20 GENERAL CHARACTERS OF MAMMALIA. 



Viviparous, and provided with teats, to suckle "] (Classes.) 

 their young. 



Lungs; respiration simple ; blood warm ; circu- }- Mammalia. 

 lation double and complete ; heart with four dis- 



" ' --- J 



tmct cavities. 



Oviparous, and 

 without teats. 



f Respiration double; 

 blood warm ; circula- 

 tion double and com- } Birds. 



Respiration '* heart with four 

 aerial; with J ^tirict cavities. 



lungs. ' Respiration simple; . 

 I blood cold ; circulation \ 



incomplete; heart ge. \-Reptiles. 

 I nerally with but th:ee I 

 L cavities, j 



Respiration aquatic ; with branchia; > . , 

 .blood cold; heart wilh but two cavities. \ * lsfte8 ' 



LESSON II. 



MAMMALIA Peculiarities of organization of Animals of this 

 Class. Division into orders. 



CLASS OF MAMMALIA. 



GENERAL CHARACTERS OF THE MAMMALIA. 



1. The class of mammalia is composed of man, and all ani- 

 mals which resemble him in the most important parts of their 

 organization ; this class is naturally placed at the head of the 

 animal kingdom as comprising those beings whose movements 

 are most varied, whose sensations are most delicate, faculties 

 most numerous, and intelligence most developed ; it interests us 

 more than any other class, because it includes the most useful 

 animals, either in affording us nourishment, assisting in our 

 labors, or contributing towards our manufactures. 



2. The mammalia are born alive, and in the early period of 

 life, are nourished by the mother with milk, which is formed in 

 glands called mammce, or teats; animals of this class alone are 

 provided with these organs, and for this reason they are called 

 mammalia, or mammiferous animals. 



What is the character of the respiration in Reptiles ? What is the char- 

 acter of the blood of Reptiles ? Is the circulation complete ? How many 

 cavities has the heart in the class of Reptiles ? 



What is the character of the respiration of fishes ? How many cavities 

 has the heart ? Is the blood of fishes warm or cold ? 



1. What animals are included in the class of mammalia? Why is this 

 class placed at the head of the animal kingdom ? 



2. How are animals of the class mammalia nourished ? Why are they 

 called mammalia or mammiferous 1 



