Vl.J 



THE COMMON FROG. 



69 



there are but seven, the eighth vertebra (to the 

 transverse processes of which the haunch bones are 

 attached) having become soHdly joined in one bone 

 with the coccvx. 



In all higher vertebrates, i.e. in all beasts, birds, 

 and reptiles, the head is supported on an especially 

 ring. like vertebra which — because it so supports — is 

 called the atlas, and this (in almost all) can turn upon 

 a peculiar vertebra termed (from this circumstance) 



^^ 



Fig. 34. — The Atlas VerteHra of Man. s, rudiment of neural spine ; d. tubercular 

 process; /, capitular process ; a, articular surface for skul ; hy, plate of boae 

 holding the pbce oi a craaium, and articulating with the odontoid process of 

 the axis vertebra. 



the axis, and provided with a toothlike [odontoidY 

 process, round which, as round a pivot, the '' atlas " 

 works. Nothing of the kind exists in any fish. 



Fig 35.— Lateral, Dorsal, and Vencial view of first Vertebra of Ampkiutna. 



In the frog (and in all its class) we find but a single 

 vertebra representing these two, but in some allied 

 forms, e.g. in Amphiiinia, this vertebra develops a 



^ From f Sot/s, a tooth, and HZos, form. 



