Passing outward from the condyle is a rounded elevated ridge, the transverse process. On the inner aspect of the condyle is a tubercle. In front of the foramen magnum is the basilar process ; it is horizontal, quadrilateral, convex, and presents an antero-posterior ridge, the pharyn- geal spine. The anterior face is concave and presents four ridges, meet- ing at right angles, about the middle, called the crucial ridge, or occipital cross. E)ach ridge is called an arm of the cross. Three of these ridges are grooved ; while the fourth, which is the inferior, is sharp and not grooved until it approaches the y \ OSTEOLOGY. 59 foramen mag"nuiii. At the point where the four arms meet there is an eminence called the anterior occipital protuberance. Above each lateral arm of the cross there is a shallow depres- sion, the cerebral fossa ; below each lateral arm is another depression, the cerebellar fossa. At the termination of the lower arm is the foramen mao-num, and on each side of this the anterior condyloid foramen. In front, and to each side of the foramen majs^num is a smooth broad groove for the termi- nation of the lateral sinus. In front of the foramen mao-num is the basilar process, which, as on its inferior surface, is nearly horizontal and quadrilateral, but is here concave to sus- tain the medulla oblong-ata. The ang-les are superior, inferior and two lateral. The lateral ang-les are each situated where the g-roove in the lateral limb of the crucial ridg-e, strikes the border of the bone. The inferior angle is the truncated extremity of the basilar process, and articulates w^ith the body of the sphenoid. The superior ang"le juts into the interval formed by the union of the posterior superior angfles of the parietal bones. The borders are two superior and two inferior, l^ach superior border is serrated for articulation with the parietal bone ; and extends from the superior to the lateral angle. Each inferior border articulates with the temporal bone, mastoid and petrous portions ; is serrated below the lateral angle and is interrupted about its middle by a protuberance, the jugular eminence, in front of which is a depression, the jug*ular fossa. Parietal. The two parietal bones form the upper and most of the lat- eral wall of cranium, and are situated between the frontal and occipital bones, in front and behind, and the two temporal bones laterally. Each bone is divided into tuo snrfaccs, four borders, 3.nd Jhur cDi^i^lcs. The cxlcrnal surface is convex and presents a decided bulg-e about the middle, the parietal emi- nence ; through this is seen running the temporal ridg-e, arch- ing across this bone from the frontal ; below the ridge, is a nearly flat surface forming- part of the temporal fossa. Near 60 DESCRIPTIVE ANATOMY. the posterior superior ang-le is seen the parietal foramen, which is frequently absent. The internal surface is mostly concave and is sunken in the middle into a fossa. It is marked by dig-ital pits for lodging- cerebral convolutions, and the arborescent furrows worn by the arteries. Along- the edg-e of the superior border is seen half of a g-roove, completed by the opposite bone, and formed by the long-itudinal sinus. The borders are four. The anterior, for articulation with the frontal bone, and the -posterior, for the occipital, are serra- ted. The superior border, for articulation with its fellow, straig-ht, serrated and thick. The inferior border, for articu- lation with the squamous portion of the temporal bone, is short, curved and beveled at the expense of the outer table. The ang-les are four. The anterior superior and the posterior supe- rior are rig-ht angles. The anterior inferior is long-, thin and marked on its inner aspect by a furrow formed by the middle mening-eal artery. '^\^t posterior Inferior is blunt and usually marked internally by the g-roove for the lateral sinus. Frontal. The frontal bone is situated at the front and base of the cra- nium. In early life the bone consists of symmetrical lateral halves, separated by a vertical suture, which, however, be- comes ossified later in life, though the bone could still be de- scribed as consisting- of two similar lateral portions. The bone is described as being- made up, in each of its lateral halves, of two portions — the vertical, or frontal, and the hori- 2;ontal, or orbito-nasal portion. The vertical portion forms the skeleton of the forehead and presents two surfaces and a lateral aspect. Upon the anterior surface, which is convex, there are seen superiorly a smooth, somewhat flattened surface ; below this a bulg-e, called the frontal eminence ; below this a broad, shallow, transverse g-roove ; below this a transverse ridge, the superciliary ; be- tween this and the opposite ridg-e, on the middle line, is a prominence called the g-labella, or nasal tuberosity. Below the superciliary ridg-e is seen the marg-in of the orbit, called OSTEOLOGY. 61 the supra-orbital ridg-e, which terminates at the inner extremity in the internal ang-ular process, and at its outer in the external angular process. About the inner third of the supra-orbital rldg-e is a notch, sometimes formei into a foramen, called the supra-orbital notch or foramen. The posterior face of the vertical portion is concave and marked by digital pits and arborescent furrows for the arte- -riesr-^n the middle line this surface presents superiorly a g-roove for the longitudinal sinus, which, as it descends, termi- nates in a ridge, at the extremity of which is a small foramen, called the foramen coecum. The lateral aspect of the bone presents a ridge curving up- ward and backward from the external angular process, and called the temporal ridge ; behind this the surface is sunken and forms part of the temporal fossa. Both the temporal ridge and fossa are only j)artially seen on the frontal bone, for, in the articulated skull, they are continued on to the parietal and temporal bones. The horizontal portion consists of two lateral parts, the orbital plates, separated by a rectangular notch, the ethmoidal fissure. Each orbital plate presents an inferior and a superior surface. The inferior face is smooth, triangular and concave, the concavity being greatest behind the external ang-ular process — the lachrymal fossa. It has, just within the supra orbital notch, a depression called the fovea trochlearis. The upper surface of the orbital plate is convex and rough, presenting irregular rough eminences. The ethmoidal fissure, the margins of which present several half cells, which, when articulated with the ethmoid, complete theethmoidal cells, is the rectangular notch separating the two orbital plates. In front of it is a roughened interval, between the two internal angular processes, called the nasal notch, descend- ing from the middle of which is a long pointed process, the nasal spine. Upon the posterior surface of the nasal spine is a vertical ridge. In the front portion of the ethmoidal notch and external to the nasal spine, are the openings of the 62 DESCRIPTIVE ANATOMY. frontal sinuses. The frontal sinus, one on each side of the middle line, is an irreofular cavity between the two tables of the vertical portion which gradually increase in size from the time it makes its appearance in early life. The borders of the frontal bone are two — ^superior and inferior. The siirperior border is semi-circular and serrated for articulation with the parietal bones. When examined closely it is seen to be beveled superiorly at the expense of the inner table, and interiorly at the expense of the outer. ThezVz/dT/or border is the posterior termination of the orbital plates, interrupted in the middle by the ethmoidal notch. It is straig-ht and articular with the lesser wing- of the sphenoid. At the ang-le of the junction of the two borders, there is a rough triangular surface, the sphenoidal triang-le, for articu- lation with the greater wing of the sphenoid. Temporal Bone. The temporal bone is divided for stud}'- into the squamous, mastoid and petrous portions. The squamous -portion occupies the upper front part of the bone and consists of two surfaces, a semi-circular border and a projection called the zygoma. The internal surface is con- cave from above downward and from before backward. It is marked by irregular, antero-posterior elevations with inter- vening depressions for the convolutions and sulci of the brain. No distinct line, in the adult, marks the point of separation between the squamous and petrous portions. The external surface may be conveniently divided into two'^parts — that which lies above and that which lies below the zygoma. The part above is convex from above downward, slightly concave from before backward, rough for muscular attachment and enters into the formation of the temporal fossa. Posteriorly it is separated from the mastoid portion by a rough line, part of the temporal ridge. The rest of this surface is occu- pied by the zygoma and the glenoid cavity. The zygoma, or zygomatic process, at its origin from the squamous portion, passes outward with a slight in- clination forward; but after a course of about one-fourth OSTEOLOGY. 63 of an inch, is twisted upon itself so that the surfaces and borders change their relative positions. At its orig-in the surfaces are superior and inferior, the first occupied by a g-roove, the second b}' a roughened tubercle ; but in the remainder of its course, where it passes forward with but a slight inclination outward, the surfaces become internal and external, the borders superior and inferior. The external surface is rough, convex both from above downward and from before backward. The internal surface is concave in both directions and smooth. The superior border is longer, thinner and sharper than the inferior, which is thick and rough and short. Anteriorly it terminates in a rough serrated extremity, obliquely cut from above downward and backward, and intended for articulation with the malar. Pos- teriorly, the zygoma rises by two rough lines called the roots of the zygoma. The anterior root is continuous with the in- ferior border and terminates in a rough projection called the tubercle of the zygoma, from which a smooth elevated ridge, the eminentia articularis, passes inward as the anterior bound- ary of the glenoid cavity. The posterior root passes back- ward, just above the glenoid cavity and the external auditory meatus, and than curving upward forms the continuation of the temporal ridge which separates the squamous from the mastoid portion. Just after it passes above the gdenoid cavity, it sends downward a prominent articular projection, sometimes called the middle root of the zygoma, which forms the poste- rior boundary of the articulation for the lower jaw. Tho. fylenoid cavily \'i concave and oval in outline, its long diameter being directed from without back weird and inward. it is bounded in front by the eminentia articularis, a smooth, rounded, oval articular ridge which is a continuation of the anterior root of the zygoma. Posteriorly it is limited by a rough, quadrilateral sheet of bone called the tympanic plate, while in the middle is a well defined slit, the Glaserian fissure, which divides the cavity into an anterior articular portion and a posterior non-articular. The articular portion is limited be- hind by the middle root of the zygoma, sometimes called the post-glenoid tubercle. 64 DESCRIPTIVE ANATOMY. The semi-circular border is roug-h, thin and sharp above, strong-ly beveled at the expense of the inner table ; thick and serrated below and slightly beveled at the expense of the outer table. The Mastoid portion consists of an internal and external surface ; superior and posterior borders and a roug-h nipple like projection, the mastoid process. The interned surface presents but one mark of note. It is smooth and has a deep g-roove which runs from above downward and backward. It is called the fossa sigmoidea. The external surface is roug-h throughout and presents near the posterior border a larg-e foramen, called the mastoid, which is sometimes found in the suture between this bone and the occipital and sometimes is altog-ether wanting. The Mastoid process is a roug-h, blunt projection of bone, marked internally by a deep g-roove, the dig-astric fossa, internal to which is a shallower g-roove for the occipital artery and known as the occipital g-roove. The interior of the mastoid portion is hollowed out into a number of cellular cavities. The superior border is roug-h, serrated and nearly straig-ht to receive the posterior inferior ang-le of the parietal. The -posterior border, longer than the superior, slopes from above downward and forward and is roughened for articula- tion with the occipital. The Petrous portion is a pyramidal projection of bone with its apex directed inward and forward and its base outward and backward. It presents three surfaces, anterior posterior and inferior ; and three borders, superior, anterior and pos- terior. The -posterior surface is the simplest of the three. Internal to its middle point it presents an oblique oval open- ing, the internal auditory meatus. This opening leads into a short canal, directed outward and forward, at the bottom of which may be seen a bony lamina perforated by numerous apertures and crossed by a transverse ridge. E^xternal to the internal auditory meatus and near the posterior border, is seen a little slit like aperture which leads to the acqueductus vesti- buli. Between the two, and near the superior border, is usu- OSTEOLOGY. 65 ally seen a slig-hter depression which lodg-es a process of the dura mater. The anterior surface presents near the middle a round elevation which marks, the position of the superior semi- circular canal ; external to this a smooth concave surface forms the roof of the tympanum ; below and in front of the bulg-e is a groove leading- outward and backward to an open- ing-, the hiatus Fallopii, while at the junction of the squamous and petrous portions may sometimes be seen another and slig-hter groove, the petrosal. Near the apex of the bone is seen a de- pression for the Gaserian g-anglion, while at the apex the roof of the carotid canal is usually wanting- and a part of the canal may be seen from the anterior surface. The inferior surface is roug-h and irreg-ular and has upon it eleven points which require examination. Near the apex of the bone is a roug-h, nearly quadrilateral surface which g-ives attachment to muscular fibres. External to this is a circular opening-, the aperture of entrance of the carotid canal. At first this canal passes upward in the bone, but it abruptly turns forward and inward and downward, pursuing- a course parallel with that of the petrous bone, to emerg-e at the apex. External and slightly behind this is a smooth, concave surface, which encroaches on the posterior border of the bone, called the jugfular fossa. On the bony partition separating- the jug-u- lar fossa from the carotid aperture, is a small foramen which transmits Jacobson's nerve : and on the outer wall of the fossa itself is another foramen, smaller in size, for Arnold's nerve. Behind and slig-htly internal to the carotid aperture, near the posterior border and directly beneath the internal auditory meatus, is a small opening", the aqueduct of the cochlea. Exter- nal and anterior to the carotid aperture, is a thin, prominent tong-ue of bone, which extends outward to become continuous with the auditory process, called the vag-inal process. At its base this process splits into two sheets, one in front of the other, to enclose a sharp pointed projection, the styloid pro- cess. This, the long-est of such processes in the body, passes downward and slig-htly forward and outward. Behind and Des Anat — 5 66 DESCRIPTIVE ANATOMY. external to this is a larg-e foramen in the bone, the stylo- mastoid ; while between the vag-inal process and the mastoid process is a slig"ht g-roove, the auricular fissure. At the junc- tion of the posterior border of the mastoid portion with that of the petrous portion, there is a rough articular surface called the jugfular facet. The borders are three, superior, -posterior and anterior. The superior border, the longest of the three, presents along its upper margin a groove for the petrosal sinus, and near the apex of the bone a nptch to lodge the fifth cranial nerve. '^\\^ posterior border, intermediate in length, usually presents near its middle a rough tongue of bone which divides the jugular fossa into two portions. The remainder of the border is rough for articulation w^ith the basilar process of the occipital. The anterior border is the shortest of the three, and is in part articular for the greater wing of the sphenoid. In the receding angle between the petrous and squamous portions there is seen an irregular opening, divided into an upper and a lower portion by a thin shelf of bone known as the processus cochleariformis. The canal above this shelf is for the tensor tympani muscle while that below is intended for the Kustachian tube. The base of the petrous portion is partly interposed between the other two portions and partly continuous with them. On the free portion is seen the opening into the ear, the external auditory meatus, which is situated between the mastoid process behind and the middle root of the zygoma in front, and between the posterior root of the zygoma above and the auditory process below. The auditory process is a rough curved sheet of bone continuous with the vaginal process, and partly circumscribing the external auditory meatus. The apex of the petrous portion is rough and presents a large irregular aperture, the aperture of exit for the carotid artery. It is received between the basilar process of the occipital bone and the spinous process of the sphenoid. The Sphenoid. The sphenoid occupies a position near the middle of the base of the skull, and maybe considered the key-stone of the cranial OSTEOLOGY. 67 arch, since it serves to bind tog; ether all the bones of the skull and five of those of the face. It has been likened to a bat with the wing's spread out, and is divided for study into a bod}'' twO wing's, g-reater and lesser, on either side, and two projections, or processes, called the pteryg-oid. The body presents six surfaces, superior, inferior, anterior, posterior and two lateral. The upper surface commences in front in a triang-ular spine which, from its articulation, is known as the eth- moidial spine of the sphenoid. Behind this projection there may sometimes be seen a line or ridge leading- backward and a slight transverse ridge, stretching between the anterior margins of the optic foramina. Behind this is a broad, trans- verse groove, the optic, and behind this a prominent, rounded elevation, the olivary ridge or process. Behind the olivary ridge is a deep pit-like depression, the sella turcica or pitui- tary fossa, overhanging which behind is a square projection, the dorsum Ephippii, whose posterior surface, running ob- liquely downward and backward is called the clivus Blumen- bachii. On either side of the mid-line in front of the sella turcica is a slight antero-posterior groove, continuous with one on the upper surface of the Ethmoid, in the articulated skull, for the olfactory bulb. Behind the optic ridge the optic «-roove extends across to terminate at either end in the corres- ponding optic foramen. The olivary ridge terminates at its extremities in a small projection, the middle clinoid process, which is sometimes connected by a spicule of bone with the anterior clinoid process of the lesser wing. The sella turcica, deep and pit like, is bounded in front by the olivary ridge, be- hind by the dorsum ephippii, laterally by the margin of the carotid groove. The dorsum sellffi terminates at either angle in a rough projection, the posterior clinoid process, sometimes connected to the anterior clinoid process by a spicule of bone. The posterior surface of the dorsum, or the clivus, is a rough, quadrilateral, sloping surface, continuous, in the articulated skull with the upper surface of the basilar process of the occipital. 68 DESCRIPTIVE ANATOMY. The ^posterior surface is rough and square, presenting- many nipple-like projections for articulation with the basilae process of the Occipital. In advanced life it is ossified to thr Occipital. The anterior face -^VQsent^ in the middle a prominent, roug-h vertical ridg^e called the crest of the sphenoid, for articulation with the posterior border of the perpendicular lamella of the Ethmoid. On either side of the crest the surface is roug-h and presents near the middle the opening- into the sphenoidal sin- uses. The marg-ins of the opening- are roug-h for articulation with the OS planum and posterior extremity of the lateral mass of the E^thmoid, the latter throug-h the pyramid of Wistar. The inferior surface is marked in the middle by the contin- uation of the crest, called the rostrum of the sphenoid. The rostrum is broad behind, narrow and more prominent in front and is received into a fissure on the upper border of the '^j Vomer. Oa either side of the rostrum is a smooth surface for articulation with theal^ of the Vomer, external to which is the vagfinal process for the under surface of each ala, beneath which is the g-roove called pteryg-o-palatine, converted into a canal of the same name bv articulation with the palate bone. The lateral surfaces are almost taken up by the orig-in of the g-reater wings. The space just above each wing- is occupied by a broad v^nnding- g-roove, the cavernous, which terminates at the lesser wing-. In front of this the lateral surfaces are smooth, slightly concave from above downward, and enter into the formation of the sphenoidal fissure and the inner wall of the orbit. The Lesser Wings. E^ach lesser wing springs by its per- forated base from the junction of the lateral and superior sur- ^ faces of the body, and passes outward, to terminate in a pointed process near the outer limit of the greater wing. They each present two surfaces, superior and inferior, and two borders, anterior and posterior. The upper surface smooth, slightly concave, broad internally and narrow without, forms a part of the anterior fossa of the skull. The inferior, narrower than the superior, is smooth and slightly convex in outline and forms OSTEOLOGY. 69 a part of the roof of the orbit and the upper boundary of the sphenoidal fissure. The anterior border is thin, straig-ht and serrated for articulation with the straig-ht border of the Front- al. The posterior, thicker than the anterior, begins internally in a bluntly pointed projection called the anterior clinoid pro- cess, which passes backward and inward. This border is concave and smooth, thinner in the middle than at either ex- tremity, and terminates externally in the outer end of the lesser wing". The perforation found at the base of the lesser wing is the continuation of the optic g-roove of the upper face, is called the optic foramen and leads downward, forward and outward to the cavity of the orbit. The Greater Wing-. The g"reater wing* spring's from the lower part of the lateral aspect of the body and passes upward, outward and forward. It is divided into four surfaces, superior, anterior, external and inferior. The circumfer- ence of the g-reater wing- will be described later. The upper surface of the g-reater wing- is concave and enters into the for- mation of the middle fossa of the skull. It is, consequently marked by elevations and depressions corresponding- to the sulci and convolutions of the temporo-sphenoidal lobe of the brain which it lodg-es. It is more deeply concave anteriorly where it is overhung by the lesser wing than at any other part. Near the junction of the wing with the side of the body, and immediately beneath the sphenoidal fissure, there is a cir- cular foramen called, from its shape, the foramen rotundum. Its direction is downward, forward and slig-htly outward and its anterior opening- is found just external to and above the base of the pterygoid process. Behind and external to the foramen rotundum is the foramen ovale, looking- directly down- ward and opening- on the inferior face of the g-reater wing-. Behind and external to this is found the foramen spinosum, also opening- directly downward. The external face enters into the formation of the temporal fossa. It is broader above than below, slig-htly roug-h for muscular attachment, concave both from above downward and from before backward, and perforated by a number of small foramina. The inferior face is a part of the y.ygomatic fossa, is small and quadrilateral 70 DESCRIPTIVE ANATOMY. in shape, looks downward and outward and is slightly rough- ened for the attachment of muscles. The g-reater part of the anterior face looks into and forms a part of, the orbital cavity. It is triang-ular in form, the apex directed backward and inward and the base outward, concave from above downward, flat from before backward and per- forated by one or tw^o small foramina. Just below this portion of the anterior face is a small flat surface of bone formino- a part of the pteryg-o-maxillary fossa and upon which the foramen rotundura opens. The borders. The circumference of the greater wing may be considered as forming the borders of its four surfaces. From the side of the body to the spine of the sphenoid is the posterior border of the upper surface ; from the spine to the point for articulation with the parietal is the outer border of the upper surface ; from this point to the body again is the upper border of the superior surface. The outer face, which is quadrilateral in form, has four borders. Its superior border extends from the outer border of the upper face to the ante- rior face ; its anterior border from this point to the pterygoid ridge ; its inferior border is the pterygoid ridge, while its posterior border is that part of the outer border of the upper face extending from the pterygoid ridge to the summit of the bone. The anterior face is bounded above, for its outer part, by a serrated edge forming the anterior boundary of the fron- tal triangle ; for its inner part by a part of the upper border of the superior surface ; anteriorly or externally, by the ante- rior border of the outer face and below by a ridge leading from the pterygoid ridge on the base of the pterygoid process. The posterior border of the upper surface is rough in its outer half for the anterior border of the petrous portion of the Temporal; the outer border is serrated for the squamous portion of the temporal ; the outer part of its upper border is rough for the Frontal. The upper border of the outer face is articular for the anterior inferior angle of the Parietal; the anterior border is articular for the posterior border of the orbital process of the Malar. The inner part of the upper border of the superior face, and the lower border of the anterior face are non-articular, the OSTEOLOGY. 71 one entering- into the formation of the sphenoidal fissure the other into the spheno-maxillary. The frontal triang-le is found at the junction of the upper, outer and anterior surfaces. It is bounded in front by the upper border of the anterior face; externally by the upper border of the outer face; behind b}^ a part of the upper border of the superior surface. The Pterygoid Process. The Pterygoid Process springs from the junction of the greater wing- and the body near the posterior surface of the body. Each process consists of two plates, internal and external, united above and diverging below. Viewed from the front the united plates present a triangular smooth surface above, forming the posterior wall for the pteryg-o- maxillary fossa, pierced above by a round opening, the anterior opening of the Vidian or pterygoid foramen. Below and internal to this is a narrow roug-h articular strip for the posteri- or border of the vertical plate of the Palate, terminating below at the divergence of the two plates. Posteriorly the united plates are grooved above and bifurcated below. Just above the groove, more on the posterior border of the greater wing than on the pterygoid process, is the posterior opening of the Vidian canal. Below this the posterior border of the inner plate shows an oblong, shallow fossa, the scaphoid, while internal to this is the opening- of a small foramen, the pteryg^o-palatine. Below and external to the scaphoid fossa is the pterygoid fossa, formed by the junction of the two plates in the separated bone but filled in below in the skull by the tuberosity of the palate. The pteryg-oid fossa is deeper and broader at its upper portion. The inner plate is longer and narrower than the outer. Its internal surface is smooth and forms the outer boundary of the posterior nares, its outer, smooth and concave, forms the inner boundary of the pterygoid fossa. The anterior border, blended with the outer plate, above, presents below a serrated margin for a groove on the palate. Its posterior border is thin and sharp and terminates below in a thin curved plate of bone, the hamular process, which projects below the level of the outer plate, and is curved outward and backward. The outer plate, broader and more massive than the inner, presents an outer 72 DESCRIPTIVE ANATOMY. face which is concave and roug-h to form the inner wall of the zyg-omatic fossa, an internal face, roug-h and irregularly con- cave, which forms the outer wall of the pteryg-oid fossa; an anterior border serrated below for the gfroove on the Palate, and a posterior border which is thin, sharp and irregular, sloping- obliquely downward and backward. The Ethmoid. The Ethmoid lies in the middle of the anterior fossa of the skull. It consists of a body and two lateral masses. A por- tion of the body can be seen by looking- into the anterior fossa of the skull, and part of the lateral masses by looking* into the orbital cavity; but the larg-er portion of the bone is con- cealed by surrounding- bones. The Siiferior Surface of the body is called the Horizontal or Cribriform Plate; and is perforated by numerous small foramina. These foramina are arranged in three rows, of which the internal and external are fairly distinct, while the middle row is irreg-ular and indistinct. The anterior foramen of the internal row is a narrow, slit-like aperture for the transmission of a nerve. The cribriform plate is a depressed surface, concave from side to side and marked on the mid-line by a projection, called the crista g-alli (Iv. A cock's comb). This projection commences near the posterior end of the bone; and rapidly rising- in height, terminates near the anterior end of the bone in a blunt, rounded point. Its posterior bor- der is narrow and sharp. Its lateral apects, smooth and slightly concave at the lower portion, are marked above by a bulging- projection, which varies g-reatly in size in different bones. Projecting- from the front of the crista g-alli are two small processes, one towards either side, called the alar ■processes (Iv. Ala, a wing-). At each side of the base of the crista Galli is a small fissure called the nasal g-roove, or slit. Posteriorly the superior sur- face presents a deep notch, the sphenoidal fissure, for the reception of the ethmoidal spine of the sphenoid bone. Laterally this surface articulates with the orbital plate of the frontal bone; anteriorly with the frontal bone by the two OSTEOLOGY. 73 alar processes which complete, posteriorly, an opening" called the foramen coecum. From the lower surface of the cribriform plate there passes downward, on the middle line, a thin sheet of bone called the perpendicular lamella, which aids in forming- the septum of the nose, articulating- in front with the nasal spine of the frontal and with the nasal bones; posteriorly it articulates above with the beak of the sphenoid, below with the vomer; inferiorly it g-ives attachment to the cartilage of the septum. Its faces are g-rooved. The lateral mass lies to the side of the perpendicular lamella, with a slight interval between; it presents an outer, inner and superior face. The outer surface forms part of the inner wall of the orbit; it is smooth, flat and quadrilateral and is called the OS planum; its upper part is marked by two g-rooves, which are the anterior and posterior ethmoidal foramina. The inter- nal surface is convex, roug-h and fissured behind; this fissure is called the superior meatus of the nose; above this is a curved portion of the bone called the superior turbinated bone; below the superior meatus is another portion called the middle tur- binated bone, which is the upper limit of the middle meatus of the nose. The superior surface of the lateral mass pre- sents numerous irreg-ular opening's into the cells, of which this part of the bone is made up; these are closed in by the over- lapping- horizontal plate. Projecting- downward and backward from the lower edg-e of the lateral mass is a thin plate of bone called the unciform process, which articulates with the ethmoi- dal process of the inferior turbinated and helps to close the opening- of the antrum maxillare. From the posterior extrem- ity of the lateral mass there projects backward a triangfular, curled, pointed process, which extends into the sphenoidal cell of that side, and, as puberty approaches, becomes detached from the ethmoid and ossified to the sphenoid; it is called the sphenoidal spong-y bone, or pj^ramid of Wistar. The cells, of which the lateral mass consists, are separated by a transverse septum into the two sets, the anterior and posterior ethmoidal cells; the anterior communicate with the middle meatus by a 74 DESCRIPTIVE ANATONY. tortuous canal called the infundibulum, with which the frontal sinusalso communicates. The infundibulum opens into the up- per front part of the middle meatus by a larg"e orifice. At the upper back part of the superior meatus is an orifice which leads into the posterior ethmoidal cells. The Nasal Bones. The Nasal Bones are two somewhat flat bones, forming- the bridge of the nose, along- the centre of which they articulate with each other. They are somewhat quadrilateral ; and pre- sent for examination two surfaces, anterior and posterior, two borders, internal and external, and two extremities, superior and inferior. The anterior face which looks forward and slig-htly outward is concave from above downward ; and slig-htly convex from side to side, the anterior surface being- a little roug-hened and marked by nutrient foramina. The ^posterior surface, which looks inward as well as backward, is convex from above downward ; and marked near the inter- nal border by a vertical g-roove. The superior extremity is thicker and more massive than the inferior ; and is roug-hened and serrated for articulation with the nasal notch of the fron- tal bone. The inferior extremity is broader and thinner than the superior ; and slopes obliquely from within outward and downward, so that v^^hen the two bones are articulated, a pear- shaped notch is found between them, its apex upward and its. base downward. The internal border is shorter than the ex- ternal ; and presents when articulated with its fellow a well- defined crest for articulation with the nasal spine of the fron- tal and the perpendicular lamella of the ethmoid bone. The external border, long-er than the internal, is serrated, thin, and sharp for articulation with the nasal process of the superior maxillary. Lachrymal Bone. The lachrymal bones are a pair of small bones, one being- found on the inner wall of each orbit in front of the os planum. The bone remotely resembles a fing-er nail and hence acquires its synonjmi of ung-uis. It presents two faces, two extremities and two borders. The external face is divided into an anterior OSTEOLOGY. 75 and a posterior portion, by a vertical ridge, which terminates inferiorly in a hook-like process called hamular. The poste- rior and larg-er portion is part of the inner wall of the orbit and is flat and smooth. The anterior portion is a vertical groove, called the lachrymal. The internal face is rough for articulation with the ethmoid bone, and presents a vertical groove corresponding to the verti' cal ridge on the opposite side ; the portion of the surface in front of this groove enters into the formation of the middle meatus. The upper extremity articulates with the internal angular process of the frontal bone. The lower extremity is divided into two parts, the posterior articulating with the orbital plate of the superior maxillary, the anterior projecting farther downward and articulating with the lachrymal process of the inferior turbinated. The anterior border articulates with the nasal process of the superior maxillary bone. The posterior border articulates with the os planum. Inferior Turbinated Bone. The inferior turbinated, or inferior spongy bone, is found on the lower part of the outer wall of the nasal fossa; the middle and superior turbinated bones are merely parts of the ethmoid. The bone is divisible into two extremities, two faces and two borders. The anterior extremity is much the larger and articulates with the inferior turbinated crest of the superior maxillary. The posterior extremity is slender and pointed aud articu- lates with the inferior turbinated crest of the palate bone. The internal face is convex and marked by apertures and grooves. The external face is concave and enters into the inferior meatus of the nose. The inferior border is rounded and free, marking the limit between the middle and inferior meatus. The superior border articulates from before backward with the sujjerior maxillary, the lachrymal, the ethmoid and the 76 DESCRIPTIVE ANATOMY. palate bones. It presents three processes, lachrymal, ethmoid and maxillary. The lachrymal process is directed upward to articulate with the lower extremity of the lachrymal bone, and with the nasal process of the superior maxillary, aiding- to form the lachrymal canal. The maxillary process is larger than the other two and is a curved plate of bone directed downward and outward from the base of the ethmoidal process and articulates with the superior maxilary by hooking- around the orifice of the antrum. The ethmoidal process is behind the lachrymal, and is directed upward to articulate with the unciform process of the ethmoid. Vomer. The vomer is a single bone found separating the nostrils behind and below, forming part of the septum of the nose; the upper part of the septum is the perpendicular lamella of the ethmoid; the anterior part is a plate of cartilage. It pre- sents two faces and four borders. The faces are lateral and each forms part of the inner wall of a nostril, the bone usually bulging toward one or the other. They are' marked by shallow furrows and by the naso-pala- tine groove, which is directed obliquely downward and for- ward on each face. The superior border presents an antero-posterior groove which receives the rostrum of the sphenoid ; the edges of the groove are projected outward into lips, or alae, each of which lies in the groove above the vaginal process of the sphenoid. The inferior border is received between the averted edges of the palate processes of the superior maxillary bones and of the horizontal plates of the palate bones. The anterior border presents a long-itudinal fissure which receives superiorly the perpendicular lamella of the ethmoid, inferiorly the triangular cartilage of the septum; the lower part is occasionally not fissured but rough. The posterior border is concave and free, terminating, posteriorly, the septum of the nose. OSTEOLOGY. 77 Malar Bone. The malar bone forms the prominence of the cheek, is somewhat quadrang-ular and presents for examination four processes and a body with two surfaces and four borders. The anterior, or external face is convex and has several fora- mina opening" on it, called malar. The posterior, or internal face is smooth and concave, entering- into the temporal fossa above and the 2jyg-omatic be- low. T\iQ frontal f>rocess projects upward to articulate with the external ang-ular process of the frontal bone. The orbital firocess is a smooth projecting- lip of bone curving- downward from the frontal process, and projecting- inward, forming- a concavity which enters into the outer wall and floor of the orbit. Its lower surface forms part of the temporal fossa. Superiorly it articulates with the frontal bone. Posteriorly it articulates with the sphenoid bone ; internal to which it ar- ticulates with the orbital plate of the superior maxillary bone ; between these two articulations there is often seen the narrow, rounded, non-articular anterior extremity of the spheno-max- illary fissure. This process presents the opening-s into one or more small canals, temporo-malar, which extend to the anterior surface of the bone and some usually to the posterior surface. The maxillary froccss is roug-h and triang-ular, articulating* with the superior maxilla. The 2yg-o?jiatic process extends backwards, is long- and nar- row and articulates with the zyg-omatic process of the temporal. The superior border is concave, smooth and rounded, and forms part of the marg-in of the orbit. The injcrior border is straig-ht and continuous with the lower edg-e of the zyg-oma. The anterior border is straig-ht and roug-h to articulate with the superior maxilla. The posterior border is sinuous and continuous with the temporal ridg-e above, and below with the upper edg-e of the zygoma. 78 DESCRIPTIVE ANATOMY. Superior Maxillary. The superior maxillary bones form the upper jaw and are, with the exception of the inferior maxillary, the largest bones of the face. E)ach bone m-ticulates with the frontal and etliinoid., and all the hones of the face except the inferior maxillary . The bone is divisible into a bodya.r\.^ four f>rocesses. The body is irregfularly quadrilateral, is hollowed out into a cavity called the antrum of Hig*hmore, or antrum maxillare, and presents four faces — anterior^ superior, -posterior ^ inte^-nal. The anterior or facial surface is somewhat concave and presents about its centre a depression, called the canine fossa, which is limited internally by a vertical ridg^e, the canine ridg-e; on the inner side of the canine ridg^e is another depression, the incisive fossa; just above the canine fossa is a foramen, the infra-orbital. This surface is limited internally by the thin concave edg-e of the nasal fossa: below by the alveolar process; externally by the malar process and a ridg-e descending- from it ; superiorly by the margfin of the orbit. The posterior or zyg-omatic surface is chiefly occupied by a roug-h bulg"e, the tuberosity of the superior maxillary bone; it presents numerous small foramina, and at its lower part a toug-h oval surface; above and internal to this is a smooth spiral g-roove, which, with a similar g-roove on the palate bone, forms the posterior palatine canal. The upper limit of this surface, separating" it from the orbital face, is a smooth rounded border, on which is a notch, the commencement of the infra orbital canal. The malar process separates this face from the anterior; below it is limited by the alveolar process. The superior or orbital surface forms the floor of the orbit. It is formed of a thin triang-ular plate of bone, is smooth, sloping- downward and forward, and marked from behind for- ward, by a g-roove, the infra-orbital canal, which disappears in the bone to terminate at the infra-orbital foramen on the anterior face. This face is bounded internally by a roug-h edge for articulation from behind foriuard, with th.Qpalate, ethmoid and lachrymal bones; anteriorly it is limited by the lower OSTEOLOGY. 79 marg-in of the orbit, internally, and externally, by a roug"h border for articulation with the malar bone; externally it is separated from the posterior surface by a rounded border on which beg"ins the infra-orbital canal by a notch ; this border forming-, in the articulated skull, the lower marg-in of a fis- sure, the spheno-maxillary. The internal or nasal surface aids in forming- the outer wall •of the nose, and presents a larg-e irreg-ular aperture leading- into the antrum of Hig-hmore ; this aperture is much reduced by articulations with neig-hboring- bones,, J)alale, ethmoid, lach- rymal and inferior turbinated. The antrum is indistinctlj'- triangular ; in it are seen numerous vertical g-rooves and on its floor several conical projections which mark the position of molar teeth. In front of the opening- into the antrum is a deep vertical g-roove, the sulcus lachrymalis. This face is limited above by the nasal process, in front, and behind this by a roug-h cellular edg-e for articulation with the lachrymal and ethmoid bones; interiorly is the horizontal palate process, which may be said to divide it into two portions, the part be- low terminating- in the alveolar process and the part above forming- the inferior meatus of the nose. The posterior bor- ber is roug-h for articulation with the palate bone. The ante- rior edg-e is sharp and concave and forms the marg-in of the anterior nares. The four processes are nasal, malar, -palate and alveolar. The nasal process is a long-, thin, triang-ular projection form- ing- a part of the wall of the nose and presenting- three borders and tzijo surfaces. The anterior border is convex, thin and serrated for articu- lation with the nasal bone. The posterior border is thick and g-rooved, the posterior marg-in of the process is roug-h for articulation with the lacry- mal bone ; the anterior marg-in is rounded, continued into the marg-in of the orbit, and presents below a small tubercle. This g-roove, in the articulated skull, is formed into a canal for lodg-ing- the nasal duct, and is nearly vertical, being- slig-htly oblique backward and outward. The upper border is blunt 80 DESCRIPTIVE ANATOMY. and serrated for articulation with the frontal bone, its internal ang"ular process. The external face is concave and marked by small foramina. The internal face is crossed from behind forward by two roug-h ridg-es, crista turbinalis inferior and superior, the former articulating- with the inferior turbinated and the latter with the ethmoid. Above the superior turbinated crest the surface is rough for articulation with the ethmoid ; between the two crests it is smooth and concave, entering- into the mid- dle meatus of the nose. The malar -process forms the upper part of the boundary'- between the anterior and posterior faces. It is concave both in front and behind, triang-ular in outline and its summit is rough for articulation with the malar bone. Tht palate process projects inward from the lower part of the internal surface, forming- a portion of the floor of the nose and the roof of the mouth. It does not extend as far back as the body of the bone, but may be said to be deficient behind. Its upper surface is transversel}'- concave and smooth. In front is a foramen which leads into the anterior palatine canal, which appears on the inner border of the process as a g-roove. Its lower surface is also concave, but /roug-h, marked by nu- merous shallow depressions and by a g-roove externally, which runs from behind forward. The inner border is roug-h to ar- ticulate with its fellow on the opposite side ; it is thicker ante- riorly than posteriorly, and its upper edg-e is raised into a ridg-e, or crest, which is slig-htly averted, so as to produce, when the bone is articulated, a narrow g-roove, for the recep- tion of the vomer. Towards the front the inner border, in its lower part, presents a g-roove, which sinks into the bone above to communicate with a foramen on the upper surface, the anterior palatine. In front the inner border terminates in a slender, pointed process, which, united with a similar ©ne on the opposite bone, forms the anterior nasal spine. The anterior border of the process is the thin concave mar- g-in of the nose, the nasal notch. T\i& posterior border is straight and serrated for articulation with the horizontal plate of the palate bone. OSTEOLOGY. 81 The areolar process projects downwards from the lower, outer part of the bone, and forms about a fourth of the circum- ference of a circle. It is marked by sockets for eight teeth, with interv^ening- septa. Palate Bone. The palate bone enters into the formation of the orbits, the nasal fossa? and the roof of the mouth. It is divided into hori- zoiital and vertical, or perpoidicular portions, or plates. The horizontal -portion projects inward, at about a right angle, from the lower limit of the vertical plate, and presents two surfaces and three borders. The superior or nasal face is smooth and concave transversely, forming the back part of the floor of the nose. The inferior face is also slightly con- cave transversely and rough, forming the posterior part of the hard palate. A transverse ridge crosses it posteriorly. The anterior border is serrated for articulation with the palate process of the superior maxillary. The posterior Ijorder is smooth, concave and free, having its inner extremity prolonged backwards by a slender, sharp pro- cess, which with asimilar projection on the opposite bone, forms the posterior nasal, or palate spine. The internal border is thick, rough and serrated for articulation with its fellow; the upper edge of this border is raised and produces, when articu- lated, a slight groove for the reception of the vomer. The vertical plate is irregularly quadrangular and presents two faces, internal and external, and three borders, superior, anterior and posterior. The internal surface presents two transverse ridges, the superior and inferior turbinated crests; the inferior to articulate with the inferior turbinated bone, and the superior with the middle turbinated bone of the eth- moid. This surface, below the inferior turbinated crest, is concave and forms the outer boundary of the inferior meatus of the nose; the surface between the two crests is also concave, and forms a part of the middle meatus; above the superior crest is a narrow groove. The exteriml surface is, to a great extent, rough for articu- lation with the internal face of the superior maxilla ; but at Des Anat — 6 82 DESCRIPTIVE ANATONY. its Upper back part there is a smooth portion, which forms a part of the spheno-maxillary fossa. At the posterior part of this face is a vertical g-roove, converted into the posterior pala- tine canal by articulation with the tuberosity of the superior maxilla. The superior border presents two processes, separated by a deep notch. The notch is called spheno-palatine, and is con- verted into a foramen of that name by the articulation of the sphenoid bone. The anterior process is known as the orbital; the posterior as the sphenoidal. The orbital process inclines outward as it ascends, is hollow and hig^her than the sphen- oidal, being- perched upon a thin plate of bone, its neck. It presents five faces^anterior, posterior, internal, external and superior — the first three being- articular, the others non- articular. The anterior face articulates with the orbital surface of the superior maxillary. ^h.^ posterior face articulates with the sphenoid bone. The internal face articulates with the ethmoid bone and usually presents the opening- into the cellular cavity in the process; but this is sometimes on the posterior face. The external face forms a part of the inner wall of the spheno-maxillary fossa. The superior face forms the back part of the floor of the orbit. The sphenoidal process is a thin plate of bone, inclining- in- ward as it ascends, and presents three faces^ — superior, ex- ternal and internal — and two borders — anterior and posterior. The superior face articulates with the sphenoid bone and presents a g-roove, converted, by articulation, into the pterygo- palatine canal. The external face partly enters into the formation of the spheno-maxillary fossa, and partly articulates with the ptery- goid process of the sphenoid. The internal face is free and forms part of the outer wall of the nasal fossa. OSTEOLOGY. 83 The anterior border of the process is the posterior boundary of the spheuo-palatine notch. The -posterior border of the process articulates with the pter3^g-oid process of the sphenoid bone. The anterior border of the perpendicular plate is irreofular, articulates with the superior maxillary bone and presents, at the intersection of the inferior turbinated crest, a thin process, the maxillary, which aids in closing* the openino- into the antrum maxillare. The -posterior border of the perpendicular plate is g-rooved and articulates with the pteryg-oid process of the sphenoid. At its lower part is a process, the pteryg-oid process, or tuber- osity of the palate bone. It is triang-ular, is directed down- ward and backward and outward, and fits into the interval between the two plates of the pteryg-oid process of the sphenoid. Descending-themiddleof the tuberosity, posteriorly, isa smooth gToove, which, when the bone is articulated, forms part of the pteryg-oid fossa; on each side of this g-roove is a roug-h g-roove, which articulates with the corresponding- plate of the pteryg-oid process of the sphenoid. Kxternally the tuberosity is roug-h and articulates with the superior maxilla. The opening-s of numerous canals, the accessory posterior palatine canals, are seen on the tuberosity, and it is perforated vertically throug-h its base by the posterior palatine canal. The Inferior Maxilla. The inferior maxilla, or lower jaw bone, is a symmetrical bone, derived from lateral halves, which blend in the middle line — each lateral half consisting- of a vertical portion, the ramus, and a horizontal portion, which is one half of the body of the bone. The j9o formed by the nasal, the frontal, the ethmoid and the body of the sphenoid. The /f cor is formed \r\. front, by Wiinous. 'Vhe sup7'aspi>io2is is a round cord, which extends from the seventh cervical vertebra to the sacrum, attached to the tips of the spinous processes. This cord is con- tinued upward by a more prominent band, which has received the name of the lig-cunentum nuchae (L. nucha, a nape). This, in man, is composed almost entirely of fibrous tissue, and is simply a division of the supraspinous lig^ament. The inter- s-pinous lig-ament consists of thin fibres, which are attached to the adjacent edg-es of the spinous processes; and is found only in the dorsal and lumbar regions. Ligaments of the Transverse Processes. Only in the lower dorsal and lumbar regions are the trans- verse processes held together by a few scattered intermediate fibres, called intertransverse ligaments, extending between the adjacent edges of the corresponding transverse processes. The Articulation of the Head with the Spine, and the First with the Second Cervical Vertebra. The Atlo-Axoid Articulation. The articulation between the Atlas and the axis consists of a diarthrodial and arthrodial joint on each side, formed by the articular processes, as seen between other vertebrse, and of a pivot joint, in front, between the posterior face of the anterior arch of the atlas and the front of the odontoid process of the axis. The anterior atlo-axoid ligament, usually described as two, consists of a broad band of ligamentus fibres attached below to the front of the body of the axis as far up as the base of the odontoid process, and above to the lower border, anterior sur- face and tubercle of the anterior arch of the atlas. That part occupying the middle line is thicker than the lateral fibres and LIGAMENTS. 115 is described as a separate lio-ament. It is merely a continua- tion of the anterior common lig-ament of the spine. The posterior atlo-axoid li^^ament is a membrane-like fold closing" in the space between the vertebrse behind. It is attached above to the posterior surface and lower border of the posterior arch, extending- from the capsular lig-ament of one side to that of the other and blending- with the capsules. Below it seizes the laminae of the axis. The transverse ligament is a strong- band, broader in the centre than at either extremity, attached firmly by either end to the inner face of the lateral mass of the atlas, stretching- across the odontoid process and firmly binding- the latter to the anterior arch of the atlas. As it passes over the odontoid process a vertical band of fibres crosses it, some of them de- rived from the transverse lig-ament, to be attached by one end to the base of the odontoid process and by the other to the basilar process of the occipital. This g-ives the lig-ament the form of a cross, hence its name, crucial lig-ament. The two capsular ligaments are attached around the mar- gins of the articular facets on the two vertebrae, blending- with the posterior atlo-axoid lig-ament. There are four synoval sacs connected with the articulation. Two belong- to the joints formed by the articular processes, one is interposed between the front of the ondontoid process and the facet on the anterior arch of the atlas, while one inter- poses between the posterior face of the odontoid process and the front of the transverse lig-ament. The Occipito-Atloid Articulation. This is a movable joint of the condyloid variety, the articu- lating- surfaces being- the two condyles of the occipital above and the superior articular facets of the atlas below. The lig-a- ments, seven in number, are Two anterior occipito-atloid Posterior occipito-atloid Two Lateral Occipito-Atloid Two capsular. The central part of the anterior occipito-atloid ligament is a rounded cord attached below to the tubercle on the ante- 116 DESCRIPTIVE ANATONY. rior arch of the atlas and above to the under face of the basi- lar process of the occipital. It is the upward continuation of the anterior atlo-axoid, and through it of the anterior common ligament of the spine. The lateral portion of the ligament is a broad and thin band attached above to the margin of the foramen magnum and below to the anterior arch of the atlas, extending to the beginning of the capsular ligaments, with which it blends. The jyosterior occipito-atloid is a broad and thin membra- nous band attached above around the margins of the foramen magnum and below to the upper border and posterior surface of the posterior arch of the atlas. It corresponds to the liga- ments between the'laminae in the vertebral column, but contains no elastic fibres. The capsular ligaments are attached around the margins of the condyles above and the receiving surfaces on the atlas be- low. Behind and in front they blend with the anterior and posterior ligaments. The two lateral ligaments blend with the sides of the two capsular ligaments and are attached below to the transverse process of the atlas, extending above to the jugular process of the occipital bone. The Occipito-Axoid Ligaments. The occipito-axoid lig-anient is a broad membranous band which continues the posterior common ligament of the spine upward to the occipital. It is attached belov/ by some fibres to the body of the third cervical vertebra and to the body of the axis. Passing upward it covers over the odontoid process and the crucial ligament and is attached to the anterior margin of the foramen magnum, passing upon the basilar process to blend with the dura. The odontoid or check liga?7ient con'^i^i^ of three parts. The lateral portions are attached below to the pit on the side of the odontoid process and above to depressions found on the inner face of the condyles. The central portion is attached below to the tip of the odontoid process and above to the margin of the foramen magnum. LIGAMENTS. 117 The vertebral artery supplies both of these articulations. The loop between the first and second cervical nerves supplies the articulation between the axis and the atlas, while the sub- occipital supplies the occipito-atloid articulation. Sacro- Vertebral Articulation. The joint between the sacrum and last lumbar vertebra, is similar to that between two vertebrae, the articulating- sur- faces being the articular processes of the two bones. The ligaments are the same as between any two vertebrae, with the addition of two ligaments on each side, the ilio-hunbar and himbo-sacral, which are generally considered among the liga- ments of the pelvis. The ilio-lumbar extends from the trans- verse process of the fifth lumbar vertebra outward to the ilium just above and in front of the ear-shaped articular sur- face. The lumbo-sacral passes from the transverse process of the fifth lumbar vertebra downward and outward to the wing of the sacrum. Movemoits. Movement between the occipital and the atlas is mainly confined to the backward and forward movements, though lateral movement is permitted to some extent. In the nodding movements of the head, flexion and extension, the condyles of the occipital glide backward and forward on the articular surfaces of the atlas. Thus, in flexion the chin is carried to the chest while the condyles pass backward in their articular cavities. In extension the head is carried backward and the condyles move forward. In the slight lateral move- ments the head is carried towards the shoulder and the con- dyle of that side passes inward while the one of the opposite side passes outward in the corresponding cavity. Motion be- tween the atlas and axis is confined to revolution of the atlas around the odontoid process of the axis. In this movement, the head is turned to one or the other side the articular facet gliding toward that side over the facet on the process, while the inferior facet of the atlas of the side to which motion is made, glides backward on the axis and the opposite facet glides forward. Moveynents of the spine as a whole. The amount of motion which may take place between any two contiguous vertebrae 118 DESCRIPTIVE ANATOMY. is but slight, yet the column as a whole enjoys a wide rang-e as well as a great variety of movements. These movements are the four ang-ular movements, flexion, bending- forward, extension, bending* backward, and rig-ht and left lateral move- ment. In addition to these a considerable amount of rotation, by twisting" of the lig-amentous fibres is permitted. In flexion the body bends forward, compressing* the anterior fibres of the intervertebral disks and putting" the posterior fibres on the stretch, the spine becoming- convex backward. This movement is limited not only by the compressibility of the disks but by the tension on the posterior fibres, while the supra and interspinous and the sub-flava ligaments are all stretched. The superior articular processes g-lide upward on the inferior in this movement. Flexion and extension are both free in the cervical and lumbar regions, the vertical direction of the articular processes limiting the movement in the dorsal. Lateral flexion is most free in the cervical region, the inver- sion of the superior articular processes limiting it in the lum- bar, while the attachment of the ribs prevents it in the dorsal, where the shape and direction of the articular processes would indicate that it should be most free. In this movement the articular process of the side away from which motion is made glides upward on the one below, the reverse movement taking place on the side flexed. The lateral margins of the disks would be compressed and the fibres of all ligaments on the opposite side put on the stretch. Rotation of the column takes place by twisting the fibres of the intervertebral disks. It is free in the cervical region, slight or imperceptible in the dorsal on account of the ribs, while the large size of the supe- rior facets as compared to the inferior allows some rotation in the lumbar region in spite of the fitting in of the superior processes between the inferior. Of course in rotation there is a certain amount of gliding of the articular processes, the movement being arrested by the stretching of the vertical fibres of the disks. The Sterno-Clavicular Articulation. This is a movable joint of the saddle shaped variety, or a joint by reciprocal reception. It is formed by the saddle shaped LIGAMENTS. 119 articular surface on the inner extremity of the clavicle, which is concave from above downward and forward and convex from above downward and backward, and a similar surface on the upper angle of the manubrium, aided b}'' a concavity on the cartilaufe of the first rib. The following- ligaments bind the bones together : Capsular Romboid, or Costo-Clavicular Interclavicular Inter-articular fibro-cartilage. The inter-articular fihro-cartilag-c is attached by one end to the upper, posterior part of the inner end of the clavicle and by the other to the junction of the cartilage of the first rib with the articular depression on the lateral aspect of the manu- brium. It serves the double purpose of holding the bones together and at the same time divides the joint into two syno- vial cavities. The ca-psnlar lig-ameiit is a thick band of fibres completely surrounding the tjoint but thicker at some points than at others. Thus it is seen to be much more thickened behind than elsewhere, being sometimes described as the posterior liga- ment of the joint. In front it blends with the tendon of the sterno-mastoid muscle, above with the interclavicular ligament while below it is continuous with the Romboid. The deepest fibres of this ligament pass from the two bones to the interar- ticular cartilage, and not from bone to bone, while the more superficial fibres pass from the margin of the receiving cavity on the manubrium and cartilage on the first rib to the margfin of the articular surface on the clavicle. The interclavicular linanieut is a strong thick band attached to the upp_'r an 1 posterior aspect of the clavicle of one side, blending with the fibres of the capsule, then passes into the interclavicular notch to be attached to the posterior part of the upper border of the manubrium, and rises to be attached to the inner back part of the opposite clavicle. The roniljoid^ or cosio-clavicular ligament is a set of short fibres resembling fibro cartilage which extend from the rom- boid impression of the clavicle downward, forward and inward to be attached to the upper face of the cartilage of the first rib. 120 DESCRIPTIVE ANATOMY. There are two synovial membranes, one interposed between the cartilag-e and the manubrium and the other between the inner extremity of the clavicle and the cartilag-e. In some cases the cartilag-e is worn throug-h and the synovial sacs communi- cate with each other, practically forming- one sac. The blood supply is mainly from a branch of the Internal Mammary. The nerve supply is from the branch to the sub- clavius. The movements of the joint, which take place in all direc- tions, are confined within a narrow rang-e and are always of a g-liding- character. The cartilage accompanies the clavicle in all of its movements except upward. Thus in movement of the shoulder backward, the inner end of the clavicle, with the interarticular cartilag-e, passes forward; in forward movement of the shoulder, the clavicle passes backward; in upward move- ment of the shoulder the clavicle passes downward; but in downward movement of the shoulder, the clavicle passes up- ward, putting- the fibres of the cartilag-e on the stretch and limiting- the extent of the movement. Scapulo-Ciavicular Articulation. This is a movable joint of the arthrodial variety. The ar- ticulating- surfaces are an oval facet on the outer extremity of the clavicle and a corresponding- facet on the anterior edg-e of the acromion process of the scapula. It must be observed that the clavicle, in its outward course, passes just above the cora^ coid process of the scapula, and, while it does not articulate with it, receives a lig-ament from it. The bones are held tog-ether by two sets of lig-aments, a capsular, surrounding- the articular surfaces, and acoraco-clavi- cular binding- the clavicle to the coracoid process. The caf>sular ligament is a strong- but lax band of fibres surrounding- the joint and attached to the clavicle beyond the articular facet. Inferiorly these fibres pass as far as the coraco clavicular lig-ament with which they blend. Above, they are streng-thened by fibres of the deltoid and trapezius. The coraco-clavicular consists of two portions, the conoid and the trapezoid. The conoid lig-ament is triang-ular in form LIGAMENTS. 121 and is attached by its apex to the coracoid process close to the supra-scapular notch, while its base is inserted into the conoid tubercle and posterior border of the clavicle. The trapezoid, blended internally with the conoid, has its surface looking- for- ward and backward. Below it is attached to a rido-e on the upper aspect of the coracoid process, while above it is attached to the oblique ridg-e running- forward and outward from the conoid tubercle to the anterior border of the clavicle. This joint has an interarticular fibro cartilag-e, which, how- ever, is often absent. When this is present there are two S3'novial sacs, otherwise, but one. The -joint is supplied by the acromial thoracic and supra- scapular arteries and by the circumflex and suprascapular nerves. The movenioits of the joint are confined to a slight g-liding- of the articular surfaces upDn one another. Usually the scapula is the bone which moves; but, of course, when the scapula is fixed, the clavicle may gflide upward, downw^ard backward or forward. Ligaments of the Scapula. Stretched between different points on the scapula are two ligaments, coraco-acromial and transverse. The coraco-acro- viial, thick and triang-ular, is attached by its apex to the tip of the acromion and by its base to the coracoid process, serving- as a protecting- arch for the shoulder joint. The transverse ligament passes over the supra-scapular notch, from one ex- tremity to the other, converting^ it into a foramen. The Shoulder Joint. The shoulder is a joint of the diarthrodial class and enar- throdial or ball and socket variety. The bones entering- into its formation are the upper extremity of the humerus, with its g-lobular head, anatomical neck and two tuberosities ; and the g-lenoid cavity of the scapula, supported b}' its neck and over- hung- by the c(;racoid and acromion processes. The lig-aments of the joint are properly but two, the g-lenoid and capsular, thoug-h some accessory bands of the latter are frequently dig-- 122 DESCRIPTIVE ANATOMY. nified as separate ligaments. The g-lenoid lio-ament is a band of fibro cartilag-e, triangular on cross section, which is attached by its base around the margin of the glenoid cavity and serves to deepen, but more especially to widen this cavity. It is connected above with the head of the biceps muscle which passes through the joint, and by its margin is attached to the capsular ligameat. The caps2ilar lig-ctment is a strong but loose sac completely investing the articulation but not holding the bones in apposi- tion with each other. It is simply a bag of which the upper end is closed by the glenoid cavity and the lower by the artic- ular surface of the humerus. Above, this ligament is attached around the margin of the glenoid cavity, extending on the neck of the scapula further above than below and blending with the glenoid ligament. Below, it is attached around the anatomical neck of the humerus but is prolonged over the tuberosities, between which it is continuous with the trans- verse band which binds the tendon of the biceps in its groove. Inferiorly it is prolonged over the surgical neck of the humer- us to a slight extent. The upper part is very much thicker than any other portion of the ligament. One portion, that extending from the base of the coracoid process to the greater tuberosity of the humerus is the portion individualized as the coraco-humeral ligament. In the interior of the joint there may sometimes be seen a fold in the synovial membrane called the gleno-humeral ligament. The capsule is nearly surroun- ded by muscles whose tendons, as they pass over it,are blended with the ligament and supply the greater part of its strength. The synovial meinhrane is extensive. It lines the interior of the capsule and is reflected over the margins of the articular surfaces, but does not reach the p.jints of greatest pressure. A prolongation of the membrane is continued over the tendon of the biceps muscle and the sac usually communicates with a bursa beneath the subscapularis muscle and frequently with one beneath the infraspinatus. The joint is powerfully reinforced and protected not only by the numerous muscles which surround it but also by a pro- tecting arch formed by the acromion and coracoid processes and LIGAMENTS. 123 the coraco-acromial lig-ament stretched between them. The muscles are, above the supra spinatus, postero-superiorly the infraspinatus and teres minor, antero-internally the subscapu- laris : while above, behind, to the outer side and in front the fibers of the deltoid form a cushion over the joint. The first four muscles blend, at their insertion, with the capsule. The arterial supply is chiefly from the anterior and posterior circumflex, but branches are derived from the dorsalis scapula? and suprascapular arteries. The nerves are the suprascapular and circumflex. Movements and mechanism. The leng-th of the capsular lig"ament, the shallowness of the receiving* cavity and the com- paratively larg-e size of the humeral head, permit this joint to enjoy a gfreater variety and extent of movement than au}^ other in the body. Like all enarthrodial joints it is capable of the four ang-ular movements, their combination, circum- duction, and axial rotation. In flexion the humerus with the forearm is carried forward, the head of the bone spinning- in the articular cavity around an axis which is drawn from the centre of the head throug-h the centre of the g"reater tuberosity, to the centre of the g"lenoid cavity. In extension the reverse movement takes place, with of course a reversal of the mechanism. In abduction the humerus is carried away from the mid-line of the body, the hand raised toward the shoulder, while the head of the humerus g-lides downward in the g-lenoid cavity until it presses on the inferior fibres of the capsular lig-ament. When the humerus is carried in abduction to arig-ht angle with the body, further movement is arrested by the impact of the bone against the arch of the acromion, further movement in this direction being- effected by the g-liding- of the scapula on the thoracic wall. Adduction is the reverse of abduction. Adduction is limited by the elbow coming- in contact with the side and cannot be carried further without first flexing- the arm. Circumduction is the combina- tion of these movements, the head of the humerus assuming the position of flexion, abduction, extension and adduction, the arm and forearm describing- a cone whose apex is at the shoulder joint. In rotation the head of the humerus moves 124 DESCRIPTIVE ANATOMY. around an axis drawn from the centre of the head downward throug-h the internal condyle, the head moving- backward in inward and forward in outward rotation. The relation of the long- head of the biceps to this joint is so peculiar as to demand special mention. Attached to the upper marg-in of the gflenoid cavity, where it is blended with the g-lenoid lig-ament, it passes across the upper outer aspect of the joint, pierces its capsular lig-ament and is covered by a prolong-ation of the synovial membrane which lines the cavity. This tendon, therefore, becomes a powerful ag-ent in retaining- the head of the humerus in apposition with the g-leniod cavity and thus strengthens the joint on its upper and outer aspect. Radio-Ulnar Articulation. The articulation between the two bones of the forearm forms a diarthrodial joint of the trochoid or pivot variety. The bones articulate at both the upper and lower extremity, being- separated by the interosseous space throughout the shafts. The lig-aments holding- the bones tog-ether are found at their npp^r and lower extremities and between their shafts. Above, the two bones are held together by one ligament, the orbicular which forms three-fourths of a ring-, the other fourth being the lesser sigmoid cavity of the ulna. The ligament surrounds the articular rim of the radius and is attached by its two ends to the extremities of the lesser sigmoid cavity. The lower fibres are tightly stretched around the radius just below the head, rendering it very difficult to release that bone from its grasp. The shafts are connected b}^ two ligaments, the interosseous and the oblique. The oblique is a narrow band which passes downward and outward from the ulna, at the base of the coro- noid process, to the radius just below the tuberosity. It is often wanting. The interosseous membrane extends from the lower extrem- ities of the bones upward about two-thirds the length of the shafts, leaving an interval, above which is the oblique ligament. Its fibres are directed downward and inward between the inner border of the radius and the outer border of the ulna. About LIGAMENTS. 125 the lower third of the forearm, the membrane is pierced by a foramen for the anterior interosseous artery. At their lower extremities the bones are held togfether by two lig-aments and the trtanfj;-ular fibro-cartilag-e. The two lig^aments are an anterior and a posterior passing- across the two bones. The triangfular cartilag-e tips the summit of the capi- tulum ulnae; and excludes it from the wrist joint. Bv its apex it is attached to the pit between the styloid processof the ulna and the capitulum ulnae; by its base to the narrow roug-h sur- face separating- the carpal and sigmoid cavities of the radius. The movements are two, and in both the radius alone moves. It can move forward, pronation, or backward, supination, and in both the hand is carried with it. In these movements of rotation, or revolution, the radius rotates around an axis repre- sented by an imaginary line drawn from the centre of the head of the radius throug-h the centre of the capitulum ulnae; conse- quently in performing- pronation the sig-moid cavity of the radius moves forward on the articular rim of the capitulum ulnae, the reverse occurring- in supination, while the head of the radius rotates in the lesser sigmoid cavity and orbicular lig-ament. The Elbow. This is a diarthrodial joint of the g-iug-lymoid variet3\ The bones entering- into its formation are the trochlear surface and the rounded eminentia capatata on the lower extremity, of the humerus, and the g-reater sig-moid cavity of the ulna with the cup- shaped upper extremity of the radius. The shape of the articu- lar surfaces furnished by the radius and humerus would render this joint one of the enarthrodial variety ; but the movements are so restricted by the close lig-amentous union ^-between the ulna and radius, that the joint presents but one of the peculiar movements of the enarthrodial joints — rotation. The lig-aments are anterior and posterior, internal and external lateral. There, as always, some thin fibres which connect the various parts of the lig-amentous bands tog-ether, completing- the capsule around the joint. The anlerior lig-aDieiit is attached above to the humerus just above the coranoid fossa, while below it seizes the lower sur- face of the coranoid process and the orbicular ligament. 