3i8 



AMPHIBIA 



The hind legs of frogs are long, giving a good leverage in jumping. 

 The tibia and fibula are united and the proximal row of tarsals is 

 reduced to two, greatly elongated and known as the tibiale (astragalus 

 or talus) and fibulare (calcaneum). The distal tarsals are reduced to a 

 total of three, bearing five 'true' digits and an extra one, the calcar or 

 prehallux. 



semL m 



Fig. 188. Deeper dissection of muscles of back 

 of frog. 



i.lr. inter-transversarii; ur. urostyle; v. vertebra; other 

 letters as Fig. 187. (Partly after Gaupp.) 



1 1 . The back and belly muscles of Amphibia 



With the change in the method of locomotion the muscular system 

 has become greatly modified from that found in fishes. In urodeles, 

 which still use the old method and hence may be said to swim on land, 

 the dorsal musculature is well developed (Fig. 189), but in anurans the 

 dorsal portions of the myotomes, the epaxial musculature, no longer 

 have to produce the locomotory effect by lateral flexion. They remain 

 in frogs only as muscles that bend the body dorsally, serving to brace 

 the vertebral column on the sacrum (Figs. 187 and 188). Short 

 muscles run between the vertebrae, and dorsal to these is a continuous 

 sheet of longitudinally arranged fibres, the longissimus dorsi muscle, 

 running from head to sacral vertebra and urostyle. This muscle, 



