662 MAMMALIA. 



muscles could not be expected : thus as the movements of pro- 

 nation and supination are, from the immovable condition of the 

 bones of the fore-arm, impracticable in the CETACEANS, the RU- 

 MINANTS, the SOLIPEDS, and others, the pronators and supina- 

 tors are denied; or, if their representatives exist, they become 

 simply assistants in flexion and extension. The flexors and exten- 

 sors of the wrist are pretty constant, but the muscles devoted to 

 the hand and fingers will vary in almost every order. The pal- 

 maris longus, although generally present where the hand is flexi- 

 ble, is wanting where its action upon the palmar fascia would be 

 useless, as, for example, in the ungulate tribes. 



In quadrupeds there are two extensor tendons appropriated to 

 each of the fingers that correspond to the four outer fingers of the 

 human hand ; whilst in Man the index and little fingers only have 

 auxiliary extensors. 



The abductor and extensor muscles of the thumb are not so per- 

 fectly developed in any animals as they are in the human hand. 

 The short extensor is, in fact, wanting even in Monkeys ; and in 

 the lower orders of quadrupeds even the extensor longus and 

 abductor are blended together, or totally wanting. 



The deep and superficial flexors of the fingers are very generally 

 met with, the number of tendons furnished by each corresponding 

 of course to that of the fingers themselves ; but in the Solipeds 

 the two muscles are almost blended together. Even in the Rumi- 

 nants, although these muscles remain separate, their tendons be- 

 come confounded together, and divide again, to be inserted into 

 the phalanges to which they are appropriated. In these Ungu- 

 lata too, as we need scarcely say, the lumbricales and mterossei 

 are quite deficient; and the short muscles of the thumb are com- 

 pletely developed only in Man and in the Quadrumana. 



It is in the human species only that the lower extremities are 

 organized so as to maintain the body in the erect position, and, in 

 consequence, the glutsei muscles in the human body are enormously 

 developed when compared with those of the lower animals ; but the 

 other muscles derived from the pelvis and thigh present but slight 

 differences throughout the whole class under consideration. In the 

 leg and foot likewise it is not difficult to identify the muscles that 

 correspond to those found in the human subject, but, as in the an- 

 terior extremity, modified in their disposition and mode of insertion 

 in accordance with the construction of the skeleton. 



The articulations whereby the different pieces composing the 