126 DESCRIPTIVE ANATOMY. ^\\Q, f)Osterior lig-aments is attached above to the humerus just above the olecranon fossa and below to the g-roove on the upper surface of the olecranon, and to the bone immediately behind this. It is much thinner and weaker than the anterior. The external lateral ligament is attached above to a depres- sion beneath the external condyle while its base is attached to the orbicular lig-ament. The internal lateral is attached above to the internal con- dyle while below it expands into two fasciculi with a triang-ular interval, filled with thin fibres, between them. The most anterior, which may be traced to its attachment to the front of the internal condyle, is attached below to the margin of the great sigmoid cavity on the coronoid process. The posterior, attached above to the back of the internal condyle, is below attached to that margin of the sigmoid cavity furnished by the olecranon process. By means of a few thin, scattered fibres, the lateral ligaments are connected with the anterior and pos- terior ligaments, thus completing an imperfect capsule. The synovial membrane is extensive. It lines the whole of the inner face of the capsule, extending upward behind to the olecranon and in front to the coranoid fossa ; while below it covers the interior of the orbicular ligament and furnishes the lining for the articulation at the superior radio ulnar articula- tion. The muscles which strengthen the joint are in front the brachialis anticus, behind the triceps and anconeus, externally the muscles arising from the external condyle, notably the supinator brevis ; and internally those which arise from the internal condyle. The move7Jients are flexion and extension, to which should be added the rotation of the radius when that bone revolves in the lesser sigmoid cavity. In flexion the greater sigmoid cavity and the cup-shaped articular surface of the radius glide upward on the corresponding articular surface of the humerus, the movement being arrested when the coranoid process impinges upon the coronoid fossa. In extension the reverse would occur and the movement would be arrested by the impact of the beak LIGAMENTS. 127 of the olecranon on the bottom of the olecranon fossa. The movement of the radius will be described with the radio-ulnar articulation. The arterial supply of this joint is derived from communi- catinof branches between the anastoraotica mag-na, the superior profunda and inferior profunda arteries, the anterior, posterior, and interosseous recurrent branches of the ulna, and from the radial recurrent. The nerve supply is derived from the ulna as it passes between the internal condyle and the olecranon, the median is said to furnish two filaments while the musculo- cutaneous contributes one filament. The Wrist Joint. This is a diarthrodial joint of the condyloid variety. The receiving- cavity, oval, transversely, concave both from before backward and from side to side, is furnished by the lower ex- tremity of the radius, aided by the triang-ular cartilag-e which shuts out the ulna from participation in the joint. The con- dyle is provided by three of the bones of the first row of the carpus, scaphoid, semilunar and cuneiform. The ligaments anterior, posterior and two lateral. All lig-aments of this joint blend with the ligaments of the carpus and can with difficulty be separated from them. Thus the anlcrior ligament is attached above to the margin of the carpal cavity of the radius and to the anterior radio-ulnar liga- ment, and to the anterior margin of the lower end of the Ulna, while below it is attached to the bones of the first row of the carpus, blending with the anterior palmer ligamentous fibres which bind together the first and second rows. The fiosterior is, in like manner, attached above to the posterior margin of the carpal cavity and to the posterior radio-ulna ligament and below to the back of the bones forming the first row of the carpus, blending with the dorsal carpal ligaments binding the two rows together. The external lateral lig-amcnt is attached above to the styloid process of the radius and be- low to the tuberosity of the scaphoid and to the trapezium. The internal lateral liij;-ament is attached above to the styloid process of the ulna, below to the inner side of the cuneiform and unciform, to the latter through the medium of the internal 128 DESCRIPTIVE ANATOMY. lateral ligament of the carpus. Between these bands are fibres which convert this lig-ament into a capsule. The synovial membrane lines the interior of the ligament- ous fibres and to a slight extent dips ia between the scaphoid and semilunar and between the semilunar and cuneiform. There are no muscles which directly strengthen the joint. Many tendons pass over it but their laxity prevents their add- ing strength except in certain positions of the joint. Thus in flexion, with the closed fist, the extensor tendons strengthen it behind, and in extension, with the hand open, some strength is given by the flexors. The tendons, also, by the tonic con- traction of the muscles, aid in retaining the bones in apposi- tion. The movements are those usual in condyloid articulations, flexion, extension, abduction, adduction and circumduction. The mechanism will be readily understood if it is borne in mind that in all movements of condyloid joints the distal ex- tremity moves in a direction opposite to that of the condyle. Thus in flexion, the hand passes forward on the forearm while the condyle moves backward in its receiving cavity, pressing against the posterior fibres of the ligament. E)xagger%ted movement as from a fall on the flexed hand, would produce dislocation. In .extension the mechanism is the reverse of flexion. In adduction the hand is carried toward the mid line of body while the condyle passes outward, the movement be- ing limited by the external lateral ligament. In abduction the reverse is true. The combination of these movements make^^ circumduction, which may be either inward or outward. In the latter the hand would pass from flexion to abduction, thence to extension, then to adduction and again to flexion. The condyle passing first backward, then inward, forward, outward and so to backward again. The wrist joint gets its arterial supply from the anterior and posterior carpal arches of the radial and ulna. The inter- osseous arteries, anterior and posterior, as well as some of the / ascending branches of the deep palmar arch also contributing / to its supply. The ulna and posterior interosseous furnish the nerve supply. LIGAMENTS. 129 Articulation of Carpus and Metacarpus. The bones of the carpus, which lie in the same row, are held tog-ether by ligfamentous fibres passing" across them in front and behind, palmar and dorsal ligaments, and by fibres which seize the adjoining- surface of opposing- bones, called interosse- ous ligaments. Between the trapezium and trapezoid there is no interosseous ligament. In the same manner the metacarpal bones of the four fing-ers are held tog-ether at their bases. The two rows of carpal bones are held tog-ether by lig-amentous fibres passing from one to the other in front and behind, pal- mar and dorsal lig-aments, and by two lateral lig-aments, the external passing- from the scaphoid to the trapezium, the inter- nal from the cuneiform to the unciform. The metacarpal bones of the four fing-ers are held to the second row of carpal bones by fibres in front and behind, pal- mar and dorsal lig-aments, and in one situation by interosseous fibres extending from the adjacent parts of the os mag-numand unciform to the bases of the third and fourth metacarpal bones. The synovial membrane between the first and second rows sends prolong-ations upward and downward between the indi- vidual bones of the two rows, as well as between the proximal extremities of the metacarpal bones into the carpo- metacarpal articulations. This is not true of the synovial sac between the metacarpal bone of the thumb and the trapezium. The Trapezio-Metacarpal Joint. This articulation belongs to the movable class and saddle- shaped variety. It is invested by a capsular ligament, and allows the four angular movements and their combination^ circumduction. The Metacarpo-Phalangeal Articulation. The knuckle joint, or metacarpo-phalang-eal, is of the mova- ble class and condyloid variety. The condyle is furnished by the head of the metacarpal bone and the receiving- cavity by the top of the corresponrling- phalanx, aided by a plate of carti- lag-e known as the anterior lig-ament of the joint. Des Anat— 9 130 DESCRIPTIVE ANATONY. The lig-aments are tzvo latercil^ seizing- both bones on their lateral aspect just beyond the articular surface. The place of a posterior llg-ament is supplied by the extensor tendons of the finger. The anterior is not a lig-ament in the true sense of the word, being only amassof fibro-cartilaginous material attached to the front edg-e of the articulating- surface on the base of the phalanx, and increasing the receiving* cavity. To this lig-ament is attached a band of transverse fibres which stretch between the distal ends of the metacarpal bones and bind them to one another. Inter-Phalangeal Articulations. These joints are of the diarthrodial class and the hing-e variety, the trochlear surface being presented by the head of one pha- lanx and the receiving- surface bv the base of the other. The lig-aments, anterior and tvjo laterrl, are attached like those of the metacarpo-phalang-eal articulations, the extensor tendons here, also, taking- the place of posterior lig-aments. The carpal articulations are supplied by the carpal arches and the deep palmar arches. The nerves are derived from the ulnar, median and posterior interosseous. The fingers are supplied by their respective dig-ital branches both for nerves and arteries. The movements of the carpal joints are confined to a slig-ht gliding- of one bone on the other, — the same state- ment applying- to the carpo-metacarpal joint, except the thumb. Movement at the metacarpo-phalangeal joint consists of the four ang-ular movements and their combination, circumduction. Movement is freer at the index and little fing-ers than at the other two. Movement at the inter-phalangeal articulation is confined to flexion and extension. Temporo-Maxillary Articulation. This articulation is formed by the condyle of the lower jaw and the g-lenoid cavity of the temporal bone. This is a diarthrodial joint of the condyloid variety, and presents four lig-aments, viz : internal and external lateral, capsular and stylo-maxillary and an inter-articular fibro-car-^ tilage, which is sometimes perforated ; when this is the case, LIGAMENTS. 131 there is but one synovial sac, otherwise there are two, one be- tween the cartilage and the condyle and the other between the cartilao^e and the g-lenoid cavity. The external lateral lig-ameut is attached to the zyg^oraa above, from its tubercle forward, and, passing- downward and backward, is attached, below, to the outer border of the neck of the condyle. The internal lateral liaament is a specialized piece of the deep cervical fascia, attached above to the spine of the sphe- noid and below to the shelf of bone forminor- the lower margin of the inferior dental foramen. The capsular ligament consists of fibres of varying thick- ness, attached above around the articular margin of the glen- oid cavity and below to the neck of the condyle of the lower jaw. This ligament is slightly thickened at its inner part, while the external lateral ligament is merely a thickening of the capsule. The capsule is attached throughout its circum- ference to the edge of the interarticular cartilage. The intcr-ariicular fibro-cartilage is oval in outline, thinner at the centre than at the circumference, concavo-convex on its upper and concave on its lower surface. Its margin is closely attached to the capsular ligament. The stylo-maxillary is, properly, not a ligament of this joint. It extends from the styloid process of the temporal bone to the angle and posterior border of the ramus of the lower jaw. The lower jaw receives its nervous supply from the auri- culo- temporal branch of the inferior maxillary. The arterial supply is from the temporal. The joint is strengthened on the outer side by the masseter, internally by the internal pterygoid and above by the tempo- ral. The movements are elevation and depression, lateral and forward movement. In depression the jaw recedes from the upper and the condyle, when the movement is not extreme, rolls on the inter-articular cartilage around an axis drawn through its own centre. When, however, the movement is 132 DESCRIPTIVE ANATOMY. carried farther, both condyle and cartilag-e roll forward on the eminentia articularis, exag-g-erated movement leading- to dislocation. Elevation is the reverse of depression. In lateral movement the jaw is twisted to one or the other side, the condyle moving" backward in the g-lenoid cavity on the side toward which motion is made. In forward movement the two condyles are drag-g-ed forward on the eminentia articularis, the lower jaw being protruded beyond the upper. Costo-Sternal Articulation. The ribs have attached to their anterior extremities the cos- tal cartilag-es, which prolong- the seven true ribs to the side of the sternum, where the cartilagfes are received into the pits found there and are held in place by lig-amentous fibres passing- from them to the sternum in front and behind. The cartilag-es of the second and third ribs have also each an inter-articular lig-ament. The Articulations of the Pelvis. The articulations of the pelvis are four, viz : that between the fifth lumbar vertebra and the sacrum, that between the sacrum and coccyx, that between the sacrum and the os innominatum of each side and that between the two ossa innominata. Sacro-Vertebral Articulation. The joint between the sacrum and last lumbar vertebra, is similar to that between two vertebrae^ the articulating- surfaces being- the articular processes of the two bones. The ligaments are the same as between any two vertebrae, ^vith the addition two ligaments on each side, the ilio-lumhar and lumbosacral, which are generally considered among the ligaments of the pelvis. The ilio-lumbar extends from the transverse process of the fifth lumbar vertebra outward to the ilium just above and in front of the ear-shaped articular surface. The lumbo- sacral passes from the transverse process of the fifth lumbar vertebra downward and outward to the wing- of the sacrum. LIGAMENTS. 133 The Sar?'o- Coccygeal lig-aments are an intervertebral disk, small and insignificant, and an anterior, posterior and lateral lig-aments passing- directly from one bone to the other. The Sacro-Iliac articulation, symphysis or synchondrosis, is formed bv the auricular facets found on the sacrum and ilium, each of which is coated, in the recent state, by a thin plate of cartilaofe. The lig^aments of the joint are an anterior and a posterior and the two sacro-sciatic, g^reater and lesser. The anterior sacro-iliac ligament is a thin plane of fibres passing- from the front of the sacrum to the inner face of the ilium. The posterior sacro-iliac lig-ament is a dense and thick mass of fibres, both oblique and horizontal, passing- between the contig-uous surfaces of the two bones and filling* in the deep depression which exists between them. The fibres are attached to the roug-h surface on the ilium behind the auricu- lar facet and to the similar depression on the lateral aspect of the sacrum as well as to the posterior face of the latter bone. The g-reater sacro-sciatic ligament is attached by its poste- rior extremity to the posterior inferior spinous process of the ilium, and to the side and posterior face of the sacrum and coccyx. Passing- forward it runs below the spine of the isch- ium and is attached to the tuberosity of the ischium, its inner edg-e being- free and curved upward upon itself. The lesser sacro-sciatic ligament is blended with part of the g-reater at its posterior extremity, being- attached to the side of the sacrum and coccyx, slig-htly in front of the greater, and not extending- so hig-h up as the former. In front it is attached to the spine of the ischium. The lesser sacro-sciatic ligament forms the lower boundary of the g-reater sacro-sciatic foramen; while that part of the g-reater sacro-sciatic which extends from the point where the two lig-aments separate to the tuberosity of the ischium, forms the lower boundary of the lesser sacro-sciatic foramen. The Symphysis Pubis. The articulation between the ossa innominata is formed between the two pubic bones, and is known as the symphysis 134 DESCRIPTIVE ANATOMY. pubis. Kach bone presents an oval articular surface, whose long- diameter is downward and backward, coated by a thin plate of encrusting- cartilag-e. The two plates are in contact only at the back part, leaving-, in front, a wedg-e-shaped space filled by fibres passing- between the two plates. Besides this interarticular lig-ament, there are four others — superior, con- sisting-of fibres passing- between the two bones above; inferior, fibres passing- between the two bones below, and filling- in the interval between the two rami, so as to form a smoothly- curved arch; anterior, fibres passing- between the bones in front, and posterior consisting- of similar fibres behind. The articulations are supplied by branches from the lateral sacral, ilio-lumbar, middle sacral and internal pudic arteries. The nerves are received from the cords of the sacral plexus. The Hip Joint. The Hi j) Joint is one of the ball and socket articulations, of course, belong-ing- to the euarthrodial, or movable variety. The bones which ent^r-fdto its formation are the three-quarter- sphere articular surface found on the upper extremity of the femur to correspond to the Acetabulum, a receiving- cavity found at the junction of the three bones, the Ilium, the Ischium and the Pubes, which compose the os innoniinatum. This cavity is articular throug-hout its entire extent. There is a lower, inner portion, at the bottom of the cavit}^ a non-articu- lar roug-hened surface, which in the articulated skeleton serves partly to form the attachment of the lig-ament w^hich lies in the interior of the joint, and partly serves for the lodg-ment of the mass of fat, which prevents jarring- of the joint, and at the same time lodg-es the blood vessels which supply the joint and prevents pressure upon these vessels. The Ligaments which hold the bones tog-ether are the Capsular lig-ament, which surrounds the joint; the Cotyloid, which surrotlnds the marg-in of the cavity, and serves to deepen it ; the Transverse, which crosses the cotyloid notch ; and in, the interior of the articulation, there is a round cord which is known as the Lig-amentum Teres. Some anato- mists add other ligaments, which are unimportant when con- LIGAMENTS. 135 sidered as separate lio*aments, being- merely portions of t capsular lig-ament which are developed by the strain upon the joint. One of these, the Ilio femoral lig-ament, extends from just behind the anterior inferior spinous process of the ilium across to a point close to the Trochanter mijor of the femur, one of the points at which the strain is very great. Another, called the Ischio-femoral, extends from the tuberosity of the ischium ; while a third, somewhat less important than the others, extends from near the femoral line of the os pubes, and is known as the Pectineal, or Pubo-femoral lig-ament. These lig-aments are not deserving- of a separate name. The proper description is to say that the capsular lig-ament is streng-thened at the superior and inferior extremities of the joint by fibres which come respectivel}'^ from the spinous process of the ilium, from the ischium, and from the os pubes. The Capsular Lig-am2)it, thick and powerful, is attached above to the brim of the Acetabulum. As it passes around downward and backward, it will be noticed that the lig-ament extends further forward on the Acetabulum; that is, the extent of its attachment increases as we pass around to the posterior aspect of the joint. On reaching- the lower portion of the joint, this lig-ament is found to occupy all the space above the g-roove on the ischium. On reaching- the upper, inner portion of the joint it expands considerably^ nearly to the ilio-pectineal line. As the li(jfa.ment passes downward it completely envelops the joint; and its attachment is ag-ain irreg-ular when the attach- ment to the femur is reached. Superiorly it extends to what is known as the superior cervical txibercle, which is found pro- jecting-from the upper front part of the neck at its junction with the trochanter major; superiorly to this, it extends behind a part of the Trochanter major; then follows the spiral line, and winds around until it passes just in front of the Tro- chanter minor; then extends until it passes upward and just misses the dig-ital pit, and reaches the starting--point. One of the most important of the lig-amentary bands com- posing- the Capsular lig-ament is the so-called ""T Lig-ament,''^ which may be seen better in the dry specimen than in the recent. The two branches rise by the "tail" or "stem" of 136 DESCRIPTIVE ANATOMY. the Y from just below and just behind the anterior inferior spinous process of the ilium; and as they pass downward, though there is never any actual Interval between them, the central fibres are very thin, and the fibres above and below, particularly above, are very thick, hence the resemblance to a Y. The superior fibres of the Y lig-ament are attached to the superior cervical tubercle: the inferior fibres are inserted into the spiral line just as they reach the inner aspect of the bone. The others are of comparatively little importance. The Ilio-^ectineal lig-ament is a long- slender baud of fibres, which starts nearly at the pectineal line of the pubes ; and passes down to reach the spine, a little lower. The band which comes from the tuberosity of the ischium arises just below the g-roove ; and then stretches across, to be inserted near the digital pit close to the Trochanter major. These ligamentous bands are of comparatively little importance. The Cotyloid cavity is deepened by a ring of fibro-cartilage, which is described as being nearly a complete circle, but fails to extend all the way around the joint ; that is, it is said to be horse-shoe shaped, the direction of the bend in the horse-shoe being downward and inward at the cotyloid notch. What is in reality a continuous ligament, extending all the way around the joint, anatomists have preferred to describe as two liga- ments, differentiating between the Cotyloid lig-amejit and the Transverse ligament^ which passes across the cotyloid notch, becoming continuous at its extremities with the cotyloid liga- ment, although the two have the same histiological structure. However, in accordance with general usage they are to be described as two separate ligaments. The Cotyloid lig-ame7it is described as being triangular upon cross section, although it is not quite so, the outer face being distinctly convex, the inner upon the cross section proving to be not a straight line, but a curved line, thus forming the concavity which is neces- sary to receive the convex head of the femur. The thin edge projects away from the bone ; the thick edge is attached to the margin of the cavity all the way around. As above described, the Cotyloid ligament upon reaching LIGAMENTS. 137 the cotyloid notch, changes its name, and becomes the Trans- verse lig-ament, which is therefore merely a continuation of the Cotyloid. The Lig-amentiim Teres is a band of lig-ameutous fibres, holding- the bones which form the joint in position. It is at- tached to the margin of the depression in the bottom of the cavity; its lower fibres are firmly attached to the transverse ligament; and at its lower extremity it passes into the depres- sion on the head of the femur. In this, as in all other movable joints, there is a synovial membrane, w^hich here presents one peculiarity. Though the Ligamentum Teres has been spoken of as a ligament, it is not a liofament in the true sense of the word. As a rule the synovial membranes disappear as they approach the region of pressure in a bone ; but the Ligamentum Teres can be dis- tinctly demonstrated as a synovial membrane at the points of greatest pressure. The synovial membrane starts at the pit on the head of the femur ; and passes downward, covering all of the head of the femur. Leaving the bone itself, it appears on the capsular ligament ; continues on the cotyloid face until it reaches the cotyloid cavity ; then sweeps across the mass of fat lying in this cavity ; and then passes all around the Liga- mentum Teres. The Ligamentum Teres, therefore, does not enter into the joint at all, and unless the synovial membrane is first cut, neither the Ligamentum Teres, nor the mass of fat which lies in the bottom of the depression have any communication with the joint. The Movements of which the hip joint is capable are, of course, all of the movements of the enarthroidal joint; viz., flexion, extension, adduction, abduction, circumduction, and rotation. Any two or more of these movements which are not antagonistic with each other may, of course, be combined ; for instance, there may be flexion of the thigh upon the pelvis at the same time with adduction, abduction, or axial rotation. Flexion, or the movement of the thigh forward, is the most extensive of the movements of the joint. In the prepared specimen flexion may be continued until there is almost a com- 138 DESCRIPTIVE ANATOMY. plete revolution of the joint. The movement consists simply of spinning- the head in tHe cavity. There is no chang-e of position with reference to the ball in the socket, the ball simply turning- in the socket on an axis drawn through the Trochanter major from the centre of the head of the femur. Complete flexion is checked by the powerful band of fibres forming the upper limb of the Y ligament, though of course in the living- man the movement is stopped long- before this by the contact between the thick muscles of the abdomen and the muscles of the thig-h. Extension, the movement of the thig-h backward, is much less free than flexion. The movement is hindered by the Pectlno-femoral band in the dead subject ; and is also limited, in the living- man, by the mass of muscles passing in front and behind. In Abduction and Adduction there are complete changes without rotation. In Abduction, which is a movement of the thig-h away from the mid-line of the body, as the limb is carried outward, the head of the femur passes downward to the bottom of the acetabular cavity, so that it can be felt throug-h the lig-amentous fibres. If the movement is carried to excess in the living- man, splitting- of the fibres takes place. Adduction is more limited in this than in almost any other joint in the body. If the body be in the anatomical position, of course the movement is arrested by the limb on the other side; if taken in a position of semi-flexion, adduction can never be equal to abduction, because it is checked by the pow- erful superior fibres of the capsular lig-ament. Circuinduction is a combination of all the preceeding- move- ments. In this movement the limb pisses from flexion to abduction, from abduction to extension, from extension to ad- duction, from adduction back to flexion. Axial Rotation is usually described as the rotation on the line which is drawn from the centre of the head of the femur to the internal tuberosity of the femur. The line is more nearly through the centre of the lower extremity of the femur. LIGAMENTS. 139 The muscles which strengfthen the joint are as follows: Above, the rectus and g-luteus minimus. In front, the psoas magnus and iliacus internus. Internally, the pectineus and obturator internus. Behind, the outward rotators of the thig-h, obturators, internus and externus, pyriformis, the g-emelli and the quadratus femoris. Or, beg-inning- at random and naming- them in the order in which they lie around the joint, we have, g-luteus minimus, rectus, iliacus internus, psoas mag-nus, pectineus, obturator externus, quaratus femoris, g-emellus inferior, obturator internus, g-emellus superior and pyriformis. The arteries supplying- the joint are derived from the obtu- rator, sciatic, internal circumflex and g-luteal. The nerve supply for the joint is draw^n from articular branches from the sacral plexus, g-reat sciatic, obturator, and a filament from the branch of anterior crural supplying- the rectus muscle. The Knee Joint. This is the largest and for many reasons the most important joint in the body. By the formation of the bones it is the weakest joint in the body, its strength consisting entirely in the powerful bands of ligamentous fibres and the muscles by which it is reinforced. It is usually classed as a "hinge joint", being the analogue of the elbow; but it is really no more of a hinge than the elbow is a pure hinge. In formation it is very complex, being a double condyloid joint, combined with a trochlea, and possessing three articulations. Its articulations may be extended to four, as some of the cartilages which enter into the formition of the joint are so arranged as to establish an articulation between themselves and the bones to which they are attached. The condyles and their receiving cavities per- mit all of the movements belonging to the usual condyloid articulations. The mistake of calling the knee a hinge joint arises from the fact that the classification of joints is based on the movements of which the joints are capible and not on the shape of the bones which enter into their formation. The Bones which compose the knee joint are the two condyles of the femur, the two glenoid cavities on the upper extremity 140 DESCRIPTIVE ANATOMY. of the tibia, and the posterior surface of the patella. The lig-aments which bind the bones together are divided into two sets: the external, or exterior lig-aments, and the interior lig-aments. The Exterior Ligaments consist of an anterior, a posterior, an external lateral, and an internal lateral. The Anterior Lig-cunent, or Liganientam Patellar, the most powerful of all the bands of lig-amentous fibres attached to the joint, is nothing- more than the tendon of the E)xtensor triceps cruris. This muscle passes downward until it reaches the upper border of the patella. There the fibres become tendin- ous, and spread out to embrace the pitella, passing- all around it, some being- attached to its upper border, others extending- so as to run down upon its lateral borders, while others run upon its anterior surface, the posterior surface being- left free. This tendon passes downward until it reaches the lower portion of the anterior tubercle, where it is inserted, leaving- a little space between itself and the upper portion of the tibia, As the lig-amentum patellje descends towards its insertion, it does not diminish in size; but it g-ives off from its lateral aspect tendinous fibres, sometimes spoken of as the lateral patellar lig-aments, which pass around until they reach the joint; in other words, they form a complete capsule for the knee joint. This can be stated of every joint which carries a syno- vial membrane. The Posterior Lig-anie)it of the joint, one of the most peculiar in the body, is a set of fibres running- in different directions. In one way or another these are attached above the condyles of the femur. Some are attached at those depressions where the Gastrocnemius and the Plantaris rise; and then extend across the upper marg-in of the condyloid notch. The central fibres extend further up on the shaft of the bone; but these instead of running- downward, run backward and out- ward. The central and enlarg-ed portion of the attachment of the Semi-menbranus muscle is inserted into the front of the femur, and spreads upward and backward, consequently forming- the middle portion of the posterior lig-ament of the LIGAMENTS. 141 joint. Where the central fibres come in touch with the external head of the Gastrocnemius muscle, they blend with the fibres of that muscle. The lower fibres of the ligament are attached to the posterior surface of the tibia. The hiternal Lateral Lig-ament is attached above to the inner tuberosity of the femur; passes downward and is attached to the internal tuberosity of the tibia; but the fibres continue down to the internal face of the tibia. The External Lateral Ligament consists of two bundles of fibres; and is described by some as having- the same attachment below and a different attachment above. It is, properly speak- ing, all one ligament. Some anatomists assert that the muscle which passes over the joint constitutes the greater portion of the ligament, while others say that it does not enter into it at all. The origin of the Popliteus muscle and the origin of the long external lateral ligament of the knee joint are precisely the same thing. They are attached to the little groove on the outer surface of the outer tuberosity of the femur. From that point the external lateral ligament descends to become attached to the styloid process of the fibula. The remainder of it is nothing further than the tendon of origin of the Popliteus muscle. The interior of the Joint consists of a set of fibres, which are not ligaments, but are cartilages, without any function in binding the bones together. They serve mainly to deepen the cavit}', but are very peculiar in their arrangement, and have an entirely different function to perform. There is a synovial memVjrane between the cartilages and the tibia ; and it is between the semilunar cartilages and the upper extremity of the tibia that the fourth articulation, mentioned above as belonging to the knee joint, takes place. In the interior of the joint there are a pair of ligaments, or cartilages, the Semi-lu- nar cartilages; running across at the anterior aspect of the joint from one cartilage to the other is a small band forming a Tranverse ligament; binding these cartilages down to the bone are a set of very short fibres, known as the Coronary Ligarnenl ; then, in the interior of the joint, are seen two 142 DESCRIPTIVE ANATOMY. strong- cords which cross each other somewhat in the form of the letter X, one called the Anterior, or External, Crucial Lig-avient, the other the Posterior, or Internal, Crncial Lig-a- ment. In addition we have the folds of synovial membrane, one called the Lig-amenticni Mucosum, and the other the Liga- ment a Alaria. The attachment of the Senii-hinar cartilages is one of the most important thing^s, both anatomically and surg-ically, in con- nection with the knee joint. ^]\q. Externarv$> nearly circular, being- but slig-htly oval in its outline; the Internal, on the con- trary, is distinctly oval, being" long-er from before backward than from side to side. The external is attached just in front of the spine of the tibia; and, in the prepared specimen, is attached just between the spine and the anterior crucial lig-ament, blend- ing- with the anterior crucial. Behind, it is attached between the crucial lig-ament and the internal cartilag-e, so that it blends at both extremities with the crucial ligaments. The internal semi-lunar cartilage, which is much long-er than the external, passes around so as to be attached in front of the anterior crucial lig-ament. It does not blend with that lig-ament at all ; and, behind, the internal cartilag-e is not attached to the crucial lig-ament. The cartilag-e can be raised up in any direction, but is attached to the bone by the fibres of the capsular lig-ament of the joint. In truth it is not really attached to the bone, except just in front and just behind the anterior spine of the tibia. On the contrary, all of the fibres which enter into the formation of the lig-aments of this joint, with the exception of those composing- the Lig-amentum patellae, become attached to the edg-es of the semi-lunar cartilag-es; and from those edges they pass down as short fibres to seek their insertion in the tibia. They bind the cartilag-es in position, but leave them so as to be movable. The Anterior Crucial Ligament takes its orig-in from a point just in front of the spine of the tibia. Prom that orig-in it passes upward, outward, and backward; and is inserted into the internal face of the external condyle of the femur. The Posterior Crucial Ligament arises from behind the spine of the tibia; and is blended with the posterior extremity LIGAMENTS. 143 of the external semi-lunar cartilag-e. From that orig"in the direction of its fibres is upward, forward and outward; and consequently the two crucial lig"araents cross each other in the joint. When they come in contact with each other, the poste- rior crucial ligfament g-ivesolf a slip of fibres which decussates with the anterior crucial lio-ament. The posterior lig-anient then passes on to its insertion in the external face of the internal cond^de of the femur. The folds of the Synovial Membrane are mixed with fat. The Ligamentum Mucosiun v^, io\xn6i attached to the front of the inter-condyloid notch; and passes from that point, lying- bet ween the patella and the inter-condyloid notch of the femur, down to become attached to the lower extremity of the patella. From the lateral edg-es of the ligamentum mucosum are sent off the fring-e-like folds with masses of fat, spoken of as the Lig-amenta Alaria. The synovial membrane is the largest in the body, and extends to surrounding struc- tures. The membrane passes down from the articular surface of the femur; and reaches the lig^amentum muco- sum, which has a few ligamentous fibres. It then ascends and reaches the patella on the posterior surface of the anterior lig-ament; but a lateral view of it would continue its course down until it reached the upper surface of the tibia. It is a continuous sack. The lateral subdivisions pass downward; and leaving- the femur, pass upward as far as the articular surface extends in the mid-line, including the crucial ligaments. Traced forward from the crucial ligaments, the folds pass over the upper surface of the tibia, run over and line the semi-lunar cartilages, and then pass between the cartilag-es and the tibia, so as to form a sack. As the fold passes down- ward, the crucial ligaments are left out of the joint, another proof that must at one time have been separate and distinct articulations. While the synovial membrane is all one continu- ous sack, there is a space above the articular surface of the femur, which covers the non-articular surface, extending* to the point where the attachment of the Gastrocnemius commences. The membrane surrounds and embraces the crucial lio-aments 144 DESCRIPTIVE ANATOMY. and cuts them off from the joint; it extends down over the patella and the Ligfamentum patellae ; passes over the tibia, and in addition lies between the semi-lunar cartilag-es and the upper surface of the tibia, forming- a movable surface between the two. The membrane frequently communicates with little bursae which are found around this joint. The External Cartilage, just before it reaches its attach- ment, extends its transverse band across to become attached to the Internal Cartilage, thus forming- the Transverse lig-a- ment of the joint. Between the Li§ amentum patellcF and the upper surface of the tibia, there is a little sack, which does not communicate with the joint, but forms a bursa, so as to have a freely g-liding- tendon over the upper extremity of the tibia. At the back of the joint, beneath the two heads of the Gastrocnemius muscle, are found two more burs^. Beneath the tendon on the inner side is found another ; and on the outer side, beneath the ten- don of the Popliteus, is found another. Any one of these may, and frequently do, communicate with the joint ; hence they are known as the Synovial Bursce. Between the skin and the front of the patella is another bursa, which can be easily found in the healthy man and which does not communicate with the joint. It is a mucous bursa. Actions. This joint never makes the movement of a pure "hinge joint." If placed in a position of extreme flexion, the posterior portion of the condyles rests upon the posterior part of the semi-lunar cartilag-es. Place the knee in a position of half-flexion, and the central portion of the cartilag-e then rests upon the central portion of the c'ondyle, the axis of rotation having- chang-ed so that the tibia has been carried forward about half an inch. Bring the leg" further forward, and the axis of rotation will have been brought further forward. When the joint is drawn into a position of extreme fl.exion, the toe is bent only slig-htly forward ; when we pass from extreme flexion to extreme extension there is an inward rotation, which bring-s the toe out until is nearly in a straig-ht line. That is, there is, in addition to the rotation of flexion, an axial rota- LIGAMENTS. 145 tion, except for the fact that it takes place on two points instead of one. In addition to the movement between the femur and the tibia, there is, therefore, an actual rotation be- tween the semi-lunar cartilag-es and the tibia. Besides these, there is an incomplete rotation, a movement between the carti- lag-es and the femur ; and at the same place a constant move- ment of the patella on the femur. When the limb is in extreme flexion, only the lower portion of the patella is in contact with the femur ; when drawn up, the central or bulg-ed portion, is in contact with the femur ; and in extreme exten- sion, the upper portion is in contact with the femur. There is a line extending- from the centre of the patella vertically and another transversely ; and some say there is a third line, which completes the division of the patella into six separate compartments. The Muscles which strengthen the articulation are, prima- rily, the Triceps extensor cruris ; behind, the two heads of the Gastrocnemius and the Plantaris ; on the outer side, the tendon of the Biceps flexor cruris ; and on the inner side, the Semi-tendinosus, which is in reality the only one that strengthens the joint internally. The Popliteus pow^erfully streng-thens the joint upon its outer side ; and it is a powerful streng-thening- agfent on its posterior aspect. The arterial supply of the joint is furnished by articular branches from the popliteal, by the anterior and posterior recurrent branches of the anterior tibial, by the anastomotica magna branch of the femoral and by the descending- branches from the external circumflex. The nerve supply is derived from the external and internal popliteal, the obdurator and from the anterior crural. The Tibio-Fibular Articulation. The upper and lower extremities of these bones are held tog-ether by lig-amentous fibres, while there is a strong- interos- seous membrane extended between their shafts. The superior tibio- fibular joint is of the arthrodial variety and the bones are held together by anterior iva(S. posterior lig-a- mentous fibres, passing- directly between the contiguous sur- Des Anat— 10 146 DESCRIPTIVE ANATOMY. faces of the two bones. They are united by a few scattered fibres to protect the synovial membrane, forming- an imperfect capsule. The synovial memhrane sometimes communicates with the knee joint. The inferior tibio-Jibular joint is an articulation of the amphiarthrodial class. A rough surface is presented by each of the bones for the reception of the powerful interosseous lig-ament which passes between them. There are also anterior and posterior fibres passing- from one bone to the other, form- ing the anterior and posterior inferior tibio-fibular ligaments. The lower part of each bone presents a small smooth surface, coated with cartilage in the recent state whose synovial mem- brane communicates with the ankle joint. The interosseous vienibrane is composed of oblique fibres directed downward and outward and extending from just be- low the knee to within a short distance of the ankle. These fibres are attached to the interosseous ridges on the two bones. Above the membrane is seen an oval aperture for the trans- mission of the anterior tibial vessels. At its lower portion the membrane is perforated for the passage of the anterior pero- neal artery. Movements. A slight gliding movement only is permitted between the two bones above while below there is practically no movement, the little permitted being confined to a slight twisting of the fibres of the interosseous ligament. The Ankle Joint. This/o/;?/ belongs to the movable class and hinge or, more correctly, the mortise and tenon variety. Its articular surfaces are contributed by the lower extremities of the tibia and fibula, above, and the upper surface of the astragalus below. The ligaments consist of anterior, posterior and two lateral. The anterior, thin and fatty, is attached above to the front of the tibia just above its articular surface and below to the upper surface of the neck of the astragalus. Tho. posterior, more insignificant than the anterior, is mainly for the protection of the synovial membrane. It consists of a few scattered fibres attached above to the tibia and below to the OS calcis. IvIGAMEXTS. 147 The internal lateral or deltoid lig-ament, is a dense and powerful mass of fibres which embraces the tip of the internal malleolus by its apex and by its broad base is attached to the tuberosity of the scaphoid, to the inner face of the astrag-alus, below the articular facet, and to the os calcis, where it also serves to bind the astragalus and the os calcis to- gether. On section this ligament is seen to consist of two layers. The external lateral ligament, usually described as one, is really three separate ligaments. The anterior fasciculus, the weakest, is attached above to the anterior border of the exter- nal malleolus and passing downward and forward reaches the upper, outer aspect of the astragalus. The middle, passes from the tip of the malleolus vertically downward to the tubercle on the outer face of the os calcis. The posterior is attached ex- ternally to a deep depression on the inner face of the malleolus and passes horizontally inward to seize the outer face of the astragalus behind its articular facet. The synovial membrane is extensive and lines the inner face of the ligaments as well as the bones. The joint is strengthened behind by the tendo Achilles, which takes the place of a posterior ligament. Antero-inter- nally is the tibialis anticus, postero-internally the tibialis pos- ticus while externally are the two peroneal tendons. The flexor and extensor tendons are too lax to add any strength to the joint. The malleolar arteries supply the joint with blood while the anterior and posterior tibials give it its nervous supply. The movements are flexion and extension, although in one position a slight degree of lateral movement is permitted. In flexion the foot is drawn up toward the leg, the articular sur- face of the astragalus moving slightly backward in the receiv- ing cavity. Extension is the reverse of flexion. In forced extension the narrow part of the astragalus is brought forward into the broadest part of the receiving cavity, and in this posi- tion a slight degree of lateral movement is permitted. The Articulations of the Tarsus. The articulations of the tarsus consist of the articulation between the bones of each row and the union of the two rows. 148 DESCRIPTIVE ANATOMY. Calcaneo-Astragaloid Articulation. The two bones of the first row of the tarsus are held together by three ligaments, external, posterior and interosseous. The exierfial calcaneo-astrag-aloid ligament extends from the outer side of the astragalus, just behind and internal and as far as the anterior fasciculus of the external lateral of the ankle, to the outer face of the os calcis. It lies between the anterior and middle fasciculi of the external lateral. The -posterior calcaneo-astragaloid passes from the posterior extremity of the astragalus to the contiguous upper aspect of the OS calcis and is but a continuation of the protecting fibres, called the posterior ligament of the ankle. The interosseous is by far the most important bond of union between the two bones. It consists of a large number of fibres, filling the sinus tarsi, and passing directly and obliquely be- tween the surfaces which form that canal. The Articulation Between the Bones of the Second Row. The bones of the second row are held together by fibres passing across the dorsal and plantar faces and by interosseous fibres between opposing surfaces. The Articulation Between the two Rows. The two rows of the tarsus are held together by three sets of ligaments, two sets passing from the os calcis to the cuboid and scaphoid, though the latter does not articulate with it, and one set passing between the astragalus and scaphoid. Calcaneo-Cuboid Articulation. The ligaments binding the os calcis to the cuboid are four, two dorsal and two plantar. The superior calcaneo-cuboid'v^ thin and narrow and passes between the contiguous surfaces of the bones on the dorsum of the foot. The internal calcaneo-cuboid, or interosseous, is a thick short band of fibres springing from the depression between the OS calcis and the astragalus and inserted into the inner side of the cuboid. At its origin it is closely blended with the superior calcaneo-scaphoid. LIGAMENTS. 149 The lo72§' inferior calcaneo-ciiboid ligament is attached be- hind to the inferior surface of the os calcis from its posterior to its anterior tubercle ; and in front to the peroneal ridge on the under surface of the cuboid and to the bases of the meta- tarsal bones of the second, third and fourth toes. It is much thicker and stronger, as well as longer, than the short inferior calcaneo-cuboid, which lies immediately above it. The short inferior calcaneo-ciiboid ligament is about one inch in length. It is attached to the anterior tubercle of the OS calcis and to the bone in front of it as far as the margin of the articular surface ; and, b}" its anterior extremity, to the under surface of the cuboid behind the peroneal ridge. Calcaneo-Scaphoid Ligaments. Connecting the os calcis and scaphoid are two ligaments, superior and inferior calcaneo-scaphoid. The superior, one arm of the Y lig-ament, the other arm being furnished by the internal calcaneo-cuboid, passes for- ward and inward from the front upper part of the os calcis to the scaphoid. The inferior calcaneo scaphoid is much stronger than the superior and passes from the inner front aspect of the os calcis, beneath the head of the astragalus, to the lower surface of the scaphoid. The Astragalo-Scaphoid Articulation. The only ligament connecting the astragalus and the scap- hoid is the superior astrag-alo-scuphoid which is thin and weak and passes from the neck of the astragalus to the upper sur- face of the scaphoid. The Tarso-Metatarsal Articulation. The first metatarsal bone articulates with the internal cunei- form ; the second, with the middle cuneiform, by its base, and laterally wMth the internal and external cuneiform bones, being jammed between these and extending farther back than the other metatarsal bones ; the third articulates with the external cuneiform, and the fourth and fifth with the cuboid. The tarsus is held to the metatarsus by dorsal "AXiA plantar lig-amentous fibres and by three interosseous lig-aments — one 150 DESCRIPTIVE ANATOMY. from the internal cuneiform to the second metatarsal and one from the external cuneiform to the third metatarsal. The metatarso-phalangeal, the inter-phcdang-eal and the '' inter metatarsaV are exactly similar to those of the hand. Costo- Vertebral Articula,tion. The parts of the skeleton which enter into a costo-vertebral articulation are the posterior extremity of the rib, the body, and transverse process of a dorsal vertebra and the interverte- bral disk. This articulation is of the diarthrodial class and the arth- rodial variety. The ligfaments which connect the head of the rib with the vertebral column are the anterior costo-vertebral, capsular and interarticular. The anterior costo-vertebral is attached to the anterior aspect of the head of the rib, and radiates in three bundles, the upper of which is attached to the body of the vertebra above, the lower to the vertebra below, and the middle to the interverte- bral disk. Owing" to the divergence of its fibres, this ligament is known as the stellate. The arrangement differs from the foregoing description in the first, eleventh and twelfth ribs, where the ligament is attached to only one vertebra, as the articular facet is furnished wholly by one vertebra. The capsular lig-ament consists of a few scattered fibres around the articulation. The interarticular lig-ament is attached to the ridge on the head of the riband to the intervertebral disk, thus dividing the joint into two parts, each furnished with a separate synovial sac. For the reason above given, the first eleventh and twelfth have no interarticular ligament and but one synovial sac. The articulation between the ribs and the transverse pro- cesses,known as the costo-trans verse articulation, presents three ligaments — anterior, middle and posterior costo-transverse. The anterior costo-transverse extends from the neck of the rib to the transverse process above; the jfiiddle, or interosseous, extends from the posterior surface of the neck of the rib di- rectly backward to the transverse process; t\iQ. posterior extends from the tubercle of the rib to the apex of the transverse process. THE VISCERA. 151 THE VISCERA. The Alimentary Canal and Appendages. . The alimentary canal beg-ins at the mouth and ends at the anus, the intermediate portions being- found in the neck, thorax and abdomen. In the neck are \h.<$. fauces , pharynx and part of the aesophag-ns; in the thorax is the remaining- portion of the oesophagus, while the rest of the canal is found in the abdomen. The Mouth. The mouth beg-ins at the lips and terminates behind in a short constricted portion called the fauces. It is bounded above by the hard palate, below by the tong-ue and on each side by the cheeks. The lips are two, upper and lower, separated by the trans- verse labial fissure. Each is formed chiefly by itsseg-ment of the orbicularis oris muscle, covered externally by skin and internally by mucous membrane, a concentric fold of which, called frcjenum labii, extending- in the middle line from each lip to the g-um behind. The cheek consists chiefly of the buccin- ator muscle, covered externally by skin and internally by mu- cous membrane, which is reflected from it to the g-um and presents, opposite to the second molar tooth of the upper jaw, the opening-, on a papilla, of Stenson's duct from the parotid g-land. The hard palate is formed anteriorly by the meeting- in the middle line of the palate processes of the superior maxillary, and posteriorly by the horizontal plate from each palate bone. It is boundfed'"in front and at either side by the aveolar processes of the superior maxillary bones, containing- the teeth of the upper jaw. It is covered by mucous membrane both above and below, forming- the floor of the nasal fossa} above and the roof of the mouth, below ; on the latter aspect the mucous membrane is roug-hened by g-lands, called palatal, and is continued on to the g-ums. 152 DESCRIPTIVE ANATOMY. The floor of the mouth is formed by the anterior two-thirds of the tong-ue, the posterior third the tong-ue forming- the floor of the fauces, and, below that, entering" into the forma- tion of the anterior wall of the pharynx. The tongue is flattened from above downward, is conical in shape and curved in direction, being- convex above antero- posteriorly, and extends from the hyoid bone behind to the incisor teeth in front, its base being- adherent to the hyoid bone and its apex free and anterior. The mucous membrane covering- the dorsum of the tong-ue passes around the sides and tip, thus enveloping- most of the org-an, and leaves the lower surface to become continous with that lining- the g-um of the lower jaw. In contact with the posterior part of the dorsum is the front of the epig-lottis, which is held to it by three folds of mucous membrane, the g-losso-epig-lottic lig-aments, middle and two lateral. The mucous membrane covering- the tong-ue and mouth is continued back throug-h the fauces to blend with that which lines the g-uUet. The Fauces. '\^\\Q. fauces, or isthmus of the fauces, is that narrow part of the alimentary canal which connects the mouth posteriorly with the front of the pharynx. It is about one and one-half inches long-, about the same in width, and rather less in depth; the size, however, varying- g-reatly, for its walls are chiefly formed of muscular tissue, which is peculiarly subject to reflex action. The roof of the fauces is the soft palate; the floor is a part of the dorsum of the tong-ue; the sides are formed by two arching- muscles, and, between them, the tonsil g-lands. The muscle in front is the palato-g-lossus, forming- the anterior pillar of the fauces; that behind is the palato-pharyng-eus, forming- the posterior pillar of the fauces. The wall, in every aspect, is covered by mucous membrane. Soft Palate. The soft palate, or velum penduluni palati, is thin and flattened from above downward and forward. It is attached THE VISCERA. 153 above to the posterior border of the hard palate aad hangs downward and backward, separating- the fauces from the upper part of the pharynx. It is prolong-ed, in the middle line below, by a nipple-like projection, some half an inch long, called the uvula. Pharynx. Food, in order to reach the stomach, passes through four successive portions of the alimentary canal. The first two of these have been described, vix : the mouth and fauces. Leav- ing the latter, food enters the pharynx, whence it passes to the (esophagus, in which the pharynx terminates, and the oesophagus conveys it to the stomach. The Pharynx is an oblong tube situated behind the larynx and extending from the lower face of the basilar process of the occipital to the fifth cervical vertebra where it terminates in the oesophagus. By the lower margin of the soft palate it is divided into an upper portion, establishing communication between the nasal cavities and the larynx below, and the same cavities and the middle ear on the side, through the Eusta- schian tube ; and a lower portion receiving the opening of the fauces above and opening into the oesophagus below. By its musculo-aponeurotic fibres is attached to all of the surround- ing firm structures, base of the occipital bone, pterygoid pro- cesses of the sphenoid, base of the tongue, hyoid bone, infe- rior maxillary and the larynx. From the occipital down to the attachment to the cartilages of the larynx it is a large cavity always held open by its attachment to the firm sur- rounding structures ; but from the larynx to its termination, the anterior and posterior walls are more or less closely in contact, except during the act of swallowing. The muscular wall is deficient above and behind, where a concave space is seen on either side above the superior constrictor where the pharyngeal aponeurosis is thicker than elsewhere. In the anterior wall, above the soft palate, the openings of the poste- rior nares are seen on either side ; while further out and oppo- site the posterior extremity of the inferior turbinated bones, may be seen the openings of the Kutaschian tubes. 154 DESCRIPTIVE ANATOMY. Below the soft palate the opening- for the fauces ocupies the whole of the anterior wall, while below this is the antero-pos- terior opening- of the larynx, behind which is the transverse, slit like opening into the oesophag-us. The pharynx is sepa- rated from the front of the bodies of the upper five cervical vertebrae by a layer of the deep cervical fascia and some loose connective tissue. It is about four and one half inches in length and tapers as it descends. Structure. The Alimentary Canal is throughout made up of an inter- nal mucous coat, resting upon a thin fibrous layer which is in turn supported by muscular fibres. In the tongue, soft palate and pharynx the muscular coat makes up the bulk of the organ, but the arrangement differs in each and will now be described. The Tong-iie consists of two sets of fibres, called intrinsic and extrinsic muscles of the tongue. The extrinsic muscular fibres seek points of attachment to surrounding hard parts, their lingual extremities then passing into the tongue to blend with the intrinsic muscles found there. These muscles are the following : Extrinsic Stylo-Glossus Hyo-Glossus Palato-Glossus Genio-Hyo-Glossus Intrinsic Superior Lingualis Inferior Lingualis Vertical Lingualis Transverse Lingualis The Stylo-Glossus arises from the anterior and outer side of the styloid process of the temporal bone near its apex, and from the stylo-maxillary ligament, and passing downward, forward and slightly inward is inserted into the side of the tongue, its fibres running as far as the tip where they meet with the muscle of the opposite side. The fibres of this mus- cle blend with those of the superior and inferior lingualis. The Hyo-Glossiis is a flat quadrilateral muscle which arises from the side of the body and both cornua of the hyoid boue. THE VISCERA. 155 passes directly upward and is inserted into the whole length of the tong-ue, to the inner side of the Stylo-Glossus, its fibres blending^ with the vertical ling-ualis. The Palato-Glossus is a small muscle found occupying the anterior fold of the fauces. Arising- in the soft palate it pas- ses downward and inward and is inserted into the side of the tongue, its fibres blending with the transverse lingualis. The Goiio-Hyo-Glossus is a thin, radiated, fan shaped mus- cle found lying close beside its fellow near the mid line and extending from base to apex of the tongue. It arises by its apex from the superior genial tubercles and is inserted into the whole length of the tongue, some of its posterior fibres being attached to the body of the hyoid bone. Its fibres blend with the vertical lingualis, running between the fibres of the longitudinal and transverse lingualis. These muscles are all, except the Palato-Glossus, supplied by the hypoglossal nerve. The Palato-Glossus is supplied by branches from the pharyngeal plexus. The lingual artery is the source of the blood. The Tongue I?, divided by a vertical fibrous septum which occupies the middle line and receives the insertion of the transverse lingualis muscle. The intrinsic fibres, largely de- rived from the extrinsic, are two superficial sets, superior and inferior, which extend from base to apex of the organ, and a transverse and vertical set, the one running from the upper to the lower surface and the other from the septum to the lateral edges. These latter fibres are mingled with each other so as to form a muscular net work extending throughout the tong-ue. Aclion. The intrinsic muscles can act only to produce changes in the shape of the tongue, while the extrinsic not only change the shape but the position as well. The Stylo- Glossiis can draw the tongue upward and backward, or, if one muscle alone acts, upward, backward and toward the side of the muscle acting. The Ifyo-Glossiis draws the tongue downward and backward, increasing the si/.e of the fauces and aiding the intrinsic fibres in shortening the organ. The Pa/a/o-Glossiis widens the tongue and elevates its base, depresses the soft 156 DESCRIPTIVE ANATOMY. palate and constricts the fauces while the Genio-Hyo- Gloss us draws the tong-ue forward by its posterior fibres, shortens it by the approximation of posterior and anterior, while the central fibres depress the org-an and make the dorsal face concave. The lower fibres can draw upward and forward the hyoid bone. Muscles of the Soft Palate. L/evator Palati Tensor Palati Azyg-os Uvulse Palato Glossus Palato-Pharyng-eus The Palato-Glossus was described with the muscles of the tongue. Levator Palati, The levator palati arises from the roug-h surface on the basilar face of the petrous bone, near its apex, and from the cartilag-inous portion of the E^ustachian tube, and descends to be lost in the soft palate. Its name indicates its action. Tensor Palati. The tensor palati is a small muscle which forms a rig-ht ang-le on itself, hence its synonym of circumflexus. It arises from the scaphoid fossa of the pteryg"oid process, from the spinous process of the sphenoid bone and from the cartilag-i- nous portion of the E)ustachian tube, and, first descending- vertically, then turning" transversely inward around the hamular process, it spreads out into a broad aponeurosis in the soft palate. Its action is indicated by its name. Azygos Uvulse. From the posterior termination of the soft palate there hang's pendulous, in the centre, a short, conical mass called the uvula, which, when dissected, is found to consist, exteriorly, of mucous membrane and, interiorly, of a. pair of minute muscles, each of which, arising from the palate spine, descends beside its fellow and is lost in the mucous membrane of the uvula. These two muscles were formerly considered as one, hence their name. It is their presence in the uvula which accounts for its constant and varied movement. THE VISCERA. 157 Palato-Pharyngeus. The Palato-Pharyug-eiis arises in the soft palate and passes downward and backward to enter the wall of the pharynx, where some of its fibres are lost, the rest being inserted into the posterior border of thethj^roid cartilag-e. Its action is the same as the preceding- muscle and its synonym is constrictor isthmii faucium posterior. The Muscles of the Pharynx. The Pharynx is lined by raucous membrane, resting on a thin fibrous coat. External to the mucous coat is a muscular coat consisting, like that of the intestines, of circular and lon- gitudinal fibres, but differing in that the muscular fibres are here red and not pale, and are gathered into bundles which are described as separate muscles. The circular fibres are arranged in flattened bundles on each side, each bundle inter- secting its fellow of the opposite side on the middle of the back of the pharynx where they form a raphe. Each pair of bundles overlaps the lower edge of the pair above. When traced from the raphe forward it is seen that these fibres do not encircle the entire pharynx but pass from its sides to seek firm neighboring points of attachment, from which to exert traction, thus leaving the front of the pharynx devoid of mus- cular fibres, this part of its wall being formed by mucous membrane alone. The larynx resting on the front of the pharynx, is in contact with the mucous membrane and is em- braced by these circular fibres. These muscles, from their action, are known as the constrictors of the pharynx; and as there are three separate bundles, they are described as supe- rior, middle and inferior constrictors. The direction of their fibres is not horizontally backward but backward and upward. Inferior Constrictor. The inferior constrictor arises from the oblique line on the ala of the thyroid cartilage and surface behind it, from the side of the cricoid cartilage and from the two upper rings of the trachea. It runs backward and upward, its upper fibres 158 DESCRIPTIVE ANATOMY. passing* obliquely upward, overlapping- the middle constrictor and is inserted into the raphe of the pharynx. Middle Constrictor. The middle constrictor 2lx\'s>q.^ from bothcornua of the hyoid bone, and from the stylo-hyoid lig"ament, a fibrous cord extend- ing- from the hyoid bone to the styloid process. The fibres radiate somewhat, spreading- out on the side of the pharynx, and are inserted into the raphe. The inferior fibres are over- lapped by the inferior constrictor, and the superior fibres overlap the superior constrictor. So g-reat is this overlapping- that when viewed from behind but little of the superior con- strictor can be seen, the raphe of the middle constrictor ex- tending- to the basilar process. Superior Constrictor. The superior constrictor lies just beneath the skull and is overlapped by the middle. It arises from the lower one-third of the internal pteryg-oid plate, from its hamuiar process, from the pteryg-o-maxillary lig-ament, from the extremity of the molar ridg-e of the lower jaw, and by a few fibres from the side of the tong-ue. It passes backward and is inserted into the raphe, which is attached to the basilar process. The upper edg-e of this muscle presents a concave border, thus leaving- an arched interval between it and the skull above, over which the fibrous tissue beneath the mucous membrane ^f the phar- ynx extends and is here so much thickened as to form a strong- fibrous membrane. The long-itudinal fibres of the pharynx are, like the circu- lar, g-athered into bundles, of which there are two pairs. These are described as distinct muscles arising- from points above the pharynx and inserted into it. One of them, the palato-pharyng-eus, has been described as a part of the soft- palate ; the other is known as the stylo-pharyng-eus. Stylo-Pharyngeus. The stylo-pharyng'eus arises from the inner side of the base of the styloid process and descends to the side of the pharynx, THE VISCERA. 159 enteriiig- its wall between the superior and middle constrictors. Some of the fibres are lost in the pharynx, while some are continued to the posterior border of the thyroid cartilag-e. Action — it elevates and widens the pharynx. (Esophagus. The CEsophagus continues the course of the alimentary canal from the termination of the pharynx, at the commence- ment of the trachea on the front of the body of the fifth cervi- cal vertebra, down the front of the vertebral column, throu^-h the neck and thorax, to pierce the diaphrag-m at the (esopha- geal opening-, opposite the tenth dorsal vertebra, and terminate at the cardiac orifice of the stomach. It is about nine inches long-. In structure the oesophag-us resembles the pharynx, but its muscular coat is not arrang-ed in distinct bundles. It is the narrowest part of the alimentary^ canal, but the most muscular. Relations of Pharynx and (Esophagus. In addition to the structures mentioned as opening- into or being- connected with the Pharynx, it has important relations to structures on the side of the neck. Thus on either side are the muscles attached to the styloid process of the temporal and internal to these the internal jug-ular vein and internal carotid artery; and, between these two, the ninth, tenth and twelfth nerves, with the sympathetic behind. Below the parotid gland the external carotid artery becomes an external relation, while the ling-ual lies on the middle constrictor. Below the upper border of the thyroid cartilag-e the common carotid becomes the external relation. Relations of the (Esophagus. The relations of VtiQ CEsophagus must be studied in the neck and in the thorax. The g-uUet is about nine or ten inches in leng-th, extending- from the disk between the fifth and sixth cervical vertebrae to the front of the body of the tenth dorsal. It is not a straig-ht tube but presents antero-posterior curves, corresponding- to the curvatures of the spinal column. There 160 DESCRIPTIVE ANATOMY. are also three lateral curvatures — two to the left and one to the risfht. At its commencement it lies on the middle line of the body but curves to the left until it reaches the root of the neck. From this point it curves to the rig^ht until it ag-ain reaches the middle line, opposite the fifth dorsal vertebra, and from there passes steadily to the left ag-ain until it terminates oppo- site the body of the tenth dorsal vertebra. In the cervical, and upper part of the thoracic portions, the oesophag-us is separated from the front of the vertebral column by a layer of fascia and by the long-us colli muscles, particu- larly the muscle of the left side. In the lower part of the thoracic portion it is more widely separated from the vertebrae. The trachea lies in front of the oesophagus which is thus shut off from contact with the thyroid gfland, except that the left lobe of the latter touches the oesophag-us on the left side. The left and right common carotid arteries are lateral relations, the left being- nearer than the right. At the root of the neck the thoracic duct is a left and slightly posterior relation while the left recurrent laryngeal nerve lies in the g-roove between the trachea and oesophag-us. In the thorax the oesophagus first lies behind the lower part of the trachea, which separates it from the transverse aorta, and then behind the bifurcation of the trachea and the left bronchus. Below the trachea the pericardium lies on the front of the oesophag-us to its termination. Laterally the g-ullet is in contact with the two pleurae, although the left is a relation for a g-reater distance than the right. To the rig-ht above, and separated from it by the trachea, is the innominate artery, and below this, the vena azyg-os major is for a moment to the right side. On the left is the left common carotid artery, while the left subclavian is a more distant relation. The descending aorta becomes a left relation at the lower border of the fourth dorsal vertebra and remains a left relation to the upper border of the seventh dorsal, below which point the aorta is behind and finally behind and to the right. Behind are the longus colli muscle above, and the recurrent laryngeal nerve of the left side from the transverse aorta upward. The thoracic duct is a posterior relation throughout the thoracic THE VISCERA. 161 portion, but, below the transverse aorta, lies in the interval between the aorta and the oesophag-us. The vena azygos major is a posterior relation, while the azyg-os minor crosses behind, opposite the sixth dorsal vertebra. The right pneumog*astric nerve lies behind while the left lies in front. The relation to the aorta is a fourfold one and should be thus stated, viz ; the oesophao-us first has the transverse aorta in front, then the descendinor aorta first to its left side, then behind and, at the termination of the oesophao-us, the aorta is to the right and behind. The Abdominal Viscera. The cavity of the abdomen is bounded above by the diaphragm, which is a thin arched muscle with its cavity downwards, form- ing the floor of the chest and the roof of the abdomen. The floor of the abdomen is the floor of the pelvis, i. e. the structures which close the outlet of the pelvis. Occasionally the floor is given as the brim of the true pelvis and the iliac fossas, the true pelvis being then considered a separate cavity Laterally and in front, from the lower ribs above to the ilium below, the abdominal wall is formed of soft tissues, muscles, &c. , and is the soft, fleshy front wall of the belly. At its upper part the cavity is partly circumscribed by the lower ribs — the last six or seven ; below, by the bony w^all of the pelvis ; behind, by the lumbar portion of the vertebral column ; while on each side are, above, the floating ribs, below, the pelvic wall, and between the two, the soft tissues. For convenience of description the abdomen is arbitrarily divided into three zones, and each of these into three regions, by two horizontal and two vertical imaginary lines. The upper horizontal line is drawn between the extremities of the ninth ribs : the lower between the anterior superior spinous processes of the ilia. The vertical lines, one on each side, are projected upward from the middle of the fold of the groin. The names of the nine regions are as follows : The central region in the upper zone is the Epigastric, the one on either side IIypocho}idriuc, right and left ; the central region in the middle zone Is the Umbilical, the one on either side Lumbar y Des Anat — 11 162 DESCRIPTIVE ANATOMY. rig-ht and left ; the central region in the lower zone is the Hypogastric, the one on either side, iliac, rig-ht and left. The contents, of the abdomen are the greater part of the alimentary canal, the accessory org-ans of dig^estion — liver, spleen and pancreas — and the g^enito-urinary org-ans — kidneys and supra-renal capsules, the bladder and its appendag-es, prostate gland, seminal vesicles and vas deferens. The testicles are considered vv^ith the abdominal viscera, althoug-h, in the '^Udult, lying in the scrotum, outside the abdominal cavity. In the female there are the uterus and its appendages and the vagina. E^nveloping most of these organs, and lining the walls of the cavity, is a serous membrane, called the peritoneum. The following are portions of the alimentary canal contained in the abdomen: 1st, iho. ^stomach; 2d, small intestine ; 3d, large intestine. The stomach is the dilated part which succeeds the oesophagus and is about twelve inches long. It terminates, about the line which separates the epi- gastric from the right liypochandriac reg-ion in the small intestine. The small intestine is divided into three parts, diiodemun, jejiiniun and ileum. The diiodemim is about nine inches long ; the jejunum and ileum, together about twenty feet, the jejunum comprising the upper two-fifths and the ileum the lower three-fifths. The duodenum is again subdi- vided into three portions, viz : first portion, ascending, or oblique duodenum, is about two inches long and terminates at the neck of the gall bladder, on the lower surf ace of the liver, in the right hypochondriac region in the second portion, called the descending or perpendicular duodenum, which passes vertically downward for about three inches into the right lumbar region, about on a level with the upper border of the fourth lumbar vertebra, where it terminates in the third por- tion called the transverse duodenum, which is rather more than three inches long and crosses the front of the vertebral column obliquely upward and terminates at the left side of the body of the second lumbar vertebra, in the jejunum. The large intestine is subdivided into three portions called caecum, colon and rectum. The caecum is the commencing THE VISCERA. 163 two and one-half inches, lies in the rig-ht iliac fossa and termi- nates in the colon at the opening- of the small intestine. The colon is divided into the ascending', transverse and descending" colon and the sigmoid flexure. The ascending passes upward throug-h the rig-ht lumbar reg-ion into the rig-ht hypochondriac. At the under surface of the liver it curves sharply to the left, forming- the hepatic flexure of the colon, and becomes the transverse colon. The transverse Q,rce~ vertebral. The two scaleni muscles are distinguished as scalenus anti- cits and posticus. A small portion of the scalenus posticus is sometimes individualized as the scalenus medius. These muscles are of great importance owing to the fact that they occupy a position in the lower part of the side of the neck, and come into important relation with the subclavian arterj^ and brachial plexus of nerves. Scalenus Anticus. The scalenus anticus, triangular in shape, arises from the anterior tubercles of the transverse processes of the third, THE MUSCULAR SYSTEM. 