2 LECTURE VII. 



tion is the same; and therefore in a general way 

 of speaking they may be properly said to have 

 what is called a unilocular heart, or furnished but 

 with a single cavity. 



The blood of the Amphibia is always far less 

 warm than that of quadrupeds and birds; for which 

 reason they are often distinguished by the title of 

 cold-blooded animals : in this particular they re- 

 semble fishes, which are also, comparatively speak- 

 ing, cold-blooded animals. 



The red particles of the blood itself both in 

 the Amphibia and Fishes, as well as in birds, are of 

 an oval shape; not round as in the viviparous qua- 

 drupeds. Their appearance when highly mag- 

 nified, is that of an oval transparent vesicle or 

 bladder, with a smaller and somewhat rounder 

 central one inclosed : they are also much larger in 

 , proportion. With respect to the structure of the 

 lungs in the animals of this tribe, the best method 

 of giving a clear general idea will be to observe, 

 that the lungs in most animals which are furnished 

 with those organs, consist of vesicles or air-blad- 

 ders more or less large in proportion to the blood- 

 vessels distributed between them. Now in qua- 

 drupeds the vascular system is so extremely large, 



