276 TBE MUSCLES. 



the radius, the interosseona nponeuroais, and the coronoid process of the ulna ; on the 

 other part,' to the second phalanx of the thumb. 



8. The square pronator, a thick, quadrilateral muscle with transverse fibres, situated 

 at the deep and inferior portion of the fore-arm. This muscle in the Dog is much more 

 extensive in length. 



B. External Region. 



The muscles of this region are four in number, two of which, the supinators, are only 

 represented in Carnivorous animals : — 



1. The long supinator forms a prominent mass at the bend of the elbow. It Is 

 attached to the inferior third of the external border of the humerus, and to the base of 

 the styloid process of the radius. It is a flexor of the fore-arm, not a supinator, as its 

 name indicates. 



2. The first external radial is represented by a portion of the anterior extensor of the 

 metacarpus of animals. It commences at the inferior part of the external border of the 

 humerus, and terminates at the posterior part of tlie base of the second metacarpal. 



3. The second external radial, also represented by a portion of the anterior extensor 

 of the metacarpus, terminates at the base of the third metacarpal. 



4. The sliort supinator, a muscle bending round the 'ipper third of the radius, is the 

 essential agent in supination. 



0. Posterior Region. 



The muscles of this region, divisible into two layers, are : — 



1. Tlie common extensor of the digits — anterior extensor of the phalanges of the Horse 

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



2. The proper extensor of the Utile finger, whose tendon is joined to the blanch .of the 

 common extensor that passes to the auricularis — the lateral extensor of animals. 



3. The posterior ulnar, corresponding to the external flexor of the metacarpus of the 

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



4. The Imig abductor of the tliumh, resembling a portion of the oblique extensor of 

 the metacarpus of animals. Tiiia 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 tlie tliumb, 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 mu=cle limits, inwardly, the excavation termed the 

 anatomical snuff-Iiox. 



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

 the common extensor passing to tliis digit. 



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

 the other auimals. 



We say nothing of the anconeus, placed in the antibrachial region by anthropoto- 

 mists, and which has been described in the posterior brachial region. 



MCSCXES OF THE ANTERIOK FOOT OB HAND. 



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

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



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

 developed, others quite rudimentary. These muscles are: J, The short abductor of the 

 thumb ; 2, The opponent of the timmb ; 3, The short flexor of the tlmmb ; i, An adductor 

 of the index— adductor of the thumb in Man ; 5, The cutaneous palmar ; 6, The adductor 

 of the STnall digit; 7, The short flexor of the small digit; 8, 'J'he opponent of the small 

 digit; 9, The three Zumin'ci ; 10, 'Four interosseous metacarpals. 



1. Short Abductor of the Thumb. (Fig. 125, 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 tome 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. 



' 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 