229 fourth, fifth and sixth cervical vertebrae by tendinous slips, which, uniting- as they descend, form the muscle. It is in- serted b}' a narrow tendon into the upper surface of the first rib. Scalenus Posticus. The scalenus posticus arises from the posterior tubercles of the transverse process of all the cervical vertebrae except the first. It descends and divides into two portions, one of which is inserted into the first rib between its tubercle and ang-le — and is the part sometimes called scalenus medius — while the other goes to the same point on the second rib. The scaleni, acting- from above, draw up the first and second ribs, being- muscles of inspiration. Acting- from below they can draw the neck downward and to the side of the muscles acting-; or, the muscles of both sides acting-, can flex the spinal column. The nerve supply is from the lower three cervical nerves. Prevertebral Group. Rectus Capitis Anticus Major Long-us Colli Rectus Capitis Anticus Minor Rectus Capitis Lateralis Rectus Capitis Anticus Major. This muscle arises from the anterior tubercles of the trans- verse processes of the third, fourth, fifth and sixth cervical vertebra by small tendinous fasciculi which terminate in a flattened muscle. The muscular fibres terminate in a flat aponeurosis which is inserted into the basilar process of the occipital, in front of the foramen mag-num. Rectus Capitis Anticus Minor. This is a small muscle lying- beneath the preceding- and fur- ther from the mid-line. It arises from the transverse process of the atlas and is inserted into the basilar process of the occip- ital, slig-htly external to the preceding-. Rectus Capitis Lateralis. This muscle belong-s properly to the lateral vertebral reg-ion and is an inter-transverse muscle. It arises from the trans- verse process of the atlas and is inserted into the jug-ular pro- cess of the occipital. 230 DESCRIPTIVE ANATOMY. Longus Colli. This muscle might be appropriately described as three. One arises from the transverse processes of the third, fourth and fifth cervical vertebrae and is inserted into the transverse pro- cess of the atlas. The second arises from the bodies of the upper three dorsal vertebrae and is inserted into the transverse processes of the third and fourth cervical. The third division arises from the three upper dorsal and four lower cervical and IS inserted into the second and third cervical. The muscles act so as to flex and rotate the head and cervi- cal vertebrae. Anterior branches from the cervical nerves supply these muscles. The Muscles of the Back. These muscles are arranged in several superimposed layers and are covered by a superficial fascia which varies in thick- ness indifferent regions. In some situations, as in the lumbar region, it usually contains a large amount of fat; in other por- tions it is a thick, loosely woven connective tissue, not easily divisible into layers, but everywhere allows free movement of the skin. Many of the muscles arise from, or are covered by, a dense connective tissue iovmin^ih.Q. vertebral aponeurosis. This fascia is attached to the spines and transverse processes of the vertebrai from which points it sends out septa which not only give origin to muscular fibres, but serve as sheaths for some of the muscles. First Layer. Trapezius Latissimus Dorsi Trapezius. The tra-pezius arises from the superior curved line of the oc- cipital bone, from the posterior occipital protuberance and from the spinous processes of all the dorsal and cervical vertebrae. The fibres converge outward, some ascending obliquel}^, some descending obliquely and some running horizontally, to reach the insertion into the outer third of the clavicle, the acromion process and whole length of the spine of the scapula. Its insertion is the same as the origin of the deltoid. THE MUSCULAR SYSTEM. 231 Extending' from the posterior occipital protuberance to the seventh cervical /ertebra, and attached to the intervening- spinous processes, is a fibrous cord called lig-amentum nuchas ; and it is in reality from this cord that the trapezius arises. Nearly the whole of the orig-in of this muscle is tendinous. The central portion of the tendon is broad and thin and forms a diamond shaped space between the two muscles. Action — According" to the direction of the fibres which act it can draw the scapula directly backward, downward and back- ward or upward and backward. Latissimus Dorsi. The latisshmis dorsi arises from the spinous processes of the lower four or six dorsal vertebrs, all the lumbar vertebrae and fhe spinous tubercles of the sacrum, from the p^osterior third of the crest of the ilium and by fleshy slips from the three or four lower ribs. The muscle is tendinous at its ori- gin except that part arising* from the ribs. As it passes up- ward and outward the fibres converg-e, become thicker and fleshy and passing- over the lower ang-le of the scapula, wind around the teres major to be inserted along- with it into the posterior bicipital ridg-e of the humerus. The tendon of the teres major is wider and extends further down on the humerus than that of the latissimus dorsi. Action — It carries the humerus downward and backward, rotates it inward, is an inspiratory ag-ent, and, when the humerus is fixed, as in climbing- or using- crutches, it moves the body forward. The trapezius is supplied by the spinal accessory and branches from the anterior divisions of the third and fourth cervical. The long- sub-scapular supplies the latissimus dorsi. Second Layer. Levator Ang-uli Scapula; Rhomboideus Levator Anguli Scapulae. The levator aiif^uli scapuhc arises by tendinous slips from the posterior tubercles of the transverse processes of the four 232 DESCRIPTIVE ANATOMY. Upper cervical vertebrae. These slips unite to form the belly of the muscle which descends obliquely outward to be inserted into the posterior border of the scapula from the angle to the intersection of the spine with that border. This muscle draws the shoulder upward and inward, or, actino- from below, inclines the neck and head to that side, rotating" them at the same time. The nerve for the levator is from the anterior divisions of the third and fourth cervical. Rhomboideus. The rhoniboideiis arises from the spinous processes of the last cervical and four upper dorsal vertebrae, and passing- down- ward and outward is inserted into the posterior border of the scapula as far as the inferior ang-le. Some make two muscles of this, calling" the portion which arises from the cervical ver- tebra rhomboideus minor and that arising" from the dorsal ver- tebrae rhomboideus major. Action — It moves the scapula upward and backward, so as to bring" the two scapulae nearer tog"ether. Third Layer Serratus Posticus Superior Serratus Posticus Inferior Splenius Serratus Posticus Superior. The serratus -posticus superior has a tendinous origin from the spinous processes of the two lower cervical and two upper dorsal vertebrae. It passes downward and outward and is in- serted by fleshy serrations into the upper borders of the second, third, fourth and fifth ribs just beyond their ang"les. Action — It is an inspiratory agent. Serratus Posticus Inferior. The serratus posticus inferior has a tendinous orig"in from the spinous processes of the last two dorsal and first two lum- bar vertebrae. It passes upward and outward and is inserted by fleshy slips into the lower borders of the last four ribs. Action — It is an expiratory agfent. THE MUSCULAR SYSTEM. 233 Splenius. The sploiins arises from the spinous processes of the four lower cervical vertebrae and four or six upper dorsal vertebras. It ascends and divides into two portions, one, known as the spioiiKs capitis, is inserted into the occipital bone between its curved lines and into the mastoid portion and process of the temporal bone ; the other, called splenius colli, is inserted into the posterior tubercles of the transverse processes of the three upper cervical vertebras. Action — It bends the head and upper part of the spine back and rotates the head toward its side. Erector Spinae. This powerful muscle occupies a larg^e portion of the vertebral ^•roove, extending- from the sacrum upward until its prolong-a- tions may be traced throug-h the cervical reg^ion. It is held down in position, throug-h a larg-e portion of its course, by the powerful vertebral aponeurosis, call by different names in the different reg-ions. In the lumbar region, where it is most powerful, it is continuous with the aponeurosis forming- the sheath of the quadratus lumborum. The erector spincc arises by tendinous fibres from the back of the sacrum, occup^ang- the whole of the sacral groove ; from the posterior part of the crest of the ileum : from the great sacro-sciatic ligament and from the spinous processes of the lumbar vertebrae. This larg-e mass passes upward and, about opposite the last rib, it divides into two portions, the ilio-costalis, which is inserted into the seven lower ribs and the lonn-issiiims dorsi which is inserted into the transverse processes of the dorsal vertebras and into nearly all the ribs, this portion of the insertion being- very variable. Between these two divisions lies an accessory muscle, called musculns ucccssorius which, arising- from the ang-les of the six lower, is inserted into the ang-les of its six upper ribs. Continuing- this upward is the cervicalis ascendcus which, spring-ing- from the ang-les of the four upper ribs is inserted into the posterior tubercles of the transverse processes of the fourth, fifth and 234 DESCRIPTIVE ANATOMY. sixth cervical vertebrae. In like manner the long-issimus dorsi is continued upward by an inner set of fibres the traiisversalis colli which spring's from the transverse processes of the six upper dorsal and is inserted into the cervical as hig-h as the second ; and the trachelo-mastoid which arises from the trans- verse processes of the dorsal vertebrae from the second to the sixth is inserted into the mastoid process. Beside these there are two small muscular masses, the spi-- nalis dorsi, in the lumbar, and spinalis colli in the cervicaj regfion which spring* from the transverse processes below and are inserted into those above. They are really part of the attachment of the long-issiumses dorsi. The complexus is a somewhat similar offshoot of the trachelo-mastoid arising- by slips from the upper seven dorsal and last cervical vertebrae to be inserted into the occipital between the curved lines. The name almost sufficiently g"ives the action of the erector spin« — it keeping- the body in the erect posture. It can also bend the spine backward, or backward and to one side when one muscle alone acts. This muscle is supplied by the posterior divisions of the spinal nerves in the cervical dorsal and lumbar reg-ions. Beneath this layer there is another of small muscles which barely deserve mention. The most important being- the rectus capitis posticus major and minor, the former spring-ing- from the spinous process of the axis and being- inserted into the inferior curved line of the occipital; the latter arising- from the tubercle of the atlas and being- inserted into the occipital internal to the preceding- muscle. The Muscles of the Thorax. Triangularis Sterni. The triangularis sterni is found on the posterior aspect of the front wall of the chest on either side of the sternum. It arises from the edg-e of the sternum and from the costal carti- lag-es from the third to the sixth or seventh, and, passing* upiL'a7'd 3Lnd outzuard, is inserted into the second, third, fourth THE MUSCULAR SYSTEM. 235 and fifth costal cartilag'es and corresponding' ribs. Its inser- tion corresponds to that of its antag-onist the serratus posticus superior. Action — It is an expiratory ag"ent. Intercostal Muscles. The interval between two ribs is occupied by two layers of muscular fibres which extend between the edges of adjacent ribs and are known as external and internal intercostal muscles. Anterior Thoracic Region. Pectoralis Major Pectoralis Minor Subclavius The muscles of this region are covered by the usual super- ficial fascia and by a deep fascia which partly blends with that of the cervical and, at the side, with that covering the axil- lary space. Pectoralis Major. The pectoralis Diajor derives its name from its position on the front of the chest, and from the fact that there is another muscle smaller than it in the same region. It is coarse in structure, triangular in shape with its base within and apex without. It arises fleshy from the sternal two-thirds of the clavicle, from the whole length of the front of the sternum and from the cartilages of five ribs, /. e. all of true ribs except the first and seventh (this origin being* by fibres which rein- force the muscle as it passes over the ribs) and from the aponeurosis of the external oblique muscle of the abdomen. The fibres converge as the}- pass outward. Those from the clavicle pass nearly vertically downward, those from the lower part of the sternum and the aponeurosis of the external oblique pass obliquely upward and outward and the intermedi- ate fibres pass hori/.ontally outward. They all terminate in a folded tendon which is inserted into the anterior bicipital ridge of the humerus. As the fibres are approaching their termination some fold over the others, those from the lower portion of the origin of the muscle passing behind and forming the upper part of the tendon, those from the clavicle passing in front and forming the lower part of the tendon. 236 DESCRIPTIVE ANATOMY. Action — It draws the humerus across the chest slig'htly rotating- the arm inward. If the arm be raised it will aid the latissimus dorsi in drawing- it downward, or, acting- from above in drawing- the body up^vard. Both it and the next muscle thus act as inspiratory ag-ents. Pectoralis Minor. The pectoralis minor derives its name from its position on the front of the chest, and from the fact that there is another pectoral muscle of larg-er size. It is found beneath the pectoralis major, is small in size, oblique in direction and tri- ang-ular in shape. It arises from the front of the third, fourth and fifth ribs, passes upward and outward, fleshy, narrows to a tendon and is inserted into the coracoid process of the scapula. Action — Rotates the scapula on the thorax and, when the scapula is fixed, aids in expanding- the chest. Subclavius. The subclavius derives its name from its position just be- neath the clavicle. It is a small round muscle which arises from the cartilag-e, and possibly the adjacent osseous portion, of the first rib by a tendon, it passes horizontally outward, becomes fleshy, and almost immediately after it ceases to rise, beg-ins to be inserted, its belly being- extremely short, into the whole length of the g-roove on the under surface of the clavicle. This g-roove occupies about the middle one-third of the clavicle. Action — It draws the clavicle downward. Thoracic Surgical Triangle. Lying- just above the subclavius, which is sometimes g*iven as its upper limit, is a triang-ular space of surgical importance. It is bounded above by the clavicle, below by the upper edge of the pectoralis minor; its apex is without and is crossed by the auxiliary vessels and nerves; its base is within and is formed by an imaginary line drawn from the inner extremity of the clavicle to the commencement of the origin of the pecto- ralis minor. THE MUSCULAR SYSTEM. 237 Lateral Thoracic Region. Serratus Magnus. The serratus mag-}ms is a larg-e thin muscle found upon the side of the chest wall. It derives its name from its extensive origin by means of diofitations or serrations. It arises by nine digfitations from the outer surface of the eight upper ribs, the lower five interlocking with serrations of the external oblique, and two arising from the second rib. Its origin is fleshy, and it continues its course, fleshy, outward and backward over the side of the chest, to be inserted into the whole length of the anterior edge of the posterior border of the scapula. Action — It moves the scapula on the thorax and, when the scapula is fixed, raises the ribs. Acromial Region. Deltoid. A single muscle constitutes this region, the deltoid, so named from its supposed resemblance to an inverted Delta. It is a large, coarse muscle, triangular in outline, forming the bulge of the shoulder, and corresponding in a measure to the Glu- teus Maximus of the lower extremity. Its base is directed upward and its apex downward. Its origin is extensive, con- sisting of musculo-tendinous fibres, which arise from the outer one-third of the anterior border of the clavicle, from the ac- romion process, and whole length of the posterior border of the spine of the scapula, and by some fibres from the intervening fascia covering the infraspinatus muscle. The fibres converge as they descend, the posterior passing forward and downward, the anterior downward and backward, and the central vertically downward, until they form a short, thick tendon, which is in- serted into a V-shaped impression about half-way down the outer surface of the shaft of the humerus. Action, Its posterior fibres carry the humerus upward and backward its anterior fibres upward and forward. By its central fibres, which act in concert with the supraspinatus, 238 DESCRIPTIVE AN ATONY. the humerus is carried directly away from the body until it is at right ang-les with the body. The posterior circumflex nerve and the circumflex arteries supply this muscle. The Scapular Group. Subscapularis Teres Minor Supraspinatus Infraspinatus Teres Major The Scapular Grouf> of Muscles consists of the subscapularis, the supraspinatus , the infraspinatus , the teres major and the teres minor (L. Teres, long- and round). Three of these mus- cles, it will be seen, are named from the fossae w^hich they occupy upon the scapula, the other two being named from their supposed shape, "round muscles". In the description of the scapula it was stated that both on the back and on the front the fossae described did not occupy the entire aspect of the bone, hence in studying the origin of these muscles it is unnec- essary to point out the exceptions of the anterior lip of the posterior border for instance, but simply to except that part of the fossa from which the muscle fails to rise, and not that part of the anterior or posterior surface of the scapula. Subscapularis. The subscapularis, the first of these muscles, is a coarse, flat muscle, which occupies the entire subscapular fossa; but does not rise from the whole of it, nor from the whole length of the scapula. It rises from the entire subscapular fossa, with the exception of its external one-third; and also from the fascia which invests the entire muscle, and from septa sent down from this fascia between the bundles of muscular fibre to seize the ridges of the subscapular fossa and from an aponeu- rosis which separates the teres major and form the long head of the triceps. These fibres converge, the superior one passing nearly directly forward and outward, the central ones having a slightly ob- lique direction upward, outward and forward, while the inferior fibres run nearly directly upward, outward and forward. It narrows to a tendon, thick and strong, which passes over the THE MUSCULAR SYSTEM. 239 neck of the scapula, crosses the head of the humerus, and is inserted into the lesser tuberosity of the humerus and into the bone for about an inch below, blending- with the fibres of the capsular ligfament of the shoulder joint. Action. It is chiefly an inward rotator of the humerus; but its inferior fibres have a slig-ht effect in drawing- the humerus downward when it has been elevated, and carrying- it back- ward after it has reached the vertical position. Subscapular nerves and arteries supply it. Supraspinatus. The siiprasf>iiiatus rises from the whole of the supraspinous fossa, except its outer one-third, and from the interveniug- fascia, which completely covers the muscle. It is a triang-ular muscle, which converg-es as it passes forward and outward, forms a tendon which runs under the acromion process of the scapula, and which is inserted into the hig-hest of the three muscular impressions found on the g-reater tuberosity of the humerus, the lower fibres of the tendon blending- with the capsular lig-ament. Action. It aids the deltoid in raising-, or abducting-, the humerus until it is at rig-ht ang-les to the body ; and is to a slig-ht extent an outward rotator. Suprascapular nerve and artery supply it and the following- muscle. Infraspinatus. The Infraspinatus rises from the whole infraspinous fossa, execpt its outer third, from the investing- fascia, which covers the muscle, and from the inter-muscular septa sent down be- tween itself and the teres major below and the teres minor above near the axillary border of the scapula. Like its predecessor, the fibres converg-e to form a tendon, which passing- behind the shoulder joint, blends with the capsular lig-ament, and is then inserted into the middle of the three muscular impressions on the g-reater tuberosity of the humerus. Action. Its action is almost entirely confined to external rotation of the humerus. 240 DESCRIPTIVE ANATOMY. Teres Minor. The teres minor rises from the upper two-thirds of the ax- illary border of the scapula, with the exception of the space occupied by the long- head of the Triceps. It also rises from the inter-muscular septum between itself and the infraspinatus internally and itself and the teres major externally, and from the fascia which covers the lower portion of the muscle. Its di- rection is upward and outward. The tendon narrows but sligfhtly and after blending- wnth the fibres of the capsular lig- ament, is inserted into the lowest of the three muscular im- pressions on the g-reater tuberosity of the humerus, and into the bone for a short distance below. Action. Like its predecessor, its chief action is that of ex- ternal rotation of the humerus. Supplied by branch from the circumflex. Teres Major. The teres major lies just below the te^-es minor, from which, after its orig-in, it is separated by a widening- interval. It rises from the lower one-third of the axillary border of the scapula, and from that portion of the dorsum, called the infer- ior angle, which does not enter into the infraspinous fossa. ' It also rises from the intervening fascia, which covers the lower portion of the muscle, and from inter-muscular septa between itself and the teres minor above and the infraspinatus below. From this origin it passes upward, outward and forward, its upward obliquity being- less than that of the teres minor; and is inserted by a broad, flat tendon into the internal bicipital ridg-e of the humerus. Action. It draws the humerus downward and backward, acting- here in concert with the latissimus dorsi; and is also an inward rotator. Supplied by lower subscapular. Between the two teres muscles is a surgical triang-le of some importance, the base of which is directed towards the humerus, and the apex towards the scapula. This triang-le is bounded above by the lower border of the teres minor, be- low by the upper border of the teres major, and externally by THE MUSCULAR SYSTEM. 241 that portion of the shaft of the humerus which intervenes between the teres muscles. This space is subdivided by the long- head of the triceps into an external quadrilateral and an internal triang-ular space. The triang-ular space, of small importance, is bounded above by the lower border of the teres minor, below by the upper border of the teres major, and anteriorly by the long- head of the triceps. The quadrilat- eral space is bounded behind by the long- head of the triceps, in front by the shaft of the humerus, above by the lower border of the teres minor, and below by the upper border of the teres major. Through this space pass important blood- vessels and nerves. The Muscles and Fascia of the Humerus, or Arm. The muscles of the humerus, or arm, are invested by fascia, constituting- a portion of the fascia of the upper extremity, which completely envelops the limb. In front it is continuous with the fascia which envelops the pectoral muscles, poste- riorly with that which invests the posterior scapular g-roup, internally with the fascia which forms the floor of the axillary space, and externally with the fascia investing- the deltoid muscle. As this fascia descends the arm it sends in two septa, one from either side. The internal inter-muscular septum is attached to the internal border of the humerus, the internal condyloid ridg-e, and to the internal condyle of the humerus. The external inter-muscular septum is likewise attached to the external border, external condyloid ridge, and external condyle of the humerus. These inter-muscular septa not only serve to separate the anterior from the posterior groups; but they also g-ive a firm and unyielding orig-in to the various muscles of the arm and forearm. The Muscles of the Arm are divided into two g-roups : the Anterior and Posterior Humeral Groups. Anterior Humeral Group. Biceps Flexor Coraco-Brachialis Brachialis Anticus Des Anat — 16 242 DESCRIPTIVE ANATOMY. Biceps. The biceps (Iv. bis, twice ; caput, head), as its name indi- cates, has a double orig-in, one called the "long-" and the other the "short" head. The short head arises by musculo-tendi- nous fibres from the coracoid process of the scapula, in common with the coraco-brachialis. It descends blended with this muscle for its upper two inches, and then no longer blended, but parallel, with the coraco-brachialis, to the insertion of that muscle, where it is joined by the lo^ig- head, which arises from the upper border of the g-lenoid cavity of the scapula, where it blends with the g-lenoid ligament. By tendinous fibres the long head passes over the shoulder joint in a sepa- rate synovial sheath ; and blends about the middle of the humerus with the short head to form the belly of the muscle. The belly of the muscle so formed passes down the front of the arm to near the elbow^ where it terminates in a tendon, which gives off a strong slip of fascia to blend with the invest- ing fascia of the forearm, while the bulk of the tendon is inserted into the posterior part of the bicipital tuberosity of the radius. Action. It is a flexor of the forearm ; but its short head, if acting alone, may to a trifling extent abduct the forearm, and the long head to some extent can adduct it. With the forearm in a position of pronation, the muscle becomes the most powerful of the supinators of the forearm. It is also a tensor of the deep fascia of the forearm. The biceps is sup- plied by the musculo-cutaneous nerve. Coraco-Brachialis. The Coraco-brachialis, arises in common with the short head of the biceps from the coracoid process of the scapula, passes down on the inner side of that muscle, adherent to it for about two inches, and then in contact with it, but no longer adherent to it, to the middle of the arm, where it is inserted in the middle of the internal face of the shaft of the hmerus. Action. It is a flexor of the arm ; and can, acting in concert with the short head of the biceps, aid that muscle, though THE MUSCULAR SYSTEM. 243 acting" more powerfully, in carrying- the arm inward, or ad- ductingf it. It is supplied by the musculo-cutaneous nerve. Brachialis Anticus. The Brachialis Anticus is a bulky mass lying- deeper than the preceding- muscles on the lower part of the front of the arm. It arises by two dig-itations, so arrang-ed as to embrace the V-shaped insertion of the deltoid, and expanding- from that point down the shaft of the humerus to within an inch of the elbow joint, its origin covering- the whole front of the humerus between these two points. It also spring-s from the whole of the internal inter-muscular septum, and from the upper portion of the external inter-muscular septum, being- cut off from the latter by the orig-in of the supinator long-us and extensor carpi radialis long-ior. It narrows to a triang-u- lar tendon, which passes over the elbow, and is inserted into the front of the coronoid process of the ulna. Action. It is a pow^erful flexor of the forearm upon the arm, thoug-h in some positions of the body — ^as in "chinning-" a bar — it flexes the arm upon the forearm, acting-, as all mus- cles do, from either extremity. It is supplied by the musculo- spiral and musculo-cutaneous nerves. Posterior Humeral Group. Triceps. The tricefts is a larg-e fleshy mass. It covers the w^hole of the posterior face of the humerus, being the onh' muscle found in that situation. It rises by three heads : the middle, or long; the internal, or short ; and the external, or intermediate. The long- head ^x'vryQ.^ from the upper one-inch of the axillary border of the scapula by tendinous fibres. The short head a.r\%c% from the inner one-half of the poste- rior face of the humerus, and the posterior face of the inter nal muscular septum and the intermediate arises from the ex- ternal half of the posterior face of the humerus, and the external inter-muscular septum. The three heads blend tog-ether to form the belly of the muscle, which passing- down- ward becomes tendinous, the tendinous fibres extending- much 244 DESCRIPTIVE AN ATONY. further up on its posterior than on its deep, or anterior, aspect, to be ultimately inserted into the depressed surface on the upper extremity of the olecranon process of the ulna. The muscle can be more briefly described by saying that the inner and the external of the heads rise from the whole of the pos- terior surface of the shaft of the humerus, the former begin- ning* at the insertion of the Teres major and the latter at the insertion of the Teres minor. Between these is found the, long head, arising at the upper inch of the axillary border of the scapula. They all blend to reach the insertion above mentioned. Action. — This muscle is the extensor of the forearm upon the arm; but its long head being attached to the scapula and passing over two joints, approximates the head of the humerus to the Glenoid cavity, and slightly aids other muscles in draw- ing the humerus backward. It may also in climbing draw the scapula, and if that be fixed, the body, upward on the humerous. It is supplied by the musculo spiral nerve. The Muscles of the Fore- Arm. Before reaching the muscles of the forearm we find that portion of the upper extremity enveloped in a strong fibrous membrane, called the Deep or Investing Fascia of the Forearm. This membrane is first attached to the olecranon process of the Ulna and passes downward attached to the posterior border of the shaft of the Ulna. Passing forward on either side, it is attached to the internal and external condyles of the humerus, and then uniting over the front of the limb forms a complete investment. From this investing sheet septa are sent off, which not only serve the purpose of dividing the different layers from one another, but which also serve to give a strong and firm attachment to the muscles which belong to this portion of the upper extremity. Some of these muscles arise from the fascia as a strictly investing membrane, while others arise from the intermuscular septa, which are tongues of fascia sent down between the different muscles or groups of muscles. Thus the whole limb is divided into separate compartments, THE MUSCULAR SYSTEM. 245 SO that could a muscle be dissolved out without affecting* the fascia, it would be found to have its separate and distinct com- partment, as would be the case for all of the muscles of the limb. This fascia becomes particularly strong" and dense at the wrist joint, where it sends across both on the front and the back strong- braces, which are respectively known as the A f/terior a.nd Posterior Annular Ligaments. The Posterior is an oblique band, which passes downward and inward across the back of the wrist, and is attached by one extremity to the lower end and styloid process of the radius and by the other to the cuneiform and pisiform bones. It binds the tendons of the Extensor muscles down upon the bones, and it sends down septa which form six separate com- partments throug-h which these tendons pass. The Anterior Annular Ligament is less well marked than is the Posterior. It is attached by one extremity to the front of the styloid process of the radius ; by the other extremity it is attached to the pisiform bone, sending" off a process which becomes attached to the unciform process of the unci- form bone. The Muscles of the Forearm. The muscles of the forearm are divided into those on the front and those on the back ; and these are ag"ain subdivided by intermuscular septa into a superficial and deep g"roup on the front of the forearm, and into three g"roups — external or radial, superficial, and deep — on the back. It must be borne in mind that every muscle found upon the front of the forearm is to produce either flexion or pronation and that every muscle upon the back of the forearm produces either extension or supination. Hence the names of the muscles upon the front will be €\\}\Q.x: Flexor o^ Pronator, on the back either i5'.v/f^v^6^o?- or Supinator', and to these names are added the particular function of the muscle, as a Plexor of the radial side of the carpus or an Kxtensor of the radial side of the carpus. The Muscles of the Front of the Forearm. The muscles of the front are eig"ht in number and are di- vided into two layers, of which the superficial contains five 246 DESCRIPTIVE ANATOMY. muscles and the deep three. The superficial muscles on the front of the forearm have a common tendon, the orig-in of which tendon is from the inner condyle of the humerus, the investing fascia which covers the muscle, and the intermuscular septa which are sent down between the muscular fibres. In addition to this, many muscles have other points of origin. Pronator Radii Teres. The Pronator Radii Teres is the first muscle of the super- ficial g-roup. It takes its origin from the internal condyle o f the humerus, from the investing fascia which covers it and from an intermuscular septum between itself and the Flexor carpi radialis. In addition to this, there is a small head, or deep head, of this muscle, which arises from the inner face of the coronoid process of the ulna, these two heads being sep- arated by the median nerve. The two heads unite after a short course, and passing downward and outward, wind around the shaft of the radius, and are inserted into the middle one-third of the outer surface of the shaft of the radius. Flexor Carpi Radialis. The Flexor Carpi Radialis is the second muscle of the su- perficial group. It arises from a common origin, — the internal condyle of the humerus and investing fascia, and two intermus- cular septa, one between itself and the Pronator radii teres and the other between itself and the Palmaris longus. It "is a long and slender muscle, which passes downward, with a slight inclination outward for the upper one-third of the fore- arm. The muscular belly then changes into a tendon, which running vertically downward, passing through a groove in the trapezium, is inserted into the base of the metacarpal bone of the index finger. Palmaris Longus. The Palmaris Longus arises from the internal condyle, the investing fascia, and the intermuscular septa, between itself and the Flexor carpi radialis on one side and the Flexor sublimis digitorum on the other. It is a small and very slender muscle, which passing straight down the middle of the front of the THE MUSCULAR SYSTEM. 247 forearm, soon becomes tendinous and is inserted into the pal- mar fascia chiefly, but partly into the anterior annular liga- ment. The muscle should be called the "middle flexor of the carpus. Flexor Carpi Ulnaris. The Flexor Carpi U/?iaris a.r\ses from the internal condyle, the investing- fascia, and the intermuscular septa between itself and the Flexor sublimisdigitorum. It also arises from the in- ner side of the olecranon process and from the upper two-thirds of the posterior border of the ulna. This muscle remains fleshy until within two inches of the wrist joint. It then becomes tendinous and is inserted into the base of the metacarpal bone of the little fing-er, its tendons enclosing- the pisiform as a sesamoid bone. Flexor Sublimis Digitorum. The Flexor Sublimis Dig-itoruin lies beneath the preceding- muscles of the g-roup and is in contact with the investing- fas- cia for only a small portion of its course, frequently not touch- ing- that fascia at all. It arises from the inner condyle of the humerus, from the internal lateral lig-ament of the elbow, from the base of the coronoid process of the ulna, and from the oblique line of the radius for about two-thirds of that line. It descends beneath the superficial layer of muscles, and at the lower third of the forearm divides into four tendons. These tendons, enclosed in a synovial sheath, enter the hand by passing- beneath the anterior annular lig-ament, and then, separating- from one another, pass forward to each fing-er, to be inserted into the side of the shaft of the second phalanx of each of the four lesser fing-ers. At the base of the first pha- lanx, each tendon splits, and throug-h this opening- the tendon of the deep Flexor pisses. The superficial tendons then unite and form a g-roove, in which the tendon of the deep Flexor lies. They then split a second time to be inserted into the sides of the second phalang-es. Second or Deep Layer. Flexor Profundus Dig-itorum Pronator Quadratus Flexor Long-US Pollicis 248 DESCRIPTIVE ANATOMY. The flexor profundus digitornm lies just beneath the subli- mis and to the ulnar side of the lon^us pollicis. It arises from the upper two-thirds of the anterior and inner faces of the ulna ; by a strong- aponeurosis from, the posterior border of the ulna, where it blends with the flexor carpi ulnaris, and from the ulna part of the interosseous membrane. It divides into four tendons, which enter the palm of the hand and, separating, run one to each of the fingers, pierce the tendon of the superficial flexor at the base of the fingers, and are inserted into the base of the last phalanx. Flexor Longus Pollicis. The flexor long-its pollicis lies to the outer side of the preced- ing- muscle. It arises from about the middle two fourths of the front of the radius and from the radial side of the interos- seous membrane. It passes downward and, becoming tendi- nous, runs beneath the anterior annular ligament, passes between the two heads of the flexor brevis pollicis and is inserted into the base of the last phalanx of the thumb. Pronator Quadratus. The pronator quadratus occupies the lower fourth of the forearm and thus prevents the origin of the preceding mus- cles for that distance. It arises from the inner side of the ulna, receiving some fibres from the front of that bone as it passes over it, and is inserted into the front of the radius as far as the outer side. Nerve and Arterial Supply. The muscles on the outer side of the forearm are supplied by branches from the radial artery ; those on the inner side from the ulnar. All of the muscles on the front of the fore- arm are supplied by the median nerve or one of its branches, except the Flexor carpi ulnaris and one-half of the Flexor profundis digitorum. The branch of the median which sup- plies the deep muscles is called the interosseous ; the nerve supplying the Flexor carpi ulnaris and the inner half of the Flexor profundus digitorum is the ulnar. THE MUSCULAR SYSTEM. 249 Action of the Muscles of the Forearm. The name indicates the action of each of these muscles, but indicates onl}' a portion of the action. The Pronator radii teres is first a pronator, of the hand; but after having- acted to its fullest extent as a pronator, it then becomes, in common with the other muscles of the g-roup, a flexor of the forearm upon the arm. The Flexor carpi radialis, Pahnaris loiigzis, and Plexor carpi iiluaris are primarily flexors of the wrist; but the pal- maris long-us in addition is a tensor of the palmar fascia, and all of the three flex the forearm upon the arm. The Flexor siiblimis dig-itoruni flexes the second phalanx on each of the four lesser fing-ers. Having* effected this, it will flex the first phalanx upon the hand; continuing- to act, it flexes the hand upon the wrist; and acting- still further, it flexes the forearm upon the arm. The Flexor longus -pollicis flexes the first phalanx of the thumb; then the second upon the metacarpal bone of the thumb ; then the metacarpal bone upon the hand, and the hand upon the wrist, and the wrist upon the forearm. The Flexor profundus dig-itorum flexes the first phalanx upon the second; but cannot do this until a superficial flexor first has flexed the second. Continuing- its action, it will act in concert with and like the superficial flexor. Interosseous Membrane. The interosseous membrane, mentioned above, is a strong- fibrous membrane stretched l)etween the two bones. It econo- mizes weig-ht, while it furnishes as stable an orig-in for mus- cles as does bone. Posterior Region. The muscles upon the back of the forearm also have a com- mon origin, viz : external condyle of humerus, investing- fascia and intermuscular septa. They are divided into three g-roups, each containing- four muscles, called radial, superficial and deep g-roups. These 250 DESCRIPTIVE ANATOMY. muscles, are either extensors or supinators,, acting- in opposi- tion to those on the front of the forearm. Radial Group. Supinator Long-us Extensor Carpi Radialis Extensor Carpi Radialis Longior Brevior Supinator Brevis Supinator Longus. The supinator longus derives its name from the facts that it is a supinator of the forearm and that there is another supinator called brevis. It arises from the upper two-thirds of the external condy- loid ridg"e and from the external inter-muscular septum, and, after descending- about two-thirds of its course, terminates in a tendon which is inserted into the outer side of the base of the styloid process of the radius. Extensor Carpi Radialis Longior. The extensor carpi radialis long-ior derives its name from the action of the muscle and from the fact that there is another radial extensor which is shorter. It arises from the lower one-third of external condyloid ridge and from the external inter-muscular septum, and descends to be inserted by its tendon into the base of the metacarpal bone of the index finger. Extensor Carpi Radialis Brevior. The extensor carpi radialis brevior^ deriving" its name from the facts stated with the preceding- muscle, arises from the common origin, which is the external condyle, the investing- fascia and an inter-muscular septum bet^veen itself and the extensor communis digitorum. It passes downward, between the extensor carpi radialis longior and the extensor communis digitorum, crosses beneath the tendons of the extensor ossis. metacarpi pollicis and extensor primii internadii poUicis, as does the preceding muscle, before reaching- the posterior annular ligament, then passes beneath the tendon of the exten- sor secundi internodii pollicis and is inserted into the radial THE MUSCULAR SYSTEM. 251 side of the base of the third metacarpal bone. This muscle and the extensor carpi radialis longior, lie in the same groove while passing under the annular ligament. Supinator Brevis. The siifiinator brevis is a thin flat muscle which encircles the upper third of the radius. It arises from the external condyle of the humerus, the external lateral and orbicular ligaments from the triangular depressed surface beneath the lesser sigmoid cavity of the ulna, and to some extent from the intermuscular septum between the deep and superficial groups. It winds around the radius and is inserted into the upper third of its oblique ridge. Back of Forearm— Superficial Group. Extensor Communis Digitorum. Extensor Carpi Ulnaris. Extensor Minimi Digiti. Anconeus. Extensor Communis Digitorum. The extensor communis digitorum derives its name from its action as the extensor common to the four fingers. It arises from the common origin, external condyle investing fascia and two inter-muscular septa; one between itself and the extensor carpi radialis brevior externally, and one between itself and the extensor minimi digiti, internally. Passing down the back of the forearm the muscle divides into three tendons, which pass beneath the annular ligament in a com- partment with the extensor indicis. On reaching the back of the hand the innermost tendon divides into two ; and the four tendons, thus formed, pass to the four lesser fingers and are inserted into the backs of the four lesser fingers after the manner of extensor iendo?is. This expression means that opposite the metacarpo-phalangeal joint each tendon becomes narrower and receives the tendon of the lumbricales. Pass- ing to the shaft, each tendon becomes broader and thinner. Upon reaching the phalangeal joints each becomes thicker and furnishes a posterior ligament for those joints. The tendon to the ring finger is usually bound by a slight band to the tendons of the little and middle fincrers. 252 DESCRIPTIVE ANATOMY. Extensor Minimi Digiti. The extensor ininimi digiti is an offshoot of the common extensor and, as its name indicates, has for its function the extension of the little fing-er. It arises from the common origin (external condyle, investing- fascia and septa between itself and the extensor communis externally and the extensor carpi ulnaris internally) and is inserted into the whole leng"th of the back of the little fing-er along" with the slip furnished that fing-er by the common extensor, after the manner of extensor tendons. This muscle is really an offshoot of the common extensor. Its claim to individuality is that it has a separate compartment in the annular ligament. Extensor Carpi Ulnaris. The extensor carpi ulnaris derives its name from its action as an extensor of the hand and from its situation on the ulnar side of the forearm. It arises from the common origin (exter- nal condyle, investing fascia and the intermusular septa between itself and the extensor minimi dig-iti externally and the deep g-roup in front) and, by a strong- aponeurosis, which blends with that g-iving- origin to the carpal flexor, from the middle third of the posterior border of the ulna. The muscle remains fleshy until just above the wrist joint when it becomes tendinous and, passing- through a groove on the back of the styloid process of the ulna, in its own compartment in the annular ligament, is inserted into the base of the metacar- pal bone of the little fing-er on its ulnar side. Anconeus. The anconeus is a small triangular muscle which arises by its apex from the external condyle of the humerus, and is inserted by its base into the olecranon process and triangular surface at the upper extremity of the ulna. It is really an offshoot of the triceps extensor, and its action is to aid that muscle in extending the forearm on the arm. THE MUSCULAR SYSTEM. 253 Deep Group. The four muscles of this group lie beneath those of the superficial g-roup, and all arise from the interosseous mem- brane as one attachment. As indicated b}^ their names, they are all extensors, three being- appropriated by the thumb and one by the index fing-er. Kxtensor Ossis Meta- Extensor Primi Inter' carpi PoUicis nodii Pollicis Extensor Secundi Inter- nodii Pollicis Extensor Indicis Extensor Ossis Metacarpi Pollicis. The extensor ossis metacarpi pollicis arises from the radius, ulna, interosseous membrane and a fibrous septum between it and the extensor primi. Its upper attachment to both bones is limited by the supinator brevis. It becomes tendinous and winding" around the radius crossing- the tendons of the exten- sor carpi radialis lang-ior and brevior, and passing- throug-h the annular lig-ament, is inserted into the base of the metacar- pal bone of the thumb. Extensor Primi Internodii Pollicis. The extensor primi internodii pollicis arises from the radius for about its middle two fourths and interosseous membrane. After becoming- tendinous it follows the extensor ossis meta- carpi pollicis, lying" internal to that muscle, crosses the same tendons, passes throug-h the same groove on the radius and is inserted into the base of the first phalanx of the thumb. Extensor Secundi Internodii Pollicis. The extensor secundi internodii pollicis arises from the ulna for about its middle third and from the interosseous membrane. Its tendon passes throug"h a separate compartment in the annular lig-ament, crosses the tendons of the extensor carpi radialis lang-ior and brevior after passing- throug-h the annular lig-ament, and is inserted into the base of the last phalanx of the thumb. 254 DESCRIPTIVE ANATOMY. Extensor Indicis. The extensor indicis arises from the tilna and interosseous membrane and is inserted into the whole leng-th of the back of the index fing-er, blending- with the tendon furnished that fin- ger by the common extensor. It passes through the annular ligament in a compartment common to it and the extensor communis digitorum. Action — The names of these muscles in a large measure indicate their action. A carpal extensor extends the hand and draws it to its own side. The radial and ulnar extensors, acting together, bend the hand straight backward. The extensors of the fingers bend the fingers backward and then extend the hand at the wrist. Of the supinators, the brevis is the stronger. It is only when the hand is in full supination that the supinator longus acts to produce supination. With the hand in full supination it becomes a pronator. It may also act as a flexor of the forearm upon the arm. The supinator longus and extensor carpi radialis langior are supplied by the musculo-spiral nerve ; the others by the posterior interosseous. The Muscles of the Hand. The central portion of the palm of the hand is depressed below the level of a prominence on either side, one, extending from the base of the little finger toward the wrist, called the hypothenar eminence, and the other, considerably more prominent, extending upward from the base of the first phalanx of the thumb toward the wrist, called the thenar eminence. When the skin has been removed a thick layer of fatty tissue is exposed, which serves as a protection for the vessels and nerves in grasping with the hand ; and beneath this is a strong fascia called the palmar fascia. It has a thick central portion and two thinner lateral portions which cover the muscles forming the thenar and hypothenar eminences. Tracing this fascia to the wrist, it is found to be continuous with a strong fibrous band which extends across the wrist THE MUSCULAR SYSTEM. 255 from one side to the other, binding- down the tendons which pass beneath it, known as the anterior annular ligament. The muscles of the hand consist of two groups, the thenar and hj^pothenar groups, and four small muscles found in the depressed portion of the hand, called lumbricales. Thenar Group. The muscles of the thenar group are appropriated to the thumb, the movements of which are as follows : {a) Abduction, or movement of the thumb outward from the index finger, {b) Adduction, a movement in the opposite direction. {d) Flexion, in which the thumb is put in contact with the palp of any of the fingers. This is effected by putting in motion the metacarpal bone of the thumb by a muscle called opponens. {c) Extension, movement in the opposite direction effected by muscles on the back of the forearm, which have been described. Abductor Pollicis Flexor Ossis Metacarpi Pollicis. Flexor Brevis Pollicis Adductor Pollicis. Abductor Pollicis. The abductor pollicis arises from the trapezium bone and anterior annular ligament, and is inserted. In the outer side of the base of the first phalanx of the thumb. The flexor of the metacarpal bone of the thumb, or the opponens pollicis, arises from the trapezium bone and anterior annular ligament, and is inserted into the whole length of the radial border of the metacarpal bone of the thumb. Flexor Brevis Pollicis. The flexor brevis pollicis consists of two parts, one of which, the superficial portion, arises from the trapezium bone and annular ligament, and the other, or deep portion, from the trapezoid, os magnum and base of the metacarpal bone of the middle finger. It Is inserted into both sides of the base of the first phalanx of the thumb, its tendons of insertion hav- ing sesamoid bones in them. 256 DESCRIPTIVE ANATOMY. Abductor Pollicis. The adductor -pollicis is a flat triangular muscle which arises by its base from the whole length of the front of the metacarpal bone of the middle finger. It is inserted into the inner side of the base of the first phalanx of the thumb. Hypothenar Group. Palmaris Brevis Abductor Minimi Digiti Flexor Brevis Minimi Digiti Adductor Ossis Metacarpi Minimi Digiti Palmaris Brevis. The palmaris brevis is a small pale muscle lying just beneath the skin of the palm. It arises from the palmar fascia and the anterior annular ligament, and passing inward, about an inch wide, is inserted into the skin on the inner border of the hand. Abductor Minimi Digiti. The abductor minimi digiti arises from the pisiform bone and is inserted into the inner side of the base of the first phalanx of the little finger. Action — It is an abductor of the little finger, /. e., draws the little finger inward away from the ring finger. Flexor Brevis Minimi Digiti. The flexor brevis minimi digiti arises from the unciform process, of the unciform bone and the anterior annular ligament, and is inserted into the base of the first phalanx of the little finger. Action — It is a flexor of the little finger. Adductor Ossis Metacarpi Minimi Digiti. The adductor ossis metacarpi minimi digiti arises from the unciform process of the unciform bone and the anterior annular ligament, and is inserted into the whole length of the meta- carpal bone of the little finger. Action — It draws the metacarpal bone of the little finger outward and forward, carrying the little finger towards the thumb. THE MUSCULAR SYSTEM. 257 Flexor Tendons of the Fingers. It has been seen that the tendons of the flexor sublimis dig-itorum split at the base of the fing-ers to allow the passage of the tendons of the flexor profundus, unite and again split to be inserted into the sides of the shaft of the second phalanx of each finger. Before its insertion each tendon gives off thread-like prolongations, called vincula accessoria, which are inserted into the sides of the bones ; and both tendons are bound down to the bones by transverse bands of ligamentous fibres called the thecal. Muscles of the Lower Extremity. The muscles of the lower extremity are divided into those of the hip, thigh, leg and foot. The hip is called the gluteal region. Gluteal Region. As in the upper extremity, the muscles are here covered by an investing fascia, which is much thicker and stronger than in the former situation, known in the thigh as the fascia lata or vagina femoris. The muscles of the gluteal region, nine in number, are ar- ranged in three layers, each of which has a muscle called gluteus. It receives its nerve supply from the lesser sciatic. First Layer. Gluteus Maximus. T\\Q. g-luteus maxhmis is a quadrilateral muscle, the largest and coarsest in the body, and forms the bulge of the buttock. It arises from the posterior fifth of the crest of the ilium, from the dorsum ilii between the superior curved line and the crest, from the posterior portion of the crest, from the poste- rior surface of the sacrum and coccyx, from the greater sacro- sciatic ligament and from the fascia covering the gluteus medius. It passes obliquely downward and outward to be inserted into the line leading from the trochanter major to the linea aspera and into the fascia lata. Des Anat— 17 258 DESCRIPTIVE ANATOMY. Action — It is an abductor and outward rotator of the thig-h, a tensor of the fascia lata and steadies the pelvis on the femur. Second Layer. Gluteus Medius Gemellus Inferior Pyriformis Obturator Internus Gemellus Superior Quadratus Femoris Gluteus Medius. The g-luteus inedhis is partially covered by the g-luteus maximus. It arises from the anterior four-fifths of the crest of the ilium, from the dorsum ilii between the middle curved line and the crest and from the investing- fascia, which covers its outer front part. It is inserted into the outer part of the trochanter major. On its outer edg^e the muscle is continuous with the g-luteus maximus. Action — Its g-reatest power is shown in abduction ; but its anterior fibres can rotate the femur inward while the posterior rotate it outward. It can twist the pelvis on the femur, draw- ing- the body to that side. It steadies the pelvis on the femur and can draw the limb forward in walking-. It is supplied by the superior g-luteal nerve. Pyriformis. The j;)yriformis is a pear-shaped muscle. It arises within the pelvis by three fleshy slips interposed between the ante- rior sacral foramina from the first to the fourth and from the adjoining- part of the ilium. It escapes from the pelvis throug-h the g-reater sacro-sciatic foramen, passes downward and outward, and is inserted into the posterior border of the upper extremity of the trochanter major, or into the dig-ital pit. Action — It is an external rotator of the thigfh. The Gemelli. The gemelli are a pair of small muscles lying- one above and the other below the tendon of the obturator internus. ^h.Q §emullu^ superior arises from the spine of the ischium, runs horizontally outward and is inserted into the digital pit of the trochanter major. THE MUSCULAR SYSTEM. 259 The gemellus inferior arises from the tuberosit}^ of the ischium, passes horizontally outward and is inserted into the digfital fossa. Action — Both are outward rotators of the thigh. Obturator Internus. The obturator internus arises within the pelvis from the inner surface of the obturator membrane, from the margin of the obturator foramen and from the inclined plane of the ischium. Its course is downward and slightly backward until, becoming tendinous, it escapes from the pelvis through the lesser sacro-sciatic foramen, and passing horizontally, out- ward, its tendon winding around the posterior border of the ischium just below the spine, it is inserted into the digital fossa of the trochanter major. Action — It is an outward rotator of the thigh. duadratus Femoris. The quadratus femoris^ as its name indicates, is a square muscle which lies below the tendon of the obturator internus. It arises from the outer lip of the tuberosity of the ischium, and is inserted across the posterior inter-trochanteric line. Its insertion is rarely marked by the presence of the linea quad rati. Action — It is an outward rotator of the femur. These muscles are all supplied by branches coming directly from the sacral plexus. Third Layer. Gluteus Minimus Obturator Externus Gluteus Minimus. The g'luteus ini7iimus lies beneath the gluteus medius and maximus. It is a triangular radiated muscle which arises from the dorsum ilii between the middle and inferior curved lines. It passes down, narrowing as it descends, and is inserted into the anterior border of the trochanter major. In front, it is continuous with the gluteus medius. Action — It is an abductor and invjard rotator of the thigh. Acting from below it steadies the pelvis on the femur. It is supplied by the superior gluteal. 260 DESCRIPTIVE ANATOMY. Obturator Externus. The obturator externus arises from the inner two-thirds of the outer surface of the obturator foramen and from the inner margin of the obturator foramen. It narrows to a tendon, which, passing- outward behind the neck of the femur, is in- serted into the digital pit of the trochanter major. It lies on the capsular ligament of the hip-joint. Action — It is an external rotator of the thigh. It is supplied by the obturator nerve. Femoral Region. The muscles of the thigh are arranged in four groups, viz: posterior, superficial, anterior and internal femoral groups. Investing the thigh, just beneath the skin and superficial fascia, is a strong , thick, fibrous membrane which descending to the knee, invests that joint and passes on to become the invest- ing fascia of the leg. From the hip to the knee it is known by three names, investing fascia of the thigh, vagina femoris, or, generally, fascia lata. It not only forms a firm resisting cov- ering for the muscles, but sends in septa between the groups. Two of these septa, attached to the lips of the linea aspera, are known respectively as the external and internal intermuscular septa. The external intermuscular septum lies between the anterior and posterior femoral groups, and gives origin to muscles of both groups. The internal, lies between the an- terior and internal groups, no septum being interposed between the internal and posterior groups. Above, this fascia is con- tinuous, on the front of the thigh, with Pouparts ligament, externally and posteriorly with the fascia covering the gluteal muscles, while internally it is attached to the tuberosity of the ischium and to the ischio pubic rami. Below it seizes the bony prominences around the knee joint and becomes, posteriorly, th.t popliteal fascia, which covers in the popliteal space. ^ The fascia lata consists of layers between which are found three muscles of the thigh forming the superficial femoral group. THE MUSCULAR SYSTEM. 261 Where the fascia covers the posterior femoral region it is thinner than in any portion of its course. Posterior Femoral Region. Biceps Flexor Cruris Semitendinosus Semimembranosus Biceps Flexor Cruris. The biceps, as its name imports, arises by two heads. The long head springs, in common with the semitendinosus, from the tuberosity of the ischium and descends adherent to the semitendinosus for several inches. In then accompanies the semitendinosus, but no longer adherent to it, to the lower third of the thigh; is joined by the short head which arises from the ijhole length of the outer lip of the body of the linea aspera and from the external intermuscular septum. The muscle thus formed after descending to the lower third of the femur in contact with the semitendinosus, leaves that muscle and makes for the outer side of the knee joint, where it is in- serted chiefly into the head of the fibula, but sends some fibres to the outer tuberosity of the tibia and to the fascia of the leg. Semitendinosus. The semitendinosiLS arises in common with the long head of the biceps, adheres to it for several inches and then descends in contact with it to the lower third of the thigh where it leaves the biceps and passes to the inner aspect of the knee-joint where it is inserted into the inner surface of the shaft of the tibia, below the inner tuberosity sending a slip to the fascia of the leg. This is known as the "'g-oose./oot'" insertion. It is made up of three muscles, viz: semitendinous, sartorius and gracilis. Semimembranosus. The semimenibranosiLs arises from the tuberosity of the ischium just in front of and external to the preceding muscles and descends, in company with them, to the lower third of the femur, whence it accompanies the semitendinous to the inner side of the knee-joint and receives a three-fold insertion, viz: 262 DESCRIPTIVE ANATOMY. into the Horizontal groove on the inner tuberosity of the tibia, into the j^ofliteal fascia and into the posterior lig-ament of the knee-joint. These three muscles are spoken of as the hamstring- muscles, the biceps being" the outer, the semimembranous and semiten- dinosus being- the inner. Action — It will be seen that these three muscles all pass over two joints. They are, of course, all flexors of the leg- upon the thig-h; but, in addition, the biceps has a slig-ht influence in rotating- the leg- outward and the others in rotating- it inward. After flexing- the leg- upon the thig-h, they can then extend the thig-h upon the pelvis. When acting- from below they draw the pelvis downward and backward, keeping- the body from falling- forward, or aid in restoring it to the erect posture after stooping-. The g-reat siatic nerve supplies the g-roup. Superficial Femoral Group. Tensor Vag-inae Femoris Gracilis Sartorius Tensor Vaginas Femoris. The tensor vag-incB femoris is a short flat muscle found lying- on the outer aspect of the thig-h between the two layers of the fascia lata. It arises from the outer lip of the crest of the ilium near the anterior superior spinous process, descends with an inclination backward and is inserted into the fascia lata about one-fourth down the thig-h. Action — It is a tensor of the fascia lata and aids in rotating- the limb inward. Sartorius. The sartoi'ius is the long-est muscle in the body. It arises from the anterior superior spinous process of the ilium and half the notch below, passes obliquely downward and inward across the upper third of the thig-h, descends vertically behind the internal condyle of the femur and then turns obliquely for- ward to be inserted into the upper inner face of the tibia below the internal tuberosity, sending- a slip to the fascia of the leg-. It forms one of the elements of the "goose foot" insertion, the THE MUSCULAR SYSTEM. 263 other two being- the semitendinous and gracilis. The sartorius is the most superficial at the insertion, then the gracilis and the semitendinosus is the deepest. Action — It flexes the thigh on the pelvis, the leg" on the thig-h and carries it inward across its fellow. It may, acting- from below, twist the pelvis so as to carry the front of the body towards the opposite side. Gracilis. The gracilis arises by a thin broad aponeurosis from the edg-e of the symphysis pubis and from the margin of the ischio- pubic-ramus. It soon becomes fleshy and passes down the inner aspect of the thigh to be inserted into the upper inner part of the tibia, below the inner tuberosity, sending a slip to the facia of the leg, /. e., it is an element of the "goose foot" insertion. Action — It flexes the leg on the thigh and aids in adducting the thigh. The tensor vaginae femoris is supplied by the superior glu- teal nerve ; the sartorius by the middle cutaneous ; the gracilis by the obturator. Anterior Femoral Region. Psoas Magnus Vastus Externus Iliacus Internus Vastus Internus Rectus Femoris. The muscles in this region are usually described as five but can very readily be considered as two, viz : Biceps flexor femoris, consisting of psoas magnus and iliacus internus and the triceps extensor cruris consisting of rectus femoris, vas- tus internus, and vastus externus. The last three are inserted by a common tendon, called the ligamentum patellai, into the anterior tubercle of the tibia, their action being transmitted through the patella to which they are attached. As might be inferred from their action they all arise from some point perpendicular to their insertion. Psoas Magnus. The -psoas mag-nus is a long spindle shaped muscle lying beside the vertebral column and descending into the thigh. 264 DESCRIPTIVE ANATOMY. It arises from the bodies and bases of the transverse processes of the last dorsal, and all the lumbar vertebra ; from the intervertebral disks between them and from tendinous arches attached to the bodies of the vertebrae, extending- from the upper lipped edg-e to the similar lower edge of each vertebra, thus leaving- between it and the central constricted portion of the vertebra an interval through which vessels and nerves pass. The muscle descends beside the vertebral column to the pel- vis and, as it pass beneath Poupart's lig-ament, is joined by the iliacus internus and their blended tendon is inserted into the trochanter minor of the femur and the bone for an inch below. Iliacus Internns. The iliacus internus arises from the whole of the iliac fossa, from the internal lip of the crest of the ilium, from the ante- rior superior spinous process backward, from the base of the sacrum, from the ilio-lumbar ligament and by a few fibres from the capsular ligament of the hip joint. The fibres converge to a tendon which, passing beneath Poupart's ligament, blends wnth that of the psoas magnus to be inserted into the lesser trochanter of the femur and the bone for an inch below. Action — Primarily these muscles are flexors of the thigh on the pelvis. Owing to the winding of the tendon around the femur, they are powerful outward rotators, acting just as the biceps does on the radius. With their fixed point below, and the muscles of both sides acting, they bend the body directly forward ; but if the iliacus of one side acts alone, it flexes the pelvis and turns the body to the opposite side. The psoas is supplied by branches of the lumbar plexus, the iliacus by the anterior crural. Rectus Femoris. The rectus femoris derives its name from the straightness of its course. It arises by a forked tendon, one fork springing from the anterior inferior spinous process of the ilium, the other from the upper margin of the acetabulum. The two soon unite, and the tendon thus formed after a short course THE MUSCULAR SYSTEM. 265 terminates in the belly of the muscle ; and that in turn terminates at the lower part of the thig-h in a strong- tendon, which is inserted into the upper end of the patella. The fibres of this muscle have a bipenniform arrangfement. Vastus Externus. The vastus externus arises from the base of the trochanter major, from the line leading- from the trochanter major to the linea aspera, from the upper half or third of the outer lip of the linea aspera, and from the external intermuscular septum. This muscle is covered over by a powerful aponeurosis from which its fibres arise. At its orig-in from the linea aspera, and the external intermuscular septum, it is intimately blended with the vastus internus. Its fibres proceed in a sfeneral direction downward and inward thougfh the inferior fibres pass more nearly inward. It is inserted into the outer edg-e of the tendon of the rectus femoris and outer edgfe of the patella. Vastus Internus. The vastus internus arises from the whole of the shaft of the femur from the anterior intertrochanteric line downward, from the inner lip of the linea aspera, from the internal inter- muscular septum, from the external intermuscular septum and from a part of the external lip of the linea aspera, where it blends with the vastus externus. It is inserted into the inner edg-e of the tendon of the rectus femoris and inner edg"e of the patella. The orig-in of the muscle is also thus stated: from the inner surface of the shaft of the femur, from the anterior trochanteric line downward, from the front and outer faces, from the internal and external lips of the linea aspera and the internal and external septa. It is inserted into the inner edg"e of the tendon of the rectus femoris and into the inner border of the patella. The crureus is here considered a part of the vastus internus. The insertion of the three muscles should be thus stated : They combine to form a common tendon, the tendon of the triceps extensor cruris, which encloses the patella as a sesa- 266 DESCRIPTIVE ANATOMY. moid bone and is inserted, as the lig-amentum patellae, into the lower part of the anterior tubercle of the tibia, a bursa being- interposed between the tendon and the upper part of the tuber- cle of the tibia. The vasti muscles envelop the entire femur except the middle lip of the linea aspera, and the two extremities of the bone. Action. This muscle, as its nam'e indicates, is an extensor of the leg- upon the thig-h. The central portion, or rectus femoris, is also a flexor of the thig-h upon the pelvis ; or, acting- from below, of the pelvis upon the thigh. Internal Femoral Region. Pectineus Adductor Brevis Adductor Ivongus Adductor Mag-nus The muscles of this region are adductors of the thigh, that is, they carry the thigh towards or across its fellow, and consequently they must all arise near the middle line of the body. Pectineus. Th.Q ;pectmeus is .a flat thin muscle which arises from the pectineal line and triangle of the pubes and the outer face of Gmibei'naf s ligament. It passes downward and is inserted into the upper part of the line leading from the trochanter minor to the linea aspera. It would not be improper to describe the remaining muscles of this group as a single muscle with a common insertion, since, at the insertion, their fibres are so intimately blended as to be inseparable without the destruction of fibres. They are arranged in three layers, the adductor longus, which lies on the same plane as the pectineus, in front, next the adductor brevis and last the adductor magnus. Abductor Longus. The adductor longus arises by a small, round tendon from the front of the pubes just below the angle and close to the symphysis. It passes downward and outward, widening as it descends, the tendon terminating in muscular fibres which. THE MUSCULAR SYSTEM. 267 becoming- tendinous in turn, are inserted into the middle third of the liuea aspera, the fibres blending with those of the other adductors. Adductor Brevis. The adductor brevis arises from the body and ramus of the OS pubis, just below the spine and between the gracilis and obturator externus. It passes downward, outward and back- ward, rapidly becoming wider as it descends, and is inserted into the whole length of the line leading from the trochanter minor to the linea aspera, its insertion extending further down than that of the pectineus, and blending with the general adductor tendon. Adductor Magnus. The adductor ma§)ius arises from the side of the tuber ischii and from the ischio-pubic ramus. It passes downward and outward in large distinct bundles of fibres and is inserted into the whole length of the linea aspera and by a rounded tendon into the adductor tubercle on the internal cond3^1e of the femur. This muscle is pierced by five apertures, one above the other, which transmit branches of the femoral arter3^ The lowest is much the largest and transmits the termination of the femoral artery itself, over which the adductor longus and magnus throw a tendinous arch to the vastus internus, forming what is called Hunter's canal. Action — These muscles are all adductors, or muscles which bring the thighs together ; but in addition, as their origin is in front of their point of insertion, the upper two are flexors. When the thigh has been rotated inward, they become power- ful outward rotators. The adductors are supplied by the obturator nerve; the pectineus, usually, by the anterior crural. Scarpa's Triangle. On the upper front part of the thigh there is an important triangle, known as Scarpa's. Its outer boundary is the sar- torius, its inner the adductor longus, its base is Poupart's ligament, its apex the intersection of the sartorius and the adductor longus. Entering this triangle at the middle of its 268 DESCRIPTIVE ANATOMY. base and passing- through it to disappear at its apex are the femoral artery and femoral vein. The floor of this space is formed by the biceps flexor femoris, pectineus and adductor brevis. Muscles of the Leg. The muscles of the leg- are divided into three regions, viz : 1st, anterior tibial ; 2d, posterior tibial ; 3d, external or fibu- lar. These muscles are enveloped by a dense fibrous membrane which is found encircling- the leg- everywhere except on the front. Above it is attached to the head of the tibia and fibula on the sides, and is continuous with the fascia, lata — forming- with it the popliteal fascia — behind. Below, it becomes at- tached to the bony prominences of the foot, forming- the ante- rior and two lateral aunular lig-aments. From its deep face it sends off three broad inter-muscular septa, besides smaller ones between individual muscles. Two septa are found on the outer side, one between the peroneal and anterior g-roups and one between the peroneal and posterior groups. The third is a broad transverse septum passing- between the super- ficial and deep muscles on the back of the leg-. Posterior Tibial Region. The muscles in the posterior reg-ion are placed in two lay- ers, superficial and deep. Superficial Layer. Gastrocnemius Plantaris Soleus Gastrocnemius. The g-astrocncinius is the larg-e muscle which g-ives shape to the calf of the leg. It arises by two heads from the upper back part of the condyles of the femur and from the ridges which connect the condyles with the linea aspera. The two heads, as thev descend, converg-e to form the lower lateral boundaries of the popliteal space, and unite to form the belly of the muscle along which a groove is confined for some dis- tance. The belly terminates just below the centre of the leg THE MUSCULAR SYSTEM. 269 in a large tendon called the tendo Achilles, which is inserted into the lower back part of the posterior tuberosity of the os calcis. It is the larg-est tendon in the body. Action — It raises the heel, and continuing" to act, raises the foot. Soleus. The soleus is a large fleshy muscle lying- beneath the gas- trocnemius. It has five points of origin, viz : the head and upper half of the posterior aspect of the fibula, the popliteal line and middle third of the internal border of the tibia and from a tendinous arch stretched between its bony origins. The muscle descends to terminate about the middle of the leg in the tendo Achilles. Action — Same as the gastrocnemius. Plantaris. The plantaris is an insignificant muscle lying between the gastrocnemius and soleus. It arises from the back part of the external condyle of the femur in common with the external head of the gastrocnemius, the belly of the muscle passing downward and inward between the gastrocnemius and soleus to terminate in a tendon which, escaping to the inner side of the two muscles, passes down either to be inserted into the posterior tuberosity of the os calcis or to be lost in the side of the tendo Achilles. Action — Same as gastrocnemius. The three muscles just described form the triceps surae. They are supplied by the internal popliteal nerve. Deep Layer. Popliteus Flexor Longus Digitorum Tibialis Posticus Flexor Longus Pollicis Popliteus. The -popliteus is a small triangular muscle resembling the anconeus in the upper extremity. It arises by its tendinous apex from a groove on the external condyle of the femur and passes downward and inward, adhering to the head of the fibula, the posterior ligament of the knee-joint and the under 270 DESCRIPTIVE ANATONY. surface of the fascia which covers it, is inserted into the tibi a above and as low down as the oblique or popliteal line on its posterior face. Action — It flexes and inverts the leg". It is supplied by the internal popliteal nerve. Flexor Longus Pollicis. Th.Q. flexor long-iis pollicis arises from the lower two-thirds of the fibula, except the last inch, and from the intermuscular septum. It descends behind the internal malleolus into the sole of the foot, crosses the tendon of the flexor long-us dig-i- torum and is inserted into the base of the last phalanx of the great toe. Action — It flexes the last phalanx of the great toe. Flexor Longus Digitorum. The flexor long'us dig-itoruin arises from the lower two- thirds of the tibia, except the last two or three inches, and from the intermuscular septum. It passes downward behind the internal malleolus, divides into four tendons, which are crossed by the flexor longus pollicis, and are inserted into the last phalanges of the four outer toes. Its action is indicated by its name, after flexing the toes it extends the foot on the leg. Tibialis Posticus. The tibialis posticus arises from the whole leng-th of the posterior surface of the interosseous membrane, from the ad- jacent edges of the tibia and fibula and from the intermuscular septum. It descends behind the internal malleolus and is in- serted into the tuberosity of the scaphoid bone and into the internal cuneiform bone. Action — It is an extensor and abductor of the foot. The three last muscles all arise from the interosseous mem- brane; and as the flexor longus pollicis arises from the outer bone of the leg and is inserted into the inner toe, it must cross the flexor longus digitorum. This crossing takes place in the sole of the foot and is known as the decussation of the tendons, which are connected at this point by a small slip. THE MUSCULAR SYSTEM. 