CLASSIFICATION OF ANIMALS. 3&7 



Tertebrated and invertebrated ; those furnished with a back. bone, 

 or vertebral chain for the purpose of inclosing the spinal marrow, 

 and those destitute of such a chain : the secondary divisions consisting 

 of vertebrated animals with warm blood, or blood warmef than the 

 surrounding medium ; and vertebrated animals with cold blood, or 

 blood colder than the surrounding medium : invertebrated animals 

 with blood-vessels, and invertebrated animals without blood-vessels. 

 The system of Blumenbach, in its general divisions, is the same as 

 that of Cuvier, and merely differs in its orders, or other subdi- 

 visions. 



It would be an useless task to run through the whole of the ar- 

 rangements we have now referred to, and explained as to their 

 principles. The scheme of Linnaeus is at present the most popular ; 

 though that of Cuvier presses hard upon it, and may, perhaps 

 hereafter take the lead of it: it is somewhat more abstruse, but 

 considerably more definite ; and offers a noble specimeu of scientific 

 ingenuity, applied to one of the noblest ranks of scientific study. It 

 is to these two methods, therefore, that we shall chiefly confine 

 ourselves. 



Linnaeus divides the whole animal kingdom into six classes. The ^ 



characters of these six classes are taken from the internal structure " 



of animals, in the following manner : 



Class 1. Mammalia, or Mammals, includes all animals that ^ 

 suckle their young. The characters of this class are these : the "* 

 heart has two ventricles and two auricles ; the blood is red and 

 warm ; and the animals belonging to it are viviparous. 



Class 2. Aves, or birds. The characters are the same with 

 those of class 1. excepting that the animals belonging to it are 

 oviparous. ( 



Class 3. Amphibia, or amphibious animals. The heart has but 

 one ventricle and one auricle ; the blood is red and cold ; and the 

 animals belonging to this class have the command of their lungs, 

 so that the intervals between inspiration and exspiration are in some 

 measure voluntary. 



Class 4. Pisces, or fishes. The heart has the same structure, 

 and the blood the same qualities, with those of the amphibia ; but 

 the animals belonging to this class are easily distinguished from the 

 amphibia, by having no such voluntary command of their lun^s 

 and by having external branchiee or gills. 



Class 5. Insecta, or insects. The heart has one ventricle, but no 

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