2 AMPHIBIA. 



Boerhaave, Haller, &c. &c. and only occasionally 

 called in question on viewing in some animals of 

 this tribe a seemingly different structure. Thus 

 the French Academicians of the seventeenth cen- 

 tury pronounce the heart of an Indian land tor- 

 toise, which they examined, to have, in reality, 

 three ventricles instead of one. Linna3us, in his 

 Systema Natura?, acquiesces in the general doc- 

 trine, and accordingly makes it a character of 

 this class of animals. Among later physiologists, 

 however, there are not wanting some who think it 

 more correct to say, that the hearts of the Am- 

 phibia are in reality double, or furnished with two 

 ventricles, with a free or immediate communica- 

 tion between them. 



The lungs of the Amphibia differ widely in their 

 appearance from those of other animals ; consist- 

 ing, in general, of a pair of large bladders or mem- 

 branaceous receptacles, parted, in the different 

 species, into more or fewer cancelli or subdivi- 

 sions, among which are beautifully distributed the 

 pulmonary blood-vessels, which bear but a small 

 proportion to the vesicular part through which 

 they ramify ; whereas, in the lungs of the Mam- 

 malia, so great is the proportion of the blood- 

 vessels, and so very small are the vesicles, or air- 

 cells, that the lungs have a fleshy rather than a 

 membranaceous appearance. In the Amphibia, 

 therefore, the vesicular system may be said greatly 

 to prevail over the vascular ; and in the Mammalia 

 or warm-blooded animals, the vascular system to 

 prevail over the vesicular. 



