CLASS AMPHIBIA. 



85 



The skin is very soft and moist, quite destitute of 

 scales, and very loosely attached to the muscles beneath. 



pjg 38.— The common Frog(iJana te^nporaria). 



The animal can to a great extent breathe by means of the 

 porous skin, and it can thus spend a long period under 

 water without the necessity of using its lungs. In an 

 ordinary way, however, it breathes air directly by means 

 of the lungs, and as it possesses no movable ribs, it obtains 

 the air necessary for breathing by a process resembling 

 swallomng. Hence it is possible to suffocate a Frog, in 

 the summer time, when the animal is active, simply by 

 holding its mouth open, and thus preventing its swallow- 

 ing the air required for breathing. 



The mouth is furnished with a row of minute teeth 

 attached to the upper jaw ; but the lower jaw is toothless. 

 The tongue is fleshy, and instead of being rooted behind, 

 it is fixed to the front of the mouth, so that its point is 

 directed down the throat. The animal can protrude it 

 to a considerable length, and uses it for the purpose of 

 catching the small animals upon which it lives. The 

 digestive system is well developed, but calls for no 

 especial mention. 



