SKELETON OF THE BATRACHIA. 441 



to notice the leading peculiarities of the skele- 

 tons of this tribe of animals. 



The skeleton of the adult frog is shown in Fig. 

 200 ; from which it will be seen that the spinal 



200 



column is comparatively much shorter than that 

 of fishes, or indeed of any other class of animals; 

 for it consists of only eight vertebrae, exclusive 

 of those which have united to form the os coc- 

 cygis. It was evidently the intention of nature 

 to consolidate the frame-work of the trunk, in 

 which flexibility was not required for progressive 

 motion : the performance of that function being 

 transferred to the hind extremities, which are 

 exceedingly large in proportion to the rest of the 

 body. There is a tendency in every part of the 

 skeleton to develope itself in a transverse direc- 

 tion, while the trunk is shortened as much as 

 possible. 



