LECTURE VII. 
2 
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, v 
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 Avell 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 tliose 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,. 
Da 
