446 THE MECHANICAL FUNCTIONS. 



of each of its toes expanded into a fleshy tubercle, 

 approaching in the form of its concave surface 

 to that of a sucker, and by the aid of which it 

 fastens itself readily to the branches of trees, 

 which it chiefly inhabits, and along which it runs 

 with great agility. 



The Salamander is an animal of the same class 

 as the frog, undergoing the same metamorphoses 

 from the tadpole state. It differs much, however, 

 in respect to the developement of particular parts 

 of the skeleton. The anterior extremities of the 

 salamander make their appearance earlier than 

 the hind legs, and the tail remains as a perma- 

 nent part of the structure. The rudimental ribs 

 are exceedingly small, and the sternum continues 

 cartilaginous. The pelvis has no osseous con- 

 nexion with the spine, but is merely suspended 

 to it by ligaments. The land salamanders have 

 a rounded tail, but the aquatic species, or Tritons, 

 have it compressed vertically ; thus retaining 

 the fish-like form of the tadpole, and the same 

 radiated disposition of the muscles. 



human conformation in its organs of progressive motion. This 

 arises from the exertions which it makes in swimming being 

 similar to those of man in walking, in as far as they both result 

 from the strong action of the extensors of the feet. Hence we 

 find a distinct calf in the legs of both, produced by the swelling 

 of similar muscles. The muscles of the thigh present, also, many 

 analogies with those of man ; particularly in the presence of the 

 long muscle ca'lid the sartorius, the use of which is to turn the 

 foot outwards, both in stepping and in swimming. 



