GENERAL CLASSIFICATION OF ANIMALS. 1? 



In animals of the second kind, there is no skeleton, and of 

 course no vertebral column. The brain and nervous system 

 are not therefore protected by any bony covering. These 

 organs do not resemble the corresponding-ones of the verte- 

 bral animals ; they are less distinct and apparently less im- 

 portant. They have not many common points of resemblance, 

 but as they none of them possess a back-bone or a skeleton, 

 they are denominated from this circumstance INVERTEBRAL 

 animals, i. e. without vertebrae. 



The two first grand divisions of the animal kingdom, then, 

 are, 1. VERTEBRAL, such as man, quadrupeds, birds, fishes, 

 &-c., having a skeleton and red blood ; and, 2. INVERTEBRAL, 

 such as worms, insects, shell-fish, &-c., having no skeleton 

 and white blood. 



But in examining the first division, we find further differ- 

 ences. Man, quadrupeds, whales, and birds, have all a tem- 

 perature above that of the air or water, in which they reside. 

 Their flesh is warm, and as this warmth is supposed to depend 

 upon the temperature of the blood, we call them warm-blooded. 

 On the other hand, frogs, toads, lizards, serpents, and fishes, 

 have all a temperature varying but little from that of the ail 

 or water in which they live. They impart to us, when we 

 touch them, the sensation of cold. Hence we call -them 

 cold-blooded. Here then is afforded ground for a subdivision 

 of the vertebral animals into the warm-blooded and the cold- 

 blooded. 



Again, the warm-blooded animals are capable of being 

 divided into two classes. A part of them produce their young 

 alive, nourish them during infancy by their own milk from 

 organs called their mammae, or breasts, and are hence called 

 mammalia or mammiferous animals. This class includes man, 

 quadrupeds, whales, porpoises, &c. Another part produce 

 their young by means of eggs which they hatch by the heat 

 of their bodies, and support them by food which they pro- 

 vide for them as soon as they come out of the egg. This clasfi 

 includes birds. 



The cold-blooded vertebral animals also form two classes. 

 The first contains those which breathe air only, and cannot 

 exist without it, as tortoises, frogs, serpents, &c. These are 

 called reptiles. The second contains those which breathe 

 by gills or branchiae, through the medium of the water. This 

 chiss includes all the true fishes; for the cetaceous animals 

 mentioned above are not properly to be numbered among 

 fishes. 