271 The Interosseous Membrane. The iuterosseous membrane is a strong- ligamentous membrane which passes from tibia to fibula and is attached to their ad- jacent edo-es, after the manner of the interosseous membrane of the forearm. On its posterior aspect it is entirely appro- priated by the tibial muscles. The muscles in the deep layer are separated from those in the superficial layer by a strong" thick fascia. Anterior Region of the Leg. .Tibialis Anticus Kxtensor Longus Dig-itorum Kxtensor Proprius Pollicis Of the three muscles in this group two have four points of origin in common. These four points are as follows: 1st, outer tuberosity of the tibia ; 2d, investing fascia of the leg ; 3d, intermuscular septum ; 4th; interosseous membrane. Tibialis Anticus. The tibialis anticus arises from the common origin (the outer tuberosity of the tibia, the investing fascia, the inter- muscular septum between itself and the extensor longus digi- torum, and the interosseous membrane) and from the upper two- thirds of the outer face of the tibia. It passes downward to terminate in a tendon which runs beneath the anterior annular ligament and is inserted into the inner and under surface of the internal cnneiform bone and into the base of the metatar- sal bone of the great toe. Action — It flexes the foot; and, according as it acts with the tibialis posticus or the peronei, it inverts or everts the foot. Extensor Longus Digitorum. The extensor loui^us di^^itoriini arises from the common ori- gin— outer tuberosity, investing fascia, intermuscular septum between itself and the tibialis anticus internally and the pero- neus longus externally, and the interosseous membrane and from the head and whole length of the anterior aspect of the shaft of the fibula. It descends and divides into five tendons, which pass beneath the anterior annular ligament and are in- 272 DESCRIPTIVE ANATOMY. serted as follows: one Into the base of the metatarsal bone of the little toe, the other four into the backs of the four lesser toes after the manner of extensor tendons. That part of the muscle inserted into the base of the metatarsal bone of the little toe, and arising from the lower fourth of the fibula, is some- times called the peroneus tertius. Action — It extends the toes; and, by its insertion into the metatarsal bone of the little toe, flexes the foot. Extensor Proprius Pollicis. The extensor proprius ■pollicis is shorter than the two pre- ceding muscles and lies between and is overlapped by them. It arises from the middle two-fourths of the shaft of the fibula and from the interosseous membrane, and terminates in a tendon which passes beneath the anterior annular ligament and is in- serted into the base of the last phalanx of the great toe. Its action is indicated by its name. The anterior annular ligament is a strong oblique ligament- ous band which binds the tendons of the three preceding mus- cles down on the front of the ankle. It consists of an upper part passing from the tibia to the fibula and containing the compartment for the tibialis anticus; and a lower portion, at- tached above to the inner malleolus and below to the lesser process of the os calcis which forms the swing ligament con- taining the sheath for the extensor longus digitorum and the extensor proprius pollicis. A small offshoot of this band passes, to the plantar fascia. These muscles are supplied by the anterior tibial nerve. External Region of the Leg. Peroneus Longus Peroneus Brevis Peroneus Longus '^\\.^ -peroneus, or fihularis, longus arises from the head and upper two-thirds of the outer aspect of the shaft of the fibula, from the investing fascia and the intermuscular septa between itself and the extensor longus digitorum on the inner and the posterior group on the outer side — Below another septum is found between the two peroneal muscles. It descends to> THE MUSCULAR SYSTEM. 273 terminates in a tendon which passes behind the external mal- leolus, through the louver groove on the outer surface of the OS calcis, reaches the sole of the foot and is directed across it obliquely forward and inward, through a groove in the cuboid bone, to be inserted into the base of the metatarsal bone of the great toe. Action — It is an extensor of the foot. Peroneus Brevis. The fieroiieiis, or Jibularis, brevis derives its name from its position and because its origin and insertion are both short of the preceding muscle, beneath which it lies. It arises from the lower two-thirds of the outer aspect of the shaft of the fib- ula and from the intermuscular septum, descends behind the external malleolus, throug-h the upper groove on the outer sur- face of the OS calcis, and is inserted into the base of the meta- tarsal bone of the little toe. Action — It extends the foot. The two peronei muscles, as they are passing the outer malleolus, are held down by the external annular ligament They are supplied by the musculo-cutaneous nerve. Muscles of the Foot. The foot is divided into two regions, dorsal and plantar. The fascia covering the dorsum of the foot is thin and membranous. Above it is continuous with the anterior annu- lar ligament, while on the sides it becomes attached to the plantar fascia. On either side there is a strong lateral annular ligament each continuous above with the fascia of the leg and below with the plantar fascia. The iutcDial cDinular ligament is attached to the internal malleolus above and to the inner face of the OS calcis below. It forms grooves for the passage of the flexor tendons. The external amuilar ligament is attached to the internal malleolus and to the outer margin of the os calcis forming grooves for the peroneal tendons. Dorsum of the Foot. Extensor Brevis Digitorum. The extensor brevis digitorum arises from the upper and Des Anat— 18 274 DESCRIPTIVE ANATOMY. outer aspect of the os calsis and passing forward and inward divides into four tendons the innermost of which is inserted into the base of the first phalanx of the great toe, the other three into the backs of the next three toes in common with the long extensor tendons. Its name indicates its action. The Sole of the Foot. The Plantar Fascia. When the thick skin on the sole of the foot has been removed, there is brought into view a thick mass of fatty tissue and beneath this a strong fascia called iho. plantar fascia. It con- sists of a strong, thick central portion and, on either side, continuous with this, a thinner lateral portion. The central portion begins behind at the under surface of the os calcis, runs forward and just beyond the middle of the sole divides into five branches each of which passes forward to the base of a corresponding toe. The muscles of the sole all lie beneath (or, in the erect position, above) this fascia and are divided into groups in accordance with the subdivisions of the plantar fascia, viz : a central and two lateral groups. The propriety of this division is shown by the fact that the plantar fascia sends up to the bone intermuscular or dividing septa from the line of union of the central aud two lateral portions. In describing these muscles, however, they are taken in layers, of which there are three. When the plantar fascia, the dissection of which is the first step, has been removed, the first layer, consisting of one muscle in each group, is ex posed. This constitutes the second view in the dissection of the sole. First Layer. Abductor Pollicis Abductor Minimi Digiti Flexor Brevis Digitorum. The three muscles forming the first layer have a common origin, viz; 1st, the under surface of the os calcis; 2d, the plantar fascia which covers them; 3d, the intermuscular septa 'which separate them. Some of the plantar fascia should be THE MUSCULAR SYSTEM. 275 left on the muscles in dissecting- them, since it is a part of their orig-in. Abductor Pollicis. The abductor pollicis is the innermost of the three muscles of the first layers. It arises from the common orig-in and is inserted into the inner side of the base of the first phalanx of the g-reat toe. Its name indicates its action. Abductor Minimi Digiti. The abductor minimi dig-iti is the outer of the three muscles in the first laj^er. It arises from the common orig-in and is inserted into the outer side of the base of the first phalanx of the little toe. Its name indicates its action. Flexor Brevis Digitorum. Th^ flexor brevis dig-itoruin lies in the centre of the first layer. It arises from the common orig-in, passes forward and divides into four tendons for the four lesses toes. Each ten- don splits to allow the passag-e of the tendon of the long- flexor and is inserted into the sides of the shaft of the second pha- lanx. Its name indicates its action. Second Layer. Musculus Accessorius Lumbricales The second layer, exposed by removing- the first, is the third view in the dissection of the sole. It consists of the musculus accessorius, the lumbricales and the tendons of the flexor longus pollicis and flexor longus digitorum. These two tendons, soon after entering- the sole from behind the internal malleolus, cross each other forming- their decussation and are also connected by slips so that one muscle cannot act independ- ently of the other, but throws the part to which it is attached into slig-ht motion. Musculus Accessorius. The musculus accessorius arises tendinous and fleshy from the under surface of the os calcis and passing- forward is in- 276 DESCRIPTIVE ANATOMY. serted into the outer side and upper surface of the tendon of the flexor longfus dig-itorum just as it splits into its four branches. Action — It corrrects the obliquity which would otherwise be imparted to the four lesser toes by the action of the long- flexor. Lumbricales. The lumbricales are four little worm-like muscles, three of which arise from the bifurcation of the tendon of the flexor long-us dig-itorum, while the fourth spring-s from the inner side of the inner tendon of that muscle. They pass between the toes and are inserted into the tibial side of the extensor tendons of the four lesser toes. Action — -They aid the flexor long-us dig-itorum. Third Layer. Flexor Brevis Pollicis Flexor Brevis Minimi Digiti Adductor Pollicis Tranversus Pedis This layer, constituting- the fourth view in the dissection of the sole of the foot, is exposed by removing- the second layer. Flexor Brevis Pollicis. 'X:\iQ fiexor brevis -pollicis arises from the cuboid bone, the external cuneiform bone and the expanded tendon of the tibi- alis posticus. It is inserted into both sides of the base of the first phalanx of the g-reat toe, each tendon having- a sesamoid bone in it. Adductor Pollicis. The adductor pollicis arises from the cuboid bone, from the sheath of the tendon of the peroneus long-us and from the bases of the adjoining- metatarsal bones (second, third and fourth). It is inserted into the outer side of the base of the first phalanx of the great toe. Flexor Brevis Minimi Digiti. 'X:\iQ flexor brevis minimi dig-iti arises from the base of the fifth metatarsal bone and is inserted into the outer side of the first phalanx of the little toe. THE MUSCULAR SYSTEM. 277 Transversus Pedis. The ti'ansversus pedis arises by slips from the heads of the four outer metatarsal bones, and passing- inward is inserted into the outer side of the base of the first phalanx of the gfreat toe. Action — It is an adductor of the gfreat toe. Interosseous Muscles. Lying" between the metacarpal bones of the hand and the metatarsal bones of the foot are certain small muscles called from their position interosseous. In each member there are seven of these muscles, four dorsal and three plantar. They are bipenniform muscles, arising- from the metacarpal or met- atarsal bone and inserted into the first phalanx. The first dorsal interosseous of the hand is much larg-er than the others and is called the abductor indicis. The Muscles of the Face. The muscles of the face are arrang-ed in g-roups, viz: those connected with the orbit, with the nose, the mouth and, a very unimportant, g-roup connected with the auricle. Orbital Group — Three Muscles. Orbicularis Palpebrarum. The orhicularis-fxilpebrariiin is an elliptical muscle, lying- just beneath the skin, in front of the orbit, the portion which lies on the lid being- thinner and paler than the rest. It arises from the tendo oculi and adjacent bone; and the fibres, form- ing- an ellipse around the orbit, return to the place from which they started. The tendo oculi is a fibrous cord, which is at- tached by one end to the orbital aspect of the nasal process of the superior maxilla, while the other end bifurcates to be at- tached to the inner extremities of the tarsal cartilag-es. Kxternally the orbicularis palpebrarum is attached to the temporal fascia. Action — It closes the eyelids. - It is one of the sphincter muscles, but in its action differs from most of them in being" 278 DESCRIPTIVE ANATONY. immovably attached at its extremities. When its fibres con- tract they bring" the eyelids togfetheJ in a line corresponding- to its points of attachment, whereas most sphincter muscles close the aperture which they surround by an approximation of all their fibres at the same time, and in the same proportion, towards the centre of the aperture, e. §-., the orbicularis oris, in the act of whistling-, since it has no bony attachment. Corrugator Supercilii. The corriigator supercilii is a small muscle, which arises from the inner extremity of the supercilliary ridg-e, on each side, passes outward and is lost in the deep face of the orbicu- laris palpebrarum. Action — It throws the skin of the forehead into vertical folds, i. e., corrug-ates the brow. Tensor Tarsi. The tensor tarsi, or Horner s muscle, is very small. It arises from the orbital surface of the lachrymal bone, passes outward and divides into Cranial Group — One Muscle. Occipito-Frontalis. The occi^ito-frontalis of either side, arises from the superior curved line of the occipital bone and the mastoid process. It is tendinous at its origin but becomes fleshy as it passes forward; and then, as it is mounting- over the vault of the cranium, it forms a broad, aponeurosis and descending- on the forehead ag-ain becomes fleshy to be lost in the orbicularis palpebrarum and corrugator supercilii, its innermost fibres forming- the pyramidalis nasi muscle. Action — It raises the brows and throws the skin of the fore- head into wrinkles. Nasal Group — Three Muscles. Pyramidalis Nasi. The pyramidalis nasi is formed by the innermost fibres of the occipito-frontalis, which descending-, are lost on the bridge of the nose. THE MUSCULAR SYSTEM. 279 Action — It draws down the inner extremity of the eyebrow and elevates the nose. Compressor Naris. The comf)ressor naris, triang-ular in shape, arises from the canine fossa on the superior maxilla by its apex and, mounting- on the side of the nose, meets its fellow of the opposite side in a tendinous raphe on the bridge of the nose. Action — The two are supposed to compress the nostrils. Depressor Alae Nasi. The depressor alee nasi is found Just beneath the mucous membrane of the upper lip. It arises from the incisive fossa of the superior maxilla and is inserted into the ala of the nose. Its name indicates its action. The muscles of the face are nearly all small and pale and fatty. As a rule they arise from bone and are inserted into soft parts. Their action produces the varying- expression of which the face is capable. Muscles of the Mouth. The muscles of the mouth consist of two g-roups, superior and inferior labial groups and one muscle, the orbicularis oris, which belong-s to both g-roups. Orbicularis Oris. The orbicularis oris is the sphincter muscle of the mouth ; as it has but slig-ht connection with bone, this attachment may be disreg-arded. It consists of two seg-ments, one in each lip, which meet at the ang-les of the mouth. Action — It can close the mouth in two ways, either by bring- ing- the lips tog-ether in a horizontal line or by approximating- the ang-les of the mouth at the same time. Superior Labial Group — Five Muscles. Levator Labii Susperioris Alaeque Nasi. The levator lahii susperioris alceque nasi arises from the nasal process of the superior maxilla and descending- divides into two slips, one of w^hich is inserted into the ala of the nose 280 DESCRIPTIVE ANATOMY. while the other continues on to be inserted in the upper lip. Its name indicates its action. Levator Labii Superioris Propius. This muscle arises from the orbital ridge of the superior maxilla and descends to be inserted into the upper lip. Its name indicates its action. Levator Anguli Oris. The levator ang'uli oris, or canine muscle, arises from the canine fossa of the superior maxilla and passes downward and outward to be inserted into the ang-le of the mouth. Its name indicates its action. The Zygomatic Muscles — Two. The zygomatic are two small muscles which arise from the Z3'g"omatic process of the malar bone and pass downward and inward. The zygomaticus major, the lower one, is inserted into the ang-le of the mouth and the zygoniaticus minor into the upper lip. Action — They carry the angle of the mouth upward and outward. Inferior Labial Group — Three Muscles. Q,uadratus Menti. The quadratus menti, or depressor labii inferioris, is a square-shaped thin muscle which arises from the oblique line on the front of the lower jaw near the symphysis and, passing upward, is lost in the lower lip. Its synonym indicates its action. Triangularis. The triang-alaris or depressor ang-iili oris, arises by its base just external to the preceding and is inserted by its apex into the angle of the mouth. Its synonym indicates its action. Levator Labii Inferioris. The levator labii inferioris lies just beneath the mucous membrane. It arises from the incisive fossa of the inferior maxilla and is inserted into the integument of the chin. Its action is indicated by its name. THE MUSCULAR SYSTEM. 281 The Ocular Group. Levator Palpebrae Superioris Superior Rectus Inferior Rectus External Rectus Internal Rectus Superior Oblique Inferior Oblique The muscles forming this group are found within the orbit. All of them, except the levator palpebral superioris, are attached to the eye-ball, and all, except the two oblique mus- cles, arise at the apex of the orbit and pass forward flat, straight and widening as the}" advance toward their insertion. Four of them, from the direction of their fibres, are called recti and are concerned in moving the eye-ball. They are distinguished as : 1st, superior rectus, because it lies above the eye-ball and draws the front of the eye upward ; 2d, infe- rior rectus, because it lies below the eye-ball and draws its front downward ; 3d, external rectus, because it lies external to the e3"e-ball and draws its front outward ; 4th, internal rec- tus, because it lies internal to the eye-ball and draws its front inward. By a combined action of these muscles the front of the eye can be moved in all directions intermediate between those mentioned. All the recti arise from the apex of the orbit, that is the margin of the optic foramen, and also receive an origin from the fibrous sheath of the optic nerve. They run forward and are inserted into the sclerotic coat about one-fourth of an inch behind the circumference of the cornea. Some give as the origin of three of these muscles the ligament of Zinn, which is a fibrous band attached around the lower portion of the circumference of the optic foramen. This, however, is an unnecessary refinement. These muscles difiFer but slightly in size and length. Levator Palpebrae Superioris. Lying just beneath the orbit, and between it and the superior rectus, is a muscle closely resembling the recti called levator f)alpchr(c superioris since its action is to raise the upper lid. It arises from the upper margin of the optic foramen and sheath of the optic nerve, passes forward and is inserted into the upper edge of the superic^r tarsal cartilage. 282 DESCRIPTIVE ANATOMY. Inferior Rectus. The inferior rectus arises from the lower margfin of the optic foramen and from the sheath of the optic nerve. It passes forward and is inserted into the under surface of the sclerotic about one-fourth of an inch behind the cornea. External Rectus. The external rectus arises by a forked origin from the outer margin of the optic foramen and from the sheath of the optic nerve. It passes forward and is inserted into the outer sur- face of the sclerotic coat about one-fourth of an inch behind the circumference of the cornea. It is important to remember its forked origin, since many nerves pass through the interval between its head. Internal Rectus. The internal rectus arises from the inner margin of the optic foramen and sheath of the optic nerve. It passes forward and is inserted into the inner surface of the sclerotic coat about one- fourth of an inch behind the circumference of the cornea. Superior Rectus. The superior rectus arises from the upper margin of the optic foramen and from the fibrous sheath of the optic nerve. It passes forward and is inserted in the sclerotic coat one- fourth of an inch behind the cornea. It is the thinnest of the recti. Inferior Oblique. The inferior oblique is a narrow and thin muscle, arising from the orbital surface of the supsrior maxilla, near the inner side of the orbit. It passes out beneath the eye-ball and inferior rectus to be inserted into the sclerotic near the entrance of the optic nerve, on the outer under aspect of the eye-ball. Superior Oblique or Trochlearis. The superior oblique arises from the inner margin of the optic foramen and sheath of the optic nerve. It passes forward along the upper inner wall of the orbit to its front, where, THE MUSCULAR SYSTEM. 283 becoming- tendinous, it plays throug-h a cartilaginous ring- fixed to the fovea trochlearis : thence its tendon passes outward and backward, beneath the superior rectus, to be inserted into the outer aspect of the sclerotic about half way between the circumference of the cornea and the entrance of the optic nerve. Action — Its action is computed from the pully at the fovea trochlearis — hence it rotates the eye-ball on itsantero-posterior axis and draws it forward. Muscles of Mastication. Masseter Buccinator Temporal External Pteryg-oid Internal Pteryg-oid Masseter. The masseter arises from the zygfomatic process of the superior maxilla and from the anterior two thirds of the zygomatic arch by a bundle of fibres which pass downward and backward to be inserted into the ang-le and posterior part of the outer surface of the lower jaw. Beneath these fibres is a smaller bundle arising- from the posterior third of the zygomatic arch and passing- downward and forward to be in- serted into the outer face of the ramus nearly to the basilar border of the bone. Action — The two muscles, acting- tog-ether, draw the lower jaw powerfully upward and press the teeth firmly ag-ainst the teeth of the upper. The superficial fibres draw the jaw forward while the deep carry it backward. The masseter is covered by a strong- fascia, derived from the cervical fascia, which is attached below to the lower jaw, and blends with the deep cervical fascia, while above it is attached to the zyg-oma and forms the parotid fascia. Buccinator. The buccinator^ or trumpeter's muscle, is the bulkiest element of the cheek. It arises from the alveolar process of the superior maxilla, from the external oblique ridg-e of the lower jaw, as far forward as the second bicuspid tooth and 284 DESCRIPTIVE ANATOMY. from the pterygo-maxillary lig-ament. Its fibres converge to be inserted into the ang-le of the mouth. Action^The buccinators compress the cheeks, keeping" food between the teeth or expelling air through the lips. The -pteryg-o-niaxillary lig-a7nent extends from the hamular process of the pterygoid plate to the posterior extremity of the molar ridge of the lower jaw. In front it gives origin to some of the fibres of the buccinator and behind to the superior constrictor of the pharynx. Temporal. This muscle is found in a fossa, and is covered by a fascia, bearing the same name. The temporal fascia is a dense, shining aponerosis which is attached above to the temporal ridge on the side of the skull ; while below it divides into two layers, one seizing the outer and One the inner edge of the upper border of the zygomatic arch. The deep surface of the fascia gives origin to part of the temporal muscle. The temporal is a radiated muscle occupying the temporal fossa. It arises from the whole of the temporal fossa, from the whole length of the temporal ridge and from the temporal fascia which covers it. It passes downward, its fibres con- verging, and is inserted into the apex and inner side of the coronoid process of the inferior maxilla. Action — It is a powerful elevator of the lower jaw, acting in concert with the masseter. Its power is greatest when the jaw is depressed, while the power of the masseter increases as the jaws are approximated. External Pterygoid. The external pteiyjo-oid arises from the lower surface of the greater wing of the sphenoid, from the pterygoid ridge and sphenoidal spine and from the whole of the outer face of the external pterygoid plate. The fibres pass backward and out- ward and narrow to a tendon which is inserted into the neck of the condyle of the lower jaw and into the inter-articular fibro-cartilage. Action — The two muscles acting together, will carry the lower jaw directly forward. One muscle alone draws the jaw THE MUSCULAR SYSTEM. 285 forward and to the opposite side. It is the alternate action of the two muscles which produces the g-rinding- motion nec- essary for bruising* the food. Internal Pterygoid. The internal pterygoid, or internal mas seter 3X\^q^ from the inner face of the outer pterygoid plate, from the g*rooved posterior face of the tuberosity of the palate and occasionally by a slip from the tuberosity of the superior maxilla. It passes downward, outward and is inserted into the inner face of the angle and ramus of the lower jaw. Action^ — It acts almost exactly like the superficial fibres of the masseter, drawing* the jaw forward and upward. Its origin being* nearer the middle line, however, it also draws the jaw inward, thus aiding* the external pteryg*oid in grind- ing* the food. All the muscles of mastication are supplied by the muscular branches of the inferior maxillary division of the fifth, except the buccinator which also receives a branch from the facial. The internal maxillary artery furnishes blood. 286 DESCRIPTIVE ANATOMY. THE VASCULAR SYSTEM. The Arteries. There are two sets of arteries: one the Pulmonary System, the other the Systemic System. The two systems communi- cate with one another. In the Systemic circulation, the blood starts from the heart in the large arteries, and passes on into the branches which spring- from those arteries, these branches disminishing-in size until the capillaries are reached. Returning-, the blood passes throug-h the veins, which increase in size as we approach the heart. The Pulrnonary circulation. The heart is divided into four chambers: two left, one above and one below; and two right, one above and one below. From the chamber on the left, under side, the systemic circulation starts. E^ntering into the chamber above on the rig-ht is the termination of the venous system; and from this chamber the blood is poured into the chamber below by means of two inlets. From there it passes down into a cavity from which the pulmonary artery starts, this artery breaking- up into two branches and passing- to the lungs. Af- ter making- the circuit of the lung-s, the blood is returned into the upper left side of the heart, from which it drops down into the other left cavity, where the aorta starts. The arteries all commence with the one g-reat trunk the aorta; but for several reasons we g-enerally begin with one of the arteries belong-ing- to the upper extremity or head and neck. Arteries decrease in size as they throw off branches; but if we consider the combined area of the two branches into which the artery is divided, we find that this area is g-reater than that of the original trunk. Similarly, if we consider the com- bined area of all the branches which spring- from any g-iven artery, we find that this area is infinitely g-reater than that of the orig-inal artery. On the other hand, the combined area of the veins, while larger than the combined area of the great THE VASCULAR SYSTEM. 287 veins which return the blood to the heart, is much larg-er than the combined area of the arteries. Consequently, as the blood conti'nues its course in circulating" throug-h the body the rapid- ity of the current decreases in proportion as the distance from the heart increases. As the veins decrease in size, or contain- ing- capacity, as they approach the heart, the current becomes swifter; but never anything- like as swift as the current in the arteries. In describing- an artery, we not only g"ive the regfion in which it lies, its course and termination; but its relations, divided for definiteness of description into muscular, visceral and cord re- lations. Often these relations include a vein, or another arter}-^; and there is usually something* else to be noticed, for instance, a tendon. Besides that, arteries have other covering's, skin and fascia; and other relations, which are neither cords, fascias nor muscles. Such, for instance, are the Thyroid gfland, the Trachea, the Pharynx, or the Thymus g-land. To describe one, for instance, let us take the g-reat vessel on the side of the neck, the Arteria Innominata. Starting* at the commencement of the transverse aorta, it passes upward and outward, and terminates in one of the most frequent ways in which arteries terminate, viz., by dividing- into two separate branches: one branch, the right common carotid, which runs nearly ver- tically upward in the neck, the other, the rig-ht subclavian, which apparently continues the course of the orig-inal vessel, with a slig-ht increase in its obliquity. There are two com- Dion carotids, di.xid.t'wo subclavians, rig-ht and left. To decide the difference between them, notice that the right common carotid and the rig-ht subclavian each pass down into the thoracic cav- ity. There is a combination of the two vessels on the right side; and no junction on the leftside, the right springing by a common branch, the left by separate branches. The Right Common Carotid. The rig-ht common carotid artery differs from the left in that it springs from the arteria innominata, whereas the left springs directly from the arch of the aorta, hence the relations of the first portion of the left common carotid would be differ- 288 DESCRIPTIVE ANATOMY. ,*, ent from the relations of the right common carotid in this por- tion. The relations after they have passed from the thoracic cavity, and have reached the back of the sterno-clavicular ar- ticulation, become identical; and then the description of one vessel will apply to the other. The right common carotid commences b}'' being- one of the two terminal branches of the arteria innominata. It then passes upward witha slight inclination backward and outward, lying- upon the anterior tubercles of the transverse process of the four lower cervical vertebrae, about on a line drawn from the upper border of the thyroid cartilag-e. After reaching- that point, it terminates by dividing- into two branches, which are known as the internal and external carotid arteries. Covering- the vessel w^e find, first, the skin ; then a layer of superficial cervical fascia; then the platysmamyoides muscle; then the first layer of deep cervical fascia ; then the sterno- cleido- mastoid muscle ; then the second layer of deep cervical fascia. After pulling- that aside, we come to the sterno-hyoid muscle ; then to the sterno-thyroid ; and anterior belly of the omo-hyoid ; then to the last layer of cervical fascia ; forming- the front of the sheath of the vessel behind ^vhich you have the artery itself. It is more convenient to divide the vessel into two portions, the first portion being- considered as lying- in the "Triang-le of Necessity" or the inferior carotid tricDig-le, the second as lying- in the superior, or "Triang-le of l^lection". The first portion commences as the artery itself commences, as being- one of the branches of the arteria innominata, and terminates where the vessel is crossed by the anterior belly of the omo-hyoid. The second portion commences where the first terminates; and ex- tends to the termination of the artery at the upper border of the thyroid cartilage. The first portion is deeply seated, difficult of access; and the triangle is for that reason known as the Triangle of Necessity. Throughout the first portion the artery is completely covered by the sterno-cleido-mastoid mus- cles; it is only at its commencement that it is covered by the sterno-hyoid and thyroid, which rapidly draw away from the vessel and cease to be relations of it. Then as we pass up to THE VASCULAR SYSTEM. 289 the seco?id portion of the vessel (the omo-hyoid being- the dividing" line, belongs partly to each portion), we find that the second portion is covered by superficial and deep fascia, plat3'snia myoides, and the sterno-cleido-mastoid, which in this situation overlaps rather than covers. Throug"hout its entire course it is covered by the sterno-cleido-mastoid and the platysma myoides; only at its beg^inning- is it covered by the bellies of the sterno-hyoid and sterno-thyroid; and only at the middle of its course is it covered by the omo-hyoid. The more important thing's to study in connection with the vessel are the cord relations, these being- always of g-reater importance than anything- else, owing- to the dang-er of wound- ing-. Every larg-e artery protects itself by passing- as closely as possible to the bone ; but another protection is the sheath, which is formed of fibrous tissue, in this case a part of the deep cervical fascia. So powerful is the sheath that many cases could be cited in which vessels have been found floating" in pus, the artery remaining- entirely uninjured. This vessel possesses one of the larg-est sheathes in the body ; and in the same sheath with it are found the internal jug-ular vein and the pneumog-astric nerve, all lying- upon the same plane, the artery being- most internal, the vein most external, and the nerve lying- between them. The nerve is sometimes described as "lying- between and behind" the vein and artery ; but this is not correct : It lies between them and not behind them. Another important structure running- downward upon its sheath is the Descendens noni, or Descendens hypog-lossi. This nerve passes downward on the front of the sheath of the com- mon carotid: and just before it reaches the upper border of the anterior belly of the omo-hyoid it receives one or two filaments from the cervical plexus of nerves forming-, just above the anterior belly of the omo-hyoid, Scarpa's Arch. In addition there is another important cord lying- just behind the artery, which has a larg-e bulg-e upon it near its upper extremity, called the cervical portion of the Sympathetic nerve. It descends upon the prevertebral g-roup of muscles directly behind the sheath. Des Anat— 19 290 ^DESCRIPTIVE ANATOMY. On the upper portion of the course of the artery are g^enerally seen the superior thyroid veins, frequently two. In the lower portion, about its middle, are seen the middle thyroid gener- ally ; and below that gfenerally the anterior jug-ular, all of these veins being- superficial. At the commencement of their course these vessels are deeply seated, and covered by a larg"e number of structures ; and they are very close to each > other, the distance increasing- as we pass upward into the neck. Owing- to the projection of the Thyroid cartilag-e, with the tissues which lie m the neig-hborhood of it, these vessels appear to be more deeply seated in the second portion than in the beg-inning- of their course. At the commencement of the artery, to its inner side, it has the Trachea : passing- above, the Thyroid g-land, passing- above that, the cartilag-es of the larynx; and then, still hig-her up, the side of the pharynx. As the Pneumog-astric nerve passes downward, it g-ives off an important branch, w^hich lies over the subclavian artery, the Recurrent Laryng-eal. This branch winds upwards behind the subclavian artery, first passes obliquely inward, and then passes behind the common carotid artery, and runs into the muscles along- the side of the neck. As the nerve runs upward, it bears a three fold relation to the common carotid artery : first behind and external, then behind and then to the inner side. A branch of the subclavian, the inferior thvroid is also a posterior relation of the first portion. Unlike nearly all arteries, the common carotid gfives off no branches in its course. The usual arrang-ement is that the arteries give off branches to those structures among which they lie. The branches of one of its terminal branches supply the upper region of its course, while the branches of the sub- clavian supply the lower region. External Carotid. The external carotid artery, one of the two terminal branches of the common carotid, begins where that artery bifurcates about on a level with the upper border of the thyroid cartilage and, continuing the direction of the common carotid, passes THE VASCULAR SYSTEM. 291 beneath the posterior belly of the dig-astric and the stylo-hyold muscles, enters the substance of the parotid g-land and termi- nates in that g-land behind the neck of the condyle of the lower jaw by dividingf into two branches, the temporal and the internal maxillary arteries. The temporal continues the course of the external carotid to mount over the zyg"oma and be distributed to the side of the head by two branches, while the internal maxillary passes inward, behind the neck of the condyle of the lower jaw to supply the deep structures of the face. This artery is divided, for convenience of description into three portions. Relations. — The first portion of the external carotid lies in the superior carotid triang-le, its length varying- as the common carotid divides on a level with, above or below the upper border of the thyroid cartilag-e, for it extends from the bi- furcation of the common carotid to the stylo-hyoid and pos- terior belly of the digastric. It is covered by the integument and platysma and deep cervical fascia, is slightly overlapped by the sterno-mastoid and is crossed in front by the hypo- glossal or twelfth nerve, near the termination of this portion, and the lingual vein near its beginning. At its commence- ment the internal carotid lies to its outer side ; but by the time the external carotid reaches the termination of its first portion, the internal carotid has passed behind it. The second portion is that which is crossed by the stylo- hyoid and posterior belly of the digastric. Its coverings are integument, platysma, stylo-hyoid and posterior belly of the digastric. The stylo-glossus and pharyngeus muscles, glosso- pharyngeal and superior laryngeal nerves cross between this and the internal -carotid about on a line between the second and third portions. The third ■a^\(S. last portion extends from the stylo-hyoid and posterior belly of the digastric to the termination of the artery behind the neck of the condyle of the lower jaw. It lies embed- ded in the substance of the parotid gland and is crossed, super- ficially, near its termination, by the facial nerve and the facial 292 DESCRIPTIVE ANATOMY. and temporo-maxillary veins. The first portion is most superficial, the second the shortest and the third the long-est and deepest. Branches. Superior Thyroid Occipital" Lingual Posterior Auricular Facial Ascending- Pharyng"eal Parotid ean. It should be remembered that the common carotid gives off no branches except its terminal ones and hence the structures in its course have to be supplied by other arteries. The ex- ternal carotid does a part of this work. Besides those into which it divides, the external carotid g-ives off six sing-le bran- ches, and a set to the parotid gland. The first three arise from the anterior aspect of the artery, low down and in the order given from below upward. The next two rise from the back of the artery higher up. I. Superior Thyroid. The superior thyroid, which is at first very superficial, being covered only by the platysma and fascia, forms a curve, first passing upward and inward, then downward and inward, crosses beneath the depressor muscles of the hyoid bone, and reaches the upper part of the thyroid gland to which it is dis- tributed. It gives off the following branches: 1st. hyoid, which passes forward just beneath the hyoid bone to be distributed to muscles and anastomose with its fellow of the opposite side. 2nd. superior laryng-eal, which passes forward on the thyro- hyoidean membrane and pierces it to be distributed to the mucous membrane of the larynx, anastomosing with Its fellow. 3rd. crico-thyroid, which passes across the crico-thyroid membrane and gives branches which pierce it to reach the mucous membrane of the larynx anastomosing with its fellow. 4th. muscular or superficial descending braiich ^hxch. passes downward and outward across the common carotid to supply the sterno-mastoid. THE VASCULAR SYSTEM. 293 II. Lingual. The lingual arter}^ is divided into four portions: 1st, it descends obliquely inward, over the extremity of the hyoid bone covered only by the skin and platysma; 2d, it passes for- ward along- and above the hyoid bone, is crossed by the digas- tric and then covered by the hyo-glossus muscle; 3d, it ascends to the under aspect of the tongue; 4th, in riins forward on the under aspect of the tongue, under the name of the ranine artery. The first two portions lie on the middle constrictor of the pharynx. Its branches are three: 1st. Hyoid, which runs inward along the upper border of the hyoid bone to be distributed to muscles and anastomose with its fellow. 2d. dorsalis lingiicc, which ascends to the dorsum of the tongue along the posterior border of the hyoglossus muscle to supph^ the back of the tongue muscous membrane and soft palate. 3d. subling-iial, which runs forward to the sublingual gland from the margin of the hyo-glossus and is distributed to that gland, to the mucous membrane of the mouth and to muscles. The ranine is the terminal branch of the lingual. It passes forward on the under surface of the tongue, beneath the mu- cous membrane is distributed to that organ and anastomoses with its fellow at the end of the tongue. III. Facial. The facial artery arises just above the hyoid bone and is divided into two portions, one while it is in the neck and the other after it reaches the face. The first portion passes forward and upward, through the submaxillary gland, to mount over the body of the lower jaw just at the anterior inferior angle of the masseter muscle and about one and one-half inches in front of the angle of the lower jaw. At its origin it is superficial, being covered only by the skin and platysma; but it soon enters the submaxillary gland and is crossed by the stylo-hyoid and pos- terior belly of the digastric. When it leaves the gland and mounts over the jaw it isagain superficial, being covered only by 294 DESCRIPTIVE ANATOMY. the integ'ument and platysma. Its pulsations can here be felt. The second portion of the artery has a tortuous upward and inward course over the face towards the angle of the mouth, thence along- the side of the nose to terminate at the inner canthus of the eye as the angular artery. Its branches are divided into those g-iven off below the jaw, five in number, and those on the face, also five in number. v 1st. inferior -palatine, which ascends to the soft palate, tonsils, E)ustacian tube, stylo-pharyng-eus and stylo-g-lossus muscles. 2d. tonsillar, which ascends to the tonsils. 3d. submaxillary , which are from three to five in number and ascend to the submaxillary g-land. 4th. submental, which runs forward beneath the lower jaw and passing- over the symphysis menti terminates by inoscu- lating- w^ith the inferior labial. It lies on the mylo-hyoid supplies neig-hboring- muscles and anastamoses with the sub- maxillary before running- over the chin. 5th. 77iuscular branches distributed to neig-hboring- branches. The five branches from the second portion are as follows : 1st. inuscular or buccal, which are branches to adjacent muscles. 2d. inferior labail, which runs forward beneath the skin of the lower lip, supplies muscles in its course and anastamoses with the submental inferior coronary and the inferior dental. 3rd. inferior coronary, which skirts the edg-e of the lower lip, anastanlose with its fellow of the opposite side, with the mental branch of the inferior dental and with the inferior labial and supplies muscles and g-lands in its course. 4th. superior coronary, which skirts the edg-e of the upper Hp, giving- off a branch to the septum of the nose, arteria septi. This artery anastamoses with its fellow and supplies struct- ures in its course. The arteria septi passes upward to ramify on the septum of the nose. 5th. lateralis nasi, which is distributed to the side of the nose, inosculating- with its fellow of the opposite side. The angular artery is the continuation of the facial. Passing THE VASCULAR SYSTEM. 295 up along- side of the nose, it g-ives off small branches to the cheek and terminates by anistaraosing- with the nasal branch of the opthalmic. The inferior labial and inferior coronary very frequently comes off by a common trunk. Sometimes it is a common trunk which divides into the inferior and superior coronary arteries. IV. Occipital. The occifiital branch of the external carotid passes upward and backward to the occipital g-roove of the temporal bone, beneath the muscles attached to the mastoid process, thence mounting- on the posterior aspect of the occipital bone and piercing- the fascia which connects the cranial attachment of the trapezius with the sterno-cleido-mastoid becomes superfi- cial and is distributed to the back of the head. The hypog-lossal nerve winds around, from behind forward — it crosses over the internal carotid artery, the internal jugular vein, the pneumo- gastric and spiral accessory nerves. Its branches are : 1st. Sterno-mastoid, which, sometimes arising- directly from the external carotid, descends to the sterno-mastoid muscle. 2nd. muscular branches to stylo-hyoid and dig-astric. 3rd. two small branches auricular to the concha and menin- geal to the membranes of the brain. 4th. f>rinceps cervicis, which passes down the neck lying- deep. It divides into a superficial branch which passes beneath the splenius and inosculates with the superficial cervical of the transversus calli; and a deep branch which passes beneath the complexus to anastomose with the profunda cervicis. V. Posterior Auricular. The -posterior auricular ya.'^'^^':^ upward and backward behind the ear and is distributed by an aiitcrior branch to the auricle and by a posterior to the back of the head. It produces three branches, the stylo-mastoid which enters the stylo-mastoid foramen to be distributed to the ear; the auricular which is distributed to the back part of the cartilag-e of the ear — the mastoid which passing- over the sterno-mastoid is distributed to the scalp behind and above the ear. 2% DESCRIPTIVE ANATOMY. VI Parotidean Branches. T)iQ parotidean branches, four or five in number, are distri- buted in the parotid g"land as the external carotid is passing- through it. Ascending Pharyngeal. The ascending- -pJiaryngeal branch spring's from the externa^ carotid just at its origin and passes up beside the pharynx to the base of the skull, where it divides into a mening-eal branch to enter the cavity of the cranium throug-h the jugular foramen, and a pharyngeal branch to adjacent parts. The Temporal Artery. The temporal artery, one of the two terminal branches of the external carotid, begins where the external carotid forks in the parotid gland, behind the neck of the condyle of the lower jaw, and emerging mounts over the zygoma and divides about one and one-half inches above that point, where it lies on the temporal fascia, into an anterior and a posterior tempo- ral. The anterior passes upward and forward, inosculating with the frontal and supra-orbital the posterior upward and backward to be distributed to the side of the head, and to inosculate with its fellov/ of the opposite side and with the occipital. These two are called the superficial temporal branches since, as will appear hereafter, there are other and deeper temporal branches. It gives rise to four branches besides those in which it terminates. 1st. transverse facial which arises below the zygoma, and passes transversel}" forward on the masseter muscle parallel with Steno's duct. It anastomoses with the facial. 2nd. anterior auricular, to the front of the auricle. 3rd. orbital, which runs forward to the outer angle of the eye. 4th. jniddle temporal, which plunges into the substance of the temporal muscle where it is distributed. Its name is derived from its situation between the two surperficial tempo- ral arteries and the deep which spring from another trunk. THE VASCULAR SYSTEM. 297 The Internal Maxillary. The internal maxillary is the larg-er of the two terminal branches of the external carotid. The course of the artery is divisible into three portions. T\\t first portio}i passes inward, forward and upward behind the ramus of the inferior maxilla, between it and the internal lateral lig-ament. The second portion passes forward and upward between the internal pteryg-oid muscle within and the temporal and masseter mus- cles without. The third portion disappears into the spheno- maxillary fossa. Its branches are sixteen in number, as follows : First Portion— Four Branches. 1st. tympanic which enters the tympanum throug-h the fissure of Glaser. 2nd. meniniy-ea media, which ascends to enter the cavity of the cranium throug-h the foramen spinosum. It then divides into an anterior and a posterior branch. The anterior passes upward and forward over the great wing- of the sphenoid, grooves the anterior inferior angle of the parietal and divides into branches which rammify over the dura. The posterior branch passes over the squamous por- tion of the temporal and divides into branches on the occipital. These branches anastamose with each other and with the ante- rior and posterior meningeal. They supply the dura and the bone. 3rd. The mcning-ea parva, which enters the cavity of the cranium through the foramen ovale. 4th. inferior dental, which descends to enter the dental fora- men of the inferior maxilla and runs forward in the bone giving- a branch to each fang of every tooth in the lower jaw. Just before entering the dental foramen it gives off a branch called mylo-hyoidean ; and when it reaches the mental fora- men it divides, sending a branch called mentalis through the mental foramen, while another, called the incisive, continues its course in the bone. The mylo-hyoidean passes in the groove of that name, and supplies the mylo-hyoid muscle. 298 DESCRIPTIVE ANATOMY. Second Portion. Six branches are derived from this portion of the artery. The deep temporal, two in number, occupy the anterior and posterior portions of the temporal fossa. They anastamose with the superficial temporal arteries and supply the temporal muscle. The ^/erv^o/rt' branches, as the name indicates, su'^- ply the pteryg"oid muscles. The masseteric branch runs through the sig^moid notch and supplies the masseter from its deep surface. The buccal passes forward between the internal pterygoid and the lower jaw and supplies the buccinator. It anastamoses with the facial. Third Portion. 1st. sttjyerior dental, which descends upon the tuberosity of the superior maxilla and sends its branches through small foramina in the bone to supply the molar and bicuspid teeth. 2nd. Infra-orbital, which runs forward along the canal in the floor of the orbit, sending branches downward to the front teeth of the upper jaw and emerges through the infra-orbital foramen to supply adjacent parts On the face. 3d. descending palatine, which descends along the posterior palatine canal to emerge in the palate through the posterior palatine foramen and send a branch forward in a groove seen on the side of the hard palate(called the anterior palatine canal) which reaches the floor of the nose through the anterior pala- tine foramen. 4th. spheno- palatine, which enters the nose through the spheno-palatine foramen and divides into two branches, one be- ing distributed to the septum and the other to the mucous membrane of the outer wall and antrum maxillare. 5th. ptergo-palatine, which runs backward in the pterygo- palatine canal to the pharynx, E^ustachian tube and neighboring parts. 6th. Vidian, which passes backward along the pterygoid canal and, like the preceding, is distributed to the mucous membrane of the pharynx and E)ustachian tube. THE VASCULAR SYSTEM. 299 The Right Subclavian. The Rig-ht Subclavian artery is one of the two terminal branches of the arteria innominata, the other being- the rig-ht common carotid. It commences upon the upper border of the rig-ht sterno-clavicular articulation, arches upward and out- ward, passing- between the Scaleni muscles; then turns down- ward and outward, and terminates by becoming- the axillary at the junction of the outer one-third with the inner two-thirds of the shaft of the clavicle on the outer border of the first rib. It is thus seen that it forms a bow, the hig-hest part of the arch being- that which passes behind the Scaleni muscles. This warrants the sub-division of the artery into three f>ortions. The -first commences by a bifurcation of the arteria innom- inata and terminates at the inner border of the scalenus anti- cus; the second lies behind the scalenus anticus; and the third portion extends from the outer border of the scalenus anticus to the termination of the artery in the axilla at the outer border of the first rib. This third portion is itself sometimes sub- divided into that part which lies between the scalenus anticus and the clavicle and the part which lies behind the clavicle; but the division is unnecessary. Relations. The covering-s of this artery are the skin, su- perficial fascia, platysmamyoides muscle, one layer of the deep cervical fascia, the sterno-cleido-mastoid muscle, with the sec- ond layer of deep cervical fascia, and the posterior belly of the omo-hyoid muscle. It is better to take the relations of the ar- tery as a whole; and then consider them with reference to the various portions of the vessel. Thus, starting- from within and passing- outward on the anterior face of the artery, we find the pneumog-astric nerve, with its recurrent laryng-eal branch, ex- ternal to that the internal jug-ular vein, then the phrenic nerve, then the scalenus anticus muscle, then the suprascapular vein and artery, the nerve to the subclavius and the subclavius muscle. More superficially, just beneath the skin, are the thoracic branches of the cervical plexus. Below it are its 300 DESCRIPTIVE ANATOMY. vein, the recurrent laryngeal nerve, the lung" and pleura, and the first rib. Behind, the recurrent laryngeal, the cervical portion of the sympathetic nerve, the vertebrae, the Scalenus anticus muscle, and the brachial plexus of nerves. Above, the brachial plexus and the omo-hyoid muscle; and to its inner side, the right common carotid. . To consider the different parts separately: First Portion. The first ^orfio)i is covered throughout by the integument, platysma, sterno-cleido-mastoid; and, at its commencement, by the right sterno-clavicular articulation, the sterno-hyoid and sterno- thyroid muscles. Superficial branches of the cervical plexus also pass over it. Crossing it in front are the pneumogastric nerve, giving off here its recurrent laryn- geal branch ; external to this, the internal jugular vein ; and external to this, usually, the phrenic nerve. The course of the phrenic is downward and slightly inward upon the anterior face of the scalenus anticus muscle. Occasionally it continues on that muscle until it passes beyond the artery; but generally it drops off from the muscle to the artery to become an anterior relation of the latter. In front near its beginning is the right vertebral vein. Just as the internal jugular vein crosses the front of the artery it communicates with the subclavian vein to form the right Vena Innominata. Hence the junction of these two veins would lie below on a plane anterior and slightly to the outer side of the first portion of the subclavian. The pneumogastric here gives off the recurrent laryngeal, which is first in front, then below, then behind the artery. To the in- ner side at its commencement is the right common carotid. Be- hind it is the recurrent laryngeal, and the cervical portion of the sympathetic, the cardiac branches of which cross its front. Below, the artery rests upon the lung and the pleura. The pleura of the right side extends upward into the root of the neck above the level of the first rib, so that the artery makes an impression upon the dome of the pleura, and a portion of that membrane lies behind the artery as well as beneath it. The Second Portion. The second portion forms the top of the bow; and runs transversely outward. It runs behind the Scalenus anticus muscle; and is co-extensive with its breadth. THE VASCULAR SYSTEM. 301 In front are the inteofument superficial fascia, the platysma first layer of deep cervical fascia, the sterno-cleido-mistoid second layer of deep cervical fascia, with branches of the cer- vical plexus extending- over the clavicle. Occasionally on its front is the phrenic nerve. The suprascapular artery and the transversa colli branches of the subclavian pass across the front of the scalenus anticus muscle; and should be considered in all operations in this situation. The brachial plexus of nerves lies behind and above the artery, separating- it from the scalenus posticus muscle. Below and behind are found the pleura and the lung-s. The subclavian vein is not a relation of the artery, lying- some distance below it and separated from it by the scalenus anticus. The Third Portion. The third portion is the downward and outward part, extending- from the outer edge of the Scale- nus anticus to the outer border of the first rib, and lying- in its lower portion between the clavicle and the first rib. It is covered entirely by the platysma ; and to a slig-ht extent, in many cases, by the outer edg-e of the sterno-cleido-mastoid ; and, in a few cases, where this muscle has a redundant orig-in, the third portion of the artery is covered completel}^ by it. The artery lies in the triangular space bounded above b}^ the omo-hyoid, internally by the sterno-cleido-mastoid, and below by the clavicle. This space is covered over by a rather dense layer of the deep cervical fascia, which is of course one of the coverings of the vessel. Crosssing- in front of it are the supra- scapular artery, a branch of the subclavian itself, which passes outward just beneath the upper border of the clavicle. This artery is accompanied by its own vein. Crossing- the front of it from above is the external jug-ular vein, which descends the neck lying- just behind the outer edg-e of the sterno-cleido- mastoid muscle ; and, after having received on the front of the artery the suprascapular and tran verse veins, it terminates in the subclavian on the outer side of the scalenus anticus. The subclavius muscle, the descending- branches of the cer- vical plexus, and the nerve to the sub-clavius muscle are also in front. Owing- to the curve in the course of the artery, what has heretofore been called its upper aspect now becomes 302 DESCRIPTIVE ANATOMY. its external. The brachial plexus of nerves has been described as being an external relation, though the plexus lies on a plane posterior to the artery as well as to its outer side. The omo-hyoid lies above and to the outer side, in front of the plexus. To the inner side is the subclavian vein, which, is in contact with the vessel for only a short distance before its ter- mination. The vein, it will be observed, is a relation of the iirst and third portions only ; that is, it is in contact with the outer front aspect of the first portion at its commencement, and with the inner front aspect of the third portion at its ter- mination, bearing no relation to the second portion, hence it presents the same relation which a string bears to a bent bow. At the very commencement of this portion it lies upon the pleura, so that it will be seen that the pleura lies below and behind all three of the portions of the artery, though for the third portion the relation is only a momentary one, the first rib quickly separating the two structures. The lig-ation of this vessel is preferably performed in the third portion of its course. Branches. Vertebral ( Inferior Thyroid Internal Mammary Thyroid Axis < Suprascapular Superior Intercostal ( Transversa Colli Profunda Cervicis. These seven branches usually rise by four trunks: the ver- tebral, thyroid axis, internal mamary, and the common trunk for the superior intercostal and cervicalis profunda. Vertebral. The vertebral is the first and largest branch of the subclav- ian. It arises from the posterior aspect of the first portion of the artery; and enters the foramen in the transverse process of the sixth cervical vertebra, usually. Occasionally it passes to the fifth; but, though the seventh is perforated, the vertebral artery never enters it. It passes upward through the fora- mina of the transverse process, winds backward around the superior articular process of the atlas, enters the cavity of the cranium through the foramen magnum, and at the lower bor- THE VASCULAR SYSTEM. 303 der of the pons Varolii unites with its fellow of the opposite side to form a sinsfle trunk, called the Basilar artery, which runs upward and forward to the anterior border of the pons, where it divides into four terminal branches, two on either side. At its orig-in the internal jugular vein and the infe- rior thyroid artery lie in front of it. On the left side, while l\4no- between the scalenus anticus and longus coli muscles, the thoracic duct passes in front of it. Besides its terminal branches it g-ives off the following- branches : 1st. lateral spinal, which are g^iveu off as the artery ascends the neck to enter the intervertebral foramina. They there divide into two branches: one for the bodies of the vertebrae, and the other for the spinal cord and its membranes. That for the spinal cord reaches its along- the roots of the spinal nerves, while the branch for the bodies of the vertebrae divides into an ascending- and a descending- branch, anastomosing- with similar branches coming- from above and below. 2nd. The muscular branches are unimportant. They come from the lower portion of the artery, and are distributed to the cervical muscles. 3d. Tho. posterior meningrcal are small branches distributed to the dura mater of the cranium. 4th. The anterior spinal zx\'$,q's, near the termination of the vertebral, unites with its fellow of the opposite side, and passes downward on the middle of the spinal cord, where it receives communications from the lateral spinal branches, before men- tioned, and forms a continuous vascular channel down the anterior aspect of the cord. 5th. The posterior spinal winds around the medulla, unites with its fellow of the opposite side, passes down behind the posterior roots of the spinal nerves, and receives similar branches from the lateral spinal. This also forms a branch passing- down the spinal cord. <)th. ^\\Q. posterior inferior ce7'ebellar 7vc\v,^'s> just before the termination of the vertebral; and passing- across the lateral as- pect of the medulla, winds around the inferior portion of the cerebellum, to which it is distributed. 304 DESCRIPTIVE ANATOMY. Basilar. The Basilar ?ivX.Qry is formed by the junction of the two ver- tebral arteries above the middle of the medulla oblongata; and after passing- upward on the lower surface of the pons varolii, it terminates on the upper border of that body by dividing into two branches, the posterior cerebral arteries. It gives off the following branches: 1st. transverse, which are numerous small branches given off to each side of the pons Varolii. 2nd. anterior inferior cerebellar, or anterior cerebellar, which arises soon after the origin of the basilar; and passing across the pons a little below its centre, reaches the anterior border and lower surface of the cerebellum, where anastomosing with the posterior inferior cerebellar, it is distributed to that organ. It is in reality scarcely more than one of the transverse branches. In addition to these way-side branches, the basilar artery gives off the following terminal: 1st. superior cerebellar, which passing across the upper border of the pons, passes into the fissure between the upper border of the cerebellum and the cerebrum, and ramifies upon the upper surface of the cerebellum. 2nd. T\\Qj^osterior cerebral also winds around the outer bor- der of the pons, passing to the inner surface of the posterior lobe of the cerebrum, to which it is distributed, anastomosing with the other cerebral arteries. These two vessels are formed by the bifurcations of the bas- ilar artery, which just before it divides, gives off numerous small branches, which enter the minute foramina constituting the locus ^erforatus at the base of the brain. Thyroid Axis. The Thyroid Axis is a short thick trunk, which arises from the upper portion of the subclavian, just at the inner border of the scalenus anticus muscle. It almost immediately divides into three branches ; the Inferior Thyroid, the Suprascapular, and the Transversa Colli. THE VASCULxVR SYSTEM. • 305 Inferior Thyroid. The inferior thyroid, the branch from which the plexus re- ceives its name, first passes vertically upward for a distance of an inch and one-half or two inches. It then turns inward, cross- es behind the sheath of the common carotid artery to reach the thyroid gland. It gives off branches, or twigs, called lary)i§eal, tracheal, and ocsopliag-cal, which are distributed to the structures named: the larynx, the trachea and the oesopha- gus. Just as it makes its transverse, horizontal turn there springs off a large branch, called the cervicalis ascendens, which passes upward on the anterior tubercles of the transverse processes to be distributed to muscles and glands in the neck. Suprascapular. The suprascapular, the next most constant branch, passes outward across the scalenus anticus muscle, where it is a dis- tant relation of the second portion of the subclavian. It then turns downward until it reaches the clavicle, behind which it passes outwafd over the scapula, crossing in its course the third portion of the sudclavian. It passes over the transverse ligament of the scapula to reach its dorsum in the supraspinous fossa, where it gives off branches to the bone, to the supra- spinatus muscle, and a branch which winding around the an- terior border of the spine, enters the infraspinous fossa, to communicate with vessels in that situation, chiefly the dorsalis scapula? branch of the axillary. Transversa Colli. Next to the inferior thyroid, the transversa colli is the larg- est of the branches of the thyroid axis, and the least frequent of its progeny. It passes across the side of the neck over the scalenus anticus muscle, above the level of the second portion of the subclavian, very frequently passing between some of the cords of the brachial plexus of nerves. On reaching the anterior edge of the trapezius it divides into two branches: the cervicalis superjicialis and tlie posterior scapular. The cer- Des Anat— 20 306 DESCRIPTIVE ANATOMY. vicalis sti-perficialis runs upward to anastomose with the superficial branch of the arteria princeps cervicis from the oc- cipital. The -posterior sca-piilar, much larger than the preced- ing-, passes to the vertebral border of the scapula; and des- cending along it, anastomoses with the dorsalis scapula branch from the subscapular artery. Internal Mammary. The internal mammary arises from the lower aspect of the subclavian at the inner edge of the scalenus anticus, and fre- quently directly opposite the origin of the vertebral. It passes downward upon the costal cartilages about half an inch from the edge of the sternum to the diaphragm, where it divides into its two terminal branches : the su-perior epigastric and mtisculo-phrenic. It is accompanied by satellite veins, lying upon either side. At its origin it is covered by the internal jugular and sub-clavian veins, and has crossing it the phrenic nerve. Its branches are : 1st. The comes nervi -phrenici, which arises at the upper portion of the vessel. It is a long and slender branch ; and accompanies the phrenic nerve, having the same relations as that nerve, and terminates by anastomosing w^ith the other arteries of the diaphragm. 2nd. The anterior intercostal, which are given off to the intercostal spaces, over which the internal mammary passes. Kach passing outward, soon divides into two branches, one for the upper and the other for the lower border of the edges of the ribs. These branches occasionally spring separately from the artery. They first lie between the intercostal mus- cles and the pleura ; and then between the two intercostal muscles. 3rd. perforating- branches. These are usually six in num- ber, corresponding to the number of intercostal spaces. They pass forward to the front of the thorax ; then running outward, are distributed to the muscles, and in the female, chiefly to the mammary gland. 4th. The mediastinal, small and unimportant branches, which supply the structures of the anterior mediastinum. THE VASCULAR SYSTEM. 307 5th. Pericardiac bra)iches, which are about the size of the mediastinal and are distributed to the pericardium. These are the way-side branches of the vessel. Of the two terminal branches, the larg-er, the superior epig-astric, leaves the thoracic cavit}" behind the seventh costal cartilage. It en- ters the sheath of the rectus muscle; and continuing" its course downward, anastomoses with the inferior epigastric, a branch which springs from the external iliac. This is the longest anastomosis in the body, establishes a connection between the arteries in the upper and the arieries in the lower extremity, and renders it conceivable that the abdominal aorta might be ligated without immediate death. It gives off branches to the muscles in its course. The miisculo-phrenic follows the curvature of the lower ribs. It passes downward and outward, giving off intercostal branches similar to those given off from the trunk of the inter- nal mammary itself, and performing the same service, and in addition giving off a branch to the diaphragm. Superior Intercostal. The superior intercostal and profundus cervicis usually spring by a common trunk from the second portion of the subclavian artery, though occasionally they rise from the third portion, and occasionally by separate trunks. The superior intercostal curves backward from the apex of the pleura until it reaches the head of the first rib, when it changes its direc- tion, and supplies the first intercostal space after the manner of all intercostal arteries. Profundus Cervicis. The profundus cervicis passes backward between the trans- verse process of the seventh cervical vertebra and the first rib, or occasionally the transverse process of the first dorsal vertebra, and passes upward in the neck to inosculate with the deep division of the princeps cervicis branch of the occipital artery, establishing a collateral circulation between the carotid and the subclavian arteries. The Axillary Artery. The Axillary is the second sub-division of the artery of the 308 DESCRIPTIVE ANATOMY. Upper extremity. It beg-ins by being a continuation of the subclavian where that artery ceases at the outer border of the first rib, passes downward and outward from the upper lateral aspect of the chest, corresponding- to the first four ribs, and down the inner aspect of the arm to terminate at the lower border of the tendons of the latissimus dorsi and teres major muscles by becoming the brachial artery. The direction of the artery will of course vary with the position of the limb; and its relations are studied with the limb in the anatomical position. Relations. The artery is covered throughout by the pecto- ralis major, and through part of its extent by the pectoralis minor, and of course by the skin, superficial and deep fascias. Throughout its course its vein lies to its inner front aspect. The brachial plexus of nerves is a continuous relation, lying to its outer side in the beginning, on all three sides in the sec- ond portion of its course, while the terminal branches bear various relations to the third portion of the artery. The rela- tionship to the pectoralis minor warrants the subdivision of the vessel into three portions, each of which should be studied in detail. ^\lq, first -portion extends from the beginning of the vessel to the upper border of the Pectoralis minor muscle; and is contained in the triangular space bounded above by the clavicle, below by the pectoralis minor, and externally by the humerus. The second -portion commences at the upper bor- der of the pectoralis minor, and terminates at its lower border by becoming the third portion. The third portion, commenc- ing at the lower border of the pectoralis minor, terminates at the lower border of the tendons of the latissimus dorsi and teres major by becoming the brachial artery. First Portion. The first portion is covered by the skin, superficial and deep fascia, and the pectoralis major muscle. It is crossed by the costo-coracoid membrane ; and by the outer anterior thoracic nerves, and the acromio-thoracic and cephalic veins. Internally it has the second serration of the Serratus magnus, the first rib, and the first intercostal muscle. Behind, it lies upon the tendon of the subscapularis. Its vein is internal and in front ; while the brachial plexus of nerves THE VASCULAR SYSTEM. 309 lies to its outer side and slio-htly above it. More superficially, in the interval between the pectoralis major and the deltoid, it is crossed by the cephalic vein. Behind it is the respiratory nerve of Bell. Second Portion. The second portion is covered by the skin, superficial and deep fascias, pectoralis major and pectoralis minor. This is the portion crossing- from the chest to the arm ; and corresponds to the position of the third serration of the serratus mag-nus. Behind, it rests upon the subscapu- laris. The cords of the brachial plexus are here divided into three : internal, external, and posterior, which bear the corres- ponding- relations to the second portion of the axillary, while the vein is still internal and anterior. Third Portion. The third portion is covered by the pecto- ralis major, and a strong- fascia, which covers over the axillary space. Posteriorly it rests upon the tendons of the latissimus dorsi and teres major and subscapularis muscles, while exter- nal to it is the coraco-brachialis and the short head of the biceps. At the beg-inning- of this portion the brachial plexus breaks up into its terminal branches; and all of these branches bear some relation to the vessel. On the front of its commencement the external and internal cords each g"ive off a branch, which unite to form the median nerve. This nerve immediately drops to the outer side of the vessel; and maintains that relation to its termination. The outer cord also g-ives off the musculo-cutane- ous, which is an external relation for a short distance, then, plung-ing- into the fibres of the coraco-brachialis, ceases to be a relation of the axillary. The inner cord, after contributing- one root to the median, g-ives off the ulna and internal cutaneous nerves, both of which are fixed internal relations. To the in- ner front aspect is the vein. Behind, it rests upon the circum- flex nerve and the subscapular artery for a short distance, while the last cord of the plexus, the musculo-spiral, is a continuous posterior relation. The Branches. Short Thoracic Long- Thoracic Acromial Thoracic Subscapular Thoracica Alaria Posterior Circumflex Anterior Circumflex 310 DESCRIPTIVE ANATOMY. The point of orig-in of the brcDiches of the axillary is very uncertain, and no perfectly accurate description applying- to all cases can be written. Usually the short thoracic and the acro- mial thoracic arise from the first portion, the thoracica alaria and long- thoracic from the second, and the subscapular and anterior and posterior circumflex from the third. Sometimes they will rise by common branches ; and almost any arrang-e- ment may be anticipated in the orig-in of the branches of this vessel. Short. Thoracic. The 5/zorz' //^or«c:^'<; usually arises by a common trunk with the acromial thoracic. It passes inward along- the upper bor- der of the pectoralis minor, then between the two pectoral muscles to be distributed to the upper intercostal muscles and a part of the serratus mag-nus, anastomosing- with the inter- costal arteries. It frequently sends branches to the pectoral muscles, and occasionally to the mammary g-land. Acromial Throacic. The acromial thoracic, usually arising- by a common trunk with the short thoracic, arises just above the pectoralis minor, passes directly forward to pierce the costo-coracoid membrane, and divides into three branches, which from their distribution have been called the acromial, the -pectoral, and the descending" thoracic. 1st. The ^^dT^ora/ passes between the pectoralis major and minor, and is distributed, in the main, to the mammary g-land, some branches g'oing to the pectoral muscles. 2nd. The acromial, thoug-h the smallest branch, g-ives its name to the trunk, and passes outward across the coracoid process, sometimes piercing- the deltoid muscle, where it anastomoses with the circumflex and suprascapular arteries, forming- the plexus around the acromion process. 3d. The descending- branch passes into the interval between the deltoid and pectoralis major muscles, and is distributed to the muscles in its course, anastomosing with the plexus formed by the preceding- branch. The thoracica alaria are not infrequently branches from the THE VASCULAR SYSTEM. 