THE MUSCLES OF TOE LIMBS. fiS 



naris to the base of the fifth metacarpal. In the hind-limb, 

 there are no homologues of the first two of these muscles. 

 The homologue of the extensor communis is the long extensor, 

 which arises, not from the femur, but from the fibula. The 

 peronmus tertius* passing from the dorsal face of the fibula 

 to the fifth metatarsal, is the only representative of the exten- 

 sor carpi ulnaris. 



On the ventral aspect of the human fore-limb, two deep 

 flexors arise from the radius, ulna, and interosseous membrane, 

 and run parallel with one another, though disconnected, to 

 the digits. These are, on the pre-axial side — the Jlexor poUi- 

 cis longus, to the distal phalanx of the pollex ; and the Jlexor 

 digitorum perforans, to the distal phalanges of the other 

 digits. 



In the hind-limb, two homologous muscles, the flexor hair 

 lucis longus and the flexor digit07'um perforans^ arise from 

 the tibia and fibula and interosseous membrane, and their ten- 

 dons are distributed to the distal phalanges of the digits. 

 But, before they divide, the tendons become connected to- 

 gether in such a way that many of the digits receive tendi- 

 nous fibres from both sources. 



In the fore-limb, there are no other deep flexors, but the 

 internal, or post-axial, condyle of the humerus gives origin to 

 a number of muscles. These, proceeding from the pre-axial 

 to the post-axial side, are the flexor carpi radialis to the base 

 of the second metacarpal ; the palniaris longus to the fascia 

 of the palm ; the flexor perforatus digitorum to the middle 

 phalanges of the four ulnar digits ; the flexor carpi ulnaris to 

 the base of the fifth metacarpal. The sesamoid, pisiform bone 

 is developed in the tendon of the last muscle. 



The only muscle which exactly corresponds with any of 

 these, in the hind-limb, is the plantar is ; which, in Man, is a 

 slender and insignificant muscle proceeding from the outer 

 (post-axial) condyle of the femur to the plantar fascia — and 

 answers to the palmaris longus. In many quadrupeds, as the 

 Rabbit and Pig, the plajitaris is a large muscle, the tendon 

 of which passes over the end of the calcaneal process en- 

 sheathed in the tendo achillis, and divides into slips, which 

 become the perforated tendons of more or fewer of the digits. 



* This muscle, which lies altogether on the dorsal face of the hind-limb, 

 and which 1 have seen only in Man, should not be confounded, as it often is, 

 with one or more muscles, the peroncni itii, iti, et iti digiti, which are very 

 often developed in other Mammalia, but arise on the ventral face of the fibula, 

 and send their tendons below the external malleolus to the extensor sheuthj 

 of the iflli, *)urth and even third digits. 



