BATRACHIA. f)l 



genera, however, retain the gills even after the ac- 

 quisition of lungs, and thus are truly amphibious, 

 being qualified to live either in air or water. But, 

 besides these two modes of respiration, there is yet 

 another found in these interesting animals. It is 

 effected through the moist and naked skin, the sur- 

 face of which has the power of extracting oxygen 

 from the atmosphere ; by which Frogs have been 

 known to sustain life for many weeks after the total 

 loss of their lungs. It is. necessary, however, that 

 the surface be moist; and to supply moisture to the 

 skin there is a beautiful provision made in a copious 

 internal reservoir, fitted to contain water. " Every 

 one knows that when a Frog is hastily seized, or 

 even quickly pursued, it voids a considerable quan- 

 tity of water, which is generally but ^erroneously 

 supposed to be the urine. This water is limpid 

 and pure, containing no traces of the usual com- 

 ponent elements of the urinary secretion. It is 

 contained in a sac, which has also been mistakenly 

 believed to be the urinary bladder. This is the 

 reservoir to which I have alluded. When, there- 

 fore, the Frog is happily placed in a damp atmo- 

 sphere or in water, the skin absorbs a quantity of 

 water, which, there is every reason to believe, is 

 secreted into the bladder just mentioned, where it 

 is kept in store until the dryness of the skin requires 

 a supply for the purpose of respiration, when it is 

 again taken up and restored to the surface by which 

 it ha.d been first absorbed."* 



* Bell's Br. Kept. p. 79. 