311 long- thoracic. They sometimss arise separately from the trunk; and are distributed miinly to the lymphatics, integument and fascia of the axilla. TaQlo}io thoracic arises either alone, or by a common trunk with the preceding-, pissing- between the pectoral muscles and the serratus magnus to reach the lateral aspect of the chest. It g-ives branches to the pectorals and to the serratus magnus, anastomoses with the intercostal arteries, and occasionally gives a large branch to the mammary gland. The subscapular is usually the largest branch of the axil- lary artery, arising generally oppDsite the lower border of the subscapularis. It runs downward and inward, following the edge of that muscle, supplies it, the teres major, the latissimus dorsi, anl serratus mignus, and gives branches to structures in the axillary space. At the inferior angle of the scapular it anastomoses with the posterior scapular, while the branches which pass to the thoracic wall anastomose with the intercostal and long thoracic arteries. From an inch to an inch and one-half after its origin it gives off a large branch, called the dorsalis scapula: , which passing through the triangu- lar space between the teres major below, the teres minor above, and long head of the triceps externally, curves around the axillary border of the scapula, and reaches the infraspinous fossa, where it is distributed to that fossa and to the infraspi- natus muscle, anastomosing with the suprascapular and the posterior scapular arteries. It also supplies the teres minor, and sometimes gives a branch to the teres major muscle. The anterior circumflex, a very small vessel, frequently arises by a common trunk with the posterior, or it may arise from the subscapular. It pisses beneath the coraco-brachialis and short head of the biceps muscle, passes over the bicipital groove ; and gives off a branch to the shoulder joint, while the remainder of the artery winds around the neck of the humerus, and anastomoses with the posterior circumflex. The posterior circumflex, quite a large ve^isel, arises from the third portion of the axillary below the subscapularis muscle, pisses through the quadrilateral spice bounded externally by the shaft of the humerus, internally by the long head of the 312 DESCRIPTIVE ANATOMY. triceps, above by the teres minor, below by the teres major, winds around the back of the humerus, and passing beneath the deltoid, breaks up into a largfe number of branches, to be distributed to that muscle throug-hout its deep surface. In addition to this work, it gives off branches to the head of the humerus and the shoulder joint, and some axillary branches, while the continuation of the artery anastomoses with the an- terior circumflex, completing- the vascular zone around the up- per extremity of the humerus. Frequently this artery arises by a common trunk with the anterior circumflex, each artery then pursuing" its usual course. The two anastomose with each other, with the supra- scapular and the dorsalis scapulse, thus establishing- a complete arterial zone around the shoulder. Brachial Artery. The brachial is the third subdivision of the artery of the upper extremity. It beg^ins by being- a continuation of the axillary at the lower border of the tendons of the latissimus dorsi and teres major and passing- downward and outward terminates half an inch, or a fing^er's breadth, below the middle of the front of the elbow-joint by dividing- into the ulnar and radial arteries. It lies first on the inner side of the arm and then on the front, so that in order to check the circulation by pressure ; in the first part of its course the force must be di- rected outward and backward and in the second part directl}^ backward. Relations. — The muscular relations are as follows: To its outer side, at first, is the lower half of the coraco-brachialis and when this relation is lost by the insertion of the muscle, its place is taken by the biceps, whose belly, when the muscle is bulky, overlaps the artery. At the bend of the elbow it lies beneath the slip given ofl" by the biceps. In the first part of its course it lies on the internal intermuscular septum which separates it from the inner head of the triceps, and in the lower part on the brachialis anticus. Its relations to cords are as follows: It is accompanied by satellite veins, one on either side, the one on the inner side being- the larger. THE VASCULAR SYSTEM. 313 To its inner side are the basilic vein and the internal cuta- neous nerve. Both vein and nerve are at first beneath the in- vesting fascia of the arm; but as the structures pass downward, they both become superficial and are, consequently, internal to and in front of the artery. The median nerve lies first to the outer side of the arter}', then crosses it, usually in front, about the middle of the arm and reraai-ns a continuous internal relation. The ulna nerve is a postero internal relation of the brachial for the upper one-half of its course, when it leaves that artery to pass to the back of the elbow joint. For a few inches the inferior profunda artery, accompanying" the ulna nerve, bears also a posterior relation to the brachial. The musculo-spiral nerve and the superior profunda artery are momentary poste- rior relations above. Brachial at the Elbow. These relations are of such importance that the}^ must be g-iven separately. It lies on the middle of the front of the joint with a satellite vein on either side. On its outer side is the tendon of the biceps muscle; on its inner side the median nerve. In front of it is the bicipital fascia and upon that fascia are found the terminal branches of the internal cutaneous nerve and the median basilic vein, which unites with the common ulnar to form the basilic. The artery here lies in a triangle bounded internally by the pronator radii teres, externally by the supinator longus and above by a line drawn from one condyle of the humerus to the other. Branches. Superior Profunda Inferior Profunda Anastomotica Magna. The snf)cri(}r -profunda arises from the upper part of the brachial, and passes downward and outward. After piercing the intermuscular septum, it winds around the humerus in the musculo-spiral groove, accompanying the nerve of that name; and on reaching the outer border of the humerus, divides into two branches. One of these pierces the external inter-muscu- 314 DESCRIPTIVE ANATOMY. lar septum; and continues downward in the interval between the supinator long'us and the brachialis anticus to anastomose with the recurrent branch from the radial, while the other branch continues its course behind the external inter-muscu- lar septum to anastomose with the posterior interosseous recurrent and also with the anastomotica mag^na, the inferior profunda and the posterior ulna recurrent. The inferior profunda ds'x'&Q-'i a little above the middle of the vessel, just below the superior. It immediately seeks the ulna nerve; and with that nerve pierces the. internal inter- muscular septum to pass to the inner back part of the elbow joint, w^here it anastomoses with the anastomotica mag-na and the posterior ulna recurrent. The anastomotica inag-)ia arises near the termination of the brachial, about two inches above the elbow joint. It runs di- rectly inward to the inner aspect of the arm, anastomoses with the anterior ulna recurrent, pierces the inter-muscular septum, passes outward beneath the triceps, or sometimes through the fibres of that muscle, anastomoses with the inferior profunda and the posterior ulna recurrent on the inner aspect of the elbow joint, with the posterior branch of the superior pro- funda upon the outer aspect of the elbow joint, and with the posterior interosseous recurrent and with the anterior ulna recurrent. Thus the only branch forming- the vascular circle around the elbow joint with which the anastomotica mag"na does not anastomose is the radial recurrent. The anastomotica mag-na is thus the chief artery in completing- the chain around the elbow. Passing- inward it receives a communication from the anterior ulnar recurrent: then from the inferior profunda and posterior ulna recurrent; then, on the outer side of the arm, from the posterior branch of the superior profunda, whose anterior branch has already inoscu- lated with the radial recurrent. The Arteries of the Forearm. The arteries of the forearm are the radial and ulnar and their branches. THE VASCULAR SYSTEM. 315 Radial Artery on the Forearm. The radial artery, one of the two terminal branches of the brachial, begins where that arterj divides about half an inch below the middle of the front of the elbow, and passes down- ward with such an inclination outward as to bring- it to the outer side of the front of the wrist joint, where it lies on the front of the styloid -process of the radius, terminating as the radial artery of the forearm by becoming the radial artery of the zL'rist. Relations. To the outer side it has throughout its course the supinator longus, whose belly overlaps it. With this excep- tion the artery is superficial. To its inner side is first the pronator radii teres, and, when that muscle is inserted, its place is taken by the flexor carpi radialis which remains to the inner side. It is accompanied by satellite veins, one on either side, and in the middle third of its course has the radial nerve to its outer side. The nerve in the upper third is too far away to be considered a relation, while in the lower third it passes be- neath the tendon of the supinator longus and disappears on the back of the forearm. Behind it lie the tendons of the biceps, the supinator brevis, the insertion of the pronator radii teres, a part of the origin of the flexor sublimis digitorum, a portion of the flexor longus pollicis, and the pronator quadratus. Below these is the front of the shaft of the radius. Ulnar Artery on the Forearm. The zilnar artery, the larger of the two terminal branches of the brachial, begins where that artery terminates about half an inch below the middle of the front of the elbow, by dividing into itself and the radial, and passes first downward and inward for the upper third of its course, to the inner side of the front of the forearm and then turns vertically downward to reach the inner side of the front of the wrist, where it terminates as the ulnar artery of the forearm by becoming the ulnar artery of the hand. 316 DESCRIPTIVE ANATOMY. Relations. In the first part of its course, while it is passing" downward and inward, it lies beneath four muscles, viz: prona- tor radii teres, flexor carpi radialis, palmaris long-usand flexor sublimis dig-itorum — all the muscles of the superficial group except the flexor carpi ulnaris. When it emerges from beneath these muscles it descends with the tendon of the flexor carpi ulnaris to its inner and of the flexor sublimis digitorum to its outer side. In its upper portion it lies on the brachialis anti- cus and in its lower portion on the flexor profundus digitorum. It is accompanied by satellite veins, one to either side, and for its lower two-thirds has to its inner side the ulnar nerve. In its upper part it is crossed by the median nerve which is also an external relation for about an inch. Ulnar Artery in the Hand. When the ulnar artery reaches the wrist it continues its course into the palm of the hand, lying close to and on the outer side of the pisiform bone and on the anterior annular ligament. After passing down a short distance into the palm, it turns outward and runs across the palm of the hand to its outer side, being- covered only by the skin and fascia and lying on the flexor tendons and on the origin of the muscles of the little finger, and on the divisions of the median and ulna nerves. Its course across the palm is known as the superficial falmar arch (arcus sublimis) and though its direction is not transverse, it is more or less clearly defined by a transverse line across the palm drawn from the bottom of the interval between the thumb and index fi^nger. The ulnar nerve continues its rela- tion to the artery in the hand, lying to its inner side. Branches. Anterior Ulnar Recurrent Interosseous Posterior Tlnar Recurrent Muscular The anterior ulnar recurrent arises from the ulnar just below its origin and passes upward to the front of the inner side of the elbow, where it inosculates with the anastomotica magna. The -posterior ulnar recurrent rises just below the preceding and passes upward and backward to the internal THE VASCULAR SYSTEM. 317 condyle. It passes to the interval between the olecranon and internal condyle and communicates with the anastomotica mag-na and the inferior profunda. The interosseous is a lar^-e trunk which arises from the ulnar just below the elbow and quickly forks into an anterior and posterior interosseous. 1st. The anterior interosseous descends on the front of the interosseous membrane, between the flexor profundus digito- rum and flexor long-us poUicis muscles, to the pronator qua- dratus, passing- beneath which it perforates the interosseous membrane and appears on the back of the forearm to inoscu- late with the posterior interosseous artery. It supplies the muscles in its route and gives off a companion branch to the median nerve. It communicates with the posterior carpal arch and the posterior interosseous. 2nd. The posterior interosseous, as soon as it is produced, passes between the bones above the interosseous membrane, to reach the back of the forearm and descend on the back of the forearm, between the superficial and deep layer of muscles, to the wrist. Just as it reaches the back of the forearm it gives off a large branch, called the posterior interosseous re- current, which ascends to the back of the elbow and commu- nicates with the anastomotica magna. The posterior interosseous artery is distributed to adjacent muscles. The muscular branches of the ulnar artery are numerous twigs to muscles in its course. Branches at the Wrist. Anterior Carpal Posterior Carpal The (Ulterior carpal is a branch which passes outward on the front of the wrist to inosculate with the anterior carpal of the radial. From this arch branches pass to the carpal ar- ticulations. The posterior carpal "^di^^ts backward and then runs outward on theback of the wrist to anastomose with the posterior carpal of the radial. From this arch are given off branches which supply the ulnar side of the back of the little finger and inter- 318 DESCRIPTIVE ANATOMY. osseous branches to the next two spaces. These branches re- ceive the posterior and anterior perforating' arteries. These branches are very small and the anterior is frequently absent. Branches in the Hand. Communicating Dig-ital The communicating- branch dips between the abductor mi- nimi digiti and flexor brevis minimi digiti to join the termi- nation of the radial, completing- the deep palmar arch. The thumb and each of the fingers have two palmar arteries, one on either side, and two dorsal, similarly arranged, running from base to tip, called respectively ^«/?;^«r and dorsal collateral dig-ital arteries. The digital arteries now under consideration are four in number, from the superficial palmar arch. The first is a small branch which supplies the inner side of the lit- tle finger ; the second supplies adjacent sides of the little and ring fingers, splitting at the cleft between the two ; the third does the same for adjacent sides of the middle and ring fingers and the fourth for adjacent sides of the middle and index fingers. These branches run along either side of the fingers until they reach the tip ; where, after giving off small branches which run beneath the nail and communicate with the dorsal arteries they inosculate with one another, completing the loop between the palmar arch and the digital arteries. Radial Artery of Wrist and Hand. When the radial artery reaches the wrist it turns outward, backward and downward beneath the extensor tendons of the thumb, viz: the extensor ossis metacarpi pollicis, extensor primiand extensor secondiinternodiipollicis,in the order named, and passing through what is known as the snuff box — the sunken interval between the extensor ossis metacarpi pollicis and extensor primi internodii pollicis on one side and the extensor secundi internodii pollicis on the other — reaches the back of the hand where its appearance is only momentary, for it immediately dips into the palm of the hand by passing between the two heads of the first dorsal interosseous muscle, THE VASCULAR SYSTEM. 319 and passinof across the palm of the hand from the outer to the inner side, terminates by anastomosing- with the communicat- ing:;- branch from the superficial palmar arch. The position of the radial in the palm is deep, lying- on the bases of the meta- carpal bones and beneath the flexor tendons which separate it from the superficial palmar arch. It is called the deep palmar arch and is situated about half an inch nearer the wrist than the superficial arch. Branches of the Forearm. Recurrent Radial Muscular The recurrent radial arises from the radial just below the elbow and passes upward and outward to the outer side of the front of tne joint, where it lies in the space between the supina- tor long-US and the brachialis anticus. It here inosculates with the anterior branch of the superior profunda. The muscular branches are numerous twig-s to muscles in the course of the artery. Branches at the Wrist. Superficialis Vols Dorsalis Pollicis Anterior Carpal Metacarpea Posterior Carpal Dorsalis Indicis Princeps Pollicis The su-perjicialis voice leaves the radial just as it turns out- ward and passes to the muscles of the thenar g-roup, usually perforating- the abductor pollicis. Sometimes it anastomoses with the termination of the ulna, forming- the superficial arch. The anterior carfal branch passes inward on the front of the joint to form the anterior carpal arch by uniting- with the anterior carpal of the ulnar artery. The -posterior carpal passes inward across the back of the wrist to inosculate with the posterior carpal of the ulnar and form the posterior carpal arch. From the posterior carpal arch there pass down on the dorsal interosseous muscle two branches called posterior interosseous besides another which runs along- the dorsal aspect of the ulnar border of the hand to supply the ulnar side of the dorsal aspect of 320 DESCRIPTIVE ANATOMY. the little fing^er. The posterior interosseous pass down- ward to divide the one at the cleft between the little and ring- fingers to form dorsal collateral dig-ital branches for the adjacent sides of those fino-ers, while the other performs a similar duty for the adjacent sides of the ring- and middle fingers. Just as the radial is passing- the root of the thumb it gives off two small branches which course along- the sides of the dorsal aspect of the thumb. They are called dorsales -pollicis. The nietacarpea is a branch which descends on the second dorsal interosseous muscle to the cleft between the middle and index fing-ers and there divides to form dorsal collateral digital branches for those fingfers. The dor salts indicis is a small branch which passes forward to form the dorsal collateral digital branch for the outer side of the index fing-ers. Princeps Pollicis. ThQ ;p7-mceps pollicis arises just as the radial dips into the palm of the hand and passes forward and outward to divide and form collateral dig-ital arteries for the palmar aspect of the thumb. Branches of the Deep Palmar Arch. Radialis Indicis Anterior Interosseous Perforating- 1st. The radialis indicis, coming- off close to the princeps pollicis, runs along- the radial border of the index fing-er to ifs extremity and there anastomoses with the collateral dig-ital artery of the superficial palmar arch. It also anastomoses with the princeps pollicis and g^ives a communicating- branch to the superficial palmar arch thus completing- the arch, thoug-h sometimes the superficial arch is completed by anastomosing- with the superficialis volae. The anterior interosseous are three or four small branches which pass forward on the front of the interosseous muscles to unite with the dig-ital branches of the superficial arch. Besides these the deep arch g-ives off two sets of unimpor- tant branches called perforating and recurrent. THE VASCULAR SYSTEM. 321 The -perforating arteries are three in number, passing- back- ward between the heads of the last three dorsal interosseus muscles they inosculate with the dorsal interosseous arteries. The Aorta. The Aorta commences at the base of the arterial ventricle, and terminates by dividing- into the common iliac arteries on the front of the bod}" of the fourth lumbar vertebra slig-htly to the left of the raid-line. It lies first in the thoracic, then in the abdominal cavity. Its direction is first upward, forward, and to the rig-ht; then backward, and to the left; and finally it turns downward until it reaches its point of bifurcation. It is divided for description into the Ascending- Aorta, the Trans- verse Aorta, and the Descending Aorta, the latter being- sub- divided into the Thoracic and Abdomiiial portion of the descending aorta. The old sub-divisions of ascending, trans- verse, and descending portions of the arch have here been abandoned. The Ascending Aorta. The Ascending- Aorta (formerly called the Ascending- Por- tion of the Arch of the Aorta) begins at the base of the arterial ventricle, at a point behind the left edg-e of the sternum, oppo- site the third intercostal space, on a plane posterior to the pulmonary artery and anterior to the left auriculo-ventricular opening. It is about two inches in length, is directed upward, forward, and to the right, presenting- a slig-ht curve, whose convexity is to the rig-ht. Behind the upper border of the sec- ond costal cartilage of the rig-ht side it terminates by becoming- the transverse aorta. Just above its orig-in it is somewhat triangular on cross-section when distended, and presents three bulg-ing- prominences, which correspond to the sinuses of Valsalva. It lies in the fibrous pericardium, about one-fourth of an inch behind the sternum; and is contained in the same fold of serous pericardium as the pulmonary artery. Relations. On its anterior aspect, at its origin, lies the pul- monary artery ; but this vessel quickly winds to the left of the aorta, owing partly to the inclination of the aorta to the Des Anat— 21 322 DESCRIPTIVE ANATOMY. right, and partly to the oblique course of the pulmonary artery. Above the pulmonary , the aorta is separated from the sternum by the pericardium, some loose connective tissue, and the remains of the thymus g-land, should any exist. At its oriofin it is over- lapped in front by the rig-ht auricular appendix ; behind it lies the right pulmonary artery, and other structures which enter into the formation of the root of the right lung, and the left auricle of the heart. To its right at its base is the right auricle ; and above this the superior vena cava. To the left, as already seen, is the pulmonary artery. The Transverse Aorta. The Transverse Aorta begins by being a continuation of the ascending aorta opposite the upper border of the second right costal cartilage ; and with a gentle curve in its course, passes from right to left from before backward, and slightly from above downward, to terminate at the left side and lower 'border of the fourth dorsal vertebra, by becoming- the descend- ing aorta. The top of this arch is about an inch below the top of the sternum ; and from it arise three large branches : the Arteria hinominata, the left Common Carotid and the Left Sub-clavian. Relations. In front it is overlapped very slightly by the right pleura, and to a much greater extent by the left pleura and lung, though the two pluras do not come in contact. It is crossed in the order from right to left by the left phrenic, the cardiac branches of the pneumogastric, and the left pneumogas- tric nerves. The left superior intercostal vein also crosses the front of the transverse aorta. Behind, it rests upon the trachea, behind that is the oesophagus, and in the interval be- tween the two the thoracic duct and the left recurrent laryn- geal nerve. Above, it is in relation with its three branches before mentioned, from right to left, and from before back- ward, the arteria innomiuata, left common carotid, and left sub- clavian ; while above and towards its front aspect is found the great transverse vein of the neck, or the left innominate vein. Below it are the bifurcation of the pulmonary artery, the left bronchus, and the left recurrent laryngeal nerve, while it is THE VASCULAR SYSTEM. 323 connected by means of the ductus arteriosus with the pulmo- nar}" artery. The portion formerly described as "the descend- ing" portion of the arch of the aorta" will be considered with the thoracic aorta. Branches of the Ascending Aorta. Coronary Arteries. The right and left coronary branches 2x\'&^ from the ascend- ing- aorta. These branches arise from the corresponding- sinuses of Valsalva, the right arising- from the right anterior sinus, and the left from the left anterior sinus. They descend into the anterior and posterior inter-ventricular furrows, and meet at the apex of the heart. Here they inosculate with one another, while each sends off a branch to supply the auriculo- ventricular grooves, anastomosing with one another, and form- ing- two vascular circles at rig-ht ang-les with one another, which completely surround the heart. Branches of the Transverse Aorta. Arteria lunominata Left Common Carotid Left Subclavian The branches which spring- from the transverse aorta are three in number, and bear a definite relation to one another; that is, the first, the Arteria Innominata, arises near the com- mencement of the transverse aorta; the left C<^mmon Carotid at the middle of the transverse aorta; and the left Subclavian near the termination of the transverse aorta. Arteria Innominata. The arteria i)i)ionii}iata is the first and doubly the larg-est branch of the aorta. It arises from the beg-inning- of the trans- verse aorta, passes upward and to the rig-ht for a little less than two inches to terminate behind the upper border of the right sterno-clavicular articulation h^ dividing- into the Right Common Carotid and Rig-ht Subclavian arteries. In other words, in it are blended the rig-ht common carotid and right subclavian vessels. Relations. In front is the sternum, from which it is separa- ted by some loose connective tissue, by the prolong-ation of the 324 DESCRIPTIVE ANATOMY. fibres of origin of the sterno-hyoid and sterno-thyroid muscles, and by the remains of the thymus g-land, should there be any. Across the front of it, just at its orig-in, passes the left innomi- nate vein, or g-reat transverse vein of the neck, and the right inferior thyroid vein. Behind, at its commencement, it rests upon the trachea ; but the obliquity of the artery soon carries it to the right of the trachea, which then becomes a left or internal relation to the arteria innominata. On the right side is the right innominate vein, the right pleura, and the right pneu- mogastric nerve, which is a rather distant relation. On the left at its commencement is the left common carotid artery, which lies to the left and on a plane slightly posterior, sepa- rated from the arteria innominata by a triangular interval in which the trachea may be seen. Higher up is the trachea. It usually produces no branches except its terminal branches. The remains of the thymus, and the left inferior thyroid vein are also relations on its left. Left Common Carotid. The left common carotid, the second branch arising from the transverse aorta, occupies a position midway between the innominate and left subclavian arteries. Relations . Its relations in the thorax are somewhat similar to those of the arteria innominata, but not identical with them. After passing above th>e left sterno-clavicular articulation, its relations become identical with those of the right common carotid, and a description of one answers for the other. It springs from the highest portion of the transverse aorta, lying with the innominate to its right and on a plane slightly ante- rior, the left subclavian to its left and on a plane slightly pos- terior. It is separated from the sternum by the origin of the sterno-thyroid and sterno-hyoid muscles of the left side, some loose connective tissue, and the remains of the thymus gland ; and is crossed in front by the great transverse vein, though at a higher level thanthatat which the same vein crosses the innom- inate artery. It is overlapped in front by the left lung and pleura. Behind it, at its origin, lies the trachea, which is be- hind and slightly to its inner side. Crossing obliquely behind THE VASCULAR SYSTEM. 325 is the left recurrent lar^^ng-eal nerve while behind and to its outer side is seen the thoracic duct. As it ascends, the tra- chea becomes an internal relation, and the oesophag-us a pos- tero-internal relation, the recurrent laryng-eal nerve lying- in the g-roove between these two structures. To its inner side at its commencement is the innominate artery; and above this, and internal and posterior to it, the trachea. To its inner side is also the inferior thyroid vein. To its outer side is the left subclavian, which is external and slig^htly posterior; while in the interval between the subclavian and the carotid is seen the pneumog^astric nerve, an antero-external relation of the carotid. The Left Subclavian. The left sKbclavicnid.ri^,^'^ from the termination of the trans- verse aorta. It passes upward and to the left; and its first or thoracic portion terminates at the inner edge of the scalenus anticus muscle by becoming the second portion of the artery. From this point to its termination, the left subclavian is iden- tical with the right. Relations. The left subclavian is almost enveloped by the left pleura, which covers it in front, to the outer side, and behind. It has the left common carotid lying internal to it and slig-htly in front of it, while more superficially^ are the origins of the sterno-hyoid and sterno-thyroid muscles, and the remains of the thymus gland, should there be any. Near its origin, but hig-her than at the point of crossing- of the left common carotid, is found theg^reat transverse vein of the neck, while near the termination of the first portion the internal jug-ular and the subclavian veins of the left side unite to form the innominate on the front of the subclavian artery. The left vertebral vein is also an anterior relation. The phrenic nerve crosses it near the scalenus anticus muscle, and then passes downward, parallel to the pneumog-astric, but external to, and in front of, that nerve. The pneumog*astric itself lies in the interval between the subclavian and the left common carotid on a plain anterior to both, but internal to the subcla- vian, while external to the carotid. Below it, as well as to its outer side, are the pleura and the left lung". The trachea, 326 DESCRIPTIVE ANATOMY. oesophagus, and recurrent lar3^ng-eal nerve migflit be considered distant internal relations. The relation of the thoracic duct should be carefully noted. It ascends nearly opposite the interval between the left common carotid and the subclavian, passes above the point at which the subclavian arches outward toward the scalenus anticus muscle, then turns to the front of the arterv to empty into the junction of the internal jug-ular and subclavian veins, so that its relationship to the artery is a three-fold one: being- first behind it, then above it, then in front of it, at its termination. The Descending Aorta. The descending- aorta commences by being a continuation of the transverse aorta at the left side and lower border of the body of the fourth dorsal vertebra, and terminates opposite the bod}^ of the fourth lumbar vertebra by dividing- into the two common iliacs. It consists of the Thoracic and Abdomi- nal Portions. The Thoracic Aorta. The thoracic -portion of the descending- aorta, commencing at the fourth dorsal vertebra, terminates opposite the body of the twelfth dorsal, slightly to the left of the mid-line, by h^- coming the addoniif ml ao)'ta. The course of the thoracic aorta is downward, with a slight inclination to the right, so that from lying first upon the lateral aspect of the body of the fifth dorsal, it changes its relative position to the bodies of the ver- tebrae to such a degree that at its point of termination it is on the front of the bodies, and but slightly to the left of the mid-line. It presents a curve in its course slightly concave in front to correspond with the dorsal curvature of the spinal column upon which it rests. Relations . This vessel is covered throug'hout its course by the pleura; and lies with other important structures in the pos- terior mediastinum. In front, opposite the body of the fifth dorsal vertebra, is the root of the left lung, consisting mainly of the pulmonary artery, the pulmonary veins, the left bron- chus, lymphatics, nerves, and small blood vessels. Below this it lies behind the pericardium; and is completely covered over THE VASCULAR SYSTEM. 327 by the left pleura and lung-. It bears an important relation to the (jesophag-us, thoracic duct, and pneumogfastric nerves. The two pneumogastric nerves course downward, one upon the front and the other upon the back of the oesophagus, and hence bear the same relation to the aorta that this structure does. Owing- to the changes in the direction of the oesophagus as well as to the obliquity of the aorta, the oesophagus above lies to the right of the descending aorta. About the middle of the course of the artery it is directly in front of it, while opposite the tenth dorsal vertebra, where the (jesophagus terminates, it is still further in front and to the left of the aorta. The thoracic duct is continuously behind and slightly to the right of the aorta, lying usually in the interval between the aorta and the great azygos vein. To the right of the aorta is the great azy- gos vein, opening into which opposite the sixth dorsal vertebra is the left azygos, which crosses behind the aorta. The extent to which the aorta is covered by the pleura decreases as it de- scends. In the upper portion of its course, all of the vessel except a small part of its right side, which rests upon the bodies of the vertebra?, is enveloped by the pleura, while near its termination the pleura covers only its outer aspect. Branches. Bronchial Intercostal Mediastinal Pericardiac (Esophageal The hrcuiclies of the th')racic aorta are small, although there are a large number of them. The bronchial arteries, usually three to the left and one to the right lung, course along the bronchi to the lungs, and ram- ify with the bronchial tubes. These vessels, it should be understood, have no connection with the pulmonary artery ; but simply furnish a nutrient supply for the lung tissue it- self. Their method of distribution belongs to the domain of histology. The (vsophafccal are a number of small twigs, four or five, which are successively furnished to the (esophagus as that 328 DESCRIPTIVE ANATOMY. tube comes into relationship with the thoracic aorta, and which communicate with one another and with other oesophageal arteries. The mediastinal and -pericardiac are small twigs furnished to the posterior mediastinum and to the pericardium respec- tively. The intercostal, the largest and most numerous of the branch- es, are ten pairs, which rise from both sides of the thoracic aorta, and run out into the intercostal spaces, the upper space being- supplied by the superior intercostal of the subclavian, while the space below the last rib, or sub-costal space, is sup- plied by one of the terminal branches of the internal mammar3^ The right intercostal arteries are, of course, longer than the left from having to cross the vertebral column. Kach inter- costal artery passes outward in its corresponding space to run along the lower border of the rib above in the groove which is formed for lodging the artery and the nerve; and after going some distance, gives off a branch, which descends to course along the upper border of the rib below. The arteries of the right side pass behind the venaazygos major and thoracic duct. Further out they pass behind the sympathetic system; and lie first upon the external intercostal muscle, and then, at the an- gle of the rib, between the two intercostal muscles. They continue their course to finally inosculate with the intercostal branches from the internal mammary for the upper spaces, and those from the musculo-phrenic for the lower spaces. Before terminating each intercostal gives off a dorsal branch, whose distribution corresponds to the dorsal nerves; that is, it divides into a muscular and a spinal branch, the spinal to enter the spi- nal canal, and the muscular to be distributed to the deep muscles of the back. The Abdominal Aorta. The abdominal aorta commences on the body of the twelfth dorsal vertebra, slightly to the left of the mid-line, being a continuation of the thoracic aorta. It passes behind the dia- phragm, through the aortic opening, and curves backward and and to the left, the convexity being to the left. About the middle of its course it changes its direction and curves slightly THE VASCULAR SYSTEM. 329 to the rig-ht, so that it finally terminates on the body of the fourth lumbar vertebra, usually to the left of the mid-line, by dividing" into the two common, or primitive, iliac arteries. This position is indicated by a line drawn from the highest point of the crest of the ilium of one side to the same point of the opposite, or by a point selected half-an-inch below and to the left of the umbilicus. In addition to the curvature to the left, it also is sligfhtly convex forward, conforming- to the lum- bar portion of the spine. Owing" to the larg"e size and g^reat number of the branches g"iven ofiF, it is gfreatly reduced in size at its termination. Relations, Posteriorly this artery rests upon the front of the bodies of the lumbar vertebrae; but at several points it is sepa- rated from these vertebra? by intervening" structures. Oppo- site the second lumbar vertebra is the commencement of the thoracic duct, the receptaculuni chyli; and throug-houtits course are found, passing behind it, the left lumbar veins, opposite the corresponding vertebras, as they mike for their points of entrance into the inferior vena cava. Above, to the left, are the left crus of the diaphragm and a portion of the sympathetic system, the left semilunar ganglion; to the right, the right crus of the diaphragm and a portion of the S3^mpathetic, the right semilunar ganglion, the right vena az3'gos, and thoracic duct, while throughout the course of the vessel the inferior vena cava lies upon its right. In front is the stomach. Opposite the apper border of the stomach one of the largest branches of the abdominal aortaarises, the C(jeliac axis; and this is surrounded by cords of the sympathetic system, forming the solar plexus of nerves with its two semilunar ganglia. These ganglia are found lying to the front and lateral aspects of the commence- ment of the abdominal aorta. Below this comes the head of the pancreas, and immediately below this the left renal vein, tVe transverse portion of the duodenum, and the mesentery. Bilow this the aorta is covered at the front and at the sides by thu peritoneum and the aortic plexus of sympathetic nerves. Another of its branches, the superior mesenteric, lies for a shfjrt distance in front of it; but curves to the left to become a '6>;//(2/, one of the two terminal branches of the opthalmic artery, emerges at the inner angle of the orbit and ascends to be distributed along the middle of the forehead, anastomosing with the anterior branch of the temporal, with its fellow and with the supra orbital. Nasal. The nasal, the other terminal branch of the opthalmic artery, emerges at the inner angle of the orbit and is distributed along the bridge of the nose, anastomosing with its fellow and with the facial through its angular and transverse nasal branches. The arteria ce)itralis retince pierces the optic nerve and runs forward in it to reach the retina and be there distributed. The opthalmic gives off numerous muscular branches in its course which are divided into two sets, superior and inferior, the superior springing by one trunk and the inferior by another. Together they supply the muscles in the orbital cavity. They are very irregular in number and in point of origin. The ciliary arteries consist of three sets, viz : 1st. Short ciliary branches, which are numerous small ar- teries which pierce the sclerotic around the optic nerve and supply the choroid. 2nd. Long ciliary, which are two branches piercing the sclerotic on opposite sides and running forward between it and the choroid to be distributed to the iris. 3d. Anterior ciliary h'CdLr\.z\\2.'^, which are the offspring of muscular branches and pierce the sclerotic near the front of the eye to reach the iris. The branches from the fourth or cerebral portion are four. 364 DESCRIPTIVE ANATOMY. Anterior Cerebral Artery. The anterior cerebral artery, one of the terminal branches of the internal carotid, runs forward in the long-itudinal fissure, ascends the genu of the corpus callosum and runs backward along- that body. It distributes branches to the frontal and parietal lobes of the brain, on their inner face, and inosculates with the posterior cerebral. Its branches are frequently given the names of the convolutions which they supply. Passing from the anterior cerebral of one side to that of the other, soon after their origin, is a communicating branch called the anterior communicating artery. Middle Cerebral Artery. The middle cerebral, arising as one of the terminal branches of the internal carotid, passes outward along the fissure of Sylvius to be distributed to the anterior and middle lobes of the cerebrum and to the convolutions forming the island of Reil. This artery gives off two sets of branches, one to the cortex and one to the ganglia in the interior of the brain. The cortical branches are distributed over the outer face of the frontal parietal and temporo-sphenoidal lobes, and receive the names of the convolutions which they supply. The ganglionic branches pierce the anterior perforated space and are distributed in the interior of the cerebrum. An important fact concerning these branches is that they do not anastomose with each other in the brain. Anterior Choroid Artery. The anterior choroid pierces the base of the brain to enter the descending cornu of the lateral ventricle and form the choroid plexus. Posterior Communicating Artery. The j^osterior communicati?i§ artery, the last of the four terminal branches of the internal carotid, passes backward to anastomose with the posterior cerebral of the basilar artery. THE VASCULAR SYSTEM. 365 From this artery are g-iven off g-ang-lionic branches which pass throug-h the posterior perforated spot to the interior of the brain. Circumscribing- the six-sided space at the base of the brain is a series of arteries and their communications forming- what is called the vascular circle of Willis. Beg-inning- in front we have the anterior communicating-, and, following- the arteries back on one side, they come in this order, anterior cerebral, internal carotid, posterior communicating-, posterior cerebral and the termination of the basilar artery. Following- them forward from the basilar artery they come in the reverse order. 366 DESCRIPTIVE ANATOMY. THE VENOUS SYSTEM. The Veins are the vessels which return the blood which the arteries have carried to the capillaries. Consequently the venous current passes in a direction opposite to that of the arterial, or towards the heart, opening- mto that org^an by means of two main trunks, called the Superior and Inferior Venae Cavae, and by small vessels which carry the venous circulation of the heart itself. The veins are divided into two sets, the superficial and the deep. The superficial veins are found between the layers of snperficial fascia; and ultimately terminate by emptying into the deep veins. The deep veins are found accompanying- the arteries, and are arrang-ed in two forms : the smaller arteries are accompanied by satellite veins, one upon either side, while the larger vessels are accompanied by a sing-le vein, bearing- usually the name of the artery itself. The venous system as a whole is very much larger than the arterial system as a whole; and this statement is particularly true of the veins found in the abdominal cavity. These veins are capable of being greatly dilated upon stimulation of the splanchnic nerves, so that it is possible for an animal to bleed to death in the venous channels of the abdominal cavity with- out a drop of blood being extracted from the body, the veins dilating to such an extent as to be able to contain all of the blood of the system. As a rule the companion veins of an artery receive accessories corresponding to the number of branches which are emitted by the artery, though there are some notable exceptions to this. The Veins of the Lower Extremity. The Veins of the Lozuer Extremity consist of two sets, superficial and deep. The deep veins, or satellite veins, commence in the sole of the foot on both sides of the plantar arteries, and on its dorsal surface, on both sides of the dorsalis pedis. THE VENOUS SYSTEM. 367 The companion v^ins of the internal and ext(Trnal f>lantar arteries, commencing' respectively on the inner and outer side of the foot, unite where the posterior tibial artery terminates to form two companion veins for the posterior tibial. These veins ascend, lying- one upon either side of the posterior tibial artery, and recieve, about an inch below the begfinning of that vessel, the two companion veins of the peroneal artery, which have united to form a single vein. The satellite veins of the dorsalis pedis artery, commencing on the dorsum of the foot at the g-reat toe, receive the veins from the tarsal and metatarsal branches of that artery to become at the front of the ankle the companion veins of the anterior tibial. These veins then receive the accessory veins w^hich accompany the branches of the anterior tibial artery, and con- tinue their course up the leg", uniting to form a single vein, which passing- above the interosseous membrane, joins the branch formed by the satellite veins of the posterior tibial artery to form the popliteal. The Popliteal Vein then passes upward accompained by the popliteal artery. It lies superficial to the artery, and between that structure and the internal popliteal nerve, lying at first behind and internal to the artery, directly behind it in the middle portion of its course, and behind and external in the beg-inning where the femoral artery terminates in the popliteal. It receives the accessory veins which accompany the five articular branches and the muscular branches given off by the popliteal artery, and becomes the femoral vein at the junction of the lower third with the upper two-thirds of the shaft of the femur. The Femoral Vein then accompanies the femoral arter3% receiving- in its course the veins which accompany the branches of that vessel. It lies first behind and external to the femoral artery, then shortly before the commencement of that vessel directly behind it, and finally internal to it, so thatat Poupart's ligament it is internal and fully abreast of the artery. About an inch and one-half below the commencement of the femoral artery, it g-ives off its profunda femoris branch, which artery is accompanied by its own vein formed by the various satellite 368 DESCRIPTIVE ANATOMY. veins accompanying- branches from the profunda femoris. At the orio-in of the profunda this vein and the femoral vein unite, forming- what is sometimes called the Common Femoral Vein, which lies internal and abreast of its artery as just described. This vein at Poupart's lig-ament terminates by becoming- the External Iliac Vein. Just before reaching- Poupart's lig-a- ment, the femoral vein, lying- then opposite the saphenous opening- of the fascia lata, receives the long- or internal, saphenous vein and the satellite veins w^hich accompany the superficial branches g-iven off from the femoral in this situation. After chang-ing- its name to become the External Iliac, the vein receives the companion branches of the deep circum- flex, and the deep epig-astric branches of the external iliac artery. It then passes upward, lying- first internal and abreast of the external iliac, and then internal and behind it to the point at which the common iliac artery divides into its two terminal branches, opposite the intervertebral disc between the fifth lumbar vertebra and the sacrum. At this point it is joined by the internal iliac vein, which is made up of a larg-e number of satellite veins accompanying- the numerous branches of the internal iliac artery. The conflu- ence of these two veins forms the Common Iliac, which vein is found lying- first directly behind its artery, then external and on a plane posterior, and finally external to the common iliac artery, at the commencement of which vessel, opposite the body of the fourth lumbar vertebra, it unites with the common iliac vein of the opposite side to form the Inferior Yena Cava. This description applies only to the common iliac vein of the right side of the body. 0)1 the left side the external iliac vein is internal and abreast of its artery at Poupart's lig-ament, con- tinues internal, but on a plane posterior to it, up to the bifur- cation of the common iliac artery, passes here behind the internal iliac, and is joined by the vein accompanying- that artery, forming- the Common Iliac Vein of the left side, which vein is internal to the common iliac artery throug-hout its course; and finally passes behind the rig-ht common iliac artery THE VENOUS SYSTEM. 369 to join with that vein opposite the fourth lumbar vertebra and form the inferior vena cava. Internal Iliac Vein. The i)iter)ial iliac vein is formed by the coalescence of the veins accompanying- the branches of the internal iliac artery, The veins of the visceral branches are so numerous and inter- secting that they form plexuses. The vein thus formed ascends behind its artery and unites with the external iliac vein on the disk between the fifth lumbar vertebra and the sacrum to produce the common iliac vein. The Inferior Vena Cava. The Inferior Vena Cava then continues its course, lying- on the right side of the abdominal aorta. As it passes upward, it receives, opposite the centre of the body of each lumbar verte- bra, the lumbar veins from the two sides of the body. These veins are usually four or five in number, those from the left side passing behind the abdominal aorta in order to reach the inferior vena cava. About opposite the lower border of the second lumbar vertebra, the renal veins, formed in the hilum of the kidneys, pass at right angles into the inferior vena cava, the vein from the left side passing across the front of the abdominal aorta generally, though occasionally behind it. The vena cava itself receives the suprarenal veins, and con- tinuing its course upward, passes behind, the posterior border of the liver, upon which it makes a deep notch, and there receives the hepatic veins. It then pierces the diaphragm on a level with the ninth dorsal vertebra, but on the right side of the body, through the highest and most anterior of the open- ings found in the diaphragm; and entering the base of the heart at the lower, inner, and back p«.rt of the venous auricle, pours its current into that organ. The Portal System. ' The l)lood which is poured into the inferior vena cava on the posterior border of the liver through the orifices of the hepatic veins is derived from a double source, a part of it coming from the veins in which the capillaries of the hepatic artery termi- Des Anat— 24 370 DESCRIPTIVE ANATOMY. nate, while a part of it is the product of the portal system of veins, which drain the circulation of a larg-e portion of the alimentary canal into the liver, where the veins ramify before uniting- to form the hepatic veins. It will thus be seen that the liver receives a double blood supply, one portion bein^ that received from the hepatic artery, the ordinary arterial blood, which is intended for the nutrition of the liver tissue itself (parenchyma), the other derived from the alimentary canal contains that blood which has absorbed the products of digestion, and which passes through the liver, not for the purpose of nourishing that organ, but in order to effect the necessary changes in the blood before it is conveyed to the circulation. This Portal System of Veins is formed in the following manner: the -portal vein commences at the upper border of the pancreas by the union of the splenic and the superior 7nesen - teric veins. The splenic vein, before uniting with the superior mesenteric, receives behind the pancreas the inferior mesenteric vein, this vein conveys the return circulation from the sig- moid flexure of the colon, and the descending colon. The superior mesenteric vein carries the return circulation from the transverse colon, descending colon, coecum, and small intes- tines. Hence it will be seen that the greater portion of the blood from that part of the alimentary canal which serves for the digestion of food is carried through the superior mesenteric vein, but little absorption taking place in that part of the large intestine which lies below the formation of this vein. After the splenic and superior mesenteric veins have united behind the upper border of the head of the pancreas, the g'as- iric veins, one of which accompanies the gastric artery and the other the arch formed by the inosculation of the gastro- epiploica dextra and sinistra, empty into the portal system, which also receives the small vein which accompanies the pancreatica magna artery and the pancreatico-duodenalis su- perior. The vein which accompanies the pancreatico-duode- nalis inferior empties into the inferior vena cava before that reaches the splenic vein. THE VENOUS SYSTEM. 371 The Sflenic itself is formed by vessels which conve}^ the return circulation from the spleen; and also receives the small veins accompanying the various branches given to the pan- creas and the vasa brevia of the stomach. The Portal Vein, formed in this way, is a short, wide trunk, about two inches in length, which passes upward, lying in the right edge of the lesser omentum. It lies behind the hepatic artery and common bile duct ; but opposite the interval be- tween these tvv^o structures, so that in naming them from right to left the order would be, common bile duct, portal vein, and hepatic artery, the usual statement being, duct to the right, artery to the left, vein between and behind the two. The vein now enters the transverse fissure of the liver, where it breaks up into numerous branches, which, following the lobules of that organ (see histology for description), unite into minute vessels, which in their turn unite again, until finally the hepatic veins are formed. These veins, three or four in number, open by orifices which remain patulous after death, into the inferior vena cava, as it is coursing along the posterior border of the liver. The Spermatic Veins. The Spermatic Veins are two in number, right and left. They begin in the scrotum, being formed by the plexus of veins surrounding each one of the testicles. These veins emerge from the back of the testicle; and receiving the tributaries from the epididymus forming a convoluted plexus, called the Pa mp in if or 771 Plexus (L. Pa77ipi)ms, a tendril; /or77ia, like). They then pass upward with the other elements of the sper- matic cord. Entering at the superficial abdominal ring, the}^ follow the course of the spermatic canal to enter the abdominal cavity through the deep abdominal ring. From this point the courses of the veins on the two sides differ. 0)1 the 7'ighi side, the vein passes across the external iliac artery, gets to the outer side of that vessel ; and passing upward with a steady inclination inward, terminates by entering at an acute angle into the inferior vena cava, the blood from the sper- matic vein going in the same direction as the blood from the vena cava. 372 DESCRIPTIVE ANATOMY. On the left side, it crosses the termination of the internal iliac artery; but ascends vertically, and empties, not into the vena cava, but into the left renal vein, at right angles to that vein, so that the whole current of blood in the renal vein passes across the aperture of the left spermatic and retards the flow of blood from this vein. It is for these anatomical reasons that enlargement of the veins of the left testicle and scrotum so frequently occurs, the surgical disease known as variocele arising from this cause. The Superficial Veins of the Lower Extremity. Returning to the lower extremity, we find that there are certain small veins belonging to the superficial system. Those which have received distinctive names are two in number, the short and the long saphenous. They commence on the dorsal aspect of the foot, the long saphenous on the inner and the short saphenous on the outer side ; and the veinlets which compose them inosculate with one another so as to form an arch, extending entirely across the foot near the web of the toes. The Short Sa-phenous Vein can be traced back from the outer edge of the little toe behind the external malleolus, where it passes to the postero-external aspect of the leg, accompan3'ing the nerve of the same name. As it passes upward, it gradually wnnds to the middle of the calf of the leg, and there lies in the groove which is found on the posterior face of the gastrocnemius muscle. It continues its upward course between the two heads of the gastrocnemius, and terminates by emptying into the popliteal vein. The Long- Saphenous Vein commences on the inner side of the great toe. It passes backward along the inner side of the arch of the foot, runs across the front of the internal malleolus, passes upward on the inner face of the calf, behind the internal condyle of the femur, until it reaches the junction of the lower third with the middle third of the thigh, where it runs slightly forward, and continues its upward course along the inner front aspect of the thigh until it reaches the saphenous opening in the fascia lata, where it pierces the cribriform fascia, and terminates by emptying into the femoral vein. Occasionally THE VENOUS SYSTEM. 373 before emptying' into the femoral the long- saphenous receives the satellite veins of the superficial branches of the femoral artery; and more frequently these branches, four in number, terminate by opening" directly into the femoral vein, the aper- tures which they make through the fascia covering- the saphe- nous opening" g-iving- it its cribriform appearance. The Veins of the Upper Extremity. The Veins of the Upper Extremity, like those of the lower, consist of a superficial and a deep set ; but unlike the lower extremity, the superficial veins are here so larg"e and so numerous that the satellite veins are small in size, and convey but a small portion of the return circulation. The deep veins commence in the palm of the hand. They commence as the companion veins of the superficial palmar arch, orig-inating- in veins which accompany the dig-ital branches of that arch. This arch receives the interosseus veins ; and forms on either side the vena^ comites of the ulnar and radial arteries. The companion veins of the radial and ulnar arteries unite with each other below the bend of the elbow, and form the two satellite veins of the brachial artery. That is, the satel- lite veins of the radial form the external satellite veins of the brachial, while the satellite veins of theulnar form the internal satellite veins of the same artery. After receiving- superficial veins and tributaries from the branches of the brachial, these two satellites pass upward to the lower border of the tendons of the latissimus dorsi and teres major muscles, and there unite to form the Axillary Vein, which follows the course of the axillary artery, lying- to its inner front aspect throug-hout the course of that vessel, receiving- tributaries from the veins accompanying- branches of that vessel, the larg-est and most important of which are the companion veins of the sub-scapular artery, and terminates at the outer border of the first rib by becoming- the subclavian vein. This vein then continues its course to join the internal jug-ular, and form the innominate vein. 374 DESCRIPTIVE ANATOMY. The Superficial Veins of the Upper Extremity. Anterior Ulnar Radial Posterior Ulnar Median Common Ulnar Basilic Cephalic Median Basilic Median Cephalic Subclavian The Anterior Ulnar. The Anterior Ulnar Vein begins on the inner front aspect of the ulnar side of the hand by small tributaries which come from the little finger and inner side of the ring- and middle fingers. Continuing its course upward it receives tributaries from adjacent portions of the forearm ; and about an inch and one-half below the elbow-joint, unites with the posterior ulnar to form the common ulnar vein. The Posterior Ulnar. The Posterior Ulnar Vein arises near the back of the little finger, passes upward on the postero-internal aspect of the forearm ; and joins the anterior ulnar to form the common ulnar. The Common Ulnar. The Comvion Ulnar Fi?/;? ascends to the inner side of the front of the elbow to unite with the median basilic vein to form the basilic vein. The Radial Vein. The Radial Vein commences on the outer side of the back of the hand, receiving tributaries from the thumb, index and middle fingers ; and passing upward, winds around to the front of the forearm about at its lower third. It then con- tinues to ascend until it reaches a point about an inch below the elbow joint, where it unites with the median cephalic to form the cephalic vein. The Median Vein. The Median Vein is a small vessel which receives the blood from the middle of the palm of the hand. It is scarcely per- THE VENOUS SYSTEM. 3/D ceptible until just above the wrist joint, where the formation of the vein may be said to take place. It then passes directly upward, lying" on the middle of the front of the forearm until it reaches a point about an inch and a half below the middle of the front of the elbow joint. In this situation it divides into two branches, an internal and an external, named respec- tiveh' the Median Basilic and the Median Cephalic. The Median Basilic. The MedicDi Basilic Vein unites with the common ulnar, the product of the anterior and posterior ulnar veins, to form the basilic. The Median Cephalic. The Media)i Cephalic Vein unites with the radial vein to form the cephalic vein. The Basilic Vein. The Basilic Veiii, formed below the elbow joint by the union of the common ulnar with the median basilic, passes upward and crosses over the bicipital slip of fascia g-iven off from the tendon of the biceps to the fascia of the inner side of the forearm. It then lies to the inner front aspect of the brachial artery to about the middle of the course of that vessel, sep- arated from it by the deep fascia, where its relation is chang-ed only to the extent of lying- beneath the investing- fascia. That is, up to the middle of the brachial artery the basilic vein is superficial to the investing- fascia ; but opposite the middle of that vessal it pierces this fascii, and becomes deeper, lying- still to the inner front aspect of the brachial artery, but more nearly on the same plane with that vessel. It finally termi- nates by uniting with the internal satellite vein of the brachial just before the latter unites with the external satellite to form the axillary vein. Some authorities describe the basilic as re- ceiving- the two satellite veins of the brachial and becoming- the axillary vein. The Cephalic Vein. The Cephalic Vein, formed below the middle of the elbow joint by the union of the radial and the median cephalic, 376 DESCRIPTIVE ANATOMY. passes upward and outward until it reaches the interval be- tween the brachialis anticus and the supinator long-us and ex- tensor carpi radialis lonofior. It then passes upward in a g-roove found on the outer aspect of the arm, caused by the bulg-ing- of the biceps anteriorly and the triceps posteriorly; and continues its course until it reaches the lower edge of the deltoid muscle, when it turns across the front of the arm to reach the interval between the deltoid and the pectoralis major. After .running- in the g-roove between these two muscles, it passes over the fibrous-covered interval between the muscles and empties into the axillary vein just before its termination in the subclavian. Before the cephalic vein enters the axil- lary it receives a communication from the external jug-ular vein of the neck. The Axillary Vein. The Axillary Vein is formed by the junction of the brachial satellites and the basilic at the termination of the axillary artery. It passes upward on the inner front aspect of the ax- illary artery throug-h the axillary space, receives the tributaries which accompany the branches of that vessel; and continually increases in size until it reaches the outer border of the first rib behind the junction of the outer third with the inner two- thirds of the shaft of the clavicle, where it terminates by becoming- the subclavian vein. The Subclavian Vein. The Subclavian Vein bears the same relation to its artery that the string- bears to a bent bow. Commencing- at the outer one- third of the clavicle on the anterior border of the first rib, it passes horizontally inward , lying- below and on a plane anterior to the corresponding- artery, so that it is anantero-internal relation of the third portion of the subclavian, and an antero-external relation of the first portion of the subclavian, being- separated from the second portion by the interposition of the scalenus anticus muscle. As this vein passes inward, it receives, first, the companion veins of the suprascapular and transversa colli arteries. These veins usually unite before entering- the subclavian; but occasionally enter by separate opening-s. The THE VENOUS SYSTEM. 377 external jug-ular vein, which sends a branch to the cephalic, also empties into the subclavian. The manner of its entrance will be described later. The subclavian then receives the companion branches from the thyroid axis, internal mammary, and vertebral arteries, and terminates behind the sterno- clavicular articulation by unitingf with the internal jug-ular to form one of the innominate veins. The Veins of the Head and Neck. The Veiiis of the Head consist of a set of channels found in the cranium, formed by divisions in the dura mater, and called "sinuses", while the veins of the neck are described under the name of "jug"ular" veins {Lt. Jug-nluni — diminutive of jiigum, the yoke — the throat), of which, however, there are three: the Internal, External, and Anterior Jug"ular. In addition to these jugular veins there are smaller veins, such as the thyroid and the vertebral, which durino- a portion of their course are found Ijnng- in the neck. Certain veins are also found upon the face, which aid in forming- the jug"ulars. The Veins of the Diploe. Ramifying between the tables of the bones of the skull are numerous veins called diploetic. They take the name of the region they occupy and finally converge to form trunks which open either into the sinuses of the interior or the veins of the exterior. Connecting the sinuses of the interior with the veins of the exterior of the head are several veins which pass through foramina such as the mastoid and parietal. The Sinuses of the Dura Mater. Superior Longitudinal Inferior Longitudinal Straight Lateral Cavernous Occipital Superior Petrosal Inferior Petrosal These Sinuses are formed by the union of veins found in two positions in the cranium : one set called the veins of the Diphe lying between the two tables of which the bones of the skull are composed, while the other set, the Cerebral veins, 378 DESCRIPTIVE ANATOMY. are found ramifying- over the surface and in the interior of the encephalon. The Cerebral Veins consist of two sets, super- ficial and deep. The superficial lie upon the surface of the brain, while the deep cerebral veins lie in the ventricular cavities of the brain, ultimately uniting- to form two ventricu- lar veins, the Venae Galeni, which leave the interior of the brain throug-h the g-reat transverse fissure and terminate in the straig-ht sinus. The Snperior Longitudinal Sinus, The Superior Long-itudinal Siruis commences at the fora- men caecum, where it communicates with the small veins of the nasal fossa. The g-roove along which it rnns may be dis- covered on the dried bones as occupying- the mid-line of the frontal bone, and g-rooving- equally the upper border of the two parietal bones. Leaving these b^nes, it appears on the occipital, grooves it in the mid-line, and pisses backward to the torcular Herophili by the side of the anterior occipital protuberance, to diverg-e on one or the other side into one of the lateral sinuses. This sinus, like other sinuses of the dura mater, is not strictly speaking- a vein : it is the spice between two layers of the dura ; and its resemblance to a vein consists only in two facts ; viz, that it conveys venous blood, and that it is lined internally by the endothelial coat, which all blood-vessels contain. As it passes along- the g-roove, this sinus receives the superficial cerebral veins. The Inferior Longitudinal Sinus. The Inferior Longitudinal Sinus is a small sinus, circular on cross-section (unlike the superior, which is triang-ular on cross-section). It commences near the anterior extremity of the falx major, follows the curvature of that subdivision of the dura miter, and passes backward to the junction of the falx major with the tentorium cerebelli, where it empties into the straig-ht sinus. The Straight Sinus. The Straight Sinus runs in the triang-ular interval between the falx major and the tentorium, to terminate in one of the THE VENOUS SYSTEM. 379 lateral sinuses. Before receiving* the inferior longitudinal sinus, the straight sinus first receives the venae Galeni, coming from the ventricles of the brain. The Occipital Sinus. The Occipital Sinus is the smallest of the cranial sinuses ; it commences by several small vein around the foramen magnum, and is situated in the attached marg-in of the falx cerebelli, communicating- with the posterior spinal vein, and finally emptying- into the torcular Herophili. The Cavernous Sinuses. The Cavernous Sinuses are found on the lateral aspect of the body of the sphenoid. They commence in front by receiving the opthalmatic veins from the sphenoidal fissure. The opthalmic veins, following- the course of the opthalmic artery, pass over the sphenoidal fissure, and empty into the cavernous sinuses. These in turn, winding- along- the lateral aspect of the body of the sphenoid, pass to the junction of that bone with the petrous portion of the temporal, and there join with the petrosal sinuses. Stretching- across between the cavernous sinuses are two small transverse vessels, which surround the pituitary body, one in front and the other behind. These tog-ether form the Circular Sinus. After the cavernous sinuses have received the superior petrosal and emptied into the inferior petrosal sinus on the side of the basilar process of the occipital bone, they are united by a small vein, extending- between the two, which is called the Transverse Sinus. The Superior Petrosal Sinus. The Superior Petrosal Sinus is situated on the upper bor- der of the petrous portion of the temporal. Its inner extremity is connected with the cavernous sinus, while its outer is connected with the lateral sinus, just as that sinus reaches the inner face of the mastoid portion of the temporal, and receives the mastoid veins. The Inferior Petrosal Sinus. The Jnfcrior Petrosal Sinus occupies the groove between 380 DESCRIPTIVE ANATOMY. the posterior border of the petrous portion of the temporal and the inner half of the lower border of the occipital. It receives the cavernous sinus in front; and terminates behind by uniting- with the lateral sinus. The Lateral Sinuses. The Lateral Simtses commence at the torcular Herophili, where the long-itudinal sinus empties. The torcular is never situated on the mid-line of the body; but to one or the other side, more frequently to the rig^ht. The blood from the superior long-itudinal sinus pours into the lateral sinus of the rio-ht side, while the current of blood from the occipital and straig"ht sinuses usually passes into the opposite lateral sinus. The lateral sinus of each side arches outward along the anterior face of the occipital bone; but leaves that bone to appear momentarily on the postero-inferior asg-le of the parietal. Leaving- the parietal, it passes downward and inward in a curved direction across the internal face of the mastoid portion of the temporal, forming- a deep depression in this bone, the fossa sigmoidea and finally at the posterior extremity of the jugular (the foramen lacerum posterius), it unites wnth the inferior petrosal sinus to form the internal jugular vein. It will be seen, therefore, that the right internal jugular conveys the blood received from the superior lougitudinal sinus, which, in its turn, receives the superficial cerebral veins, w^hile the left internal jugular conveys most of the blood carried by the venaj Galeni, and from this by the straight sinus, into the left lateral sinus. The veins of the base of the brain are about equally distributed by means of the petrosal, transverse and circular sinuses into the corresponding jugular veins. It must never be forgotten that the veins of the diploe com- municate with the sinuses of the dura mater on the one hand, while on the other they communicate with the superficial veins of the cranium. These communicating veins are described as emissary veins, so that any infection of the tissues occupying the surface of the skull may readily pass along the course of the emissary veins into the interior of the skull, and so estab- lish an inflammation of the brain itself. THE VENOUS SYSTEM. 381 The Internal Jugular. The Liternaljiignlar F^/;/, formed, as above described, by the union of the inferior petrosal with the lateral sinus, is a larg-ely dilated aperture at the base of the cranium ; but it quickly contracts to about twice the size of the internal carotid artery. At its origin it lies immediately behind the internal carotid ar- ter}^ with the twelfth, or hypo-glossal, nerve behind it, and the ninth, tenth, and eleventh cranial nerves emerging- in the interval between itself and the internal carotid. It then passes downward as an external relation of the internal carotid to the point at which that vessel is derived from the common carotid artery ; then becomes a relation of the common carotid artery, and maintains that relation to the origin of that vessel behind the sterno-clavicular articulation, where it terminates by join- ing the subclavian vein to form the innominate vein of thatside. In its course down the neck, the glosso-pharyngeal and hypo- glossal nerves pass forward between the artery and the vein, to cross the front of the artery and cease to be relations of the vein. The eleventh, or spinal accessory, nerve passes behind the vein near the upper portion of its course ; but the tenth continues an internal relation of the internal jugular through- out the entire course of that vein. Its tributaries are the Facial, Lingual, Pharyngeal, Super- ior and Middle Thyroid Veins. The Vertebral Veins. The Vertebral Veins commence by tributaries at the upper part of the back of the neck, pass downward in the foramina of the transverse processes, which transmit the vertebral artery ; and the two satellites unite, one passing through the sixth and the other through the seventh transverse process, to form a single vein, which empties into the innominate vein of the corresponding side. The Veins of the Face. The Veijis of the /^«6'6' consist of numerous branches, which correspond to the arteries of the face. Of these, the Supra- 382 DESCRIPTIVE ANATOMY. orbital commencing- on the forehead, communicates with the temporal vein, and joins the frontal to form the Facial vein. This, after receiving* the Nasal, Superior Labial, Transverse Facial, and Inferior Labial, passes over the lower border of the jaw, about an inch in front of the angle, or opposite the internal border of the masseter muscle, receives a communi- cation from the tempero-maxillary vein, and empties into the internal jug-ular. The Temporal Veins. The Tenifioral Veins commence on the lateral aspect of the skull by numerous tributaries, pass downward in an interval between the internal auditory meatus and the tempero-maxil- lary articulation, run into the substance of the parotid g-land, and receive the internal maxillary vein, made up of tributa- ries accompanying" branches of the internal maxillary artery, and behind the neck of the condyle of the lower jaw forms the tempero-maxillary vein. This vein divides into two branches, one of which has been already alluded to as uniting* with the facial vein to empty into the internal jug-ular, while the other unites with the pos- terior auricular to become the external jug"ular vein. The External Jugular. The External Jug-ular Vein, commencing* in the substance of the parotid g-land, receiving- the g-reater portion of the blood from the exterior of the cranium and the deep parts of the face, runs down the neck in the direction of the fibres of the platysma myoides muscle, which covers it. It runs nearly parallel w^ith the posterior border of the sterno-cleido-mastoid muscle until it reaches a point just above the clavicle, where it chang-es its direction, and passing- downward and inward, empties into the subclavian vein. The Innominate Veins. The Innominate Veins of the two sides differ in direction, though but little in formation. On the right side the innominate vein has already been described as formed behind the rig-ht sterno-clavicular articu- THE VENOUS SYSTEM. 383 lation by the union of the subclavian and internal jugular veins. 0)1 the left side the vein is formed in the same way ; but usually the internal jugular lies to the outer front aspect of the left subclavian arter}', instead of crossing directly over the front, as is the case on the right side. The innominate vein on the right passes downward and in- ward, parallel with and anterior to the innominate artery, and a little to the right side of that vessel. On the left, the innominate vein, also called the Great Transverse Vein of the Neck, crosses successively the thoracic portions of the left subclavian and left common carotid arteries and the arteria innominata, and lying above and on a plane anterior to the transverse aorta. At the commencement of the transverse aorta the two innominate veins unite to form the Superior Vena Cava. The Superior Vena Cava. The Superior Vena Cava descends anterior and external to the ascending aorta, pierces the fibres of the pericardium, and enters the venous, or right, auricle of the heart on the upper front aspect of that organ. Besides these veins there are several smaller veins which are found mainly in the thoracic cavity and lower portion of the neck. Of these, the satellite veins of the Internal Mammary Artery empty into the corresponding innominate vein. The Inferior Thyroid Veins, accompanying the artery of the same name, pass likewise into the corresponding innominate veins. The Superior Intercostal Veins, returning the blood from the upper intercostal spaces, except the first, empty, the right one into the vena azygos major, the left usuall}" into the left innominate vein. The A2yfi'os Vei?is connect the superior and inferior venae cava,'. They are two in number, the right azygos, or vena azygos major, and the left azygos, or vena azygos minor. The Vena Azygos Major. ^):\{t Azygos ^^/tt/V^r commences in the abdominal cavity oppo- 384 DESCRIPTIVE ANATOMY. site the first or second lumbar vertebra, sometimes from the first lumbar vein, sometimes by a branch from the renal vein. It enters the thorax throug-h the aortic opening- of the diaph- ragm; and receiving- branches from the lower six intercostal spaces, finally terminates by crossing the vertebral column opposite the sixth dorsal vertebra behind the thoracic aorta, and empties into the superior vena cava just before that vessel passes into the heart. The Vena Azyg-os Minor. Just before the azygos major crosses the vertebral column it is joined by the Vejia Azyg-os Minor, which conveys the blood from the intercostal spaces between the superior azygos, already described as the Left Superior Intercostal, and the highest branches entering into the azygos minor. At its lower extremity this vessel frequently communicates with the inferior vena cava, and thus directly establishes a communication be- tween the superior and inferior venae cavae. Occasionally, however, the communication consists entirely of a brancH from the renal vein, w^hich in its turn empties into the inferior vena cava, and thus indirectly establishes this communication. The Spinal Veins. The spinal veins consist of three sets, as follows : Dorsal Spinal Veins. The dorsal spinal veins are numerous veins forming a net- work on the exterior of the vertebrae. Meningo-Rachidian Veins. The meningo-rachidian are four veins perpendicular in di- rection, which lie within the spinal canal between the bone and dura mater, two in front and two behind. Medulli-Spinal Veins. The meduUi-spinal are numerous veins ramifying beneath the arachnoid membrane of the spinal cord. THE VENOUS SYSTEM. 