86 REPTILES DIAGRAM 5. 



CLASS OF REPTILES. 



DIAGKAM 5. 



Reptiles are vertebrated animals ; that is, they have a skeleton 

 like mammals, birds, and fish, but their shape is very different, 

 as may be seen by the tortoises, lizards, serpents, frogs, and 

 salamanders, which are reptiles. They are at once distinguished 

 from the birds and mammals in not having warm blood ; they 

 are cold. Among all animals, birds and mammals alone have- 

 warm blood. 



The bodies of many reptiles are covered with scales. They 

 nearly all, like birds, lay eggs from which the young ones 

 emerge ; they breathe air by lungs like mammals and birds, but 

 their respiration is very slow, and their heart does not beat so 

 fast. The rapidity of their breathing increases a little when 

 they are warm, and they are then sometimes very lively ; but 

 cold benumbs them, and they can scarcely move. They are 

 generally silent animals, only uttering a rather low hissing. 

 The frogs must be excepted, which make a loud and very 

 disagreeable croaking. 



Eeptiles have been divided into four orders; the Chelonia, 

 which comprises the tortoises ; the Saurians, which are the 

 lizards, the crocodiles, and the blindworms; the Ophidians, 

 including all serpents, whether venomous or not ; lastly the 

 Batrachiam, under which are arranged the frogs, salamanders 

 and newts. These four words are derived from the Greek, and 

 exactly indicate in that language the animals which represent 

 each order. 



