476 



TEXTBOOK Of zoology 



The skin not only protects the underlying tissues from excessive 

 light but also has other functions. With its pigment it helps to 

 regulate temperature by transformijig light into heat. A most im- 

 portant function is its use as a respiratory organ. As previously 

 mentioned, one large group of salamanders, the plethodontids, lack 

 lungs and use the skin and buccal cavity for respiration. During 

 hibernation, practically all of the respiration of frogs is taken care 

 of through the skin. In Africa there is a frog, with greatly reduced 



^ 5^ 



Pig. 263. — "Hairy frog." (Redrawn and modified from Noble, AmpMiia of North 

 America, publislied by McGraw-Hill Book Company.) 



lungs, which, in the male sex, has developed a strange aid to respi- 

 ration. It has patches of vascular villosities on the thighs and sides 

 to such an extent that it has been named the ''hairy frog." These 

 villosities help provide sufficient oxygen for its increased metab- 

 olism during the breeding season. 



Since amphibiajis have moist skins, they are in constant danger 

 of drying out, and therefore seek moist places where they may 

 absorb water through their skins. Most of them are nocturnal in 