385 The Cardiac Veins. The veins of the heart are two, as follows : The Great Cardiac Vein. The great cardiac vein ascends in the anterior ventricular g-roove, winds around the left auriculo-ventricular g-roove and opens into the rig-ht auricle. The last inch of its course is known as the coronary sinus. The Posterior Cardiac Vein. The posterior cardiac vein is small and ascends in the pos- terior ventricular groove to open into the g^reat cardiac vein. Des Anat — 25 386 DESCRIPTIVE ANATOMY. THE LYMPHATIC SYSTEM. The lymphatic system consists of numerous small vessels ramifyinof in nearly every tissue of the body, and of small, reddish, pea-like bodies called h^mphatic g^lands, found at intervals along- the lymphatic vessels. The lymphatic vessels are intended for the most part to remove from the tissues the detritus of assimilation, consisting- mainly of unexpended plasma ; consequently the course of their circulation is from the circumference towards the centre, and in their route they will be found to accompany the veins. Wherever they are found the lymphatics consist of two sets, superficial and deep. In the extremities the superficial set is found just benseth the skin ; the deep in and among- the muscles. In the viscera the superficial set ramifies on the surface, while the deep is found in the structure. The g-reater portion of the lymphatics of the body converg-e to form one larg-e vessel, the thoracic duct, which empties into the venous current near the heart. Thoracic Duct. The thoracic duct beg-ins on the front of the body of the second lumbar vertebra by a considerable dilatation called receptaculum chyli, which, narro\ving- to a tube the size of a g-oose quill, ascends the front of the vertebral column behind the descending- aorta, passes throug-h the aortic opening- of the diaphrag-m and continues upward as hig-h as the fourth dorsal vertebra, w^here it inclines to the left and continues thence an oblique ascent behind the arch of the aorta to a point on a level with the seventh cervical vertebra, where it arches forward and downward and opens into the commence- ment of the left vena innominata. Opening into the commence- ment of the rig-ht vena innominata is another and much smaller lymphatic duct (ductus lymphaticus dexter) which conveys lymph furnished it by the right upper extremity and rig-ht side of the head and neck. THE LYMPHATIC SYSTEM. 387 Lymphatics of the Lower Extremity. The superficial lymphatics of the lower extremity are found crowding" upward in immense numbers along- the course of the saphenous veins and, reaching- the saphenous opening- in the fascia lata, where the vein terminates near Poupart's lig-- ament, they then pass throug-h a set of lymphatic g-lands. The deep lymphatic vessels accompany the deep veins upward to the g-roin, where they are connected with a set of g-lands, lying- beneath the fascia lata and superficial muscles, called the deep lymphatic g-lands of the g-roin. Along- the course of these vessels are found a few g-lands, some in the popliteal space and one on the front of the interosseous membrane of the leg-. The lymphatic vessels from the external organs of g-eneration and from the abdominal parietes can be traced to a third set of g-lands, which form a chain along- Poupart's ligament, lying- superficial and above the g-lands around the saphenous opening-. All these vessels pass beneath Poupart's lig-ament to become the external iliac lymphatics which accompany the external iliac vessels and unite with the internal iliac lymphatics to form the common iliac lymphatics, which accompany the common iliac vessels and unite with those of the opposite side to form the lumbar lymphatics. Scattered at intervals along- these vessels from Poupart's lig-ament are lymphatic g-lands. The lumbar lymphatics ascend along- the aorta, constantly increas- ing in size by accessions from the abdominal viscera, and having- passed throug-h numerous g-lands, and lessened in number as they increased in size, they eventually open into the receptaculum chyli, which is so named from the fact that the lymphatics which it receives from the small intestine are, during the process of dig-estion, filled with chyle. The Lymphatics of the Upper Extremity. The lymphatics of the upper extremity, like those of the lower, consist of a superficial and a deep set. The superficial ascend in company with the superficial veins and the deep 388 DESCRIPTIVE ANATOMY. accompany the deep veins, both converg-ing- to the arm pit where there are some twelve or fifteen lymphatic glands. Besides the vessels from the upper extremity these g-lands also receive those from the chest wall and mammary g-land. A few g-lands are found along- the course of the lymphatics before they reach the axilla, some at the elbow and some along- the brachial vessels ; these, however, are small and unimportant. From the axillary g-lands the vessels proceed along- the course of the subclavian vein, opening on the left side into the termi- nation of the thoracic duct and on the right into the ductus lymphaticus dexter. Lymphatics of the Head and Neck. The lymphatics of the head and neck consist of vessels which have come from the exterior of the head and others which have converged from veins supplying- the internal and external jug-ular veins, no lymphatics, however, being- found in the substance of the brain. These vessels descend along the external, and especially the internal, jugular veins and on the right side open into the ductus lymphaticus dexter while on the left they join the thoracic duct. The Lymphatics of the Thorax. The lymphatics accompanying- the intercostal vessels open into the thoracic duct. Those from the right lung-, some portion of the thoracic parietes, diaphrag-m and even some portion of the upper surface of the liver and the short border of the heart seek the ductus lymphaticus dexter ; while those from the left lung-, left side of the thorax and most of the heart join the thoracic duct. The vessels from the lung-s pass through a set of glands situated around the bifurcation of the trachea called the bronchial glands. THE CENTRAL NERVOUS SYSTEM. 389 THE CENTRAL NERVOUS SYSTEM. Cerebro- Spinal Centres. The chain of nervous centres known as the Cerebrospinal axis is divided into two portions, one contained in the spinal canal, and called the spinal cord, or Medulla Spinalis (L. Me- dins, middle), the other contained in the cranium and called the Brain, or Encephalon, the latter name including the brain and its membranes. Enveloping each of these portions and lining its containing cavity are three membranes, lying one within the other, called the Investing- Membranes^ or Meninges. The Membranes of the Brain. The membranes of the Brain are the Dura Mater (L. Hard mother), lying next to the cranial wall ; the Pia Mater (L. Delicate mother), lying next to the brain ; and the Arachnoid between the two. The Dura Mater. The Dura Mater is a grayish white, strong, fibrous mem- brane which lines the inner surface of the cranial wall, adher- ing closely to the bone, and supplying the place of an internal periosteum. Its internal surface is glistening and smooth because lined by the arachnoid, which performs the functions of a serous membrane. Besides lining the interior of the cra- nial cavity, the dura mater gives off septa, which passing between the different portions of the brain, serve to separate them from one another and to support the brain in its position, besides carrying blood-vessels which receive and return the circulation from the interior of the cavity. These processes are three in number : the Falx Major, or Falx Cerebri, the Tentorium Cerebelli, and the Falx Minor, or Falx Cerebelli. The Falx Major (L. Falx,^ scythe), or Falx Cerebri, is a sickle-shaped process which lies in the great longitudinal fissure of the brain. It is attached in front to the crista galli and extends along the mid-line to the anterior occipital pro- tuberance, and is attached to the superior surface of the tentorium along its middle line. Along its attachment to the 390 DESCRIPTIVE ANATOMY. cranium, the Falx major divides into two layers, which are attached to the marg-ins of the g-roove found on the frontal, parietal, and occipital bones. Between these two layers is a triangular space, which lodg^es one of the important sinuses, the siifierior long-itudiiial sinus. The concave lower margin is hollowed out into a small canal, circular on cross section, which extends from the foramen caecum to the attachment of the falx major to the tentorium. This is called the inferior longitudinal sinus. The Tentorium (L. Tendere, to stretch) commences at the posterior occipital protuberance, and passing- transversely forward, extends into the g-reat transverse fissure of Bichat separating- the cerebrum from the cerebellum, serving- to sup- port the posterior lobes of the cerebrum and at the same time to bind the cerebellum in the cerebellar fosss. Along- its upper surface from before backwards is attached the posterior extremity of the falx major. Its posterior border, divided like the falx major into two layers, is attached along- the marg-in of the lateral limbs of the occipital cross ; and leaving- this bone, passes forward on the superior border of the petrous portion of the temporal bone, at the apex of which it is joined by the concave free anterior border. This anterior border presents a horseshoe-shaped appearance, and when the two borders, anterior and posterior, meet with one another, they cross, so that the free border continues forward to be attached to the anterior clinoid process, while the attached border reaches the posterior clinoid process. Between these attach- ments is left an opening- through which is transmitted the mid-brain. At the attachment of the posterior border is a sinus, a continuation of the great longitudinal sinus on one side, forming the lateral sinus. Where the tentorium is attached to the upper border of the petrous portion of the temporal is another sinus, the superior petrosal ; and where the falx major is attached on the superior surface of the ten- torium is found a third sinus, the straig-Jit sinus passing back- ward to the torcular Herophili. The Falx Cerehelli is a small narrow process of the dura, which extends from the margin of the foramen magnum THE CENTRAL NERVOUS SYSTEM. 391 Upward to the under surface of the tentorium to the posterior part of which it is attached, at the anterior occipital protuber- ance. It projects between the two lobes of the cerebellum, and serves to separate them from one another. The Arachnoid. The Arachnoid^ like all serous membranes, presents a closed sac, one of its layers lining- the inner surface of the dura, and being- called the parietal layer, while the other invests the brain, from which it is separated by the pia, and is called the visceral layer. It does not dip into the sulci of the brain ; but leaps from convolution to convolution, so that a space is interposed at various portions of the brain between the arachnoid and the pia mater. This space has received the hybrid name of Sub-Arach)ioidean. It-can be easily demon- strated at some portions of the brain, while at others it is scarcely perceptible. On the inferior surface of the brain, stretching- between the two peduncles of the cerebrum, and covering the inter-peduncular space, a considerable distance exists between the pia and the arachnoid ; and ag-ain in the great transverse fissure of Bichat the space can be easily made apparent. The Pia Mater. The P/« J/«/6'r is an extremely thin and very vascular mem- brane, consisting almost entirely of small interlacing- bloodves- sels, held tog-ether by layers of connective tissue. It covers the entire surface of the brain ; and not only does this, but dips into every sulcus and every depression of the brain. Thus, it passes throug-h the g-reat transverse fissure of Bichat, covering- not only the cerebellum and the under surface of the cerebrum; but continuing- through this fissure, it passes even into the interior of the brain itself, so that prolong-ations of the pia are found in the ventricles, in the interior of the hemispheres, and connecting with the blood vessels which perforate from the base of the brain and supply the structures in the interior of each hemisphere. It serves also in one portion of the brain to form the roof of one of the ventricles. An examination of the brain with its frec^uent elevations and depressions forming- 392 DESCRIPTIVE ANATOMY. the convolutions and sulci would show that if this membrane were stripped off, its area would be enormously g-reater than the apparent area of the brain itself. E^very sulcus into which the membrane dips forms a corresponding- fold, so that it bears a close resemblance in its folds to a dress or other garment which has been taken out of a trunk. The Brain. The Ence-phalon is divided into four parts: the Cerebrum, the Cerebellum, the Pons Varolii, and the Medulla Oblongata, the Pons and its appendages being frequently described as the iJiid-brain. The zveight of the entire brain varies with the period of life, with the sex of the individual, with the cause of death, the period after death at which the weight is taken, and with various other circumstances. The average w^eight is about forty-eight ounces for the male, and about forty-four or forty- five for the female adult. The intellectuality of the individual bears scarcely any relation to the weight of the brain, some of the heaviest brains having been those of people by no means distinguished for ability, while comparatively small brains have been found in people of a high order of intelligence. The intellectuality varies more with the variety and number of the convolutions, and consequently with the amount of "gray matter," than it does with the actual bulk of the brain. The Cerebrum is seven or eight times the size of the rest of the brain, presenting an uneven, convoluted surface. When closely examined these convolutions are seen to be dissimilar on the two sides of the brain, nor do we ever find any two brains with precisely the same convolutions. Certain depres- sions which separate these convolutions from one another, from the fact that they appear at an early stage of foetal life, are called "primary fissures," and from these primary fissures we get the great subdivisions of the cerebrum. These pri- mary fissures are the Great Long-itiidiiial Fissure^ the Great Transverse Fissure of Bichat, the Fissure of Sylviiis, the Fissure of Rolando, and the Parieto-occipital Fissure. The THE CENTRAL NERVOUS SYSTEM. 393 _g-)-eat lo)i§iti(di)ial Jissitrc serves to separate the two lobes of the cerebrum ; the trcDisvcrsc /iissi(7'c of Bichat to separate the cerebrum from the cerebellum ; the^'^^^rr^^ of Sylvius to separate the frontal from the tempero-sphenoldal, and by its horizontal limb, the parietal from the tempero-sphenoidal ; the fissure of Rolando to separate the frontal from the parie- tal ; while the parieto-occipital of course separates the parietal and occipital lobes. The Convolutions of the Cerebrum. In studying- the convolutions of the cerebrum we beg-in with the five principal, or primary, fissures. The Great Lo)igitudinal Fissure commences on the base of the brain, extends upward between the two hemispheres, turns backward toward the posterior extremity, and cutting- between the two hemispheres behind, separates them from one another. It will therefore be seen that the two hemispheres of the cerebrum are united in the middle, but are separated in front and behind. The bond of union between them, the corpus callosum, extends further in front than behind and is thicker there than in front. The Fissure of Sylvius. Commencing- on the base of the brain near the g-reat long-itudinal fissure, or, more correctly, at the anterior perforated spot, is the fissure of Sylvius. It is first directed outward, forming- a means of separation between the frontal and tempero-sphenoidal lobes. On leaving- the base of the brain to appear on the outer surface of the hemisphere, chang-es its direction and passes upward and backward, forming- what is called the horizontal limb of the fissure of Sylvius, which separates the tempero-sphenoidal below from the parietal above. The liorizoiital li))ib of the fissure of Silvius extends backward as far as the commence- ment of the occipital lobe, or the junction of about the posterior one-fifth with the anterior four-fifths of the cerebrum. Just as the main fissure reaches the outer surface of the hemisphere, the vertical limb is g-iven off, which ascends in the convolutions of the frontal lobe, forming- in this situation an overhang-ing- appearance, which is described as the Operculum {L. Operire, to cover.) 394 DESCRIPTIVE ANATOMY. The Fissure of Rolando is situated about the middle of the outer surface of either hemisphere. It beg-ins near the lono-i- tudinal fissure and runs first downward and forward about one-half of its course. It then makes an abrupt knee-like bend; and passing- nearly vertically downward, terminates near the' division of the fissure of Sylvius into its horizontal and its vertical limbs. The Parieto- occipital Fissure is but slig^htly seen on the outer surface of the hemisphere, the main portion of the fissure lying- on the inner face. It commences beneath the g"yrus fornicatus opposite the splenium of the corpus callosum ; and passes upward and forw-ard to emerge on the outer surface of the hemisphere, just in the g-reat longitudinal fissure. By these primary fissures the hemisphere is divided into five lobes, frontal, parietal, occipital, tempero-sphenoidal, and cen- tral, or island of Reil. The Frontal Lobe is all of that portion of the brain situated in front of the fissure of Rolando, hence it would be bounded above by the g-reat long-itudinal fissure, on the outer surface, behind, by the fissure of Rolando, on the lower surface, behind, by the main portion of the fissure of Sylvius. It should be noted that the inner face of the various lobes of each hemi- sphere is not described along- with the external and inferior faces, the reason being- that the convolutions and fissures on the internal face do not confine themselves to lobes, but extend in many cases throug-hout the entire leng-th of the hemisphere. The Parietal Lobe is bounded above by the great longitudi- nal fissure, in front by the fissure of Rolando, below by the horizontal limb of the fissure of Sylvius, and a line connecting this with the lower end of the superior occipital sulcus, and behind by the parieto-occipital fissure and a line drawn in continuation of that sulcus. This fissure lies mainly on the inner face of the hemisphere, so that on the outer face, the convolutions of the parietal become continuous with those of the occipital lobe. The Occipital Lobe is cut off on its inner face by -the Pari- eto-occipital fissure from the parietal lobe, this fissure being- its anterior boundary. Above it is bounded by the longitudi- THE CENTRAL NERVOUS SYSTEM. 395 nal fissure, while below its convolutions run into the convolu- tions of the parietal and tempero-sphenoidal lobes, there being- no fissure to form a separation. The Temi)oro-sj)henoidal Lobe is that portion which lies in the middle fossa of the skull. On the inferior surface of the base of the brain it is bounded in front by the fissure of Syl- vius ; externally, it is bounded above by the horizontal portion of the fissure of Sylvius ; while posteriorly it blends around this horizontal limb of the fissure of Sylvius with the occipital and parietal lobes. The Island of Rcil is a cluster of five or six convolutions, situated in the bifurcation of the fissure of Sylvius ; and hidden under the fused lower extremity of convolutions which belong- to the frontal and parietal lobes. The Convolutions and Sulci of the /^r<9;z/rt/Zo<^^ are usually described as consisting^ of two sets, those found on the exter- nal surface, and those on the inferior surface, which is fre- quently described as the Orbital Lobe. The subdivision is unnecessary, the convolutions being- continuous with one another. In brains with a small number of convolutions it will be seen that in front of the fissure of Rolando, and running- parallel with it, is a sulcus of the same character, but of less depth. This is called the prccoitral sulcus. It commences near the bifurcation of the fissure of Sylvius and passes upward nearly to the g-reat long-itudinal fissure. This sulcus cuts off a convolution bounded in front by the precentral sulcus and behind by the fissure of Rolando, which is known as the ascending frontal convolution. Two small sulci extend forward from near the precentral sulcus. Sometimes they run into the precentral sulcus ; but as a rule they do not. These extend straight forward to the anterior extremity of the frontal lobe, cutting- off short convolutions, which are known from above downward -^l^ first, seco/id, and third fron- tal convolutions, or occasionally as superior middle, and inferior frontal convolutions. If these convolutions be traced around to the inferior surface of the frontal lobe, it will be seen that here also are three convolutions, sometimes described as they/r67, second, and third orbital co}ivolutions, numbered 396 DESCRIPTIVE ANATOMY. from within outward and backward ; but in reality the con- tinuation of the first, second, and third frontal convolutions. On the orbital surface, close to the g-reat longitudinal fissure, is a narrow but deep sulcus, which lodg-es the olfactory nerve. External to this is another sulcus, less well-marked, which is the external boundary of the first orbital convolution, the con- tinuation of the first frontal. The second sulcus, marking off the second and third orbital convolutions, or middle and infe- rior frontal convolutions, runs transversely, and is usually divided into two or more limbs, so that the second orbital con- volution lies in front of the third. The ascending- frontal convolution begins below near the bifurcation of the Sylvian fissure, and is connected, around the lower end of the precentral sulcus, with the third frontal con- volution, forming a part of the operculum. Generally, also, it is connected, around the lower end of the fissure of Rolando, with the ascending parietal convolution ; and these two con- volutions are nearly always united around the upper end of the Rolandic fissure. The first, or superior, frontal convolution is limited above by the longitudinal fissure and below by the first frontal sul- cus. It passes directly forward from the precentral sulcus, around the upper end of which it is connected with the ascend- ing frontal convolution, and, winding around the anterior extremity of the frontal lobe, becomes continuous with the so called first orbital convolution. On its orbital surface this convolution is marked by a deep antero-posterior sulcus — the olfactory. The second, or middle frontal convolution is bounded above by the first, and below by the second frontal sulcus. It is shorter than the preceding convolution, with which it fuses around the end of the first sulcus. Passing around the front of the frontal lobe, it becomes continuous with the second orbi- tal convolution, which occupies the antero-external aspect of the orbital surface of the frontal lobe. The third, or inferior, frontal convolution is cut off from the second by the second frontal sulcus, but fuses, around the THE CENTRAL NERVOUS SYSTEM. 397 posterior extremity of that sulcus, with that convolution. It is very short and does not reach the anterior extremity of the hemisphere, but winds around its outer aspect to become con- tinuous with the third or posterior orbital convolution. The Convolutions of the Pai'ietal Lobe are the Ascending" Parietal, the Superior Parietal, and the Inferior Parietal. The Ascending- Parietal is cut off by the intra-parietal sulcus. This is one of the most variable sulci on the outer surface of the hemisphere. It consists of three limbs, which may or may not be joined tog-ether. Commencing" above the fissure of Sylvius, it passes upward and backward parallel with and behind the fissure of Rolando to near the g-reat longitudinal fissure. From a little above its centre a branch passes nearly directly backward, separating" the superior from the inferior parietal convolutions. The vertical portion of this sulcus is named the Post-central; the whole is called the Intraparietal Sulcus. This may consist of three separate and distinct sulci, or any two of these may be united, and the third one exist as a separate sulcus. That portion of the lobe which is bounded in front b}^ the fissure of Rolando, and behind by the ascending" portion of the post-central sulcus is called the ascending parietal convolution. That portion between the g"reat long"itudinal fissure above, the horizontal portion of the post-central sulcus below, and the external portion of the parieto-occipital fissure behind, is called the superior parietal convolution. That part which lies be- tween the horizontal limb of the fissure of Sylvius below, and the intra-parietal sulcus above and in front, is called the inferior parietal convolutioji. This inferior parietal convolution is frequently divided by a small secondary sulcus into two por- tions, an anterior lying" above the fissure of Sylvius, called the supramarginal , and a posterior, which extends around the horizontal limb of the fissure of Sylvius and blends with the occipital lobe, called the angular gyrus, or convolution. It will be seen that the fissure of Rolando reaches neither the g-reat longitudinal fissure nor the fissure of Sylvius, hence 398 DESCRIPTIVE ANATOMY. around the two extremities of this fissure the ascending frontal and ascending parietal convolutions communicate with one another. At the lower extremity of the fissure of Rolando the ascending frontal convolution communicates with theascend- ing parietal, and also with the third frontal convolution. That portion which connects with the third frontal convolution lies in the interval between the two limbs of the fissure of Sylvius, and forms the overhanging portion of brain substance, the Operculum, which conceals the Island of Reil. The Convohitions of the Occipital Lobe are three in number, superior, middle, and inferior. These convolutions are separa- ted by tw^o sulci, called the superior and middle occipital sulci. These sulci are indistinct and poorly marked, each extend- ing backward on the occipital lobe, the convolutions being named from above downward. First, Second, and Third, or Superior, Middle, and Inferior. The superior occipital con- volution is connected with the parietal lobe ; the middle and inferior with the temporo-sphenoidal lobe. The Convolutions of the Temporo-Sphejioidal Lobe. This lobe is divided by three sulci into five convolutions, though two of these convolutions are found on the inner surface of the hemisphere. The two sulci found on the outer surface are the superior, or parallel sulcus and the middle, or second tem- poral, sulcus. The superior, or parallel, sulcus receives its name from being parallel with the fissure of Sylvius ; the second, or middle temporal, sulcus is smaller and much less distinctly marked. Ti\lq. first temporo-sphenoidal convolution 'v^ bounded above by the horizontal limb of the fissure of Sylvius, and below by the parallel sulcus. At its posterior extremity it is continuous vs'ith the ang'ular gyrus of the parietal lobe. The second teniporo-sphenoidal convolution lies between the parallel sul- cus and the second temporal sulcus, and is continuous poste- riorly with the angular gyrus of the parietal and the second occipital convolution. The third temporo-sphenoidal, lying below^ the second tern- THE CENTRAL NERVOUS SYSTEM. 399 poral sulcus, is continuous posteriorly with the third occipital convolutton. The Island of Rcil. On reaching;- the operculum a o-roup of five or six convolutions (thouo-h as few as three have been observed)are found lyincr in the interval between the diverg-ing- limbs of the fissure of Sylvius. These convolutions constitute the island of Reil. The sulci are only slig-ht depressions, and the convolutions slig-ht elevations. They all run in the same direction, upward, backward, and inward. Sulci and Convolutions on the Internal Face of the ^ Hemisphere. The Calloso-mar^inal Sulcus commences near the base of the brain beneath the termination of the corpus callosum. It runs at first forward, following- the rostrum of the corpus callosum, winds around its jgenu, thence backward, parallel with the body of the corpus callosum, until it reaches the posterior third of the brain, when it abruptly turns upward and passes to the g-reat long-itudinal fissure. The Parieto-occipital, the second sulcus found on the inner face, begfins at the splenium of the corpus callosum, and passes upward and backward to terminate on the external face of the hemisphere. The Calcarine Fissure, or Sulcus, is the third of the sulci found on the inner face. It commences by a forked extremity near the end of the occipital lobe, and runs nearly directly for- ward, with a slight inclination downward ; and joins the parieto-occipital sulcus at an acute ang-le. The Collateral Sulcus. The fourth is a long- sulcus which extends across the inner face of the temporo-sphenoidal lobe, separating- the fourth and fifth temporo-sphenoidal convolu- tions. It is called the Collateral Sulcus. The Dentate Sulcus, the last one, passes beneath the splen- ium of the corpus callosum to terminate near the commencement of the fissure of Sylvius. Of these sulci, the calcarine, the collateral, and the dentate all make appearances in the cavities found in the interior of the brain. The calcarine sulcus forms the Hippocampus Minor, 400 DESCRIPTIVE ANATOMY. or Calcar Auis (L. A bird's spur), in the posterior horn of the lateral ventricle. The collateral sulcus forms the eniinentia collateralis ; and the hippocampal, or dentate, sulcus forms, the Hippocampus Major in the descending- horn of the lateral ventricle. These sulci divide the internal surface into a marginal con- volution, the g"yrus fornicatus, the quadrate lobe, the cuneate, the uncinate g-yrus, and the fourth and fifth temporo-sphenoidal lobes. The Marg-inal Convolution is the inner face of the frontal lobe. It commences at the anterior parf orated space, follows the winding's of the calloso-marg-inal sulcus, then runs forward beneath the rostrum of the corpus callosum, winds upward around the g^enu, and passes backward until the calloso-mar- ginal sulcus turns upward to the g-reat longitudinal fissure, where the convolution terminates, and is separated from the parietal lobe by the end of this sulcus. It will be seen that this convolution corresponds to the inner face of the first orbi- tal, the first frontal, the ascending frontal and ascending parietal convolutions. The Gyrus Fornicatus . Below the marginal convolution and between the calloso-mirginal sulcus and the corpus cal- losum is the Gyrus Fornicatus , or convolution of the corpus callosum. It follows the same course as the preceding sulcus until it reaches the posterior extremity of the corpus callosum, where it blends with the quadrate lobe, winding around the splenium of the corpus callosum. Here it changes its name to become the uncinate, or hypocampal, convolution. The .Quadrate Lobe is bounded in front by the upturned portion of the calloso-marginal sulcus, behind by the parieto- occipital sulcus. Above, it is limited by the great longitudi- nal fissure ; and below it blends with the gyrus fornicatus. It is the internal face of the superior parietal convolution. The Cuneate Lobe (L. Cuneus, a wedge) is bounded in front by the parieto-occipital sulcus, and below by the calcarine sulcus ; and is the internal face of the first and second occipi- tal convolutions. THE CENTRAL NERVOUS SYSTEM. 401 The Hippocanipal, or Uiicinate, Lobe (L. Unciiius, hooked) is a continuation downward and forward of the gyrus foruica- tus. It is bounded above by the dentate fissure, and below by the collateral fissure. It extends as far forward as the com- mencement of the fissure of Sylvius; and innerwards to the point where the g'yrus fornicatus commences. Here it turns back- ward upon itself, forrainof the hook-shaped appearance which g-ives the convolution its name. It is the fifth temporo-sphe- noidal convolution, the fourth temporo-sphenoidal lying- beneath the collateral sulcus. In addition to these convolutions, when the hemispheres are separated by cutting' throug-h the corpus callosum we of course see the fibres composing- the corpus callosum and the inner face of the optic thalamus. The Base of the Brain. The lower surface, or base, of the brain, is very irreg-ular in outline, because it is fitted into the fossae of the skull. A^teriorl^^ on either side, is seen the orbital face of the frontal lobe which is somewhat triang-ular with the base backward and apex forward. Behind, and prolong-ed downward to fit in the middle fossa, is the temporo-sphenoidal lobe, and, behind this, the occipital, also triang-ular with its base forward, flat- tened by pressure on the tentorium. The numerous appear- ances found on the base of the brain may be best studied by dividing- them into two sets, viz: those which occur in pairs, and lie on either side of the mid-line; and those which are sing-leand occupy the mid-line. Beginning- on the mid-line in front and passing- backward, we find the following- appearances, viz : The g-reat long-itudinal fissure, with the rostrum of the corpus callosum seen at its bottom; the opticchiasm; the pituitary body, infundibulum and tuber cinerium leading- the one to the other; the posterior perforated space ; the transverse fibres of the pons ; the slig-ht median depression on the pons; the fissure between pons and medulla, and the anterior median fissure of the medulla. The appearances occurring- in pairs and described on one side only, are: The orbital face of the frontal lobe with its two sulci Des Anat— 26 402 DESCRIPTIVE ANATOMY. and three convolutions; the peduncles of the corpus callosum; the groove or sulcus for the olfactory nerve and, the olfactory bulb, and nerve, with the three roots of the latter; the beginninof of the fissure of Sylvius; the optic nerve, internal to the roots of the olfactory; the anterior perforated space ; the optic tract crossing: the crus cerebri, and, internal to this, a corpus albi- ans; and, from this point backward, the roots of the cranial nerves. The long'itudinal fissure and the corpus callosum are else- where described. The optic chiasm is formed by the union of the two optic tracts and gives off the optic nerves. It will be described with these nerves. The pituitary body, or hypo- physis cerebri, is situated in the sella Trucica, bound down by a process of the dura mater. It consists of two lobes, anterior and posterior, separated by a fibrous lamina, the latter, during- foetal life, communicating with the third ventricle through the infundibulum. The infundibuluin is a small tube of grey matter attached above to the lamina cineria and below to the infundibulum. It always communicates with the third ventri- cle. The laviina cineria, or tuber cinerium, is a small mass of g"rey matter which forms part of the floor of the third ventricle. It is connected with the upper face of the optic chiasm and extends back to the carpora albicantia. ^yx^s^ posterior perforated space is in the triang-le formed by the crura on either side and the pons behind. It is made by a number of small vessels which here pass into the optic tha- lami. The remaining- appearances require no further descrip- tion. The olfactory bulb (usually destroyed in removing- the brain) is an oblong- rounded mass of grey matter which lies on the cribriform plate of the ethmoid and gives off numerous fila- ments to the nose. This bulb contracts to become the olfactory nerve which leads back to the fissure of S34vius and divides into its three roots, which are described with the other cranial nerves. The anterior perforated space lies in the commencement of the Sylvian fissure. Antero-internally it is bounded by the optic THE CENTRAL NERVOUS SYSTEM. 403 nerve; internally, by the optic chiasm, postero-internally, by the optic tract. Externally are the Sylvian fissure and the outer root of the olfactory nerve, while the middle root runs near the centre of the space. It is crossed by the peduncles of the corpus callosum, is connected with the lamina cinerium, lies beneath the corpus striatum, and receives its name from being- perforated by numerous small vessels which pass into the latter body. The optic tract will be described with the cranial nerves. The cms cerabri is a round cord which serves to connect the pons with the cerebrum. It is about three fourths of an inch in leng-th and is composed of two sets of long-itudi- nal white fibres, superficial and deep (or anterior and poste- rior; and an intermediate bundle of gray matter called locus )iigcr. The superficial white fibres pass through the pons from the anterior pillars of the medulla to the internal capsule. They form what is called the crusta. The deep lono-itudinal fibres, or tegmentum, pass from the olivar}^ body and lateral and posterior columns of the medulla through the pons to the optic thalamus and cerebral cortex. Situated at the base of the brain is a six-sided space called the inter-peduncular space. It is bounded in front, on the mid-line, by the optic chiasm; behind, on the mid-line, by the transverse fibres of the pons; antero-laterally, by the optic tract; postero-laterally, by the crura cerebri. The corpora alljicantia or niamilluria are a pair of small rounded bodies, situated just behind the tuber cinerium, formed by the anterior pillars of the fornix which pass down to the base of the brain and then turn upward to reach the optic thalami. It is the knuckle formed by reversing their course which forms the corpora albicantia. This space contains the pituitary body, infundibulum, lamina, or tuber, cinerium, corpora albicantia, or mamillaria, and the posterior perforated spot. It, and its contents, form the floor of the third ventricle. Structure of the Cerebrum. When a horizontal slice, an inch or so thick, is removed from the upper surface of one hemisphere, the cut surface shows a central, oval, white portion surrounded, on the exterior, by a 404 DESCRIPTIVE ANATOMY. serrated grayish border; this is known as the centrum ovale minus. When both hemispheres have been cut to the same level, and this level corresponds to the depth of the central portion of the longitudinal fissure, two centra ovalia minora are produced, connected in the centre by transverse fibres, forming- a connect- ing band, called the corpus callosum; and the whole appearance, formed by the two centra ovalia minora and the corpus callosum, is called the centrum ovale majus. Corpus Callosum. The corpus callosum consists almost entirely of transverse fibres passing from one hemisphere to the other. Upon its upper surface there is a shallow groove, extending from before backw^ard along the middle line, called the raphe; bordering each side of the raphe is a slight ridge produced by a bundle of longitudinal fibres, the two ridges being- called the nerves of Lancisi. E^xternal to these are seen a few other longitudi- nal fibres, producing slight ridges which are called the lateral longitudinal strise. When the corpus callosum is bisected longitudinally it is seen to be about four inches long and to bend vertically downw^ard both in front and behind. The bent, rounded, posterior extremity is called the splenium, or pad, or bulb, the central portion the body, and the anterior bent portion the genu, which turns backward beneath the body for a short distance under the name of the rostrum. The rostrum divides into two cords called peduncles, which pass downward and backward to the base of the brain to terminate at the anterior perforated space. Contained in the substance of the brain, between its base and the corpus callo- sum, is an irregular cavity divided into several parts, two of which are known as the lateral ventricles, while the space is spoken of as the general ventricular cavity. The General Ventricular Cavity. The Ventricular Cavity is a space found in the interior of the brain, divided into two lateral, or first and second ventri- cles, and third and fourth ventricles, these cavities all com- municating with one another by means of small foramina. THE CENTRAL NERVOUS SYSTEM. 405 The g-eneral ventricular cavity exists between the corpus callosum and velum interpositum above, the interpeduncular space at the base of the cerebrum, and the upper surface of the pons varolii and the medulla oblong-ata below. The lateral ventricles exist in the two hemispheres of the cerebrum, sepa- rated from one another on the mid-line by a thin septum. The third ventricle lies below the two lateral ventricles, and the fourth is below and behind the lateral ventricles, occupy- ing- a position on the medulla and the pons. The Lateral Ventricles. The rig-ht is usually described as the first, and the left as the second, lateral ventricle. The corpus callosum forms a part of the roof of the ventricular cavity ; and upon its re- moval, the floor, formed of various objects, is brougfht into view. Bach lateral ventricle consists of a body, and three extensions, called the horns of the ventricle, anterior, posterior, and middle. The entire cavity is roofed over in part by the cor- pus callosum, and in part by the frontal, parietal, occipital, and tempero-sphenoidal lobes. The inner zuall is formed in part by a portion of brain tissue called the Seftiun Liicidum (L. Transparent Septum). The outer zuall is the point of junction of the corpus callosum with the fibresof the cerebrum, while the floor is composed of a larg-e number of objects, which will be enumerated later. The body of the ventricle is all of that portion which exists between the anterior horn and the middle and posterior horns. Its upper boundary is the lower surface of the corpus callosum; its inner boundary is, in front, the septum lucidum, and, behind that, the junction of the fornix and the corpus callosum; its outer wall is the junction of the corpus callosum with the fibres of the cerebrum. The floor from before backward is made up of the corpus striatum, the tenia semicircularis, or horny bind of Tarinus, the optic thalamus, the choroid plexus, and the fornix. E)ach of these requires a separate description. The Corpus Slriatinn{\^. .S7m///^6-,g-rooved or furrowed) is an oblong-, or pear-shaped, g-ravish mass, with its larg-e end in front. It is divided into two portions, called the ititra- and 406 DESCRIPTIVE ANATOMY. extra- ventricular -portions^ the former being- also known as the caudate nucleus and the latter as the lenticular nucleus. Between these two, on the outer wall of the ventricle, is a portion of white matter, called the inte7-nal capsule. External to this comes the extra- ventricular portion, the nucleus lenticu- laris (Iv. lense-shaped) ; and on the outer face of this ag-ain is a mass of white matter, called iho, etxer7ial capsule. The white matter which descends between the two portions of the corpus striatum, and on the outer side of the nucleus lenticularis, transmits impulses from the surface of the hemisphere to the medulla oblong-ata, and throug-h that to the spinal cord. The Tenia Semicircularis is a rounded cord, which lies in the groove between the corpus striatum and the optic thalamus • It may be traced into the descending- horn of the lateral ventri- cle, where it joins with the anterior pillar of the fornix ; and thence backward into the roof of the descending* horn, where it terminates in a projection of gray matter, the Corpus Amyg-dalce. The Optic Thalamus \% amass of gray matter which projects into the floor of the body of the lateral ventricle, and forms the lateral walls of the third ventricle. It will be described in connection with that ventricle. The Fornix (L. Fornix, an arch, or vault) is a long"itudinal band of white matter lying- beneath the corpus callosum; and blended with its fellow of the opposite side behind, but separate in front. Behind it thins out into a broad, flattened band, the outer edg-e of which is called the corpus fimbriatum (L. Fim- bria., an edg-e, or border). It descends into the floor of the descending- horn, covering- the projection in that space known as the hippocampus major. Between the two posterior pillars of the fornix transverse fibres are stretched, which from their supposed resemblance to a harp have g-iven the name of lyra to this portion of the fornix. These posterior fibres blend with the white matter forming- the hippocampus major. Anteriorly the two pillars descend to the base of the brain, not connected by transverse fibres, and pass downward to the corpora mamillaria, where they reverse their course and turn upward, THE CENTRAL NERVOUS SYSTEM. 407 to be lost in the optic thalamus of the corresponding" side. The anterior pillars of the fornix are connected with the pe- duncles of the pineal g-latid, and receive fibres from the septum lucidum. The Choroid Plexus passes along- the edg"e of the most in- ternal object in the ventricle, the fornix. It is a mass of blood vessels arrang-ed in the folds of the pia mater, which here projects into the interior of the brain. These vessels enter the descending- horn of the lateral ventricle, pass upward through it, pass throug-h the body of the ventricle, and continue their course into the descending horn, at the bottom of which other small vessels unite with them. The choroid plexus of each side passes beneath the bod}- of the fornix, unites with the choroid plexus of the opposite side, and forms the true roof of the third ventricle. Prom the under surface of the fornix it passes backward through the transverse fissure of Bichat> joins with the velum interpositum, forming there a portion of the roof of the fourth ventricle ; and becomes continuous with the general pia matral covering of the brain. Of the three horns of the lateral ventricle the descending is the largest, the anterior intermediate in size, and the posterior the smallest. The Anterior Horn passes downward, forward, and outward, curving around the anterior extremity of the corpus striatum; and being entirely contained in the frontal lobe of the brain. The Posterior Horn is curved like a half-bent finger, or cockspur, extends backward into the occipital lobe ; and pre- sents on its floor a slight projection, the hippocampus minor, or calcar avis, which is formed by the calcarine sulcus already described, on the inner face of the hemisphere. The Descendin-ala, which effects the junction between the various portions of the brain and the spinal cord. It is about an inch and one-half in length and three quarters of an inch wide at the widest por- tion of it ; and presents for examination anterior and posterior surfaces, superior and inferior extremities. Many writers 414 DESCRIPTIVE AXATOMY. describe it as having- lateral surfaces in addition to the anterior and posterior ; but as the lower portion of the med- ulla is almost completely circular, it is unnecessary to g-ive it more than two surfaces. The anterior surface, which looks downward as well as forward, rests upon the basilar process of the occipital bone ; while the posterior surface, a part of which is flattened and looks upward as well as backward, lies beneath the cerebellum. Just where the medulla joins the pons there is a deep con- striction, or g-roove, which extends completely around the medulla : but is deeper on the anterior than on the posterior face. As the medulla transmits the fibres to and from the spinal cord, it must correspond nearU' to the arrangement of the cord itself, consequently we find pillars in the medulla corre- sponding- in a g-reat measure to the same pillars found in the cord. They are however, not so numerous, nor are they arranged in preciseU^ the same w^ay. The medulla, like the cord, is divided along its anterior and its posterior face by two vertical fissures, which are continuous with the anterior and posterior median fissures of the cord. Lying by the side of the anterior median fissure, and separated by that fissure from its fellow, is a small portion of the medulla, called the anterior pyramid. It is the direct continuation upw^ard of the anterior pyramid of the cord, but also receives fibres belonging to the crossed pyramidal tract of the cord, so that the decussation of these fibres takes place before the cord terminates in the medulla. Behind this anterior pyramid, near the upper ex- tremity of the medulla, is an oblong projection, called the olivary body. This olivary body is concealed in the lower portion of the cord, where the fibres are deepl}^ seated and are covered b}" other portions of the medulla, and above it is made prominent h^ the divergence of the anterior pyramid and the fibres forming the restiform bod3^ Behind the olivary body is a large and prominent body, the restiform (Iv. Restis, a rope ; forma, shape) -which carries the direct cerebellar tract of the cord, and terminates by forming the inferior peduncles of the cerebellum. THE CENTRAL NERVOUS SYSTEM. 415 Next to the rest'form body is the fourth and last portion of the medulla, \h.^ posterior pyramid, this portion of the medulla carrying- the fibres which in the cord are known as the columns of Goll and Burdach. The posterior pyramid, as it passes upward, blends with the restiform body; and the two pass to- ofether into the cerebellum to form its inferior peduncles. The anterior pyramids passing- throug-h the pons Varolii, enter into the formation of the crura cerebri. The olivar}- fibres disap- pear at the upper extremity- of the medulla, sinking- deeply into the pons, and probably aid in forming- the commissural fibres which exist betw^een the two lobes of the cerebellum as the superficial fibres of the pons. The appearances on the posterior face of the medulla have already been described in connection with the fourth ventricle of the brain. The Cerebellum. The Cerebellum, or Little Brai)i, is divided into two hemi- spheres by a deep fissure found on its inferior aspect and a projection found on the superior face. In the adult its relation in weig-ht to the cerebrum is variously stated as one to thirteen and one to twenty, Cruveilhier g-iving- the latter proportion. It is usually described as being- divided into three lobes, a middle and two lateral, the middle being- generally called the "worm", and the two lateral the "hemispheres". The hemi- spheres and the worm present a superior and an inferior surface. When viewed from above, the entire cerebellum seems undivided, the hemispheres being- directly continuous throug-h the middle of the worm. They slope from before downward, backward and outward. On the inferior surface the appearance is entirely different. Here a deep groove separates the two hemispheres; but the g-roove itself is partially filled by the lower aspect of the worm, which in its turn is subdivided by fissures into three portions. The g-rfjove in which the worm lies terminates anteriorly and posteriorly in notches, the incisura cercbelli, a)ilcrior and posterior. The anterior is the wider, and is not so deep as the 416 DESCRIPTIVE ANATOMY. posterior. The worm extends into these notches, but does not completely fill them. The upper aspect of the worm is g-enerally called the superior vermiform process, and the lower the inferior vermiform process. Its sides are attached directly to the hemispheres of the cerebellum; and probably act as commissural fibres. On the upper face the worm has no subdivisions; but when viewed from below it is seen to be divided into a flattened mass of gray matter, the Posterior Medullary Velum, behind that a projection called the Uvula (L. Diminutive of Uva, a gfrape), and behind that the Pyramid. Each hemisphere of the cerebellum is divided into lobes; but we do not find in the cerebellum the convolutions which appear in the cerebrum. The cerebellum presents a laminated appearance, the fissures, or sulci, beino- deep and narrow, while the laminae overlap one another throug-hout the entire area of each hemisphere. Certain of these sulci, however, are deeper and more distinctly marked than others, so that it becomes possible to divide the cerebellum into lobes which are less distinctly bounded than "the lobes of the cerebrum. There names are fanciful; and derived in the main from a sup- posed resemblance to other portions of the body. On the lozoer surface of each hemisphere, close to the median fissure, is a small projection of the cerebellum cut off by a deep fissure, called the Tonsils from their supposed resemblance to a gland in the throat. Beyond the tonsils, and cut off by the second inferior cerebellar fissure, is a curved lobe, which is called the Digastic. Next to this, and between the second and third cerebellar sulci, is a long narrow, curved lobe, which extends from the median fissure behind the pyramid around to the front of the cerebellum nearly as far as the anterior median fissure. This lobe is very narrow, and is called the Slender Lobe. Behind the slendar lobe, and occupying-the posterior extremity of the cerebellum, is another long and slender lobe, which borders the slender lobe, extendinof from the posterior extremity of the median fissure around to the front of the flocculus. This is known as the -postero- infer'ior Lobe. THE CENTRAL NERVOUS SYSTEM. 417 On the upper surface the lobes are very indistinct, and can scarcely be described as separate lobes. There are really but two lobes on the superior surface, the f>ostero- superior and the anterior, or square, lobe. It will be noticed that the infe- rior vermiform process is that portion of the cerebellum which overhangs the fourth ventricle, and is its indirect roof, the pia mater intervening- between the ventricle and the inferior vermiform process. The Spinal Cord. The Sphial Cord is the great connecting link between the brain and the various members of the body. It seems to correspond partially to a mass of insulated wires, a large por- tion of its work being the transmission of impulses to and from the brain ; but it contains nerve centres which in them- selves originate impulses, hence it is not merely a bundle of transmitting fibres. It is markedly similar to the brain in the arrangement of its membranes, and to some extent in its functions ; but is dissimilar in the arrangement of the mass of gray and white matter. The Membranes of the spinal cord, like those of the brain, are three in number, and bear the same names as those of the brain, the Dura Mater, the Pia Mater, and the Arachnoid. The Dura Mater of the spinal cord is, hov^^ever, unlike that of the brain, much too large for the cord which it envelopes. It lines the interior of the spinal canal, is firmly attached to the bodies of the vertebrae, and sends off prolongations for each of the thirty-one pairs of spinal nerves, which accompany these nerves until they leave the spinal column. The inner face of the dura mater is lined by the arachnoid, as is the case in the brain ; and it should be borne in mind that the membranes of the spinal cord are all directly continuous with those of the brain. The Arachnoid, forms here, as in the brain, a serous mem- brane, covers the entire surface of the cord, and lines the inner face of the dura. It does not closely hug the cord ; but between it and the cord is found a continuation of the mis-named sub- arachnoidean space. Between the visceral layer covering the Des Anat— 27 418 DESCRIPTIVE ANATOMY. cord and the parietal layer covering- the dura is a second space which is known as the sub-dural, and it really lies between the folds of the arachnoid itself. The Pia Mater covers the cord nearly as it does the brain, but with some slig-ht differences. It sends prolong-atious to accompany the nerves which leave the spinal cord, it conveys the blood-vessels as in the brain; but it also gives lig-amentous fibres, which are not found in the cranium. Between each pair of spinal nerves will be found a wedge-shaped portion of fibrous tissue, which is derived from the pia, and which, passing- to the lateral aspect of the cord, becomes attached to it, while the point of the wedg-e extends outward to blend with the dura. These prolong-ations form the Ligamentum Denticulatum, and serve the purpose of retaining- the cord steadily in position, and of preventing its movement in the large chamber furnished for it by the dura. The Cor^ itself is nearly, though not quite, cylindrical, be- ing slightly flattened in the antero-posterior direction. It is seventeen or eighteen inches in length, and varies in weight, as does the brain, with the period of life, cause of death, and even with the period after death when the cord is removed. It corresponds in length to the upper tw^o-thirds of the spinal canal in the adult, though it is longer comparatively in the foetus, extending here to the bottom of the sacral canal ; but apparently the vertetwae grow more rapidly than the cord and hence the cord is carried upward in the canal until it reaches about the level of the second or third lumbar vertebra. The cord presents an enlargement in the cervical region, where the branches are given off which supply the upper extremity ; and a similar enlargement in the lower lumbar region, where 'he branches are given off which supply the lower extremity. Of course, in the living being, its curvature corresponds to the! curvature of the spinal column. When the membranes are removed, it will be seen that the cord presents two Median Fissures, one Anterior, and one Posterior. z' The anterior is very wide, but shallow; w^hile the, ^posterior s very deep and narrow. In addition to these two fissures. THE CENTRAL NERVOUS SYSTEM. 419 the spinal nerves, rising- by two bundles of roots, called the anterior and posterior, make an incomplete and irreg-ular fissure, which extends throug-h the length of the cord, and serves to form the two lateral fissures. Hence it will be seen that the cord is divided into an anterior column, a posterior column, and a lateral column, the last being- separated from the other two by the anterior and posterior roots of the spinal nerves. There are, however, other columns in the cord, determined more by pathalog-ical than by anatomical examination. It will be seen that the cord, unlike the brain, is arranged with all of its g'ray matter in the centre, and the white matter surrounding it; and on section oE the cord in living- animals deg-eneration takes place in two directions. Those fibres which convey impulses to the brain deg-enerate upward, while those which convey impulses from the brain deg-enerate downward. These pathological changes warrant the division of the cord into a number of tracts, not noted anatomically. As in all portions of the brain, the two lateral divisions of the cord, separated by the anterior and posterior median fis- sures, which correspond in fact to the great longitudinal fissure of the brain, communicate across this fissure by means of commissural fibres. The roots of the spinal nerves extend through the white matter of the cord, and communicate with the gray matter in its interior. This gray matter, in addition to furnishing trophic centres, contains centres which act apparently of their own volition without stimulation from the brain. As a matter of course these centres are, however, presided over by the brain, and can be restrained in their action by the higher centres. The total number of tracts in the cord is large; and we do not find the corresponding tracts in the medulla, but in many cases two or more tracts are blended into one in the trans- mission from the cord to the brain. Commencing at the ante- rior median fissure the first tract is called the Anterior Pyramid ., or Anterior Pyramidal Tract, ■a.nA next to this is found the Anterior Ground Zone, or Anterior Root Zone, being that portion of the cord in front of the anterior roots of the spinal 420 DESCRIPTIVE ANATOMY. nerves. Then comes behind the spinal nerves a second ground zone, which is, however, called the Lateral bujidle, and external to both of these and superficial to them is the Antero-lateral tract, v^^hich conveys both ascending- and descending fibres to the cerebrum. Behind this tract, also on the superficial sur- face of the cord, is the Direct Cerebellar tract which extends as far as the posterior root zone; and between the direct cere- bellar and the gray matter in the interior of the cord is the Crossed Pyramidal Tract. Behind the posterior root zone are tw^o tracts, the one next to the roots of the nerves being Burdacli s Column, or the postero-lateral column, while the one next to the postero-median fissure is the column of Goll, or the postero-median column. When these columns are traced upward into the medulla, it will be found that the column of GoU and the column of Bur- dach unite to form iho. ^posterior column of the 'medulla^ or, as it is frequently called, funiculus cuneatus (Iv. Dim. of funis, a cord ; cuneatus, wedge-shaped) ; that the direct cerebellar tract passes into the restiform body ; that the crossed pyram- idal and the direct pyramidal enter into the anterior pyramid of the medulla, when the direct pyramidal will pass upward on its own side, while the crossed pyramidal passes to the pos- terior side. The antero-lateral or ascending and descending cerebellar tracts, with the anterior root zone, pass upward into the lateral column of the medulla, to ascend with it to form the central fibres of the pons Varolii. In addition to these white transmitting fibres, the cord con- tains in its interior the mass of gray matter before alluded to, which is arranged like the letter "H", the projections in front of and behind the cross-bar of the "H" being called the "horns." The posterior horns are long and slender, while the ante- rior horns are bluntly pointed. These masses of gray matter contain the fibres furnishing the various centres in the spinal cord. It will of course be seen that the branches which proceed from the spinal cord are collectively enormously larger than THE CENTRAL NERVOUS SYSTEM. 421 the cord itself, and it can be readily understood that large quantities of fibrous tissue, serve in a measure to make up a portion of the bulk of the spinal nerves. The cord is nourished by the blood vessels which it carries in its pia matral covering- ; and these blood vessels are derived partly from the anterior and posterior branches of the vertebral arteries, and partly from the branches which enter the spinal canal springing from the intercostal and lumbar arteries. The Spinal Nerves. The Spinal nerves consist of thirty-one pairs, which taking their origin from the spinal cord, pass outward from the spi- nal canal through the intervertebral foramina, and are distrib- uted throughout the body. These nerves differ materially from the cranial nerves, for, whereas the latter are usually divided into separate nerves, having motor, general sensory, or special sensory functions, the spinal nerves are composed of bundles, performing all nervous functions. Some convey tactile sensations, some painful, some motor, and some various other functions. While these nerves may be traced into the spinal cord, their fibres pass through the various columns of the cord to reach different portions of the brain ; and hence while the nerves are described as spinal nerves simply from their origin, they are controlled by the higher centres located in the cerebrum. They differ from the cranial nerves also in their manner of distribution. The cranial nerves pass out as individual nerves to break up into branches distributed to various portions of the head, face, and viscera, having but slight communications with one another. The spinal nerves on the contrary unite very intimately with one another after their emergence from the spinal column; and form plexuses from which branches are given off to carry out the distribution of the plexus. There are four of these plexuses, called the Cervical^ Brachial, Lum- bar, and Sacral. Interposed between the brachial and the the lumbar are a set of spinal nerves, the Dorsal, which do not unite to form plexuses, but are distributed individually 422 DESCRIPTIVE ANATOMY. like the cranial nerves. Some writers mention a coccygfeal set ; but these in reality belong- to the sacral plexus. E)ach spinal nerve as itemerg-es from the cord is surrounded by a prolongation of the dura mater, which lines the spinal canal and forms a sheath for the nerve as far as the interver- tebral foramen. From this point it becomes continuous with the ordinary fibrous sheath, which envelops every nerve, and ceases to have the characteristics of the dura mater lined by its arachnoid membrane. Moreover each nerve presents upon it at its emerg^ence an enlargement; and as every nerve arises by an anterior and a posterior root, this enlargement, or ganglion, is confined to one of these roots. The posterior root of a spinal nerve conveys its sensory fibres, while the anterior root conveys the motor fibres. The anterior root also has its trophic centre situated in the spinal cord, so that cutting that nerve causes degenera- tion downward into the nerve, which has been cut loose from its trophic centre, while cutting the posterior root between the ganglion and the cord causes degeneration upward into the cord, because the trophic centre is located in the ganglion and not in the cord. It must be always remembered that while these fibres con- veying the various impulses exist in the spinal nerves they cannot be demonstrated anatomically. E^ach spinal nerve immediately after it emerges from the spinal canal divides into an anterior and a posterior branch. The posterior branches are small in size and comparatively unimportant. They convey motor and sensory impulses to the muscles found in the back and neck, the posterior fibres of the sacral plexus, the lowest, conveying impulses to the lowest muscles of the trunk, while the limbs are supplied entirely from the anterior cords. It is the anterior cords which enter into the formation of the plexuses. The Cervical Plexus. The first plexus formed by the spinal nerves is called the Cervical. It Is the product of the four upper cervical nerves. The plexus is formed by the intercommunication of the ante- THE CENTRAL NERVOUS SYSTEM. 423 rior cords of these four cervical nerves ; and Is found opposite the middle of the sterno-cleido-mastoid muscle. Its principal distribution is to the muscles and integfument of the neck. The plexus itself is formed in the following- manner : The first cervical nerve divides into an anterior and a posterior branch, the posterior branch forming- what is known as the Great Occipital Nerve {^Occipitalis Major), while its anterior division, after receiving a communication from the eleventh and twelfth cranial nerves, sends downward a communication to the second cervical. The second cervical, after g-iving- oif its posterior branch, sends a communication to the third and the third in like manner sends a communicating- branch to the fourth, which in its turn sends a branch to the fifth, which enters into the formation of the brachial plexus. Prom this loosely formed cervical plexus branches are g-iven off which are dis- tributed to the head, face, neck, and chest. These branches are, for convenience of study, divided into two sets, superficial and deep, the superficial set consisting- of three named branches, and certain unnamed branches, which are called descending superficial branches. The deep set consists of muscular branches. The named branches of the superficial set are the Snperfi- cialis Colli, Auricularis Mag'nus, and Occipitalis Minor. Superficial Branches. Superficialis Colli Auricularis Mag-nus Occipitalis Minor The Superficialis Colli. The Superficialis Colli, the first branch, is the product of the sccotzd and third cervical nerves ; and like all the superfi- cial branches from this plexus, it winds around the posterior border of the sterno-cleido-mastoid muscle, about at its middle, and becomes superficial in that situation. It then passes up- ward and forward, crosses the sterno-cleido-mastoid, runs to the lower border of the inferior maxilla, and spreads out into a fan-shaped set of twigs, which, after communicating- with the facial nerve, are distributed to the skin covering the lateral aspect of the face. 424 DESCRIPTIVE ANATOMY. The Auricularis Magnus. The Auricularis Magnus is the product of the second and third cervical nerves. After emerg-ing- from the posterior bor- der of the sterno-cleido-mastoid, it crosses that muscle, and divides into two branches, mastoid and auricular. The mastoid branch ascends to the mastoid process of the temporal bone and is distributed to the skin in that reg"ion after communicating" with the seventh nerve. The auricular branch divides into several twig^s, which are distributed to the skin on the back of the pinna. The Occipitalis Minor. The Occipitalis Minor is derived from the second cervical nerve. It passes upward nearly parallel with the posterior border of the sterno-cleido-mastoid muscle; and gives off three sets of branches, one passing- to the back of the ear, one over the mastoid process of the temporal, where it communicates with the auricularis magnus, and the third, the larg-est, passing to the occipital bone, where it runs over the occipito-frontalis muscle, and is distributed to it and to the skin covering the occipital bone. The Descending Superficial Branches. The unnamed Descending- Superficial Branches are produced by the third -dM^^ fourth cervical nerves. They emerg-e from beneath the sterno-cleido-mastoid muscle, like the preceding branches, about opposite the middle of its posterior border- They are irregular in size and number. One set passes down- ward and inward toward the mid-line of the body, crossing the clavicle near its inner extremity and ending in the integu- ment which covers the front of the thorax. The second set passes nearly vertically downward, to cross the middle of the clavicle, and be distributed to the integ-ument covering the pectoral muscles, while the third set, called sometimes the acromial, or deltoid, passes outzvard, and is distributed to the skin in the neig-hborhood of the shoulder. THE CENTRAL NERVOUS SYSTEM. 425 Deep Branches. Muscular Phrenic Communicans Noni The Muscular Branches. The muscular branches are distributed to all of the muscles of the front of the neck with the exception of the depressors of the hyoid bone. They consist of a branch to the sterno- cleido-mastoid muscle, which arises from the second cervical and communicates with the eleventh cranial in the substance of the sterno-raastoid muscle ; a branch to the scalenus medius, coming- from the third ^nA fourth nerves ; one to the levator anguli scapulas ; and several branches to the trapezius, which are the product of the third and fourth cervical nerves and which communicate with one another. Besides this, there are some branches, sometimes described as internal, which supply the rectus capitis lateralis, the rec- tus capitis anticus minor, and the long-us colli. The Communicans Noni. The most important communicating branch is the Commu- nicans Noni. This nerve is the product of the second and third cervical nerves. It passes downward, forward, and inward, and unites with the descending- branch of the hypo- g-lossal on the front of the common carotid artery, immediately above the point at which the omo-hyoid crosses that vessel. After this communication it passes with the descendens noni to be distributed to the muscles of the infra-hyoid group, or depressors of the hyoid bone, with the exception of the thyro- hyoid, which is supplied by a branch from the hypog-lossal nerve itself. The Phrenic. The last and most important branch of the plexus is the l^hrenic Nerve. It is formed by contributions from the third and fourth cervical nerves, reinforced by a small filament from the fifth. The course of the nerve on the two sides of the hody differs. 426 DESCRIPTIVE ANATOMY. On the rig-ht side it descends on the front of the scalenus anticus muscle, reaches the inner side of that muscle just be- fore it crosses the subclavian artery, drops off to the inner side, and becomes an anterior relation of the first portion of the subclavian, thoug-h occasionally it remains on the scalenus anticus until after it has passed the artery. It then runs in the interval between the subclavian artery and vein, continues its downward course into the thorax, lying- to the outer side of the right vena innominata and then the superior vena cava, passes in front of the root of the right lung, then lies on the pericardium between it and the right pleura, and finally pierces the dia- phragm, and is distributed to that muscle from its under surface. The left nerve, formed in the same way, passes on the scalenus anticus muscle to cross over the front of the first portion of the subclavian, then to descend in front of that vessel and opposite the interval between it and the left common carotid, lying to the outer side and in front of the pneumogastric nerve. Then it crosses the end of the transverse aorta, passes downward on the left side of the pericardium, lying next to the left pleura, and then, like its fellow of the opposite side, enters the dia- phragm and is distributed to it from its under surface. The Brachial Plexus. The Brachial Plexus is the second great plexus formed by the anterior cords of the cervical nerves. It is the result of inter- communications between the four lozuer cervical nerves and a portion of the first dorsal nerve. The manner of its forma- tion differs indifferent individuals; but it is usually formed ia the following way: The fifth and sixth cervical nerves unite to form a single cord; the eighth cervical and the first dorsal unite to form one cord, while the seventh cersiical passes out alone. Then the seventh unites with the cord formed by the fifth and sixth, so that at one time there are but two cords in the plexus, one resulting from the union of the fifth and sixth with the seventh, and the other formed by the eighth cervical with the first dorsal. Shortly after, however, each of these two cords gives off a branch; and these branches unite to form THE CENTRAL NERVOUS SYSTEM. 427 a third cord in the plexus, this middle cord being the product of all of the cords which enter into the formation of the brachial plexus. The plexus is triang-ular in outline, with its base directed to- wards the spinal column and its apex extending- downw^ard. back- ward and outward towards the axillary space. It passes between the scaleni muscles ; and comes into relationship with the sub- clavian artery in the second portion of its course. Here most of the cords lie above that vessel ; but the branch derived from the dorsal nerve lies behind it. In the third portion of the subclavian artery the plexus lies above and to the outer side ; but on a plane posterior to it. It then continues forward and outward, coming into relationship with the axillary artery, and lies first to its outer side ; but in the second portion of that vessel ; viz., that part behind the pectoralis minor muscle ,the plexus consists of three cords, one to the inner side, one to the outer side, and one lying behind the axillary artery. Just at the termination of the second portion the inner and the outer cord each give off a branch ; and the two branches formed in this manner unite to form the median nerve, so that, on a line drawn from the tip of the coracoid process of the scapula downward and inward to the lower part of the third intercostal space, it will be seen that the axillary artery is completely surrounded by the cords of the plexns. The outer and inner cords lie on the outer and inner sides of the artery, the posterior cord behind it, and the branches which form the median nerve lie upon its front. Immediately after the formation of the median, that nerve drops to the outer side of the axillary artery, and maintains that relation to the termination of that vessel, while the re- maining cords of the plexus break np into their terminal h) ranches. Branches of the Brachial Plexus. The distribution of the brachial plexus is chiefly to the upper extremity, supplying the muscles and integument ; but before reaching its point of termination it gives oflf way-side branches, some muscular and some cutaneous, which are dis- 428 DESCRIPTIVE AX ATOMY tributed to the lateral aspect of the chest, as well as to the muscles of the scapular group and the skin covering* them. Wayside Branches. Above the Clavicle f Suprascapular Rhomboid Posterior Tho- racic Communicating- Subclavian Scaleni lyong-us Colli Below the Clavicle Anterior Tho- racic, internal. Anterior Tho- racic, external. SubscaDular The Suprascapular. The Siiprasca^idar hrancJi is derived from the fifth and sixth cervical nerves. It passes downward and outward par- allel with the posterior belly of the omo-hyoid muscle. Reach- ing" the upper border of the scapular it passes throug-h the suprascapular notch beneath the transverse lig-ament. and consequently below the corresponding- artery, enters the supraspinatus muscle, gives motor fibres to that muscle and a twig- to the shoulder joint, while the remaining- portion of the nerve passes around the anterior border of the spine of the scapular to be distributed to the infraspinatus muscle. The Rhomboid. The branch to the Rhomboideus is a product of the nftli cervical nerve. It passes throug-h the fibres of the scalenus medius, and is then distributed to the rhomboid muscle, or muscles. The Posterior Thoracic. The Posterior Thoracic, or External Respiratory Nerve of Bell, is the product of the fifth, sixth, and seventh nerves. It passes downward behind the brachial plexus and the first por- tion of the axillar\^ and is distributed to the serratus mag-nus muscle. Communicating. The communication with the cervicle plexus is by means of the fifth cervical, which joins with the phrenic nerve. THE CENTRAL NERVOUS SYSTEM. 