50 TUE ANATOMY OF VERTEBRATED AXIIIAI.S. 



liquely fiom the post-axial condyle of the humerus to the radi- 

 us, in the hind-limb, a corresponding muscle, i'm' 'i/uiillt(inis^ 

 proceeds from the post-axial condyle of the femur to the tibia. 

 The pronator quadnitas, which passes from the ulna to tlie 

 radius, has its analogue, in some 3l(trsi(pialia and Reptilia, 

 in muscles which extend from the fibula to the tibia. 



The Muscles of the Digits. — The remaining muscles of llie 

 two limbs are, primarily, muscles of the digits, and are at- 

 tached either to tlie basi-digital (metacarpal or metatarsal) 

 bones, or to the phalanges, though they may acquire second- 

 ary connections \vith bones of the tarsus or carpus. Tlie 

 plan upon which they are arranged, when they are most com- 

 pletely developed, will be best understood by commencing 

 with the study of their insertion in any one of those digits 

 which possesses a complete set ; such, for example, as the 

 fifth digit of the manus, or little finger, in Man and the higher 

 Primates. 



On tlie dorsal aspect this digit presents : first, attached to 

 the base of its metacarpal bone, the tendon of a distinct mus- 

 cle, the extensor carpji ulnaris. Secondly, spreading out over 

 the phalanges into an aponeiiiosis, which is principally at- 

 tached to the first and second, is a tendon belonging to another 

 muscle, the extensor minimi di<jiti. Thirdly, entering the same 

 expansion is one tendon of the extensor communis digitorum. 



On the ventral aspect there are : first, attached to the base 

 of the metacarpal, the tendon of a distinct muscle, the flexor 

 carpi ulnaris ; secondly, ai-ising from the sides and ventral face 

 of the metacarpal, and inserted into either side of the base of 

 the proximal phalanx, two muscles, the interossei ; thirdly, 

 inserted into the sides of the middle phalanx by two slips, a 

 tendon of the flexor perforatus ; and fourthl}', passing be- 

 tween these two slips, and inserted into the base of the distal 

 phalanx, a tendon of the flexor perforans. Thus there are 

 special depressors, or flexois, for each segment of the digit. 

 There appear, at first, to be but three elevators, or extensors, 

 but, practically, each segment has its elevator. For the ten- 

 dons of the extensor CO mtnunis and extensor mini)ni digit! are 

 attached to the middle and the proximal phalanges; and the 

 distal phalanx is specially elevated by the tendons of two Ut- 

 ile muscles, which, in Man, are usually mere subdivisions of 

 the interossei, and pass upward, joining the extensor sheath, 

 to be Snally inserted into the distal phalanx. 



The fifth digit of the pes, or little toe, sometimes presents 

 the same disposition of muscles, name! 3' : 



