THE ANTERIOB LIMBS. 



119 



Fig. 78. 



is wilier and less elongated than tlie internal. They articulate with each other and with 

 the first phalanx, by small diarthrodial facets. 



The second phalanx is hollowed internally by a small medullary cavity. 



The ungual phalanx, as a whole, resembles one of tlie lateral moieties of the os pedis of 

 Solipeds. This phalanx has no complementary fibro-cartilage, basilar process, or retrossal 

 eminence, nor yet a cavity for insertion on the sides of the pyramidal eminence. The semilunar 

 crest is replaced by an obtuse, thick, and rugged ridge, which occupies quite the posterior limit 

 of the inferior face of the bone. Three large canals penetrate the third phalanx— two to the 

 base of the pyramidal eminence, and one towards tho origin of the preplantar fissure. They 

 form, in the interior of the bone, a vast sinus, giving rise to several vascular canals which open 

 on the surface. There is only one foramen at the base of the pyramiilal eminence in the smaller 

 Buminants. 



B. Camel, — In this animal, there are in each digit only three phalanges and two large 

 sesamoids. The direction and form of these phalanges 



differ notably from what is seen in Ruminants. The 

 first phalanx is long, very oblique, constricted in the 

 middle, and very thick at both ends. On the superior 

 articulating surface is a single glenoid cavity, divided 

 posteriorly by a median groove. The inferior surface is 

 prolonged on tlie posterior face of the bone, wliich is 

 converted into a kind of pulh y. The second phalanx is 

 nearly horizontal, and much flattened above and below. 

 The ungual phalanx is somewhat like an irregular 

 trifacial pyramid with a blunt summit; neurits base, 

 on its upper face, it has a roughened tubercle. 



C. Pig. — The Pig has four complete digits articu- 

 lating from the mefacarpals ; the thumb is absent. The 

 index and auricularis — or fourth and fifth digits — are 

 short, and do not usually rest on the ground (Fig. 

 76). 



D. Dog, Cat, Rabbit.— The five digits of the 

 7 og aii<l Cat are exactly analogous to those of Man. 

 Thus, the external corresponds to the auricularis, the 

 second to the annularis, the third to the medius, the 

 fourth to the index, and the internal to ti.e thumb. 

 The latter, very small, has only two phalanges, and does 

 not come into contact with the ground. Each of the 

 first four is composed : 1. Of a first phalanx, to which are 

 annexed two sesamoids. 2. A second phalanx, which 

 represents a veritable long bone. 3. A conical phalan- 

 gette, pointed, curved downwards, and hollowed at its 

 base by a circular groove, in whieh is lodged the matrix 

 of the claw. The .small sesamoid (or navicular bone) 

 is absent, but is replaced by a prominence of the ungual 

 phalanx. The auricularis and index are alike, and not 

 80 long as the annularis and medius, which are the same 

 in length. 



HCTMAN SCAPULA (EXTERNAL ASPECT). 



1, Supra-spinous fossa; 2, infra-spinous 

 fossa ; 3, superior border ; 4, supra- 

 scapular notch; 5, anterior or axil- 

 lary border ; 6, head of the scapu- 

 lar and glenoid cavity ; 7, interior 

 angle ; 8, neck of the scapula ; 9, 

 posterior border; 10, spine; 11, 

 triangular smooth surface, over 

 which the tendon of the trapezius 

 glides, with the tubeixulum spinae 

 scapulae between it and 10 ; 12, 

 acromion process ; 13, nutrient fora- 

 men ; 14, coracoid process. 



Comparison of the Thoracic Limb of Man with that of the Domesticated Animals. 



A. Shoclder. — The shoulder of man has for its biise two well-developed bones — the scapula 

 »nd clavicle. The scapula (Fig. 78) is more distinctly triangular than that of all the domesti- 

 cated animals; its vertebrtil border is also more extensive. The scapular spine, verv elevated 

 is continued by an acromion whose extremity reaches to above the scapulo-humeral articulation. 

 The latter is separated from the remainder of the spine by a constriction called the pedicle of 

 the acromion. The coracoid process is voluminous, and resembles a semi-flexed finger. The 

 clavicle extends from the acromion to the sternum ; it is flattened above and below, and flexed 

 like an italic S. This inflection of the clavicle is more pronounced in the male than the 

 female. 



B. Arm.— The humerus (Fig. 79) of Man is much longer than that of animals. Its dia- 

 physis is prismatic, and divisible into three faces ; the deltoid imprint has the form of a V with 

 its point directed downwards. The voluminous articular head is turned inwards ; the bicipital 



