[ 1/6 ] 



CLASSIFICATION OF MAMMALIA. 



We propose in the following pages to lay before our readers 

 a sketch of the principal methods which have been adopted for 

 the classification of the Mammalia. 



Animals in general are distinguished from every other form 

 of matter by possessing sensation ; for although nerves have 

 not been detected in some of the more minute and simple 

 forms, yet the living phenomena of these, when attentively 

 studied, sufficiently indicate the existence of this faculty. 

 Every animal has been observed, at least at some period of 

 its existence, to exhibit spontaneous locomotion. An internal 

 digestive cavity or stomach is a third characteristic of this 

 division of organized matter. 



Various — almost infinitely various — as are the outward con- 

 figurations of animals, it has been observed that they are re- 

 ducible to four principal forms : — 1st, A radiated form, as in 

 the polype and star-fish ; 2nd, A jointed symmetrical form, 

 as in the worm and insect ; 3rd, An irregular and mostly un- 

 symmetrical form, where the body is soft, as in the oyster and 

 snail ; 4th, A symmetrical form, supported by an internal 

 jointed column or spine. The last, which is called the ver- 

 tebrated division of animals, is divided into fishes, reptiles, 

 birds, and mammalia. 



The animals of the latter group are those which have always 

 attracted most attention from mankind ; since it is from them 

 that we draw the greatest services, and in them we observe 

 the properties of animal life manifested in the highest degree. 

 The mammalia were first separated from other animals and 

 distinguished as a Class by Aristotle, the founder of Natural 

 History, by whom they were denominated Zootoka, or vivi- 

 parous animals. 



One of the most learned and acute naturalists of the present 

 age (Mr. W. S. MacLeay,) has reduced Aristotle's subdivi- 

 sions of this Class into a tabular form *, which may be con- 

 trasted, without the least disadvantage, with the classifications 

 of the best modern systematists. 



The Greek philosopher first arranges the Zooto/ca, accord- 

 ing to the nature of their locomotive organs, into three sec- 

 tions : — 1st, Dipoda, or bipeds ; 2nd, Tetrapoda, or quadru- 

 peds ; and 3rd, Apoda, or impeds, which comprehends the 

 whale tribe. 



The second of these primary divisions, which includes by 

 far the greater part of the Class, and, in common language, 

 is considered as the Class itself, — the quadrupeds, — Aristotle 



* Linn. Trans., vol. xvi. p. 24. 



