LECTURE VIII. 
HE course of our Zoological investigations has 
now led us to a very extensive tribe of Animals, 
distinguished by the title of Fishes. Like the 
Amphibious animals their heart, in the language 
of anatomists, is unilocular, or consists but of one 
chief cavity, and their blood is far less warm than 
that of the higher order of animals, as quadrupeds 
and birds : the red particles of their blood are also 
of an oval shape. The organs of breathing in 
Fishes, analogous to the lungs in quadrupeds and 
birds, are distinguished by the name of gills, and 
consist of a vast number of ramifications of blood- 
vessels, curiously disposed in rows, and supported 
on a certain number of bony arches, generally 
four, on each side the breast. By the gills the 
air contained in the waters they inhabit, is sup- 
posed to afford oxigen to the blood in its passage 
through the very delicate ramifications of the 
blood-vessels on the gills j so that the same pro- 
