52 THE ANATOMY OF VERTEBEATED ANIMALS. 



axial bone of the leg, the fibula. The long head of the 

 biceps femoris, which proceeds from the ischium, appears to 

 have no representative in the fore limb. 



In the fore limb, a muscle, the pronator teres, passes 

 obliquely from the post-axial condyle of the humerus to 

 the radius. In the hind limb, a corresponding muscle, the 

 poplitceus, proceeds from the post-axial condyle of the 

 femur to the tibia. The pronator quadratus, which passes 

 from the tdna to the radius, has its analogue, in some 

 Marsupialia and Beptilia, in muscles which extend from 

 the fibula to the tibia. 



The Muscles of the Digits. — The remaining muscles of 

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

 attached either to the basi-digital( metacarpal or metatai'sal) 

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

 daiy connections with bones of the tarsus or cai-pus. The 

 plan iipon which they are aiTanged, 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 the dorsal aspect this digit presents : first, attached to 

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

 muscle, the extensor carpi ulnaris. Secondly, spreading out 

 over the phalanges into an aponeurosis, which is principally 

 attached to the first and second, is a tendon belonging to 

 another muscle, the extensor minimi digiti. Thirdly, enter- 

 ing the same expansion is one tendon of the extensor com- 

 munis digitorum. 



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

 base of the metacai-pal, the tendon of a distinct muscle, the 

 flexor carpi ulnaris ; secondly, arising from the sides and 

 ventral face of the metacarpal, and inserted into either side 

 of the base of the proximal phalanx, two muscles, the inter- 

 ossei ; thirdly, inseried into the sides of the middle phalanx 

 by two slips, a tendon of the flexor perforatus ; and f oxu'thly, 

 passing between these two slips, and inserted into the base 



