340 THE MUSCLES. 



3. Posterior Region. 

 The muscles of this region, divi8il)le into two layers, are:— 



1. Tiie common extensor of the digits— &\denoT extensor of the phalanges of the Horse — 

 divided iiito four tendinous branches which pass to all the fingers, except the thumb. 



2. The proper extensor of the little finger, whose tendon is joined to the brancli of the 

 common exlen^or tliat passes to the auricularis — the lateral extensor of animals. 



3. The posterior ulnar, corresponding to the external iiexor of the metacarpus of tiie Horse. 

 It goes to the epicondyle at the upper extremity of the fifth metacarpal. 



4. Tiie long abductor of the thumb, resembling a portion of the oblique extensor of the 

 metacarpus of animals. This muscle is attached to the posterior face of the ulna and radius, 

 and the upper extremity of the first metacarpal. 



5. The short extensor of the thumb, which is also represented in animals by a portion of the 

 oblique extensor of the metacarpus. 



6. The long extensor of the thumb, arising from the ulna, and inserted into the second 

 phalanx of the thumb. This muscle limits, inwardly, the excavation termed the anatomical 

 snuff-hox. 



7. Tiie proper extensor of the index, whose tendon is confounded with the branch of the 

 common extencor passing to this digit. 



These two latter muscles, blended in the Dog, exist only in a rudimentary state in the 

 other animals. 



We will say nothing of the anconeus, placed in the antibrachial region by anthropotomists, 

 and which has been described in the posterior brachial region. 



Muscles of the Anterior Foot or Hand 

 These will be studied successively in Carnivora, the Pig, Solipeds, and Ruminants. 



A. Muscles of the Anterior Foot or Hand of Carnivora. 

 All the muscles of the human hand are found in that of Carnivora, tome perfectly developed, 

 others quite rudimentary. These muscles are: 1. The short abductor of the thumb. 2. The 

 opponent of the thumb. H. The short flexor of the thumb. 4. An adductor of the index— adductor 

 of the thumb in Man. 5. The cutaneous palmar. 6. The adductor of the small digit. 7. The 

 short flexor of the small digit. S. The opponent of the small digit. 9. The thvee lumbr id. 10. 

 Four interosseous metacarpals. 



1. Short Abductor of the Thumb (Fig. 188, d, 9). 

 This is rudimentary, like the digit it is intended to move, and is situated behind the 

 metacarpal bone of the thumb ; it is composed of very pale fleshy fasciculi, which are continued 

 inferiorly by some tendinous fibres. It has its origin at the carpal arch, and terminates on the 

 metacarpal bone of the thumb, as well as at the external side of the superior extremity ' of the 

 first phalanx. It is a flexor and abductor of the thumb. 



2. Opponent op the Thumb (Fig. 188, d, 10). 

 This vestige of the thick short muscle which bears the same name in Man is situated 

 beneath and within the preceding, in a slightly oblique direction downwards and outwards. 

 Pale and almost entirely muscular, it is attached to the posterior ligament of the carpus and 

 the metacarpal bone of the thumb. Owing to the conformation of this digit in Carnivora, this 

 muscle cannot act as it does in Man in producing the opposition of the thumb ; it only draws 

 it towards the axis of the hand, and is therefore merely an adductor of the thumb. 



3. Short Flexor of the Thumb (Fi^'. 188, d, 11). 

 A very small muscle, deeper in colour than the other two, and situated between them, the 

 adductor of the index, and the fourth interosseous muscle. It is fixed, by its superior extremity, 

 in the mass of the posterior carpal ligament, and attached, below, to the internal side of the 

 first phalanx. It is a somewhat extensive flexor of the thumb. 



4. Adductor op the Index (Fig. 188, d, 12). 

 Synonym.— The adductor of the thumb in Man. 

 Elongated, prismatic, compressed on each side, included between the third and fourth 



' It is necessary to remember that the position of the digits is considered in relation to the 

 axis of the hand— that is, the median line separating the medius from the annularis. 



