66 



THE COMMON FROG. 



[chap. 



has also been proved by the experiment of confining 

 frogs in cages under water for more than two months 

 and a half, and by the cutting out of the lungs, the 

 4' creature continuing to live without them for forty 

 days. Indeed it is now certain that the skin is so 

 important an agent in the frog's breathing that the 

 lungs do not suffice for the maintenance of life 

 without its aid. 



It is no less true that in Batrachians which breathe 

 by means of permanent gills—as, e.g. the Axolotl — 



Fig. 30.- 



- Backbone of the Frog (dorsal 

 aspect). 



Fig. 31. — Backbone of the Frog (ventral 

 aspect) 



such gills are not necessary to life, as the late M. Aug. 

 Dumeril and Dr. Giinther have established by cutting 



