CHAPTER X 

 THE MUSCLES OF THE HIND-LIMB 



IN the hind-limb we may make a brief review of those 

 muscles which are the homologues of the rotators, the 

 history of which we have followed in the fore-limb. The 

 power of rotation of the second segment of the hind-limb 

 is, as we have seen, very readily lost when any supporting 

 function is demanded of the limb. This demand for 

 support is made at the outset of terrestrial life, and, as 

 a consequence, the rotator muscles of tibia and fibula 

 undergo a change very early in the vertebrate series. 



In Cryptobranchus japonicus there is a muscle which 

 arises from the upper and outer aspect of the fibula, and 

 is inserted to the inner border of the tibia at a lower level. 



This muscle rotates the tibia around the fibula; it 

 corresponds to the ulnar portion of the M. pronator radii 

 teres of the arm, and it is named M. pronator tibiae. 



Superficial to this is a longer muscle, which, arising 

 from the outer condyle of the femur, passes to the inner 

 side of the foot. This muscle is the M. pronator pedis, 

 and though the comparison cannot be maintained for all 

 its connections, it contains the element homologous with 

 the humeral portion of the M. pronator radii teres. In 

 the hind-limb there is perhaps no true homologue of the 

 whole of the M. pronator quadratus of human anatomy, 

 but the M. accessorius is, in all probability, derived from 

 an element equivalent to its lowest carpal fibres. The 

 interosseous M. tibio-fibularis is present upon a deeper 

 plane. 



In Varanus, as an example of a reptilian form whose 

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