429 The Subclavian. The nerve to the Subclaviiis jiiuscle is a slender twig*, which is derived from the fifth cervical, and crosses the front of the third portion of the subclavian artery to enter the subclavius muscle. The Branches g-iven below the clavicle, besides the terminal ones, are the external and internal anterior thoracic and the subscapular nerves. The External Anterior Thoracic. The Exteriial Anterior Thoracic, derived from the outer cord of the plexus, is distributed to the pectoralis major muscle. The Internal Anterior Thoracic. The Internal Anterior Thoracic, the product of the inner cord, passes between the first portion of the axillary artery and its vein, occasionally perforating- the vein itself; and after re- ceiving- a communication from the external anterior thoracic, is distributed to the pectoralis major. /or^ The Subscapular. The Subscapular nerves are three in number ; and the}'' are derived from the posterior cord. They are known as the upper, middle, and lower. The upper is distributed to the subscapularis muscle alone, the middle accompanies the sub- scapular artery, and terminates near the latissimus dorsi ; while the /oz.'cr is distributed to the teres major, furnishing" some twig-s to the subscapularis. Terminal Branches. Musculo-cutaneous Internal Cutaneous Median Lesser Internal Cutaneous Ulnar Musculo-Spiral Circumflex The terminal branches of the Brachial Plexus orig-inate from the cords of the plexus as follows : The internal cord produces the internal cutaneous, the lesser internal cutaneous, the ulnar, 430 DESCRIPTIVE ANATOMY. and one head of the median. The externcd cord divides into two branches : one forms the outer head of the median, while the other is the musculo-cutaneous. The -posterior cord di- vides into the circumflex and the musculo-spiral. The division of the plexus takes place on the beg-inniag- of the third portion of the axillary artery, which is here completely surrounded by the cords of the plexus; but immediatelvaf ter the formation of the median, that nerve drops to the outer side of the axillary artery; and the relation is then, median and musculo- cutaneous to the outer side, internal and lesser internal cuta- neous and ulnar nerves to the inner side, musculo-spiral be- hind, and circumflex behind as far as the interval between the teres major and lower border of the subscapularis, where it passes to the back of the humerus and ceases to be a relation. The Musculo-Cutaneous. The Musculo-cutaneous Nerve, the product of the outer cord of the brachial plexus, receives fibres which can be traced to the fifth, sixth, and seventh nerves, passes downward as an external relation of the third portion of the axillary artery until it reaches the coraco-brachialis muscle. It then passes through the substance of that muscle, supplying* the muscle with branches as it is transmitted through it. E^merging from the coraco-brachialis, it passes between the brachialis anticus and the biceps, runs into the interval between the brachi- alis anticus and the supinator longus, where it becomes superfi- cial a little above the elbow joint, and passing across the outer front aspect of that joint, divides into two branches. The -posterior branch passes downward and backward; and is distributed to the skin on the postero-external aspect of the forearm as far as the wrist. The anterior branch, supplying the integument on the antero-external face of the forearm, communicates with the radial nerve near the wrist, and extends as far as the skin covering the thenar eminence. The nerve in its course gives off muscular branches to the coraco-brachialis, the biceps, and the inner portion of the brachialis anticus. THE CENTRAL NERVOUS SYSTEM. 431 The Internal Cutaneous. The Internal Cutaneous Nerve is the product of the inner cord of the plexus ; and is probably derived from the eiofhth cervical and first dorsal. It is an internal relation of the third portion of the axillary arter}^ to the termination of that vessel ; and then becomes an antero-internal relation to the brachial artery, lying- in close companionship to the basilic vein. At the middle of the brachial artery the nerve, with the basi- lic vein, pierces the investing- fascia ; and still remaining* an antero-internal relation of the brachial artery to its termina- tion, is, for its lower half, separated from that vessel by the deep fascia of the forearm. At the elbow-joint it breaks up into branches, some of which, lying on the front of the bicipital fascia, are anterior relations of the brachial artery, but separated from it by this fascia. The remaining branches continue their course down- ward, being divided into an anterior and a posterior set. the anterior supplying the integ-ument of the inner front aspect of the forearm as far as the wrist, while the ^o^/'t'r/or supply the integument on the postero-internal aspect of the forearm down to the wrist. The Lesser Internal Cutaneous. The Lesser Inter)ial Cutaneous^ or Nerve of Wrisberg, aris- ing from the internal cord, receives its branches from the eighth cervical and first dorsal. It is very irregular in its origin, and ma}' be the product of the lateral cutaneous branch of the second intercostal nerve ; but, as a rule, it simply re- ceives a communication from that nerve. At first it is an internal relation of the axillary artery, and is separated from that artery by the axillary vein. It continues downward, too distant to be considered a relation of the brachial artery, to thj postero-internal aspect of the arm, and near the elbow turns backward to be distributed to the integ-ument on the 1 jwer third of the arm and in the neig-hborhood of the olecra- non process. 432 DESCRIPTIVE ANATOMY. The Ulnar. The Ulnar Nerve is the last branch of the internal cord of tHe plexus; and like the preceding- branches, contains fibres from the eigfhth cervicle and first dorsal nerves. It is first an internal relation of the axillary artery, lying- between it and the lesser internal cutaneous nerve. It then becomes an internal relation of the brachial for the upper half of the course of that vessel; and at the middle of this artery it reaches the inferior profunda branch of the brachial. Accompanied by this latter branch, it passes backward, pierces the internal inter-muscular septum, and runs to the space between the internal condyle of the humerus and the olecranon process of the ulnar, forming'^^ what is g-enerally known as the "funny bone". The nerve then passes between the two heads of the flexor carpi ulnaris muscle; and at the junction of the upper third with the lower two-thirds of the forearm it becomes an internal relation of the ulnar artery. It then passes downward, lying- on the fibres of the flexor profundus digitorum, and maintains a continuous internal relation to the ulnar artery to the wrist joint. At this point it becomes superficial to the anterior annular liga- ment, passes to the outer side of the pisiform bone, and enters the palm of the hand, where it divides into a superficial and a deep branch. In the commencement of its course the nerve lies on the an- terior face of the internal inter-muscular septum. At the middle of the arm it pierces this septum, and passes downward in the fibres of the triceps muscle, then behind the internal condyle of the humerus, then between the two heads of the flexor carpi ulnaris, separated from the ulnar artery for the upper third of the course of that vessel. Then the nerve lies with the flexor carpi ulnaris to its inner front side, and the flexor profundus digitorum behind it, and with the ulnar artery to its outer side for the lower two-thirds of its course. The nerve gives off no branches until after it has passed the elbow joint, where it supplies muscular branches to the flexor carpi ulnaris and the inner half of the flexor profundus digfi- torum. About three inches above the wrist joint it g-ives off a THE CENTRAL NERVOUS SYSTEM. 433 cutaneous branch, the dorsal cutaneous branch of the Ulnar, which will be described later ; and then a superficial branch which enters the palm of the hand. A few small twig's are given olT to the elbow joint. Superficial Branch. After entering- the palm, the super- ficial branch supplies the palmaris brevis, and the skin cover- ing the hypothenar eminence, a twig to the inner side of the little finger, and a branch which bifurcates to supply the ad- jacent sides of the little and ring fingers, and lastly a commu- nicating branch to the median nerve. The distribution of the collateral digital branches to the fingers is accomplished by the median and ulnar nerves. These branches pass to the clefts between the fingers, divide into two, which course along superficial to the corresponding arteries, and opposite the posterior extremity of the nail send dorsal branches around which ramify between the nail and its matrix, each nerve communicating with its fellow of the opposite side around both the palmar and the dorsal aspects. The ulnar nerve sup- plies the little finger and the inner side of the ring finger. Deep Branch. The Deep Branch of the Ulnar passes be- tween the flexor minimi digiti and the abductor minimi digiti, runs along the palm of the hand accompanying the deep palmar arch, supplies the two inner lumbrical muscles, the two outer interosseous muscles, the muscles of the hypothenar eminence, with the exception of the palmaris brevis, and in the thenar group, supplies one muscle and a half, viz., the adductor poUi- cis, and the deep head of the flexor brevis pollicis, the remaining portion of the hand being supplied by the median nerve. The Dorsal Ciilancoiis Branch of the Ulnar arises three inches above the wrist joint, passes to the back of the forearm, and descends behind the styloid process of the ulnar to the back of the hand. Here it divides into cutaneous branches, the most internal of which is distributed to the ulnar side of the little finger. The second passes to the cleft between the little and ring fingers, where it divides into dorsal collateral digital branches for these two fingers. The third cutaneous /jranch communicates with a branch from the radial nerve, passes to the cleft between the ring and middle Des Anat— 28 434 DESCRIPTIVE ANATOMY. fing"ers, and divides to supply the adjacent sides of these two fing-ers. These dorsal collateral digfital branches communicate in the matrix of the nail with the palmar branches already noticed. The Median. The Median Nerve is the joint product of the internal and external cords of the brachial plexus ; and derives fibres from all of the anterior cords entering- into the formation of that plexus. It is formed at the commencement of the third por- tion of the axillary artery by the junction of a branch from the inner with a corresponding* branch from the outer cord of the plexus. Formed on the front of the third portion of the axillary artery, it immediately drops to its outer side, and maintains that relation to the termination of the vessel. It then becomes an outer relation of the brachial artery, lying- between that artery and the coraco-brachialis muscle. About opposite the insertion of the coraco-brachialis it passes to the front of the brachial artery, crossing- it very obliquely, so as to remain on the front of that vessel for the middle one-third of its course. It then drops to the inner side of the brachial artery, and maintains that relation to the termination of that vessel, a fing-er's breadth below the middle of the front of the elbow joint. It should here be noted that in cases of hig-h bifurcation of the brachial, the median nerve almost invariably passes between the two branches, the branch in front usually corresponding- to the radial artery, and the branch behind to the ulnar. In some cases the median nerve passes behind instead of in front of the brachial artery. Reaching- the elbow joint it lies in the triangular space, the base of which is directed upward, and is formed by a line drawn from the inner to the outer condyle of the humerus, th external boundary being- the supinator long-us and the innei boundary the pronator radii teres. The nerve exactly bisects this space, passes between the two heads of the pronator radi' teres muscle, the deep head of which alone separates it from the ulnar artery. Crossing- over the ulnar artery, and sep- arated from it by the deep head of this muscle, it then passes down the middle of the front of the forearm, covered by the THE CENTRAL NERVOUS SYSTEM. 435 superficial head of the pronator radii teres and overlapped by the flexor carpi radialis on its outer side and the flexor sublimis dig"itorura on its inner side, and lying- nearly directly behind the palmaris long-us. It then passes to the front of the wrist joint, crosses beneath the anterior annular lig-ament into the palm of the hand, and breaks up into its terminal branches. Like the ulnar nerve it g-ives off no branches in the arm. It gives off a few small branches to the elbow joint ; and just below the bend of the elbow g*ives off a large branch, called the anterior interosseous. The Anterior Interosseous Nerve arises opposite the bicipi- tal tubercle of the radius, runs downward on the interosseous membrane, accompanied by the anterior interosseous artery, as far as the upper border of the pronator quadratus muscle, where after giving- branches to the deep surface of that muscle, it pierces the interosseous membrane and communicates with the posterior interosseous nerve. Immediately below the elbow joint the median gives off branches to all of the muscles on the front of the forearm with the exception of the flexor carpi ulnaris and the inner half of the flexor profundus digitorum. In other words, it supplies muscular twig-s to six and one-half out of eig-ht of the muscles of the forearm ; viz., the pronator radii teres, flexor carpi radi- alis, palmaris long-us, flexor sublimis digitorum, flexor long-us pollicis, pronator quadratus, and outer one-half of the flexor profundus digitorum. Just before reaching- the anterior annular ligament it gives off cutaneous branches, which are distributed to the integument covering- the thenar eminence of muscles, and which commu- nicate with the superficial branch of the ulnar nerve, distrib- uted to the hypothenar eminence. The remaining branches are divided into two sets. The first set supplies the superficial muscles of the thenar eminence, the abductor pollicis, the flexor ossis metacarpi pollicis, and the superficial head of the flexor brevis pollicis ; or, in other words, all of the muscles which arise from the trapezium and the anterior annular lig-ament, the remaining- muscles of the group being supplied by the ulnar nerve. The other set 436 DESCRIPTIVE ANATOMY. divides into palmar collateral branches, of which thejii'st tvjo pass, one to the radial and the other to the ulnar side of the thumb on its palmar aspect, communicating- with one another and with dorsal cutaneous branches, w^hich will be described later. The third hi'anch passes to the radial side of the index finger ; Va'^ fourth to the cleft between the index and middle fingers : and the fifths after receiving a communication from the ulnar, passes to the cleft between the middle and ring fingers, and supplies the adjacent sides of those fingers, all of these branches communicating with one another and also with the dorsal nerves. The Musculo-Spiral. The Musculo- S;piral,ih.& largest branch of the brachial plexus, arises from the posterior cord ; and is said by some authorities to get fibres from all of the cords of the brachial plexus, though others deny that it receives any from the fifth cervical nerve. It passes downward as a posterior relation of the third portion of the axillary artery. At the termination of that vessel it passes between the internal head of the triceps muscle and the shaft of the humerus ; and at the junction of the lower third with the upper two thirds of the shaft of the humerus, pierces the external intermuscular septum, and appears opposite the interval between the brachialis anticus and the supinator longus. At the elbow joint, while still ly- ing between these two muscles, it divides into its two terminal branches, the radial and the ^posterior iyiterosseus. Before its division it gives off both cutaneous aud muscular branches. Branches of the Musculo-Spiral. Way- Side ( Internal | Radial Cutaneous K Upper Kxternal Terminal ■( Posterior ( Lower E^xternal ( Interosse Muscular The Internal Cutaneous B7'anch is distributed to the skin covering the middle of the back of the arm ; and extends as far as the distribution of the nerve of Wrisberg, with which it communicates. The Upper External Cutaneous pierces the external inter- THE CENTRAL NERVOUS SYSTEM. 437 muscular septum ; and is distributed to the skin covering" the outer portion of the biceps muscle. The Lo'.ver External Cutaneous Branch pierces the exter- nal intermuscular septum ; and is distributed to the skin cov- ering- the supinator longus muscle, lying- in the interval between the musculo-cutaneous nerve on its outer side, and the posterior branch of the internal cutaneous, on its inner side. The Muscular Branches are distributed to the three heads of the triceps muscle, a branch to the anconeous, which is a continuation of the triceps, to the brachialis anticus, supinator longus, and extensor carpi radialis long-ior, that is, to all of the muscles which take their orig-in above the external con- dyle of the humerus. The Radial. Of the two terminal branches of the median, the Radial is purely a nerve of common sensation. It commences in the interval between the supinator long-us, externally, and the brachialis anticus, internally. It then passes downward ; and in the upper part of its course is a distant external relation to the radial artery. In the middle third it is a close external re- lation of that vessel ; but at the junction of the middle and lower thirds of the radius it passes beneath the tendon of the supinator longus and appears upon the back of the forearm, ceasing to be a relation of its artery. Emerg-ing from beneath this tendon, it becomes superficial, g-ives a branch which divides to supply the radial and ulnar sides of the thumb on their dorsal aspect, a second branch to the radial side of the index fingfer, a third, which divides to supply the adjacent sides of the middle and index fing-ers, and a fourth, which after receiving a communi- cation from the dorsal cutaneous branch of the ulnar, divides to supply the adjacent sides of the middle and ring fingers. The Posterior Interosseous. The Posterior hiterosseous Nerve, the second terminal branch of the musculo-spiral, commencing while the latter nerve lies between the supinator longus and brachialis anticus, passes across the elbow joint to the supinator brevis muscle, and runs directly through the substance of that muscle. It passes through the supinator brevis to the back of the 438 DESCRIPTIVE ANATOMY. forearm ; and runs downward on the posterior face of the interosseous membrane to reach the back of the wrist, where it has a small g-ang-liform enlargement upon it, and receives a communication from the anterior interosseous branch of the median. Its distribution is to all of the muscles on the back of the forearm, with the exception of the anconeus, supinator longus, and extensor carpi radialis long-ior. The muscles supplied are the extensor carpi radialis brevior, the supinator brevis, the extensor communis dig-itorum, the extensor minimi digiti, the extensor carpi ulnaris, the extensor ossis metacarpi pollicis, the extensor primi internodi pollicis, extensor secundi internodi pollicis, and the extensor indicis. The above description of this nerve, the usually accepted one, appears to be incorrect. It should be said that the musculo- spiral nerve supplies all the muscles on the back of the arm and forearm without using- the useless term "posterior inter- osseous nerve ;" and the radial should be described as a way- side branch of the nerve, as it really is. The above description is g-iven in conformity with custom. The Circumflex Nerve. The Circumflex Nerve is the last of the terminal branches of the Brachial plexus. Arising- from the posterior cord, in common with the musculo-spiral, it passes downward on the subscapularis to the lower border of that muscle, being- a posterior relation of the third portion of the axillary artery. It now passes to the back of the humerus, running- throug-h the quadrilateral interval bounded above by the teres minor, below by the teres major, internally by the long- head of the triceps and externally by the shaft of the humerus. It accompanies the posterior circumflex artery. The nerve now divides into an upper and a lower branch — the upper to accompany the posterior circumflex vessels, winding- around the surg-ical neck of the humerus, beneath the deltoid muscle, which it pierces, supplying- that muscle and the skin over its lower part. The lower branch distributes filaments to the teres minor and back of the deltoid and pierces the deep fascia to reach the skin covering- the lower part of the deltoid and the long- head of the triceps. The nerve gives an articular filament to the shoulder joint. THE CENTRAL NERVOUS SXSTEM. 439 Dorsal Spinal Nerves. The dorsal spinal nerves are izuelve pairs, the posterior branches of which are distributed to the structures of the back, while the anterior cords form the intercostal nerves, and, un- like other spinal nerves, do not form a plexus but are distrib- uted separately. The Intercostal Nerves. The Intercostal Nerves are the anterior cords of the twelve dorsal nerves, and derive their name from their course forward between the ribs. The first dorsal nerve sends almost all its bulk to the bra- chial plexus, and the tzcelfth usually gives a branch to the lumbar plexus. The intercostal nerves are intended for the supply of the muscles among- which they course, and of the integ-umenton the front and sides of the thorax and abdomen. Each intercostal nerve runs forward in the intercostal space between the intercostal muscles to near the edg-e of the sternum where it turns forward and becomes superficial, being- called the anterior cutaneous. It is then distributed to the integ-ument of the front of the chest and abdomen, most of the filaments passing- outward in a recurrent course. The six upper nerves appear as the anterior cutaneous throug-h the corresponding- intercostal spaces, while the six lower pierce the sheath of the rectus muscle, and are called the anterior cutaneous of the abdomen. After reaching- the extremities of the intercostal spaces these last nerves pass on between the broad muscles of the abdomen, and the last one, thoug-h called intercostal, is really not one since it lies below the last rib. Whilst running- forward the intercostal nerves supply the intercostal muscles and the broad muscles of the abdomen, and about midway in its course each nerve g-ives off a branch called lateral cutaneous y which divides into two, one branch passing- forward and the other backward, both being- distributed to the integ-ument on the side of the chest or abdomen. The first intercostal nervCy owing- to the fact that most of the cords from which it is de-' rived g-o to the brachial plexus, gives off no lateral branch, and, to compensate for this delinquency, the lateral cutaneous branch of the second nerve is remarkably larg-e, and not only fulfils the office of the lateral cutaneous branches for itself 440 DESCRIPIVE ANATOMY. and the first, but under the name of intercosto-humeral , passes into the axilla, where it communicates with the lesser internal cutaneous. The lateral cutaneous branch of the twelfth nerve descends over the crest of the ilium, and is distributed to the integ-ument of the gluteal region. The Lumbar Spinal Nerves. The Lumbar Spinal Nerves are five pairs, the posterior cords of which are distributed to the structures of the back, while the anterior form a plexus, called the Lumbar Plexus, the last cord of the lumbar nerves, however, passing- downward to enter into the formation of the sacral plexus. The Lumbar Plexus. The manner of formation of the Lumbar Plexus is g-enerally as follows: The tzuel/th (for^a/ ^zeri'e 'g-ives a branch which descends in the substance of the psoas mag-nus muscle to unite with the fi7'st lumbar. The cord thus formed g-ives off the ilio-hypog^astric and ilio-lumbar nerves, and a branch which descends to unite with the second lumbar. The second lum bar, after receiving- this branch, g-ives off a branch of distribution, the g-enito-crural, and a communicating- branch, which descends to unite with the third lumbar, so that the g-enito-crural is the product of the first and second lumbar. The cord formed by the union of the branch from the second and third lumbar nerves g-ives off an external cutaneous branch and a branch which unites with the fourtli lumbar, conveying to that nerve some of the fibres derived from the second as well as the third. The union of these branches produces the anterior crural, which, therefore, contains fibres from the second, third, and fourth lumbar nerves, while the last nerve of the plexus, the obturator, is the product of the third and fourth. The remain- ing- portion of the fourth unites with the last lumbar to form the lumbo-sacral cord, which passes down into the pelvic cavity to aid in the formation of the sacral plexus. The Lumbar Plexus resembles in the manner of its formation the cervical. It is situated in the posterior fibres of the psoas mag-nus muscle ; and its branches, with the exception of the g-enito-crural, pass outward beneath the posterior surface of that muscle, the g-enito-crural perforating- the muscle and appearing- upon its anterior surface. THE CENTRAL NERVOUS SYSTEM. 441 Branches of the Lumbar Plexus. Ilio-Hypog-astric Ilio-Ing-uinal External Cutaneous Genito- Crural Anterior Crural Obturator Muscular Communicating- The Branches of the Lumbar plexus, named in the order in which they arise from above downward are the ilio-hypog"astric, ilio ing-uinal, external cutaneous, g-enito-crural, anterior crural, and obturator. Some authorities mention the accessory obtu- rator, which is an infrequent branch. In addition to these the plexus also gives muscular branches, which supply the psoas magfnusandquadratus lumborum muscles, and arise irregularly from the plexus. Ilio-Hypogastric. The Ilio-Hypog-astric, the product of the first lumbar nerve, appears at the outer border of the psoas magnus, crosses the quadratus lumborum near the upper end of that muscle, pass- ing- downward and outward and lying behind the peritoneum, pierces the transversalis muscle, and lies for a short distance between that muscle and the internal oblique until it reaches a point from two to two and one-half inches behind the anterior superior spinous process of the ilium, where it divides. The iliac brancli, piercing- successively the internal and ex- ternal oblique muscles, passes downward on the thigh toward the trochanter major, to be distributed to the integument behind the lateral cutaneous branch of the last dorsal nerve. The hypogastric branch continues the direction of the main trunk, at first lying between the internal oblique and the transversalis, and then between the internal and external oblique muscles, finally piercing the aponeurosis of the exter- nal oblique, and becoming superficial, to be distributed to the integument over the lower portion of the abdomen. Ilio-Inguinal. The Ilio- Inguinal Nerve arises from the first lumbar in common with the ilio-hypogastric, and passes downward and outward, parallel with and below that nerve, across the quad- ratus lumborum muscle. After crossing the iliacus internus, it pierces the transversalis muscle ; and between that muscle 442 DESCRIPTIVE ANATOMY. and the internal oblique, communicates with the hypog-astric branch of the ilio-hypog-astric. It then becomes more super- ficial near the superficial abdominal ring-, and leaving- the abdominal cavity throug-h that aperture, passes to the thigh, where it is distributed to the skin covering- the inner, upper front aspect of the thig-h, and to the scrotum in the male and to the labium in the female. Genito- Crural. The Genito- Crural is the product of the first and second lumbar nerves. It passes first directly forward throug-h the fibres of the psoas magnus muscle, and descends upon that muscle to just above Poupart's lig-ament, where it divides into a g-enital and a crural branch. The g-enital branch enters at the deep abdominal ring- ; and following- the course of the spermatic cord, is lost in the male in the cremaster muscle, which it supplies. In the female this branch is rudimentary ; but follows the course of the round ligament and is lost upon that structure. It crosses the ex- ternal iliac artery near the termination of that vessel. The crural branch passes beneath Poupart's ligament ; and runs down on the thig-h, to be distributed to the integ-ument of its inner front aspect as far as the middle. It is an anterior relation of the femoral artery. The External Cutaneous. The External Cutaneous Nerve is the product of the second and third Lumbar nerve. It passes downward and outward across the iliacus internus muscle behind the peritoneum, and reaches the notch found below the anterior superior spinous process of the ilium. It here leaves the abdominal cavity, and lies beneath the fascia lata for the upper inch or two inches of its course. It then pierces the fascia lata, and becoming- superficial, is distributed to the skin on the outer front aspect of the thig-h, its distribution lying- in the interval between the iliac branch of the ilio-ing-uinal and the middle cutaneous branch of the anterior crural. Fibres from this nerve descend as far as the knee joint. THE CENTRAL NERVOUS SYSTEM. 443 The Obturator. The Ohtiirator Nerve arises from the third and fourth lumbar nerves and occasionally receives fibres from the second lumbar. It passes beneath the psoas magnus muscle, runs over the brim of the pelvis, and crossing- along just beneath the pelvic brim, where it lies above the obturator vessels, reaches the upper angle of the thyroid foramen, and piercing that foramen it divides into two branches, an anterior and a posterior. The anterior branch is distributed to the hip joint, to the adductor longus, adductor brevis, the gracilis, sometimes to the pecti- neus, and has a cutaneous branch which passes to the skin of the inner side of the thigh. The posterior branch also drops a twng to the hip joint, and supplies the obturator externus and adductor magnus muscles. The Anterior Crural. The Anterior Crural Nerve is the largest branch of the lumbar plexus ; and receives fibres from the second, third, and fourth lumbar nerves. It passes downward in the interval be- tween the psoas magnus and iliacus internus muscles, and runs beneath Poupart's ligament, where it lies from one-fourth to one-half an inch to the outer side of the femoral artery. After descending for a very short distance, rarely more than one inch and generally about half-an-inch, it divides into branches, which are usually described as suferficial, or cutq,neoiis, branches, and deep^ or muscular branches. Superficial Branches. Middle Cutaneous Internal Saphenous Internal Cutaneous The Middle Cutaneous. The Middle Ciitaneoiis Jjranch passes forward superficial to the femoral artery ; and is distributed to the integument which covers the front of the thigh, lying between the internal cuta- neous and the external cutaneous, which is a direct branch of the lumbar plexus, and communicating with both of these nerves. The middle cutaneous generally perforates the sar- torius muscle, and in doing so, gives off branches which sup- ply that muscle. The Internal Cutaneous. The Internal Cuta^icoiis is smaller than the middle. It passes 444 DESCRIPTIVE ANATOMY. inward over the femoral arter}^ ; and dividing" into an anterior and a posterior branch, passes to the inner side of the thigh. The anterior branch communicates with the middle cutane- ous while the -posterior branch suns along the edge of the sartorius muscle, pierces the fascia lata, and is distributed to the integ-ument of the inner side of the thigh as low down as the knee joint, communicating in its course with the cutaneous branch of the obturator nerve. The Internal, or Long, Saphenous. The Internal, or Long' Saphenous Nerve descends in close contact with the outer side of the sheath of the femoral vessels until it reaches Hunter's canal, where it becomes superficial to these vessels. In the upper portion of its course it is in close relationship with the muscular branch to the vastus internus muscle, the two nerves bearing" almost exactl}^ the same relation to the femoral artery, with the saphenous slightly in front. At Hunter's canal the nerve sometimes passes across that fibrous structure, and is separated by it from the front of the femoral artery ; but usually lies on the femoral arter}^ in Hunter's canal, but not in the femoral sheath. At the lower extremity of Hunter's canal the nerve passes beneath the tendons of the sartorius muscle ; and accompanies that muscle downward to its inser- tion, where it pierces the insertion between the sartorius and the gracilis to become superficial just below" the knee. It now comes into relationship with the internal saphenous vein ; and accompanies that vessel to pass in front of the internal malleolus, and then to continue its course onward to the inner side of the great toe, which it supplies. It g"ives off throug-hout its course cutaneous branches, which are distributed throug"hout the course of the nerve. At the knee joint it g-ives one large branch, the -patella, which pierces the sartorius, and running- downward and outward, aids in the formation of the patella plexus. Deep, or Muscular Branches. The deep, or muscular, branches are a nerve to the iliacus internus, given off while the anterior crural is in the abdomi- THE ce:stral nervous system. 445 nal cavity ; branches to the pectineus (usually two in number, thoug-h sometimes but one) which pass beneath the femoral vessels ; a separate branch occasionally to the sartorius, thougfh that muscle is usually supplied by the middle cutaneous ; and a long- branch, already mentioned, the nerve to the vastus in- ternus, which is in close relationship to the femoral artery and the internal saphenous nerve, enters the vastus internus just above Hunter's canal, and there orives branches to the vastus externus and to the rectus, each of these entering- the corresponding- muscle from its deep surface. It will be seen, therefore, that the anterior crural nerve by means of one of its superficial branches, the middle cutaneous, supplies one of the muscles of the front of the thig-h, the sartorius ; while the two vasti and the rectus are supplied by deep branches of the anterior crural. The one remaining* muscle on the front of the thig^h, the tensor vag-ina^ femoris, is supplied by a branch from the sacral plexus of nerves. The Lumbo-Sacral Cord. The last branch of the lumbar plexus is a communicating" branch, called the Lumho-Sacral Cord. This cord is the joint product of the fifth lumbar nerve with a branch from the fourth ; and passes over the brim of the pelvis to unite with the first sacral nerve, commencing- the formation of the sacral plexus. The Sacral Plexus. The Sacral Plexus itself is the product of the lumbo-sacral cord, with Wio. first, second, third, ■a.nA /ml/ oi the /'oicrt/i sn.craX nerves. The fibres entering- into this plexus are more inti- mately united than in any other nervous plexus of the body. It is triangular in outline, the base of the triang-le extending- to the anterior sacral foramina, the apex being- directed down- ward and outward to the g-reat sacro-sciatic foramen. The Lumho-Sacral Cord, passing- behind the common iliac artery, unites with the first sacral nerve, then at a short dis- tance from the anterior spinal foramina the second sacral unites with this cord, then the third, and lastly the upper half of the fourth, so that while lying- upon the pyriformis muscle the sacral plexus consists of but a single, broad triangular 446 DESCRIPTIVE ANATOMY. cord, there being' no such communication, followed by subdi- vision, as there is in the case of the brachial plexus. The plexus, after being- formed in this way, extends down- ward and outward to the upper margin of the g-reat sciatic foramen, lying- upon the pyriformis muscle, having- the internal iliac artery in front of it, some branches of which vessel pass between the cords entering- into the formation of the plexus and having- the second portion of the rectum (more correctly, the first portion of the rectum) resting- upon the cords as the}^ emerge from the sacral foramina. On the left side, though separated from it by the peritoneum, the end of the sigmoid flexure of the colon would also rest upon the front of this plexus. Branches of the Sacral Plexus. Way-side Terminal Muscular Visceral Gluteal Internal Pudic Lesser Sciatic Great Sciatic Besides its terminal branches, this plexus also gives off certain zvayside, or collateral branches, which are distributed to the muscles and viscera in the pelvic cavity. The muscular branches come in part from the plexus and in part from the cords before they unite to form the plexus. They supply the pyriformis, obturator internus, the gemelli and the quadratus femoris. The Terminal Branches are the Gluteal, Internal Pudic, Lesser Sciatic, and Great Sciatic Nerves. The Gluteal. The Gluteal or Superior Gluteal Nerve, as it is frequently called, arises from the upper portion of the sacral plexus, and leaves the pelvic cavity by passing above the pyriformis muscle through the greater sacro-sciatic foramen. It then appears in the interval between the gluteus medius and the gluteus minimus muscles, where it divides into two branches, superior and inferior. The su-perior follows the origin of the gluteus minimus, and is supplied to the gluteus medius from the under surface of that muscle, while the inferior passes downward, forward, and outward, distributing fibres to the gluteus min- THE CENTRAL NERVOUS SYSTEM. 447 mus, its terminal branch ending- in the tensor vaginas femoris. Inferior Gluteal. The lumbo-sacral cord and the first and second sacral nerves g"ive oriofin to the second sacral nerve, which frequently arising in common with the one above men- tioned, is sometimes distinguished as the inferior g-luteal. It also passes above the pyriformis muscle through the greater sacro-sciatic foramen, and enters the deep face of the gluteus minimus muscle, being- distributed to it by a number of small branches. The Internal Pudic. The Internal Pudic Nerve arises from the lower part of the sacral plexus, leaves the pelvic cavity throug-h the g-reater sacro-sciatic foramen, below the pyriformis, crosses the spine of the ischium, and re-enters the pelvic cavity through the lesser sciatic foramen. It then courses along- the internal face of the ischium about an inch above its tuberosity, passes to the ramus of the ischium, and is enclosed in the fibrous sheath called Alcock's canal. It then passes between the two layers of the perineal fascia, and terminates by dividing into two branches, an upper one, the nerve to the dorsum of the penis, and an inferior branch, called the Perineal. Prior to this division the internal pudic nerve g-ives off an Inferior Hemorrhoidal Branch, corresponding- to the artery of the same name, which is distributed to the sphincter ani muscle and to the integ-ument around the anus. Terminal Branches of The Internal Pudic. Dorsalis Penis Perineal The Dorsalis Penis. The Dorsalis Penis Nerve, the branch to the back of the penis, passes upward and forward along- the ramus of the ischium and pubes, accompanying the artery of the same name, pierces the suspensory lig-amentof the penis, and runs forward upon that org-an to be distributed to the integument that cov- ers it and to the corpus cavernosum, while its terminal branches end in the g-lans psnis. In its course along- the back of the penis it g-ives off lateral cutaneous branches, which are distri- buted to the skin upon the sides of the org-an. 448 DESCRIPTIVE ANATOMY. The Perineal. The Perineal Nerve, the second branch of the internal pudic» divides into two sets of bra.nches, superficial and deep, or cu- taneous and muscular. The cutaneous branches are two, anterior and posterior, and pass upward and forward, to be distributed to the scro- tum, perineum, and under surface of the penis, in which latter situation they communicate with the dorsal nerve of the penis. In the female of course the upper of these two branches would be distributed to the labia majora, the analog-ue of the scrotum in the male. The muscular branches are distributed to the muscles of the perineum ; that is, the transversus perinei, erector penis, ^ accelerator urinae and compressor urethrae, these names being" g-iven to the muscles in the m.ale subject, each having- its ana- log"ue in the female. That branch which passes to the trans- versus perinei corresponds to the transverse perineal artery. Some deeper branches of this nerve also enter the corpus, spongiosum, and supply that body, with its attached muscles. The Lesser Sciatic. The Lesser Sciatic Nerve usually arises by two roots. It passes from the pelvic cavity throug-h the g-reater sacro-sciatic foramen below the pyriformis muscle, and runs down opposite the middle of the interval between the trochanter major and the tuberosity of the ischium, lying- beneath the g-luteus maximus muscle. It emerg-es from the lower border of this muscle : and pursuing" its course down the back of the thig-h, beneath the fascia lata reaches the superior ang-le of the popliteal space, where it breaks up into its terminal branches, which after being- distributed to the skin covering- the popliteal space, anastomose with the cutaneous branch from the g-reat sciatic and with the plexus around the patella. This nerve is almost entirely a cutaneous branch, except for the set of fibres which enters the g-luteus maximus muscle, that muscle receiving- its nerve supply entirely from the sacral plexus, thoug-h some of the fibres pass to it from the inferior THE CENTRAL NERVOUS SYSTEM. 449 g-luteal while the remaining- branches come from the lesser sciatic. The latter branches emerg-e from below the lower border of the muscle, and then reverse their course to enter it from its deep surface. The cutaneous branches are distributed to the skin on the back of the thig-h as far down as the popliteal space. One branch of larg^e size is individualized as a separate nerve, called the Inferior Pudendal. The Inferior Pudendal curves forward, running- below the tuber ischii, passes to the scrotum in the male and the labia in the female, communicating- with the superficial perineal and the terminal branch of the inferior hemorrhoidal. The Great Sciatic. The Great Sciatic is the long-est and~ larg-est nerve in the body. It appears to be, and in reality is, a continuation of the sacral plexus. Triang-ular at its commencement, it soon becomes circular in form. It emerg-es from the pelvic cavity below the pyriformis muscle throug-h the g-reater sacro- sciatic foramen, being- the last of the numerous structures which emerg-e from this foramen. These structures are seven in number. Two of them pass above the pyriformis, and the remaining- five below that muscle. Those which pass above the pyri- formis are the g-luteal nerve and artery; those passing- below it are the internal pudic, the lesser sciatic and g-reat sciatic nerves, the internal pudic and ischiatic, or sciatic, arteries. This does not complete the total number of structures which pass throug-h this foramen, because in addition should be mentioned the pyriformis muscle itself and the companion veins of the arteries named. After escaping- from the pelvis, the g-reat sciatic nerve passesdown the middle of the back of the thig-h, resting- on the adductor mag-nus muscle, and covered by the muscles which arise from the tuberosity of the ischium. Two of these mus- cles, the semi-tendinosus and semi-membranosus, quickly pass to its inner side, while the biceps covers the nerve for some distance down the thig-h. At the upper ang-le of the popliteal space (formed externally by the biceps and internally by the Des Anat— 29 450 DESCRIPTIVE ANATOMY. semi-tendiuosus and semi-membranosus muscles) the nerve appears between these muscles, called the "ham-string*" mus- cles. It then passes into the> popliteal space, and divides into its two terminal branches, the Internal and External Popliteal Nerve. The point of division is variable, and may exist anywhere between the sacral plexus and the centre of the popliteal space. In a few rare cases the internal and external popliteal nerves come off separately from the sacral plexus; and in such cases they are sometimes separated from one another by the fibres of the pyriformis muscle. In other cases the division takes place below the tuberosity of the ischium, and in still other cases at the middle of the popliteal space. As the nerves are bound tog-'ether simply by connective tissue, the dissector may split them up to any point between the popliteal space and the orig"in of the two nerves from the sacral plexus. The point of termination usually g^iven for the g"reat sciatic is the superior angfle of the popliteal space ; but it rarely di- vides before reaching- a lower point, so that the gfreat sciatic itself, instead of its internal popliteal branch, becomes a rela- tion of the popliteal artery. Before dividing- into terminal branches, the great sciatic g-ives off muscular branches to supply the posterior femoral group, cutaneous branches which communicate with the lesser sciatic nerve, and a branch to the adductor magfnus. Branches of the Great Sciatic. Internal Popliteal Ij^xternal Popliteal The Internal Popliteal. The Internal Popliteal Nerve, the larg-erof the two terminal branches of the g-reat sciatic, commences below the upper angle of the popliteal space, to pass throug-h that space, and terminate by becoming-theposterior tibial nerve. As it enters at the apex of the popliteal space, it necessarily lies to the outer side of, and superficial to, the popliteal artery and vein; but the nerve has an inclination inward, while the inclination of the artery is outward, hence at the middle of the popliteal THE CENTRAL NERVOUS SYSTEM. 451 Space, opposite the posterior lig-ament of the knee joint, the nerve is found directly behind the artery, with the vein inter- posed between itself and the artery, while at the termination of the popliteal space both nerve and vein have become inter- nal to the artery, the vein still lying- between the nerve and the artery. At the lower border of the popliteus muscle, at a point which corresponds to the junction of the upper one-fifth with the lower four-fifths of the shaft of the tibia, the internal popliteal nerve terminates by changfino- its name to the Poste- rior Tibial. The nerve, like the other important structures contained in this diamond-shaped space, has the internal ham-string- muscles to its inner side above, and the inner head of the gas- trocnemius below, while to its outer side are, above, the biceps, and below, the outer head of the g-astrocnemius and the plan- taris muscles. It is covered by the strong- fascia which extends between these muscles and roofs in the entire space. Branches of the Internal Popliteal. Articular Muscular, or Sural Cutaneous The Branches of the Internal Popliteal are divided into three sets, articular, muscular, and cutaneous. The Articular Branches are three in number ; and are known as Superior and Inferior Internal Articular, and Azygos Articular. They accompany the arteries of the same name ; and are distributed in the same way. They anastomose with one another, and with the other nerves which surround the knee joint, passing- as far as the patella plexus, while the azygos articular, piercing, with the corresponding- artery, the posterior ligament of the knee, is distributed to the s^^no- vial membrane in the interior of that joint. The Muscular, or Sural (L. Sura, the calf of the leg). Branches accompanying the sural branches of the popliteal artery, are distributed to the two heads of the gastrocnemius and to the plantaris muscle. In addition to these sural branches, the internal popliteal nerve gives off the branches which supply the popliteus muscle. These branches, two in number, pass down to the lower bor- 452 DESCRIPTIVE ANATOMY. der of the popliteus muscle, and, reversing- their course, pass upward between that muscle and the posterior surface of the interosseous membrane, to enter the muscle from its deep face. The only Cutaneous Branchy the External Saphenous, or Communica7is Poplitei, passes downward in the interval be- tw^een the two heads of the g-astrocnemius muscle, lies in the g-roove upon the posterior surface of the belly of that muscle, accompanied by the external saphenous vein ; and, about the middle of the calf of the leg-, receives a branch of communica- tion from the external popliteal nerve, this branch being- called the Conimunicayis Peronei. After receiving- this branch it continues downward, with a slig-ht inclination out^yard, passes behind the external malleolus, and reaching- the dorsum of the foot, is distributed to the integ-ument on the back of the leg-, the outer, back part of the ankle, and the outer side of the foot as far as the little toe, where it commumicates with a branch of the musculo-cutaneous nerve. The Posterior Tibial. The Posterior Tibial Nerve is a continuation of the internal popliteal ; and commences where that nerve terminates at the lower border of the popliteus muscle. It at first lies to the inner side of the posterior tibial artery ; but about two inches below the orig-in of that vessel, crosses it superficially opposite the orig-in of the peroneal branch, and lies for a short distance in the interval between the peroneal and posterior tibial arte- ries. It then descends to the outer side of the posterior tibial, and remains a continuous external relation of that vessel to its termination, but lies on a plane posterior to it. It divides midway between the inner malleolus and the pos- terior tuberosity of the os calcis into the internal and exter- nal plantar branches. Branches— Way-Side. The Branches of the Posterior Tibial Nerve are muscular branches, which supply the tibialis posticus, flexor long-us pol- licis, and the flexor long-us dig-itorum. At the ankle joint, however, itg-ives off calcanean branches, which, accompanying- THE CENTRAL NERVOUS SYSTEM. 453 the corresponding- arteries, are distributed to the skin on the inner aspect of the heel, and an articular branch which supplies the ankle joint. Terminal or Plantar. Internal Plantar External Plantar The Internal and External Plantar Nerves differ from one another, and more distinctly from the internal and external plantar arteries, because while the internal plantar artery is smaller in size than the external, aud has a less extended dis- tribution, the internal plantar nerve is largfer than the exter- nal. The internal plantar nerve corresponds in in its distri- bution to the median nerve of the hand ; while the external plantar corresponds to the ulnar nerve in the hand. That is, the internal plantar nerve supplies three toes and a half, equal to the three and one half fing-ers of the median ; while the ex- ternal plantar supplies one toe and a half, the equivalent of the ulnar of the hand. The Internal Plantar. The Internal Plantar Nerve passes forward as the companion of the internal plantar artery, supplies the inner half of the flexor brevis dig-itorura, then continuing- its course it g-ives a branch to the abductor pollicis and to the two internal lumbrical muscles, and to the flexor brevis pollicis and articular branches to the tarsus and metatarsus. It then divides into its terminal branches, the most internal of which passes to the inner side of the g-reat toe, the second to the cleft between the second and g-reat toes, where it divides into branches for the inner side of these two toes, the third to the cleft between the second and third, and the fourth, after giving- off a brauch of communication to the external plantar, runs to the cleft between the third and fourth toes and supplies the adjacent sides of these toes. The External Plantar. The Exter7ial Plantar Nerve ^ccom\idimQ^ the external plan- tar artery, passes beneath the orig-in of the flexor brevis digitorum, and lies between that muscle and the Abductor 454 DESCRIPTIVE ANATOMY. minimi digiti. It then runs forward as far as the posterior extremity of the fifth metatarsal bone. It then plunges be- neath the second layer of muscles on the sole of the foot, and accompanies the arch formed by the external plantar artery. In this course it supplies the abductor minimi dig-iti, the outer half of the flexor brevis minimi dig-iti, the second layer of muscles on the foot, then the flexor accessorious, and the two outer lumbricals, and g-ives branches to the interosseous mus- cles occupying- the third and fourth interosseous spaces. As it passes between the second and third layers of the foot it supplies all the muscles of the third layer of the sole. Its digital branches are, one to the outer side of the little toe, and one, which after communicating- with the internal plantar, divides at the cleft between the fourth and fifth toes and supplies the adjacent sides of these toes. The External Popliteal. The External Popliteal nerve beg-ins as a branch of the great sciatic, near the upper ang-le of the popliteal space, passes downward and outward and is only momentarily a relation of the popliteal artery, lying- superficial to it and to its outer side. It then passes behind the external tuberosity of the femur, crosses the head of the fibula, and plung-ing- into the substance of the peroneus long-us muscle, terminates there by dividing- into the anterior tibial and the musculo-cutaneous nerves. The relation of this nerve to the popliteal artery is, as before mentioned, only momentary, except in those cases in which the nerve is so closely bound to the internal popliteal as to di- verg-e from that nerve at the middle of the popliteal space. Branches. Way- j Articular Termi- j Anterior Tibial Side \ Communicans Peronei nal ( Musculo-Cutaneous In all cases the external popliteal nerve gives oJ0P tzvo articu- lar branches corresponding- to the superior external and infe- rior external articular arteries, these branches accompanying* the arteries and being- distributed in the same way. A recur- rent articular branch is also g-iven off which accompanies the anterior tibial artery and supplies the front of the knee. THE CENTRAL NERVOUS SYSTEM. 455 The Communicans Peronei. Below the knee joint the external popliteal g-ives off the Communicans Peronei, which unites with the communicans poplitei to form the External Saphenous Nerve and to be distributed with that nerve. The Anterior Tibial. Of the two terminal branches of the external popliteal the Anterior Tibial, after passing- throug-h the fibres of the pero- neus long-US, lies between that muscle and the extensor longus dig-itorum. It then passes to the front of the interosseous membrane, having- passed obliquely beneath the extensor lon- g-us dig-itorum, and becomes a relation of the anterior tibial artery, having- the same muscular relations with that vessel ; viz., for the upper third to its outer side is the extensor long-us dig-itorum, to its inner side the tibialis anticus : in the middle third the extensor proprius pollicis to the outer side and the tibialis anticus still to the inner side. In the lower third it has the extensor long-us dig-itorum to the outer side and the extensor proprius pollicis to the inner side, which muscle has crossed to the front of the nerve and displaced the tibialis anticus. To the artery it bears a triple relation, lying- first to the outer side and resting- on the interosseous membrane, then for the middle third of the anterior tibial artery the nerve rests on its front, separated by the artery from the interosse- ous membrane, and in the lower third of the vessel the nerve drops to the outer side, and maintains that relation to the front of the ankle joint. At the front of the ankle joint the nerve passes beneath the anterior annular lig-ament, but does not chang-e its name as the artery does. To the dorsalis pedis artery it maintains the same relation which it bore to the anterior tibial, lying- on the outer side of that vessel. It continues as far as the cleft between the g-reat and second toes, where it divides into two branches to supply the adjacent sides of these two toes, after having- com- municated with the long- saphenous branch of the anterior 456 DESCRIPTIVE ANATOMY. crural nerve on the inner side of the great toe, its outer branch communicating with the musculo-cutaneous. Branches. The Anterior Tibial Nerve in its course over the leg supplies branches to the tibialis anticus, extensor long-us digitorum, and extensor proprius poUicis, while on the outer side it has a gangliform enlargement which corresponds to that on the posterior interosseous of the forearm from which are given off branches to supply the flexor brevis digitorum muscle and the tarsal and metatarsal articulations. The Musculo-Cutaneous. The Musculo-Cutaneous Nerve, after being formed bv the division of the external popliteal, passes downward, first in the fibres of the peroneus longus muscle, then in the interval between that muscle and the peroneus brevis, then between the tvi/^o perouei muscles and the extensor longus digitorum. Running across on the front of the external malleolus, it passes on to the dorsum of the foot, where it breaks up into cutane- ous branches to supply the toes between the outer face of the second toe and the inner face of the little toe, and gives a twig to the inner side of the great toe. In its course through the leg it gives off branches which supply the peroneal muscles. As it passes across the external malleolus it gives a branch w^hich corresponds to the external calcanean branches of the anterior tibial artery; and these branches are distributed to the skin on the outer aspect of the heel. The distribution of the nerve on the dorsum of the foot is very irregular. The most frequent arrangement is that it communicates on the outer side of the little toe with the exter- nal saphenous nerve, then gives a branch which passes to the cleft between the little and the fourth toes and supplies them, a third branch to the cleft between the fourth and third toes, and a fourth branch to the cleft between the third and second toes — which branch communicates with the anterior tibial THE CENTRAL NERVOUS SYSTEM. 457 nerve, — and a branch to the inner side of the great toe which communicates with the long saphenous. It will be seen that the distribution of the nerves on both the back of the hand and the back of the foot is quite as irreg- ular as the distribution of the arteries in the same situation. In some instances the anterior tibial nerve has been seen to suppl}' the great, the second, and half of the third toe; and, in other cases, the musculo-cutaneous supplies the little, fourth, third, and second toes; while in but few cases have I been able to trace the internal saphenous to the extremity of the great oe, or the external saphenous to the extremity of the little toe. 458 DESCRIPTIVE ANATOMY. THE CHANIAL NERVES. The crauial nerves comprise twelve pairs, one on each side, those of one side having" their counterpart on the other. The definition of a cranial nerve is that it appears at the base of the brain and emerges throug-h an aperture in the skull. The point on the base of the brain where the nerve appears is called its apparent origin, since it may be traced into the interior of the brain to what is called its real, or deep, origin. The real origin of many of the nerves is still a matter of dispute. The cranial nerves are named numerically, in pairs, from before backward ; besides which each pair is known by another or, in some cases, several other names derived from the part to which the nerve is distributed. The following table gives the synonyms of the twelve pairs : •First Pair, Olfactory. Second Pair, Optic. Third Pair, Motores Oculorum. Fourth Pair, Pathetic (Trochleares). Fifth Pair, Trifacial (Trigeminus). Sixth Pair, Abducentes. Seventh Pair, Facial (Portio Dura). E^ighth Pair, Auditory, (Portio Mollis). Ninth Pair, Glosso- Pharyngeal. Tenth Pair, Pneumogastric, Par Vagum, Vagus. Eleventh Pair, Spinal Accessory. Twelfth Pair, Hypoglossal. These twelve pairs were formerly considered as only nine from the fact that, as will be seen, thej^ emerge through nine foramina of the cranium at the base. The classification into nine pairs is known as that of Willis and the one just given as that of Sommerring. The two classifications are similar for the first six pairs, the seventh pair, in Willis' classification, THE CRANIAL NERVES. 459 consisted of the seventh and eighth, while the eig-hth consisted of the glosso-pharyng-eal, pneumog*astric and spinal accessory, and the ninth of the hypoglossal, A general outline of the cranial nerves successively, from their apparent origin to their point of emergence, will first be given and afterwards each pair will be taken up and described. The first seen on the base of the brain from before back- ward is WiQ first pair. The first nerve lies on the under sur- face of the anterior lobe of the cerebrum in a groove a little external to the longitudinal fissure, having its commencement by a three forked origin just, in front of the anterior perfo- rated space. Near the anterior extremity of the anterior cere- bral lobe it enlarges into an oval-shaped mass which lies upon the cribriform plate of the ethmoid bone and sends its branches of distribution through the foramina seen there. The second nerve is first seen under the name of the optic tract, approaching its fellow from the outer aspect of the crus cerebri and passing beside the tuber cinereum and uniting in front of it with its fellow to form the optic chiasm or com- missure from which the two optic nerves diverge forward to enter the orbit through the optic foramina. The third nerve is seen emerging to the inner side of the crus cerebri, just in front of the pons Varolii, and runs forward to leave the cranium through the anterior lacerated foramen. Th.Q/ourth nerve has its apparent orign external to the third, on the optic side of the crus cerebri, and also has its exit through the anterior lacerated foramen. Th.Q fifth is the largest of the cranial nerves and is first seen just behind the origin of the fourth. It pierces the lateral aspect of the pons Varolii and splits into three portions, opthalmic, superior and inferior maxillary, which require three apertures of exit from the cranium. The opthalmic leaves through the anterior lacerated fora- men, the superior maxillary through the foramen rotundum, the inferior maxillary through the foramen ovale. The sixth nerve takes its apparent origin behind that of the fifth from the upper constricted portion of the medulla oblon- 460 DESCRIPTIVE ANATOMY. gata, just behind the pons Varolii, and passes forward to gain eg'ress throug-h the anterior lacerated foramen, which is thus seen to transmit three entire cranial nerves, viz : third, fourth and sixth, and a part of another, viz: the opthalmic branch of the fifth. The seventh^ eig'hth, ninth, tenth and eleventh all arise in the order named, from above downward, in the g'roove between the corpora olivare and restiformia of the medulla oblong-ata. The seventh and eig'hth leave the cranium through the same opening-, the internal auditory meatus, while the ninth, tenth and eleventh all g-ain exit through the posterior lacerated for- amen. The tzvelfth has its apparent orig-in to the inner side of the five preceding- nerves, from the groove between the corpora olivare and pyramidale, by numerous filaments which are speedily collected into two cords, which unite to form the nerve as it emerg-es through the anterior condyloid foramen. The First Nerve. The first or olfactory nerve arises by three forks or roots, close to the anterior perforated space. The external or long* root consistsof white fibres and may be traced along the fissure of Sylvius into the middle lobe of the cerebrum; the middle root is of g"ray matter and springs from the posterior part of the anterior lobe ; the inner or short root is of white fibres and also arises from the posterior part of the anterior lobe. The three roots unite to form the nerve, just in front of the anterior perforated space, which passes forward, triangular in shape and grayish in color, lying- in a groove on the under surface of the anterior lobe of the cerebrum a little external to the longitudinal fissure. The nerve swells into an oblong- g-rayish enlargement, called the hnlbiis olfactorius, which lies beside the crista g-alli on the cribriform plate of the ethmoid bone. From the under surface of the olfactory bulb are g-iven off some twenty filaments, which descend into the nose throug-h the foramina of the cribriform plate to be distri- buted to the mucous membrane of the nose as far down as the middle turbinated bone. These filaments are arrang-ed in THE CRANIAIv NERVES 461 three sets, viz: those to the septum, those to the external wall and those to the roof of the nose. Second Nerve. The second ov optic nerve has its apparent orig-in just exter- nal to the crus cerebri, whence it may be traced to its deep or real origin from various parts of the optic thalamus and from the corpora quadrigemina. Winding- around the outer side of the crus cerebra, it passes forward and inward beside the tuber cinereum and in front of it unites with its fellow to form the optic commissure or chiasm. The portion extending- from the orig-in to the optic chiasm is called the optic tract. From the optic chiasm the two optic nerves diverg-e anteriorly to enter the orbit through the optic foramina, each piercing" the sclerotic and choroid coats of the eye-ball to expand into the retina. The connection between the optic tract, chiasm and nerve is as follows: The optic tract is composed of filaments, the outermost of which pass into the nerve of that side, while the innermost curve over, throug-h the chiasm, to form the inner- most fibres of the opposite tract, and the middle fibres of the tract of one side pass through the chiasm to form the middle fibres of the nerve of the opposite side; and the innermost fibres of one nerve pass through the chiasm and become the innermost fibres of the opposite nerve, thus accounting for all the filaments. The Third Nerve. The third nerve, or motor ocidi, leaves the brain just to the outer side of the crus, near the front of the pons. The deep origin can be traced to the locus niger and tegmentum. It pierces the dura below and to the outer side of the posterior clinoid process. It then passes forward lying in the outer wall of the cavernous sinus, with the fourth and opthalmic di- vision of the fifth below and external to it, and the sixth in- ternal and separating the third from the internal carotid. Continuing its course the nerve reaches the anterior lacerated foramen, or sphenoidal fissure, and splits into two divisions. Both divisions enter the orbit, passing between the two heads 462 DESCRIPTIVE ANATOMY. of the external rectus muscle and being- separated from each other by the nasal nerve. In the sphenoidal fissure the third lies on the lower wall of the fissure with the nasal and the sixth, the upper division of the third being- most external, then the nasal, lower division of the third and sixth in the order named. The terminal branches are now g-iven off, the nerve supplyingf all the muscles of the ocular g-roup except the ex- ternal rectus and the superior oblique. The upper division, which passes above the optic nerve, supplies the superior rec- tus and the levator palpebrse. The lower division passes beneath the optic nerve and supplies the inferior and internal recti and the inferior oblique. While lying- in the cavernous sinus the nerve communicates with the cavernous plexus. Sometimes the superior division receives a communication from the nasal ; while the branch to the inferior oblique gives off the motor root of the ciliary g-ang-lion. The branches to the muscles enter on their deep or ocular surface. The Fourth Nerve. The fourth, ox fatheticus, appears just external to the ap- parent orig-in of the third on the outer surface of the crus cerebri. Its deep orig-in is a nucleus on the floor of the aque- duct of Sylvius. After winding- around the crus cerebri the fourth pierces the dura below the posterior clinoid process and runs forward in the sinus with the third above and the opthalmic division of the fifth below it. On reaching- the sphenoidal fissure the fourth passes throug-h that fissure at its hig-hest and most internal point. On reaching- the orbit it crosses over the orig-in of the levator palpebrae and enters the superior oblique on the ocular surface of that muscle. It communicates with the cavernous portion of the sympathetic and g-ives off a small and unimportant branch to the tentorium. The Fifth Nerve. Theyf/?/^, or trifacial nerve, appears just behind the fourth, emerg-ing- from the side of the pons. It has its superficial, or apparent origin, by two roots which spring from the lateral as- THE CRANIAL NERVES . 463 pect of the pons, the anterior, consisting- of two or three bun- dles, beintr the motor, and the posterior the sensory, root. The deep origin is from the floor of the fourth ventricle. The two roots pass throug-h the dura just above the internal auditory meatus and continue forward to the apex of the pet- rous portion of the temporal bone, where a g-angliform enlarg-e- ment, called the Gctsserian ganglion, is formed on the posterior or sensory root. The motor root passes beneath the g^anglion of Gasser without being- connected with it. The g"anglion divides into three branches, opthalmic, supe- rior maxillary and inferior maxillary. The latter is joined bodily by the small root of the nerve and is, therefore, the only one of the three divisions possessing motor endowments. Besides its terminal branches the ganglion gives off branches to the dura and middle fossa of the skull and receives a com- munication from the cavernous plexus. The Opthalmic Nerve. The opthalmic branch passes forward and soon divides into three branches, lachrymal, frontal and nasal, which enter the orbit through the foramen lacerum anterius. This nerve passes through an opening in the dura l^nng below and external to that for the fourth. It then runs forward on the outer wall of the cavernous sinus, its place being below and to the outer side of the third and fourth. The terminal branches are given off just before the nerve reaches the sphenoidal fissure. Branches. Lachrymal Frontal Nasal The Lachrymal branch of the opthalmic pisses through the upper, external portion of the sphenoidal fissure and enters the orbit where it runs along the external wall lying above the external rectus muscle. It continues its course until it reaches the lachrymal gland, which it supplies, and then sends fila- ments which pierce the palpebral ligament and are distributed to the skin of the upper eyelid and communicates with the facial nerve. 464 DESCRIPTIVE ANATOMY. The Frontal is tHe largest branch of the opthalmic division. It enters the orbit through the sphenoidal fissure, lying- be- tween the lachrymal, externally, and the fourth, internally. It then runs forward on the levator palpebrae and divides into the supra- trochlear ?indi. siipra-orhital. The supra-orhital emerges from the orbit through the supra- orbital foramen, gives off branches to the upper eyelid and the muscles and integument of the head as far back as the vertex. While lying in the orbicularis palpebraum, it communicates with the facial nerve. The supra-trochlear branch advances to the inner angle of the orbit where it emerges above the fovea trochlearis, hence its name, and is distributed to the inner angle of the eye and the integument of the root of the nose and middle of the fore- head. It gives a communicating branch to the infra-trochlear branch of the nasal. The Nasal Nerve enters the orbit between the heads of the external rectus, lies beneath the superior oblique and the levator palpebr^ crosses the optic nerve, advances along the inner wall of the orbit, re-enters the cranium through the anterior ethmoidal foramen and is there found lying in the slit beside the crista galli, whence it sinks into the cavity of the nose and divides into a branch for the mucuous membrane of the nose, and another to descend along the posterior aspect of the nasal bone to its lower edge, where it emerges through the notch found there and supplies the integument of the nose to its tip. Just as the nasal nerve is entering the ethmoidal foramen it gives off a branch called the infra-trochlear, which passes for- ward to emerge at the inner angle of the orbit below the fovea trochlearis and supply the lachrymal sac and inner angle of the eye. Besides the infra-trochlear it gives off in the orbit three other branches; one to the opthalmic g-anglion of the sympa- thetic system and two ciliary branches which pierce the sclerotic coat, pass forward between it and the choroid and are distributed to the iris. Superior Maxillary Nerve. The superior maxillary division of the fifth nerve, like the opthalmic, has a forward course. It gains egress through the THE CRANIAL NERVES. 465 foramen rotundum, continues its forward direction across the spheno-maxillary fossa, along- a g-roove on the floor of the orbits sinks beneath the floor and emerges at the infra-orbital foramen on the face to give sensibility to adjacent parts, viz: the lower lid, cheek, side of the nose and upper lip. Branches. Besides the terminal ones, the branches of the superior maxillary are the following-, emitted in the order g*iven: The orbital or tem^oro-iualar .hr-a^woh. enters the orbit throug-h the spheno-maxillary fissure and divides into two branches, temporal and malar. The temporal branch enters the tempo- ral fossa through the outer wall of the orbit, while the malar branch continues along- the outer wall of the orbit to emerg-e on the cheek at the outer angle. The sfiheno-palatine are two branches of communication which descend to Meckel's g-ang-lion of the sympathetic in the spheno-maxillary fossa. The chief distribution of the superior maxillary is to the teeth and g-ums of the upper jaw and this is effected by two branches, anterior and -posterior dental. The -posterior dental is first emitted and supplies the molar and bicuspid teeth. The anterior dental leaves the main trunk just as it is about to emerge on the face and supplies the two incisors, the canine and the front bicuspid. The anterior and posterior dental nerves anastomose in the bone and supply each tooth with as many filaments as the tooth has fangs, besides g-iving- twigs to the g-ums. Inferior Maxillary Nerve. The inferior maxillary division of the fifth nerve consists of a branch from the gang-lion of Gasser and the small motor root of tiie fi fth nerve, which unite and pass downward throug-h the foramen ovale, immediately after emerg-ing from which the nerve divides into an anterior and ^.posterior trunk. The distribution of each trunk is as follows : The anterior trunk breaks up into branches which supply the muscles of mastication, each branch bearing the name of Des Anat— 30 466 DESCRIPTIVE ANATOMY. the muscle to which it -is distributed and conveying' motor influence. The masseteric branch runs out above the external ptery- goid muscle, crosses throug'h the sig^moid notch and is dis- tributed to the deep face of the masseter. The deef temporal branches anterior and -posterior, are distributed to the deep face of the temporal muscles. The buccal branch pierces the external pteryg"oid, some- times lying- beneath the coronoid process and sometimes run- ning- through the temporal muscle, to be distributed by an upper and a lower branch to the buccinator. The pterygoid branches are one to each pterygoid muscle ; that to the external pterygoid being frequently a branch of the buccal nerve. The p>osterior trunk divides into three branches, inferior dental, gustatory and auriculo-temporal. Inferior Dental. The inferior dental branch curves forward and downward to enter the dental foramen of the lower jaw and run along a canal in the bone giving filaments to all the teeth of the lower jaw. It first lies beneath the external pterygoid muscle and then between the internal lateral ligament and the ramus of the lower jaw. As it passes the mental foramen it gives off a branch which escapes through that foramen and supplies the integument of the lower lip. Just before entering the dental foramen the nerve gives off a branch called the ?7iylo-hyoidean, which de- scends along the groove on the inner surface of the inferior maxilla and is distributed to the mylo-hyoid muscle and the anterior belly of the digastric. Gustatory Branch. The gustatory nerve passes downward and forward, first behind the external pterygoid muscle, then between the two pterygoid muscles and then between the internal pterygoid and ramus of the lower jaw, and reaching the side of the tongue splits into many filaments to supply the anterior part of that THE CRANIAL NERVES. 467 oro-an. While between the two pter^^gfoid muscles it receives at an acute angle the chorda tympani a branch of the seventh nerve, which it transmits to the submaxillary g-ang-lion of the sympathetic. Beneath the tono-ue the gustatory gives off a branch of communication to the twelfth. It distributes branches to the filiform and fungiform papillae, the mucous membrane of the tongue, mouth, and gums. Auriculo-Temporal. The auriculo-temporal branch arises by two roots. It first passes backward behind the articulation of the lower jaw, then ascends between the meatus auditorius externus and condyle of the lower jaw and emerging from beneath the paro- tid gland divides into branches called anterior and posterior temporal which supply the integument of the temporal region. It gives off branches to the articulation of the lower jaw, to the parotid gland, to the pinna, to the meatus auditorius and two communicating branches to the facial nerve. Sixth Nerve. The sixth nerve , or abducens, has its apparent origin from the upper constricted portion of the medulla, just behind the pons, while its deep origin can be traced to a mass of gray matter lying in the floor of the fourth ventricle. The nerve, after piercing the dura over the sphenoid, runs through an opening in the dura just below the posterior clinoid process and passes forward in the cavernous sinus, lying internal to the preceding nerve and in close contact with the internal carotid artery. Continuing its course it passes into the orbit through the sphenoidal fissure just external to the opthalmic vein, runs between the two heads of the external rectus and is distributed to that muscle from its deep surface. Seventh Nerve. The seventh, or facial, nerve (the motor nerve of the face) is the uppermost of the five nerves which spring from the groove between the corpora olivare and restiformia. Its deep origin is from the floor of the fourth ventricle, where it com- municates with the sixth nerve. Just beneath it, in the same 468 DESCRIPTIVE ANATOMY. groove, is another nerve called the portio intermedia which unites with it. If this be counted as a separate nerve, it may be said that there are six nerves spring-ing- successively from this groove. It makes for the internal auditory meatus which it enters in company with the auditory nerve ; and, when the two reach the bottom of the canal, the facial parts from its companion and enters another canal in the petrous bone called the aqueduct of Pallopius, which conducts it first outward, then backward and then downward to the stylo-mastoid fora- men, emerg-ing- from which it passes forward through the parotid g-land, over the external carotid artery, and divides into numerous branches which are distributed to all the mus- cles of the face except those of mastication, and of these the buccinator g-ets a branch. Branches. Ivike other cranial nerves, its branches may be divided into two sets, viz : communicating' and branches of distribution. While in the auditory meatus, it communicates with the audi- tory nerve. In the aqueductus Fallopii the larg-e su-perficial petrosal is sent to Meckel's g-ang-lion, the small -petrosal to the otic g^ang-lion and the external petrosal to the sympathetic on the middle meing-eal artery. After the nerve emerg-es from the stylo-mastoid foramen, communications are estab- lished with the ninth and tenth cranial nerves, with the caro- tid plexus, with the auricularis magnus of the cervical plexus and with the auriculo-temporal branch of the fifth. All of the divisions of the fifth communicate with the seventh on the face. The branches of distribution the tympanic and chorda tym- ■pani, arising" within the aqueductus Fallopii ; the posterior auricular, stylo-hyoid and dig-astric arising- outside the stylo- hyoid foramen, and two terminal branches, the temporo-facial and cervico-i?i.QA'al. The tympanic, which arises from the facial while it is in the aqueduct of Fallopius and is distributed to a muscle of the tympanic cavity. The chorda tympani, which is emitted from the facial just THE CRANIAL NERVES. 469 above the stylo-mastoid foramen and first ascends throug"h the petrous bone and enters the tympanum at the base of the pyramid on its posterior wall, then crosses on the inner surface of the membrana tympani and leaves throug"h the fissure of Glaser, having- emerged from which it joins the gustatory branch between the two pteryg-oid muscles and continues with it to the submaxillary g-ang-lion. The stylo-hyoid which supplies the stylo-hyoid muscle. The digastric, which is distributed to the posterior belly of the dig-astric muscle. The posterior auricular, which ascends behind the ear and after communicating" with the auricular branch of the pneumo- gastric is distributed by an anterior branch to the auricle and by a posterior to the back of the head. The temporo-facial \^ the larg-er of the two terminal branches of the seventh. It passes throug-h the parotid gland, which separates it from the external carotid artery, and breaks up into three sets of branches, temporal, malar and infra-orbital, the first supplying- the attrahens aurem, occipito-frontalis and orbicularis palpebraum muscles; the second the orbicularis and corrug-ator supercillii, while the last, the largest branch, sup- plies the pyramidalis nasi, levator labii superioris and levator anguli oris. The cervico-facial d\v'\'^\ovL passes downward in the substance of the parotid gland, which separates it from the external carotid. It communicates with the auricularis magnus and divides into <^2^cc«/ branches, which supply the buccinator and orbicularis oris; supra-maxillary for the depressor anguli oris; and infra-maxillary, some of which supply the platysma while others pass to the skin over the supra-hyoid region, communi- cating with the branches of the cervical plexus in that region. Eighth Nerve. The eig-Jith nerve, or portio mollis, or auditory, is the sec- ond of the nerves arising from the groove between the corpora olivare and restiforme, its deep origin being from the floor of the fourth ventricle. It passes forward and enters, along with the seventh, the internal auditory meatus, at the bottom 470 DESCRIPTIVE ANATOMY. of which it divides into a cochlear and three vestibular branches, which are distributed to corresponding- parts of the labyrinth. Ninth Nerve. The ninth nerve, or g-losso-fharyngeal, is the third nerve arising" in the g-roove between the corpora olivare and restiforme. Its deep orig-in is from the floor of the fourth ventricle between the eig^hth and tenth. It escapes from the cranium, along- with the tenth and eleventh, throug"h the pos- terior foramen lacerum, lying- behind the internal carotid artery ; it then passes forward between the artery and the in- ternal jug-ular vein to the outer side of the artery, then crosses the artery in front of the posterior border of the stylo- pharyngeus, and then crosses that muscle to be distributed by its terminal filaments to the mucous membrane of the poste- rior part of the tong-ue. This nerve presents two g-ang-liform enlargements called superior, or jug'ular, and inferior, ov petrous. The superior which is very small, is situated in the jug-ular foramen and does not involve all the fibres of the nerve. The inferior g-ang-lion is situated in a depression on the posterior border of the petrous portion of the temporal bone and g-ives off branches of cummunication to the pneumog-astric and sympathetic. Branches. Besides its terminal branches the ninth nerve g-ives off four branches of distribution. The tympanic branch, Jacohson s nerve, passes to the tym- panum throug-h a canal which opens on the ridg-e of bone be- tween the carotid and jug-ular foramina. After reaching- the tympanum it is distributed by six branches, as follows: {(i) One to the lining- membrane of the tympanum and E^usta- chian tube. (^) One to the fenestra rotunda. {c) One to the fenestra ovalis. {d) One to the carotid plexus of the sympathetic. {e) One to the g-reat superficial petrosal nerve. (_/) One to the lesser superficial petrosal nerve. THE CRANIAIv NERVES. 471 A muscular branch which supplies the stylo-pharyngeus. The ■pharyngeal branches, which are found on the poste- rior part of the pharynx aiding- to form a plexus called the pharyngeal from which the pharynx is supplied. The other nerves antering- into the formation of this plexus are the phary- geal and superior laryngeal of the tenth and the sympathetic. The tonsillar branches which form a plexus on the tonsils. The branches of communication of the ninth nerve are as follows: One to the gangflion of the tenth nerve. One to the superior cervical ganglion of the sympathetic. One to the seventh nerve. Carotid filaments which descend with the carotid artery. Tenth Nerve. The tenth nerve, or pneiunog'astric, or par vag'um, is the fourth nerve arising from the g-roove between the corpora olivare and restiforme. It escapes from the cranium through the jugular foramen and, descending the neck, enters the thorax through which it passes along with the oesophagus and gains the abdomen where it is found running from left to rig-ht along the lesser curvature of the stomach. In the neck the course and relations of the nerve are the same on both sides, /. erinei,, which arises on each side from the spot w^here the ramus of the ischium is continued into the tuberosity, and passes transversely inward to meet its fello^v in the centre. The point where the two perinei are inserted into each other is called the perineal centre. It should be observed that the course of these muscles corresponds with the transverse line. Accelerator iirincE, This muscle arises from the perineal centre and from the raphe between it and its fellow. The THE OUTLET OF THE PELVIS. 489 greater portion of its fibres surround the corpus spong-iosutn to meet the opposing- muscle on the top of the corpus, but some of the fibres, posteriorly, are inserted into the deep perineal fascia and ramus of the pubes, while some in front are lost ~in:^-ihe corpus cavernosum. Its chief action is to drive the urine forward by contracting on the corpus spong-iosum, in which is the urethra. Erector Poiis arises from the rami of the ischium and pubes, and passings forward is lost on the upper aspect of the corpus cavernosum. After removing: these muscles and the root of the penis the deep perineal fascia is displayed. This, as stated, is contin- uous at tne transverse line with the superficial perineal fascia, the line of reflection being- around the posterior aspect of the transverse perineal m uscles. From this point it passes forward to the arch of the pubes, attached on either side to the rami of the ischium and pubes. Just below the arch of the pubes it presents a small, round opening- for the passage of the urethra. When the deep perineal fascia is dissected it is found to consist of two layers, called the superficial and deep layers of the deep perineal fascia, which is sometimes called the triang-ular liga- ment of the pubes. Between the two layers are found blood vessels and nerves and a pair of muscles called compressors urethras. The compressor urethras arises from the point of union between the rami of the pubes and ischium and running transversely inward divides into two fasciculi, which meet those of the opposite side and surround the urethra. 490 DESCRIPTIVE ANATOMY. ORGANS OF GENERATION IN THE FEMALE. The org-ans of generation in the female are divided into those within and those external to the pelvic cavity. The ex- ternal organs, vulva clito7'is, &c., occupy the perineal space. The boundaries of the outlet of the pelvis are the same in both male and female subjects, but the ischio-rectal region is wider and longer in the female. In the mid-line are seen the open- ing of the vagina and the anus separated by a mass of tissue about one inch thick called the perineal body. The external organs consist of Hvo labia viajora surrounding the aperture of the vagina, composed externally of skin, which is covered with hairs and internally of mucous membrane, and united both in front and behind. Internal to these are two thinner projecting folds, one on eich side, called labia minora ■> which enclose in front a projecting body, the clitoris. Be- tween the clitoris and the mouth of the vagina is a space about one inch long called the vestibule, at the hinder part of which, near the mouth of the vagina, is an opening, the meatus urinarius . The pelvic organs consist of an o.^^ producing body — the ovary — and a channel to convey the ^^^ to the exterior. This channel is modified to perform the function of hatching — the uterus — and that of copulation — the vagijia. The ute7'us consists of an upper part or fundus, a middle portion or body, and a lower part or neck. The vag-ina is a short, bent canal which serves the double function of convey- ing the seamen to the uterus and of conducting the foetus to the external world. The relations which the uterus and its so-called appendages bear to neighboring structures consti- tutes the remainder of the study of the female generative organs. The peritoneum passes over the brim of the pelvis, envelop- ing the first portion of the rectum completely, and covering the upper one inch of the second portion in front, as in the ORGANS OF GENERATION IN THE FEMALE. 491 male. From the front of the rectum it passes to the posterior wall of the vag^ina, which it covers for its upper one inch or inch and a half ; passes to the back of the uterus and mounts upon it to its top, where it spreads out upon either side to envelop the appendag-es of the uterus ; descends upon the front of the uterus, covering- all of the front except that part contained within the vag"ina, and thence passes to the bladder, which is covered, as in the male, for its posterior half, the peritoneum leaping- from the top of the bladder to the posterior surface of the anterior abdominal wall, forming the false lig^a- ments of the bladder as in the male. That fold of peritoneum which extends transversely outward from the top of the uterus, envelops the appendag^esof that org-an in a double-layered fold which forms a vertical septum extending- transversely across the pelvic cavity, striking the lateral pelvic walls a little be- hind their middle, is known as the broad ligament of the uterus. The folds of peritoneum between the uterus and vagina and rectum posteriorly and the uterus and bladder anteriorly are known as the posterior and anterior ligaments of the uterus respectively, divided by the mid-line into two anterior and two posterior. Another lig-ament, a round cord, extends, in the folds of the broad ligament, from the lateral aspect of the uterus to the internal abdominal ring-, to follow the ing-uinal canal and be finally lost in the labium majus, under the name of the round lig*ament. The depression be- tween the vag-ina and the uterus in front and the rectum be- hind is known as the pouch of Douglas, the posterior lig-aments bounding- it on either side. The broad lig-ament encloses between its folds the fallopian tube, lig-ament of the ovary, round lig-ament and ovary. The fallopian tubes occupy the higfhestpart of the broad lig-ament, extending- outward from the upper ang-le of the uterus to become closely connected with the ovary. They enlarg-e as they pass outward and form at the extremity a trumpet-shaped mouth, fring-ed by diverging- processes or fimbriae, one of which is attached to the ovary. The tube is tortuous through the greater part of its course and when stretched out is about five inches long-, A little behind and below the fallopian tube is a small 492 DESCRIPTIVE ANATOMY. round cord, the lig-ament of the ovary, which attaches the ovary to the upper part of the side of the uterus. The ovary is about one and a half inches long, one inch v^ude and half an inch thick. One end looks toward the uterus, one end outward, one surface upward and forward, the other downward and backward. It is completely invested by peri- toneum, bulg-ing- the posterior folds of the broad lig-ament and appearing" not to be in contact with the anterior fold. It is held to the uterus by its lig-aments and the ova formed by it are conducted to the uterus by the fallopian tube. The lower end of the uterus projects into the vag-ina, which thus surrounds the neck of the uterus, cutting- off the lower portion of that org-an from relation with surrounding- viscera. The vag-ina extends hig-her up on the uterus posteriorly than anteriorly. The rectum is about the same leng-th as in the male, and is divided into three portions for study. Its lateral and posterior relations are the same as in the male, while the anterior rela- tions are different. The first part of the rectum has in front of it the uterus, separated from it by convolutions of the small intestine. The upper inch of the second portion, that part covered by peritoneum in front, is separated, by convolu- tions of the small intestine, from the posterior wall of the vag-ina, which in turn cuts off the neck of the uterus. The remainder of the second portion is adherent to the posterior wall of the vagina. The third part of the rectum passes downward and backward, diverging- from the vagina, the interval between the two being filled by a triangular mass of connective tissue forming the perineal body and corres- ponding to the tissue between the bulb of the corpus spongiosum and the rectum in the male. The ureter bears the same relation to the rectum as in the male, and lies upon the side of the vagina, which cuts it off from relation with the neck of the uterus. The. female bladder occupies the same position as in the male, lying behind the symphysis pubis and bearing the same rela- tion to the peritoneum. The anterior and lateral relations are also the same, except that there is no vas deferens, the position ORGANS OF GENERATION IN THE FEMALE. 493 of this structure being in part occupied by the round lig-ament, which lies above and internal to the external iliac artery. The posterior surface of the bladder is separated from the anterior wall of the uterus bv some convolutions of the small intestine. The base of the bladder looks more nearl}^ downward than in the male and rests for its anterior three-fourths upon the an- terior wall of the vagina, to which it is firmly adherent, its posterior one-fourth being covered by peritoneum. The urethra is nearly straight, but has a slight upward concavity. It lies on the anterior wall of the vagina, is about two inches long, runs through an opening in the triangular ligament about one inch below the symphsis pubis, is surrounded by muscular fibres forming what is called the compressor urethrae, and terminates in the vestibule at the meatus urinarius. The vagina is the canal of communication between the uterus and the vulva. It is directed obliquely downward and forward, corresponding to the axis of the outlet of the pelvis, while the uterus corresponds to the axis of the brim, the two thus forming a curve whose concavity is forward. It is com- pressed, so that its anterior and posterior walls are in contact. Its anterior wall is about two and a half inches in length, its posterior about three and a half. It is partly closed in the virgin by the hymen. The relations of the vagina have been given in connection with other structures. 494 DESCRIPTIVE ANATOMY. Inguinal hernia is the protrusion of some portion of the abdominal contents through the abdominal wall, making its way along the inguinal canal. The parts concerned are the lower fibres of the broad muscles of the abdomen, their super- ficial and deep coverings, and the structures composing the scrotum. There is no deep fascia investing the broad muscles of the abdomen. When the integument is removed, two layers of superficial fascia are seen, separated from each other by the superficial blood vessels and nerves, the deeper of the two being the stronger. The removal of the deep layer exposes the lower portion of the aponeurosis of the external oblique muscle, known as Poupart's ligament, which extends from the anterior superior spinous process of the ilium to the spine of the pubes, the inner portion forming the outer, or lower, pillar of the external, or suferflciaU abdomijial ring. Poupart's ligament is folded upon itself, backward and upward, forming a groove directed upward and inward. To its posterior face is attached the transversalis fascia, where it becomes continu- ous with the iliac, while its anterior face is continuous with the fascia lata and has adherent to it the deep layer of the superficial fascia. Before reaching the spine of the pubes, Poupart's ligament sends downward and backward a mass of fibres, with its base outward and apex inward, to be attached to the spine and pectineal line of the pubes, under the name of Gimbernat's ligament. Turning down Poupart's ligament we expose the combined origin of the internal oblique and trans- versalis muscles, which arches upward and inward, muscular, to form the conjoined arch, becomes tendinous and arches downward and inward as the conjoined tendon, which is in- serted into the crest and pectineal line of the pubes behind the superficial abdominal ring. The outer abutment of this arch is at the middle of Poupart's ligament, the inner one-half inch INGUINAL HERNIA. 495 external to the spine of the pubes, while the centre of the arch is one-half inch above Poupart's lig-ament. Cutting- away these structures we come to the transversalis fascia, behind which is the parietal layer of the peritoneum, the two being- separated by some loose connective tissue and fat. In the transversalis fascia is a second opening-, called the deep or in- ternal abdominal ri)ig: At the lower, inner, part of the aponeurosis of the external oblique muscle there is atriang-ular opening-, caused by the diverg-ence of the fibres of the aponeu- rosis, known as the superficial or external abdominal ring-; the apex of the opening- being- directed upward and outward, its base downward and inward and corresponding- to the crest of the pubes. The lateral boundaries of this ring- are known as its pillars — internal, or superior, attached to the front of the symphsis pubis, external, or inferior, attached to the spine of the pubes. The latter is simply the inner portion of Poupart's lig-ament. Around the marg-ins of this ring- the deep layer of the superficial fascia is attached, forming- what is called the inter-columnar fascia. The two layers become continuous below with the dartos of the scrotum. The apex of the trian- g-le is obscured by a few fibres which cross the others at rig-ht ang-les and prevent a further divergence of the fibres and consequent widening- of the triang-le. These are called the inter-columnar fibres. About one and one-half inches above and external to this opening-, nearly opposite the centre of Poupart's lig-ament, there is a hole in the transversalis fascia called the deep or internal abdominal ring-, situated a little less than one-half an inch above Poupart's lig-ament and internal to the outer abut- ment of the arch. Externally this ring- is bounded by the conjoined arch, internally by the deep epig-astric artery, below by Poupart's lig-ament. The ring- does not exist in a healthy subject. Throug-h this ring- the testicle descends in the foe- tus, and to its marg-ins is attached a prolong-ation of the transversalis fascia, the infundibuliform tube of fascia, which forms one of the coats of the hernia. Extending- be- tween the two ring-s there is a canal, about one and one-half inches long-, the inguinal or spermatic canal, which, in health, 496 DESCRIPTIVE ANATOMY. transmits the spermatic cord, in the male, or the round lig'a- ment, in the female, while, patholog"ically, it transmits the g-ut in a hernia. The sperynatic canal is limited internally by the superficial abdominal, externally by the deep, abdominal ring-, and its walls are formed as follows : Below by the g-rooved upper surface of Poupart's lig-ament ; above by the conjoined arch ; in front by the aponeurosis of the external oblique ; behind, by the transversalis fascia and parietal layer of peritoneum throug-hout its extent, while, for about its inner half, the conjoined tendon lies in front of those structures. The canal contains the neck of the infundibuliform tube of fascia, arteries, nerves, lymphatics and the duct from the testicle. On the visceral face of the peritoneum there may sometimes be seen a dimple which corresponds to the deep abdominal ring-, and, internal to this, a ridg-e which is formed by the deep epig-astric artery. The space between the ridg-e and the mid-line of the body is called the internal inguinal fossa, that external to the ridg-e the external inguinal fossa. The testicles, in their descent, enter at the deep ring-, pass throug-h the ing-uinal canal and make their exit at the super- ficial ring-. The cause of this descent is not accurately known, but it is aided by the g-ubernaculum testis, a mass of unstriated muscular fibres, attached by one extremity to the testicle and by the other to the marg-ins of the superficial abdominal ring-. In its descent the testicle carries with it the structures closing" the two abdominal ring-s. Thus, it presses upon the perito- neum at the deep abdominal ring-, invag-inates it and forces along- a process of this membrane which becomes the deepest layer investing- the testicle and is known as the tunica vag-i- nalis; next it forces along- a process of the transversalis fascia, which, after the descent of the testicle, becomes attached to the deep ring- forming- the infundibuliform tube of fascia ; then, while passing- beneath the conjoined arch, muscular fibres, arrang-ed in loops around the cord, are contributed forming- the cremaster muscle, which is attached internally to the sheath of the rectus and externally to Poupart's lig-a- ment. These loops are attached to each other by fascia called INGUINAL HERNIA. 497 the cremasteric fascia. Lastly, the testicle carries with it a process of the intercolumnar fascia, forming- the external cov- ering- of the cord, which is, of course, covered by the super- ficial fascia and integ-ument. Shortly after birth the tunica vaginalis is obliterated from the internal ring- to within a short distance of the testicle. When, from weakening of the abdominal wall, or other cause, an inguinal hernia is produced, it usually follows the course of the testicle in its descent, and, hence, its coverings would be similar to those of the testicle. This form is known as an oblique inguincd hernia, subdivided into complete, when it escapes from the superficial abdominal ring-, and incomplete, or bubonocele, when it remains in the ing-uinal canal. A complete inguinal hernia pushes before it the peritoneum closing the deep abdominal ring-, which forms the hernial sac, enters the inguinal canal, receiving- an investment from the infundibulum tube of fascia and the cremaster muscle, passes through the superficial abdominal ring-, carrying- with it a covering- furnished by the intercolumnar fascia, descends in front of the cord into the scrotum and is invested by the super- ficial fascia and the integ-ument. In incomplete hernia the coverings cease at the superficial abdominal ring. When the peritoneal pouch is not obliterated, there is a direct communication between the abdominal and scrotal cavi- ties, and the peritoneal covering of ,the hernia is the tunica vaginalis. This form of hernia constitutes what is known as cong'enital hernia. In infantile hernia the pouch is closed at the deep abdo- minal ring- only, and the gut descends behind the tunica vaginalis, having- three peritoneal layers in front, viz: the two layers of the tunica vaginalis and one layer of the proper investing sac of the hernia. In the encysted form the gut, carrying its own sac, projects into the tunica vaginalis, leaving- in front of it but two serous layers, viz: one of its own sac and one from the tunica vaginalis. Des An at— 32 498 DESCRIPTIVE ANATOMY. Direct Inguinae Hernia. — Hesselbach's triangle is bounded externally by the deep epigastric artery, internally by the rectus abdominis, below by Poupart's ligament. It is crossed by the conjoined tendon of internal oblique and transversalis muscles. Hernia m.ay occur either external to or through this tendon. When the hernia is external to the tendon it follows a part of the inguinal canal and has the same coverings as an oblique inguinal hernia, except that the infun- dibuliform tube is replaced by another prolongation of the transversalis fascia. When through the tendon the latter is pushed before the gut, which has the same coverings as in the oblique form, except that the infundibuliform tube is replaced by another portion of the transversalis fascia, and the conjoined tendon replaces the cremaster muscle. Occasionally the hernia may split the tendon instead of pushing it before it. FEMORAL HERNIA. 499 FEMORAL HERNIA. Definition. — The protrusion of an abdominal viscus throug-h the femoral or crural ring". Parts Concerned. — Behind the femoral arch is found the upper border of the pubic bone, marked, from within outward, b}' the ang-le, crest, spine, pectineal line, triang-le and eminence and the psoas g-roove. Stretching- from the anterior superior spinous process of the ilium to the pubic spine and pectineal line, is Poupart's ligament, forming- the femoral or crural arch. Gimbernat's lig-ament is the^ portion of Poupart's lig-- ament which is inserted into the pectineal line. The other structures concerned are the iliac artery and vein and their sheath, the peritoneum and fascia closing- the mouth of the ring-, the fascia lata, cribriform and superficial fasciae and the integument. The space between Poupart's lig-ament and the upper bor- der of the pubes is filled from without inward by the psoas and iliacus muscles, the anterior crural nerve and the femoral sheath containing the femoral artery and vein and having- in it an unoccupied space internal to the vein. This sheath is formed in front by the transversalis, behind by the iliac fascia. Femoral Ring. — ^h^ fonoral 7-ing- is the upper opening- of the femoral canal. Internally it is bounded by the outer edg-e of Gimbernat's ligament ; externally by a septum in the sheath separating the open space from the femoral vein ; above is Poupart's lig-ament ; below, the upper border of the pubes and the orig-in of the pectineus muscle. The femoral canal extends downward in the sheath for about one inch and is lined by a prolong-atiQn of fascia which covers the vessels and is known as the fascia propria. The canal terminates b}'' the con- traction of the sheath so as to closely hug- the vessels. The femoral ring- is closed above by the peritoneum and a thin layer of fascia called septum crurale, or femorale, which usually has lying- upon it a lymphatic g-land. 500 DESCRIPTIVE ANATOMY. Blood Vessels. — Just beneath Poupart's ligament the external iliac vessels terminate by becoming* the femoral; but, before its termination, the external iliac artery g-ives off a larg-e branch called the deep epigastric, which lies above and ex- ternal to the femoral ring and betw^een it and the deep abdominal ring. The external iliac vein lies to the outer side of the ring, so that in all cases there are blood vessels above and external to the ring. The deep epigastric artery sometimes gives off a branch called the obdurator, which may descend next the iliac vein and on the outer side of the ring ; but it sometimes passes inward and downward, arching above and internal to the femoral ring, which is thus surrounded by blood vessels on all sides except below. The epigastric also gives off a small pubic branch which lies above the ring, but is, from its size, unimportant. Fascia Lata. — The investing fascia of the thigh, or fascia lata, presents, about one inch below Poupart's ligament, an oval opening called the saphenous opening. The opening is closed in the recent state. It runs obliquely downward and outward, is about one inch in its vertical by three-quarters of an inch in its transverse diameter; its inner edge is straight and prolonged outward behind the outer edge; its outer is curved, runs downward and outward from Gimbernat's liga- ment to the inferior cornu and is called Hey's ligament or the falciform process of Burns. The external part of the fascia is known as the iliac portion and is attached to the crest of the ilium and the outer portion of Poupart's ligament, sending in- ward a spur which is attached to the pectineal line, runs over the femoral vessels and forms the outer boundary of the saphe- nous opening. The inner part, called the pubic portion, is thin and weak, is attached to the ischio-pubic ramus and is prolonged beneath the femoral vessels. The saphenous open- ing is covered by the skin and two layers of superficial fascia, of which the deep, under the name of cribriform fascia, be- comes adherent to the margins of the opening. The cribri- form fascia is attached more firmly below than above, and hence tends to direct a protruding gut upward. FEMORAL HERNIA. 501 Course. — A femoral hernia passes downward through the femoral ring-, thence down the canal as far as the saphenous opening", turns forward through this opening and then runs upward on the front of the thigh. The main causes of the ascent are the firmer attachment of the cribriform fascia below, the narrowing of the femoral canal and the movements of the thigh. Coverings. — Femoral hernia pushes before it, first the parietal layer of peritoneum and fat covering the femoral ring, then the septum femorale, fascia propria, cribriform fascia, superficial layer of the superficial fascia and, lastly, the skin. 502 DESCRIPTIVE ANATOMY. THE AXILLA. The space known by this name lies between the chest wall internally, the humerus externally and the muscles in front and behind. In the skeleton only the apex of the space is complete, being- bounded in front by the clavicle, behind by the upper border of the scapula, internally by the first rib. Below the apex the space corresponds to the upper five ribs internally, the scapula behind and the bottom of the bicipital groove externally. In the recent subject the space has the shape of a three-sided pyramid. The apex is above, the base below and the sharp angle external at the bicipital groove. The whole space is closed in by soft structures. The ante- rior wall is furnished by the pectoralis major, which covers the whole of the space, while beneath this, forming only the middle of the anterior wall, is the pectoralis minor. The pos- terior wall is formed by three muscles, subscapularis, teres major and latissimus dorsi; but the order in which they come changes in different parts of the space. Near the inner wall the order, from above downward, is subscapularis, teres major, latissimus dorsi; but near the external wall, owing to the fact that the tendon of the latissimus dorsi winds around the teres major and is inserted above it, the order is subscapularis, latissi- mus dorsi, teres major. The inner wall is formed by the upper six serrations of the serratus magnus muscle and the intercos- tal muscles corresponding to the upper five intercostal spaces. The lower border of the muscles which enter into the anterior and posterior boundaries of the axilla form the anterior and posterior axillary folds, of which the posterior is the thicker and more prominent. Stretching across from one fold to the other, and continuous with the investing fascia of the arm, is a strong fascia which forms the floor of the space. The con- tents of this space are the brachial plexus of nerves and its terminal branches, the axillary artery and vein and their branches, lymphatic glands and a quantity of areolar tissue and fat. THE ORGAN OF HEARING. 503 THE ORGAN OF HEARING. The org-an of hearing- is connected with the temporal bone of each side, and properl}^ speaking-, consists of two organs, one to each side. In the prepared bone a portion is still pre- served, for upon the base of the petrous portion of the tempo- ral bone the bony portion of the external auditory meatus is seen ; and on the posterior surface of the petrous portion the internal auditory meatus, at the bottom of which is seen the internal wall of the inner chamber perforated by numerous apertures. The external wall of the inner chamber is seen by looking into the external auditory meatus. On the anterior face of the petrous portion are seen the bulge of the superior semicircular canal and just external to this a depression corre- sponding- to the roof of the middle chamber, or tympanum, the floor of which is the jug-ular fossa, on the basilar face of the petrous portion of the temporal. The org-an of hearing is described as consisting- of three portions, or chambers, lying- the one internal to the other, upon the base and in the substance of the petrous portion of the temporal bone. These three chambers are known from without inward as — 1st, external ear consisting of three por- tions, (<^)/>/;^««, or auricle', {b) meatus auditorius externus \ {c) nienibrana tynipani; 2nd., middle ear or tympanum ; 3rd, internal ear, or labyrinth. The External Ear. The external ear consists of three portions named above. Its function is to connect the sonorous vibrations and convey them to the middle ear, which in turn transmits them to the internal ear, where they encounter the sentient nerve of hear- ing. The -piwia, or auricle is the expanded outer extremity of the external chamber found on the base of the petrous portion of the temporal bone, contracting- to its termination in the exter- 504 DESCRIPTIVE ANATOMY. nal auditory meatus. It presents a very uneven surface and the various elevations and depressions have received individual names. The central concavity, leading- to the external audi- tory meatus, is called the concha ; the more or less folded marg-in, or rim, the helix ; the pendant, lower, softer portion, the lobulus ; the triang-ular prominence jutting- out in front of the concha, the trag-us ; behind and somewhat below this, separated from it by a notch, is another projection, the anti- trag"us ; the curved elevation between the helix and the concha, or rather behind the concha, is the anti-helix, which divides superiorly enclosing* a depression called the fossa ovalis ; the deeply sunken surface between the helix and the anti-helix is the fossa scaphoidea, or innominata. Tho, pimia varies g-reatly in different^ people, and this is especially true of the lobule. In structure it consists of a plate of fibro-cartilage, whose folds produce the depressions and elevations mentioned. This cartilag-e is covered by integu- ment and alveolar tissue, supporting* various insignificant muscles, intrinsic, intended to vary its shape, and giving attachment to other small muscles, extrinsic, intended to move the pinna. Of the latter some few people have use, but the former never act to produce visible effect. The cartilag*e is not continuous throug-hout the auricle, for it is altog^ether wanting- in the lobule and, besides, presents several fissures which have received names. The pinna is held in position by the integ-ument. by the extrinsic muscles mentioned above and by two lig-aments, anterior and posterior. The anterior extends from the helix to the zygoma; the posterior, from the concha to the mastoid process. Besides these there are several small ligaments passing- from one part of the cartilag-e to another, the larg-est of which is that between the trag-us and helix. The external auditory ineatus is the canal which extends from the concha to the tympanum, from which it is separated by the tympanic membrane. It is rather more than an inch in length, its direction being inward and slig-htly forward and its course somewhat curved, with its convexity upward. It is smaller in the centre than at either end. It consists of an THE ORGAN OF HEARING. 505 external cartilag-inous portion, taking- up one-third of its lengfth, and an internal, osseous portion, taking" the remaining- two- thirds. The osseous portion terminates internally at an oblique g-roove for the attachment of the membrana tympani. This portion can be seen in the dried bone, althoug-h the septum in the botton is of course absent. The outer extremity is roug-h and prominent for the attachment of the cartilag-inous portion. It is lined throug-hout by the integ-ument which, toward the exterior, is studded with hairs and contains g-lands for the secretion of the ear wax. The hairs and wax are intended to obstruct the entrance of insects, &c. The niembrcuia tympani is the septum separating- the exter- nal from the middle chamber, being- situated at the inner extremity of the external auditory meatus, attached to the ob- lique g-roove there found. It is frag-ile, semi-transparent, nearly round, oblique in its direction from above downward and inward, striking- the floor at an ang-le of 45°, and is seen to bulg-e toward the tympanum, having- a corresponding* con- cavity externally. Its frame work is fibro-elastic, consisting- of radiating- and concentric jQbres, the latter especially seen near its circumference; it is covered externally by the integ-u- ments lining- the externally auditory meatus, which is exceed- ing-ly sensitive. Internally it is coated by mucous membrane of the typanum. The Middle Ear. The middle ear, chamber, or tympaimm, lies in the petrous portion of the temporal bone, separated, externally, from the meatus auditorius externus by the membrana tympani ; and separated, internally, from the inner chamber, or labyrinth by a bony wall and its roof corresponds to the depression on the anterior face of the petrous bone, its floor to the jug-ular fossa on the basilar face of that bone. Its anterior wall is a bony partition interposed between it and the internal carotid artery and its posterior wall is the cellular substance of the mastoid portion of the temporal bone. Owing- to the obliquity of the inner and outer walls, the tympanum is much narrower trans- versely, below than above. The leng-th of its roof from with- 506 DESCRIPTIVE ANATOMY. out inward is about three lines, the floor being- scarcely more than one line. It presents for examination six walls, two of which — floor and roof — have nothing- noteworthy. The outer wall has been described as the membrana tympani, having- attached to it a chain of bones, which extends to the inner wall. The internal wall is the bony partition between the tympa- num and the labyrinth, upon which are seen the following' appearances : {a) a ridg-e at its upper part corresponding- to the acqueduct of Fallopius ; {b) just beneath this a kidney- shaped aperture, opening- into one of the apartments of the labyrinth, called the fenestra ovalis. This is closed during- life by a membrane to which is attached the foot of the stapes ; (6') below this is a bulg-ing- surface known as the promontory ; {d) beneath this is a second opening- oval, or triang-ular in shape, called the fenestra rotunda, which is likewise closed by a membrane and establishes communication with another part of the labyrinth called the cochlea. The posterior wall presents several small opening's into the mastoid cells and the opening- for the entrance of the chorda tympani, iter chordae posterius, which crosses the tympanum to g-ain exit on its anterior wall. There is also a conical pro- jection, the pyramid, which has at its summit an opening- for the stapedius muscle. On the anterior wall are seen : {a) the fissure of Glaser ; {b) the opening- of exit of the chorda tympani, iter chordae an- terius, or canal of Hug-uier ; {c) two small opening-s, separated by a thin plate of bone, the upper called the opening- for the tensor tympani. the lower the opening- for the Eustachian tube, and the dividing septum the cochleariform process. Stretch- ing- across the tympanum from the membrana tympani, extern- ally, to the fenestra ovalis internally are seen three smiU bones, malleus, incus and stapes. The malleus is the outer- most of the three, resting- ag-ainst the membrana tympani ex- ternally and articulating- with the incus internally. It consists of a head, for articulation with the incus, a neck and three processes. One of the processes is called the handle, manu- brium, and lies embedded in the membrana tympani, half way THE ORGAN OF HEARING. 507 to the floor from above downward. Another, the long- process, processus g-racilis, passes downward to the fissure of Glaser ; while the third, the short process, bulges outward from the neck. The incus is so called from its resemblance to an anvil. It consists of a body, for articulation with the head of the malleus, and two processes. The short process passes back- ward to the opening" of the mastoid cells in the posterior wall; the long", passes downward to articulate with the head of the stapes, terminating- in an enlarg-ement, called the os orbiculare. The stapes, stirrup, projects inward from the os orbiculare, with which it articulates by a head. Succeeding- the head comes the neck and diverging from this are the two crura, one to either side, which are connected at their distal extrem- ity by a plate, called the foot, which is exactly fitted into the fenestra ovalis. When the child is born those bones have at- tained nearly their full size. They are held tog-ether by lig-a- ments and g-ive attachment to several small muscles which are intended to move the bones on one another and thus relax, or tig-hten the membrana tympani, or the membrane of the fenestra ovalis. This latter membrane is in fact composed of two layers, and the fenestra ovalis is closed successively by the following- parts from without inward, viz : 1st, the mucous membrane of the tympanum ; 2d, beneath this the foot of the stirrup ; 3d, on the labyrinthine surface this foot is coated by the serous membrane lining- the labyrinth. The arrang-ement for closing- the fenestra rotunda is similar in consisting- of three elements : (1st), a fibrous membrane coated by (2d) the mucous membrane of the tympanum externally and (3d) internally by the serous membrane of the labyrinth. It is constructed so much like the membrana tympani that it has been called the membrana tympani secundaria. The ossiculaauditus are held to one another and in position by means of small lig-aments. The head of- the malleus is held to the body of the incus by a capsular ligament ; and another capsular lig-ament binds to- gether the os orbicularis and the head of the stapes. The lig-aments holding- the bones tog-ether are three in nnmber: 1st, the foot of the stapes is held to the fenestra ovalis by means of lig-amentous fibres ; 2d, there is a suspensory lig-ament of the 508 DESCRIPTIVE ANATOMY. malleus consisting- of a few lig'amentous. fibres passing- be- tween its head and the roof of the tympanum ; 3d, a band of fibres attaches the short process of the incus to the opening- of the mastoid cells. These bones, thus permitted motion by means of the lig-aments, are moved not only by the vibrations of the membrana tympani but by two small muscles, viz : The tensor tympani which spring's from the apex of the basilar surface of the petrous bone and the upper aspect of the carti- laginous portion of the E^ustachian tube and enters the open- ing- in the tympanum known by its name, and found just above the processus cochleariformis, which separates it from the opening- of the E^ustachian tube ; it also derives a few fibres from the canal it traverses. When it reaches the anterior wall of the typanum its tendon turns outward and is inserted into the malleus at the junction of the manubrium and long- process of the malleus. The stapedius is far the smallest mus- cle in the body. It arises within the hollow pyramid, on the posterior wall of the tympanum, emerg-es from the opening- on the summit of the pyramid and is inserted by a tendon into the neck of the stapes. The action of the stapedius is to reg-- ulate the pressure of the foot of the stapes ag-ainst the fenestra ovalis. The Eustachian Tube. The Eustachian tube is a canal, which establishes communi- cation between the air in the tympanum and the outside atmosphere. It passes from the anterior wall of the tympanum, where its opening- is seen just beneath the processus cochlear- iformis, downward, forward and inward, to terminate in the phar3mx, just behind the opening- of the posterior nares. Its lower third is cartilag-inous; its upper two-thirds osseous. The Internal Ear. The internal ear, or labyrinth is the innermost of the three chambers, which constitute the org-an of hearing- and is intended for the terminal ramifications of the auditory nerve, which reaches it throug-h the internal auditory meatus, on the centre of the posterior face of the petrous bone, and for the reception of the communicated vibrations of air, which reach it throug-h THE ORGAN OF HEARING. 509 the tympanum. It consists of an osseous and a membranous lab3'rinth, the osseous being- divided into three chambers, which, however, communicate with one another. These three parts are placed one behind the other: the anterior is called the cochlea, the middle the vestibule, the posterior the three semicircular canals. They are all lined by a serous coat. The Vestibule. The Vestibule is a three cornered cavity, having- communi- cation with the tympanum throug-h the fenestra ovalis. Kach corner is called a ventricle and the three are known as anterior, superior and posterior. In the anterior are seen the following" objects: 1st, a depression, called fovea hemispherica; 2d, a number of minute apertures, called the macula cribrosa; 3d, a ridge, the eminentia pyramidalis; 4th, the opening- into the cochlea, scala vestibule. In the superior we have: 1st, a depression — the fovea hemi-elliptica; 2nd, the two openings of semicircular canals — the dilated extremities of the superior and horizontal. The posterior presents: 1st, a depression — fovea sulciformis; 2d, the opening of the aqueduct of the ves- tibule; 3d, the dilated extremity of the oblique semicircular canal, the common aperture for this canal and the superior and the opening of the horizontal canal. The Semicircular Canals. These canals are channels hollowed in the petrous portion of the temporal bone. They are three in number, each about one-twentieth of an inch in diameter, and placed at right angles to one another. Kach forms rather more than a semi- circle and presents near one extremity an enlargement, called the ampulla, and opens by both ends into the vestibule. The three canals are called : 1st, superior, which is vertical in direction and produces the ridge seen on the anterior face of the petrous bone ; 2nd, the posterior, or oblique, which is also vertical ; 3rd, the external, or horizontal. These three canals present but five openings into the vestibule, owing to the fact that the posterior and superior have a common opening- into the posterior corner of the vestibule. The other 510 DESCRIPTIVE ANATOMY. " Opening's were mentioned in the description of the vestibule — three being* into the posterior and two into the superior corner. The Cochlea. The cochlea lies in front of the vestibule and by its base forms the promotory, seen on the inner wall of the tympanum. When entire it resembles a snail's shell and may be discribed as consisting- of a tube divided into two apartments by a longi- tudinal septum, one end of the tube being- closed and much smaller than the open end from which it rapidly tapers. The septum is not complete, for it fails to reach to the small, closed end, thus allowing- a communication between the two chambers. This tube is coiled by two turns and a half around a stem, or tapering- pillar, called the modiolus. The septum subdividing- the two chambers, which are called seals, is named the lamina spiralis. It consists of two layers, between which is a narrow space, called scala media, and it terminates in a hook-like projection called the hamulus. When examined closely the lamina spiralis is seen to consist of three structures; the portion next the modiolus is bony, farther out it is mem- br2,nous and the utermost portion is muscular and sometimes called the cochlearis muscle. The small space, existing- be- tween the extremity of the lamina spiralis and the cupola, is called the helicotrema ; it establishes communication between the two chambers, one of which is called the scala tympani, the other the scala vestibuli. The scala vestibuli is seen to communicate, at the base of the cochlea, next the vestibule, with the anterior corner of the vestibule. The scala tympani communicates with the tympanum, by means of the fenestra rotunda. The modiolus is the tapering- pillar around which the two scalae wind. In its centre there is a canal called the tubulus centralis modioli. Its base is next the vestibule. The Membranous Labyrinth. Beside the parts above described, the labyrinth contains others for, within each semicircular canal is a membranous counter part, two thirds smaller, separated from the bony wall by liquid. The membranous canals present the same dilations at one end, ampulla, as the bony. THE ORGAN OF HEARING. 511 In the vestibule also are two membranons sacs, one above the other. The upper one receives the opening's of all the semicircular canals and lies in the fovea hemi-elliptica. It is called utriculus, or sacculus proprius. In the membranous labyrinth, as the above parts are collectively called, are found crystalline particles, carbonate and phosphate of lime, called ear-dust, or otoliths. The auditory nerve gains the labyrinth through the internal auditory meatus. At the bottom it divides into a vestibular and a cochlear branch, the latter dividing into filaments which run in channels in the modiolus and turn outward to ramify in the lamina spiralis. The vestibular branch divides into three, one for each of the membranous sacs, and one for the semicircular canals. 512 DESCRIPTIVE ANATOMY. THE OEGAN OF VISION. The org-an of vision is situated in the orbits, two conical cavities found on the face. Like the organ of hearing, it consists of two similar portions, one on each side, called the eye-ball and its appendages. The Appendages of the Eye. The Appendages of the eye, tutamina oculi, are mere accessories to the true organ of vision, the eye-ball, for the purpose of protection and ornament. They are: JSyebrozu is a prominence of the integument, curved, covered with hair and situated above each orbit. They are intended for ornament and protection from dust, perspiration and too vivid light, and to break the force of any blow falling on the front of the orbit. The eyelids consist of two movable curtains, which are constantly playing over the front of the eye-ball. The aper- ture, which separates the two lids, one called upper, superior palpebra, the other lower, inferior palpebra, is known as the palpebral fissure and can be extinguished, or dilated atpleasure. The two lids meet externally at an acute angle called the external canthus; internally when they seem about to meet they refrain from doing so and the interval between is pro- longed inward towards the nose for some distance before forming the internal canthus. The triangular space thus left between the lids at the inner canthus is called the lachrymal lake, lacus lachrymalis, in which is seen a reddish, conical projection, called the caruncle, which is bounded externally by a curved fold of mucous membrane, called the plica semi- circularis. The concavity of this fold is external. At the commencement of the lachrymal lake, just where the two lids are apparently about to unite, there is a projection from the edge of each lid, called the lachrymal papilla, or tubercle, on the summit of each of which is an opening, the THE ORGAN OF VISION. 513 punctum lachrymale. The free edg-e of each lid is provided with several rows of short curved hairs, the eye-lashes, in- tended for ornament, to render the contact of the lids more intimate and to protect ag"ainst dust, etc. In structure the eye-lids consist of the following- parts: externally there is a layer of thin, loose skin with subjacent areolar tissue; inter- nally, a layer of mucous membrane called the conjunctiva, which not only lines the inner surface of the lids, but is reflected over the front of the ball — palpebral and ocular portions. The palpebral portion is studded with papillae. Just beneath the integfument, on the outer surface of the lid, is a pale thin muscle, the orbicularis palpebraum, so named from the fact that it is somewhat round, passes from one lid to the other and surrounds the palpebral fissure, its function is to close the lids. Beneath the orbicularis palpebrarum, in each lid is a curved plate of cartilage, about an inch in length, called the tarsal cartilage. The superior is the larger and is semi- lunar in shape; the inferior is much the narrower and oval. The two are attached along their circumference to the edge of the orbit by ligamentous fibres. Externally, they are held to the outer angle of the orbit by a ligament called the external palpebral, or tarsal ligament; internally, they terminate in a ligament, called the tendo oculi, which holds them to the edge of the orbit. Lying on the posterior surface of the lids be- tween them and the mucous membrane, and opening on the edge of the lids is a number of vertical, beaded bodies, the Meibomiam glands, the secretion from which is discharged on the edge of the lids. There are thirty of these glands for the upper lid, but a smaller number for the lower. Lachrymal apparatus. Lying in the depression, seen, on the orbital plate of the frontal bone, just behind the external angular process, is the lachrymal gland. It is about the size and shape of an almond and rests on the posterior part of the upper tarsal cartilage. The ducts, seven to twelve in number, which convey the secretion of the gland, tears, being dis- charged on the surface of the conjunctiva, is constantly swept toward the inner canthus of the eye by the frequent movement of the lid; there it disappears in the lachrymal puncta from 514 DESCRIPTIVE ANATOMY. each of which there leads a small canal called the lachrymal canaliculi. The upper first ascends, then bends inward to terminate in the nasal, or lachrymal duct; the lower first de- scends, then turns inward to terminate in the nasal duct beside the superior. The nasal duct extends a little way above the opening's of the canaliculi in a portion, called the lachrymal sac; and from this point the duct extends downward, outward and slig"htly backward to terminate in the inferior meatus of the nose. The Globe of the Eye. The eye-ball is situated in the front part of the orbit, em- bedded in a mass of fat. It is nearly g-lobular, its antero- posterior diameter being" one inch and its transverse seven- twelfths of an inch. Posteriorly it receives the optic nerve, at a point about one one-tenth of an inch to the nasal side of the centre. The ball consists of concentric layers enclosing- a bag- of liquid , which forms about four-fifths of it. These coats or layers are sclerotic, choroid and retina. The Sclerotic Coat. The sclerotic, familiarly known as the white of the eye, is a dense fibrous membrane, which serves as a protecting" enve- lope for the rest of the eye-ball. Its anterior one- sixth is wanting", the aperture being" filled by a transparent membrane, the cornea. Posteriorly the sclerotic is perforated by the optic nerve, not en masse, for the nerve splits into a number of fibres, which pierce the coat separately, producing" the appearance known as macula, or lamina cribrosa, the fibrous sheath of the nerve becoming" continuous with the sclerotic, while in front the sclerotic is continuous with the cornea. The Cornea. The cornea forms the anterior one-sixth of the first invest- ment of the eye-ball. It forms a seg-ment of a smaller sphere than the sclerotic and being" more convex it causes the increase of the antero-posterior diameter over the transverse. The cornea, instead of being" opaque, like the sclerotic, is transpa- rent and its circumference is received beneath the anterior THE ORGAN OF VISION. 515 bevelled edge of the sclerotic with which it is continuous in some of the structures. It consists of five layers. The ante- rior surface is an epithelial layer, derived from the conjunc- tiva ; the posterior layer is also epithelial, the lining- membrane of the anterior chamber. Next each of these is found a layer of elastic tissue, the two la3^ers constituting- what is called the elastic cornea, and separating- these is a layer of fibrous tissue, called the cornea propria, which can be split into sixty layers of spindle-shaped cells with branching intervals, in w^hich circulates the colorless plasma of the blood. It is with this cornea propria that the sclerotic is continuous. The cornea is of varying- convexity in different people and at differ- ent periods of life. It is more convex in youth and becomes less so in old age, at which period there is often seen around the cornea a yellowish band, called arcus senilis. The Choroid. The c/207-o?d Wes within the sclerotic, with which it is con- nected by areolar tissue, sometimes called lamina fusca, which is pierced by the optic nerve. At the point in front where the sclerotic ceases the choroid terminates in a flattened mem- brane, the iris, which, in its centre presents a round aperture, the pupil. The choroid consists of three layers, the outer two red and the inner black. Between the two red and the black layers some make a fourth layer, the membrana limitans- The external red layer is called the venous layer; the interna^ red layer the capillary, arterial, layer, or the tunica Ruyschiana. The internal layer, or membrana pigmenti, or tapeta is of a black color, consisting of cells, filled with coloring matter. On the anterior surface of the choroid, just around its anterior margin, is a whitish band, one-fortieth of an inch wide, called the ciliary ligament, which binds together the cornea and sclerotic and the choroid and iris. Extending back, about one- eig-hth of an inch, on the anterior aspect of the choroid, is a gray circular band, called the ciliary muscle. On the poste- rior aspect of the front of the choroid are, about, sixty ridges, diverging- from the rim of the choroid, called the ciliary processes. 516 DESCRIPTIVE ANATOMY. The Iris. The iris is the thin flat membrane, which continues the choroid in front. In its centre is seen the opening-, called the pupil. The various colors of the iris are due to the difference of color of the pig-mentary matter found in its cells and to the varying- arrang^ement of the blood vessels. The color is darkest usually near the centre. Towards the middle of the iris is a circle of little shaggy projections. The foundation of the structure of the iris is fibrous tissue, consisting- of circular and radiating- fibres inter- posed between which are pig-ment cells. In front and behind this fibrous layer is a layer of pig-ment cells. In the iris are also seen unstriated muscular fibres, circular around the pupil and radiating- toward the circumference: by the action of these fibres the pupil is constantly dilating and contracting-. Blood vessels and nerves ramify throug-hout the structure. On the posterior surface the iris consists of a black layer, called the uvea, which is, in fact, a continuation of the mem- brana pigmenta of the choroid. Anterior Chamber — Between the iris and pupil behind, and the cornea in front is a small cavity, called the anterior cham- ber. Posterior Chamber — Between the iris and pupil in front, and the lens behind is another, smaller cavity, called the pos- terior chamber. These two contain a liquid, called the aque- ous humor, and they communicate throug-h the pupil, after the sixth month of foetal life, up to which time the pupil, is closed by a membrane, called the papillary. Both chambers are lined by a membrane which secretes the aqueous humor. The Retina. The retina is the innermost of the three coats of the eye, lying- just within the choroid. It is wanting- in front even for a g-reater distance than the two preceding- layers, for it ceases, as it reaches the ciliary processes in a roug-h jag-ged marg-in, called ora serrata, and is continued thence to the crys- talline lens by a vascular membrane, called the suspensory ligament of the lens. The outer surface of the lig-ament is THE ORGAN OF VISION. 517 fluted to correspond with the ciliary processes, ag'ainst which it rests. The retina is non-resisting- and translucent, being partially formed by the expansion of the optic nerve, with which it is continuous posteriorly. Exact!}' in the centre, posteriorly, is a round, yellowish spot, called the macula lutea, and in the centre of this spot a depres- sion called fovea centralis. About one-tenth of an inch to the inner side of this is seen the termination of the optic nerve — optic disk, or papilla— showing- in its centre the arteria centralis retinae, breaking- up into branches. From this point forward the retina gradually thins to its termination. The Vitreous Humor. Just within the retina is a bag, called the hyaloid membrane, containing a liquid, called vitreous humor. This is similar in composition to the aqueous humor, being 98% water. Travers- ing the centre of this, in the foetus, is a branch of the arteria centralis retinae, making its way to the lens, called the capsular artery. It disappears at birth. The Crystalline Lens. Indenting the front of the hyaloid membrane is found a doubly convex transparent body, called the crystalline lens. Its posterior surface is much more convex than the anterior, the latter forming the posterior wall of the posterior chamber. The lens forms only the bulging portion of the wall, the circumference of which is formed by the suspensor}' ligament of the lens, which extends from the ora serrata of the retina to the rim of the lens. This ligament is formed of two layers and when it lays hold of the lens it leaves a circular canal around it, called the canal of Petit. The lens is invested b}'' a trans- parent homogeneous, elastic membrane, the capsule of the lens. In structure the lens consists of a series of concentric layers of parallel fibres, which gradually harden towards the centre of the lens. It can also be splitinto three triangular segments, which meet by their apices in the centre of the lens. In youth the lens is more convex and much softer than in old age, as it gradually becomes, with advancing life, firmer and less convex. iis:db:x:. Abdomen, boundaries of, 161 lymphatics of, 386 muscles, 214 reg-ions 161 viscera of , 161-193 Abdominal aorta, 328 branches of, 330 ring", external, 215 " internal, , 495 viscera, relations of, 161-177 Abducent nerve, 467 Abductor minimi digiti (hand), 256 " (foot) 275 poUicis (hand), 256 " (foot), 275 Accelerator urinae, 488 Accessorius muscle, 275 Acetabulum, 39 Acromial muscle, 237 thoracic artery, 310 Acromio-clavicular joint, 120 Acromion process, 20 Alai of vomer, 76 Alar ligaments, , 143 thoracic artery, 310 Alimentary canal, 177-182 Al veolar process, lower ja w 84 upper jaw, 81 Anconeous muscle, 252 Angle, jaw, 85 pubes 38 rib, , 14 520 INDEX. Atigfular convolutions, 397 movements, Ill process, external and internal, 61 Ankle joint, 146 Anuulus ovalis, 210 Anterior ethmoidal cells, 73 fossa skull, 93 reg"ion skull, 95 Antitrag-us, 504 Antrum of Highmore, . . . : 78 Anus, 182 Aorta, 321 abdominal, 328 branches of, 330 arch of, 321 descending-, 32b Aortic opening- diaphrag-m, 220 semilunar valve, 211 sinuses, 212 Appendages of eye, 512 Appendix, right auricle, 209 left auricle, 211 vermiform, 168 Aqueductus vestibuli, 64 Fallopii, 65 Sylvius, 408 Aqueous humor, 516 Arachnoid of brain, 391 cord ' 417 Arm, arteries of, . . 304 fascia, ; ^- 241 lymphatics 387 muscles, 241 nerves, 429-438 veins, 374 Artery, or arteries : acromial thoracic, 310 alar thoracic 310 I INDEX. 521 Artery, or arteries ( Continued) : ang-ular, 294 anterior cerebral, , 364 choroid, 364 ciliary, 363 communicating- 364 articular of knee, 349 axillary, 307 basilar, 304 brachial, 312 calcanean, 351 carotid, common, left. 324 rig-ht 287 external 290 internal, 360 circumflex, arm, 211 thig-h, 347 colica dextra, 336 media 336 sinistra, 337 coronary, heart, 323 '^ lips, 294 dig-ital, 318 epig-astric, 342 facial 293 femoral 343 deep 345 g-astric 332 g-astro-epiploica dextra, 333 sinistra, 334 j^^luteal, 359 hepatic 333 ileo-colic 336 iliac, common, 340 external, . . . : 341 internal, 355 innominata ■. . .. 323 5<22 INDEX. Artery, or arteries (Continued) : internal mammary ,.....,....,.,,,, 306 maxilllary, ..,.,. 297 plantar, 352 intestini tenuis, , , 33S lateralis nasi, , 294- ling-ual, , , . , , 295 long- thoracic,... ,.. . .., , ,. 311 obturator, , » . , . . . 356 occipital, , 295 opthalmic, 362 plantar, . , , 352 perineal, 358 peroneal , 351 phrenic, 330 radial, forearm, 315 hand and wrist, 318 renal, 340 sciatic, . , 351 temporal, superficial, 296 deep, 298 thyroid axis, 304 tibial, anterior, 353 tibial, posterior, 350 transversalis colli, 305 ulnar, forearm, 315 " hand, 316 vertebral, 304 Articulations in g-eneral, 108 Articulation, ankle, 146 atlo-axoid 114 calcaneo-astrag-aloid, 148 cuboid, 148 carpal, 129 costo-vertebral, 150 costo-sternal 132 elbow, 125 INDEX. 523 Articulation, ( Coyitinued) : hip, 134 knee 139 occipitoatloid, 115 pelvis, 132 Articulation, radio-carpal, (wrist) 127 ulnar, 124 shoulder, 121 sterno-clavicular, 118 temporo-maxillary, 130 tibio-fibular, 145 vertebral column, 112 wrist, 127 Arytenoid cartilage, 195 Ascending" colon, 168 Astragfalus, 51 Atlas, 6 Auditory nerve, 464 Auricle, of ear 504 heart 209-211 Axilla, 502 Axillary artery, 307 vein, 366 Axis, 7 B. Back, muscles of, 230 Base of brain, 401 skull, superior surface, 92 inferior surface, 89 Basilic vein, 375 Bicipital fascia, 242 g-roove, 21 Bladder, relations in female, 176 male, 175 description of, 189 524 INDEX. Bone, or Bones: 1-107 astragalus, 51 atlas, 6 axis, 7 calcaneum, = 50 carpal, 27 clavicle 16 coccyx, 10 cranial , 57 cuboid 52 ethmoid, 72 articulations of, 102 femur, 46 fibula 48 frontal, 60 articulations of, 100 humerus -. 20 hyoid, 106 ilium, 35 inferior maxillary, 106 turbinated , 75 articulations of, 105 innominata, 35 ischium, 37 lachrymal 74 malar, 77 articulations of, 106 nasal 74 articulations of, 103 occipital, 58 articulations of, 99 palate, 81 articulations of 104 parietal 59 articulations of, 100 patella, 45 radius 25 INDEX. 525 Bone, or bones, (Continued)'. rib, 13 sacrum , 8 scaphoid 53 scapula, 17 sphenoid, 66 sphenoid, articulations of, 101 sternum, 11 superior maxillary, 78 articulations of, .... 103 temporal, 26 articulations of, 101 tibia, 45 ulna, 23 vomer, 76 articulations of, 105 Brain, 392 base of 401 convolutions, 363 interior, 403 membranes, 389 Bronchi, 204 c. Canal, auditory, 504 Capsular lig-ament, hip, 134 shoulder, 121 Cartilage, arytenoid, 201 cricoid, 197 Cava, inferior, 369 superior 383 Cerebellum, 415 Cerebrum 392 Clavicle 16 Cfjeliac axis, 331 Coraco-acromial ligament, 121 clavicular, 120 Corpus callosum, 404 fimbriatum 406 526 INDEX. Costal cartilages, ,....,... 15 Cranial bones, 57 nerves, 458 Cranial nerves, eigbth 469 eleventh ■••... 474 fifth, . , 462 first, 460 fourth, 462 ninth, 470 second, 461 seventh, 467 sixth, 467 tenth, , 471 third, 461 twelfth, 474 Crystalline lens, 517 Ear,.. ,... ' •• ■ 503 Elbow, bend of ........ . 313 joint, 125 Epididymis, 195 Epiglottis, 198 Ethmoid bone, 72 articulations of, 102 Eye, 512 tunics of, 514 muscles of, 281 F. Pace, arteries of 293 bones, 74 muscles, -. 277-285 Fauces, isthmus of, 152 Female generative organs, 490 Femoral artery, 343 canal, ... 499 hernia, 499 Fifth nerve, 462 First nerve, 460 INDEX. 527 Fissure of brain, 393 Foot, arteries of 351-351-267 bones, ^^ muscles, -73 ligaments, 147-150 nerves, 453-323 Fossa, spheno-maxillary 89 of skull, anterior, 91 middle and posterior, 91 temporal, °° zygomatic, °° G. Ganglion, cervical, 4-/6 ciliary, or opthalmic, 482 Meckel's 483 otic 484 semilunar, 480 H. Hand, bones of , . . . 2^ ligaments, .... • • • 129 Heart 207 Hernia, femoral, 439 inguial, 494 Hip joint, 1*^4 I. Ileum, 167 Iliac arteries, common 340 external, • • . 341 internal, 355 veins, external, 368 internal 369 Ilium, . • ■ 35 Inferior vena cava, 369 Inguinal canal 406 hernia, 494 528 INDEX. Intestine, large, description of, 178 small, discription of, 178 relations of • 166 Iris, small divisions of ....■•• 516 Ischio-rectal reg^ion, 486 Ischium, 37 Island of Reil, 399 K Kidney relations of, 187 structure of, 188 Knee joint, 139 L. Larynx, cartilages of , . . 196 ligaments of, • ■ • 199 muscles of, 200 Ligaments: acromio-clavicular, 120 ankle, 146 atlanto-axoid, 114 calcaneo-astragaloid, 148 cuboid, 148 scaphoid, 149 common vertebral 112-114 costo- vertebral, ■ .... 150 of elbow,.. 125 of hip, 134 of jaw^, 130 of knee, 139 radio-carpal, 127 radio-ulnar, 124 sacro sciatic 133 of shoulder, . . . . : 121 tibio-fibular 145 Liver, relations of 171 structure of, 185 Lungs, relations of , 205 structure of, 205 INDEX. 529 Tvymphatics : V 386 arm 387 cervical, 388 lower extremity, 387 thorax,.... 388 M. Malar bone,..., 77 articulation of, 106 Manubrium 12 Mediastinum 207 Medulla oblong-ata, 410 Membranes of brain, 380 cord, 417 Munro, foramen of 409 Mouth 151 Muscle, or Muscles : 213 abductor minimi dig-iti (hand), 256 (foot), 275 poUicis (hand), 255 hallucis, 275 accessorius, 275 adductor brevis, 267 long-US, 266 mag-nus, 267 anconeus, 252 arytaenoideus, 261 biceps (arm), 242 (thig-h), 261 brachialis anticus, 243 buccinator, 203 compressor naris 276 constrictor pharyng^eus, inferior 157 medius, 158 superior, 158 coraco-brachialis, 242 crico-arytoenoideus lateralis, 201 posticus 201 530 INDEX. Muscle, or Muscles, (Continued) : crico-thyroid, ..,,,.. 200 deltoid, 237 diaphrag-m,... . 219 dig-astric, . 225 erector spinae...... 233 extensor brevis dig-itorum, 273 extensor carpi radialis brevior, ...... 250 longior, 250 ulnaris, . 252 communis digfitorum 251 indicis,.... 254 long-US digitorum,... ... 270 minimi dig-iti, 252 ossis metacarpi pollicis, 253 primi internodli pollicis, 253 proprius pollicis, 272 of face...... 277 flexor brevis minimi dig-iti, (hand),.. — 256 (foot), 276 digitorum, 275 pollicis (hand),... 255 (foot),. 276 flexor carpi radialis, 246 ulnaris, 247 long-US dig-itorum, 270 pollicis (hand),... 248 (foot),..... 270 ossis metacarpi pollicis, 255 profundus digitorum, 248 sublimis dig-itorum 247 gastrocnemius, 268 gemellus, superior, 258 inferior, 259 g-enio-hyo-g-lossus, 226 g-enio-liyoid,.... 226 gluteus maximus, 257 medius, 258 INDEX. 531 Muscle, or Muscles, (Continued): minimus 259 ofracilis .. = 263 of hand . 254 of hip, 237 iliacus 264 infraspinatus, 239 intercostal • ■ • 235 of larynx,... 200 latissiraus dorsi, _ 231 levator ang-uli scapulae 231 long-US colli, 229 masseter, •. 283 mylo-hyoid 226 of neck 222-229 obliquus abdominus externum 214 internus, 216 obturator externus, 260 internus, 219 omo-hyoid, 225 of palate, 156 pectineus, , . 266 pectoralis major, 235 minor, 236 of perineum, ■ • 488 peroneus brevis 273 long-us, 272 plantaris, 269 platysma myoides, 223 popliteus, 269 pronator quadratus, 248 radii teres, 246 psoas maj^nus, 263 pteryg-oid, external, 284 internal, 285 pyramidalis abdominis 218 pyriformis, 258 532 INDEX. Muscle, or Muscles, (Continued) : quadratus femoris, 259 lumborum 221 rectus abdominis, . ... 217 rectus capitis auticus major, 229 minor 229 lateralis, 229 femoris, 263 rhomboid, 232 sartorius, 262 scalenus anticus 228 posticus, 229 semimembranosus 261 semitendinosus, 261 serratus mag^nus, 237 posticus, inferior, 232 superior, 232 soleus, 269 splenius, 233 sterno-cleido-mastoiu ^ 223 sterno-hyoid, 224 sterno-thyroid, 224 stylo-hyoid, 226 stylo-pharyng-eus, 158 subclavius, 236 subscapulars, 238 supinator brevis, 251 long-US, 250 supraspinatus, 239 temporal, 284 teres major, 240 minor 240 thyro-aryt^noideus, 201 thyro-hyoid, .' 224 tibialis anticus, 271 posticus, ...... 270 transversalis abdominis, ...... 216 trapezius 230 INDEX. 533 Muscle, or Muscles, ( Contiimed ) : triceps extensor cubiti, . . . 243 cruris, 263 vastus externus. . 265 internus, 265 N. Nares, anterior, 95 posterior, 96 Nasal bones, 74 articulations of, 103 Neck, muscles of, 222-229 triangles of, 227 veins of, 281-282 Nerves, or Nerve : 421 anterior crural, 443 anterior interosseus, 435 auditory, 469 auricularis magnus, 424 chorda tympani, . 468 ciliary, 464 circumflex, 438 cranial, .... 458 dental, anterior 465 inferior, 466 posterior, .... 465 descendens noni, 475 dorsal spinal, 439 eighth pair, . 469 eleventh 'pair, 474 external cutaneous, 442 facial, 467 fifth,. . . 462 fourth, 462 frontal. 464 genito-crural, 442 glosso-pharyngeal, 470 gluteal, superior 446 great petrosal, 468-484 534 INDEX. Nerves, or Nerve, (Continued) : g-ustatory, 446 hypoo-lassal, 474 ilio-hypog-astric, 441 ilio-ing-uinal, ... ... 465 intercostal, . 439 intercosto-humeral, , , , 431-439 internal cutaneous, 443 lachrymal, 463 larynofeal, recurrent, , 473 superior, 473 lesser sciatic, 448 long- saphenous, 444 lumbar, 440 ' ' plexus, 440 lumbo-sacral, 445 maxillary, inferior, 469 superior, 464 median, 434 middle cutaneous, , 443 musculo-cutaneous (arm), 430 (leg-), 456 musculo- spiral, 436 ninth, 470 obturator, 443 occipital, small, 424 olfactory, 460 opthalmic, 463 optic, 461 orbital, 464 perineal, 448 peroneal, 456 phrenic, 425 plantar, external, 453 internal, 453 pneumog-astric, 471 popliteal, external, 454 internal, 450 INDEX. 535 Nerves, or Nerve, (Continued) : posterior interosseous, 437 pudic, internal, 447 radial, 437 recurrent laryng-eal, 473 sacral plexus 445 saphaneous, long- 444 short 45 sciatic, great, 44 small, 449 sixth, 467 spinal , accessory, , 474 splanchnic, great, 480 small, 480 subscapular, 429 superficialis colli, 423 suprascapular, 428 sympathetic, 476 tenth, 471 third, 401 thoracic, anterior, , 429 posterior, 428 tibial, anterior 455 posterior, 452 twelfth, 474 ulnar, 432 vagus |71 O. <^)bturator artery 356 externus muscle 260 internus, .... 259 Occipital artery, 295 bone, 58 articulations of, 99 fossa 94 Occipito-atlantal articulation 115 Occipito-axial, 116 536 INDEX. Oesophagus, 159 Omentum, great 164 lesser, ■ • 164 Orbit, . . 96 Orbit, arteries of,... 362 muscles of, 281 Os calcis, 50 innominatum, -. 35 Ovary, • • • • 492 P. Palate bone, • ■ • 81 articulations of, 104 hard,.. 90 muscles of, 156 Palmar arch, deep, 320 superficial, 316 Pancreas, relations of, 173 structure of...... 186 Parietal bones, . 39 articulations of, 100 Patella,-... 45 Pelvis 40 Penis 193 Perineum,. 488 Peritoneum, 163 Pharnyx 153 Pleura, 206 Pouch of Douglas, 491 R. Radial artery, arm '. 315 forearm, 318 nerve, 437 Radius 25 Rectum, relations of, female, 492 male, 170 structure of 180 Renal artery, 340 INDEX. 537 Retina 516 Ribs 13 Rino^. abdominal external, 495 internal, 495 crural, or femoral, 499 S. Sacral arteries 359 foramina, 9 plexus 445 Sacrum 8 Scaleni muscles, 228 Scapula 17 Scarpa's triangle 267 Sciatic artery 357 nerve, g"reat 449 lesser 448 Shoulder joint, 121 Skull, anterior reg-ion, 95 base of, lower surface 89 upper surface, 92 lateral region, 87 vertex 87 Soft palate 152 Spermatic artery 339 canal . 495 Sphenoid bone, 66 articulations of, 101 Sphenoidal fissure ... 95 Spinal cord 417 nerves . 421 Spine in general 10 Splanchnic nerves, 480 Spleen, relations of 172 structure of, 186 sternum, 11 ?>tomach. relations ol 166 structure of, 177 538 INDEX. Subclavian artery, left, ....,..,..,/.,. 325 rig-ht, 299 Sulci of brain, . . 393 Superior maxiliary bone, , , 78 articulation of, 103 Sympathetic nerves, 476 T. Tarsus, bones of, , 49 lio-aments of.. . 148 Temporal bone, - . 62 articulation of, , . , 101 Temporo-maxiliary articulation 130 Testes, ......... ...... 194 Thalami optici, 406 Thyro-hyoid membrane -. . . 199 Thyroid cartilage, 196 Tibia, 45 Tong-ue, 154 Trachea, ......... 203 Trapezium bone, 29 Trapexoid " 29 Triang-le of Hesselbach 298 Scarpa's, 267 Trochanter, g-reat^r. 42 lesser, 42 Turbinated bone, inferior, , 74 middle 73 superior 73 articulations of 105 Tympanum, 505 U. Ulna, 23 Ulnar artery of forearm. ... 315 of hand 316 nerve, 432 Ureter 189 INDEX. 539 TTrethra', female 493 male 190 Uterus. 490 V. Vao-ina - 493 Valves of heart, 207 Valvulae conniventes 180 Vas deferens, = 192 Veins, or Vein : 366 axillar3^ 376 azyg-os, 384 basilic, 375 cardiac, 385 cava, inferior, 269 superior 383 cephalic, 375 cerebral, 377 deep or comites, 366 femoral , 267 of Galen 378 iliac, common 368 external, 368 internal 369 inferior cava 369 innominate, left 383 rijrht 382 jugular, anterior, 377 external 382 internal '. 381 popliteal,.. 367 portal , 36^) saphenrius, lon^, 372 short 372 spermatic 371 subclavian, 376 ulnar, anterior 374 common 374 posterior 374 540 INDEX. Velum, interpositum, 408 Ventricle of brain, third 408 fourth 411 lateral 405 VertebrdB, cervical, 3 dorsal 4 .lumbar 4 peculiar, .. 5 sacral 8 Vesiculse seminales, 192 Vocal cords, true 199 false, 199 Vomer, 76 articulations of 105 W. Willis, circle of, 365 Winslow, foramen oi 165 Wrisber^, nerve of 431 Wrist joint 127 Zinn, ligament of 281 Zygoma 62 Zygomatic fossa, 88 muscles 280 COLUMBIA UNIVERSITY LIBRARIES This book is due on the date indicated below, or at the expiration of a definite period after the date of borrowing, as provided by the library rules or by special arrangement with the Librarian in charge. DATE BORROWED DATE DUE DATE BORROWED DATE DUE 1 i ! • ! i 1 C28(955)100MEE COLUMBIA UNIVERSITY LIBRARIES (hsi.stx) QIVI23T651898C.1 Descriptiveanato