ZOOLOGY. 



off 

 vt 



Fig. 287.* 



but little oxygen, and can remain alive for along tina- without 

 air; but this activity dill'crs according to the temperature of 

 the season. The lungs are composed of large cells, and in 

 consequence are not very vascular. The tortoise and turtle 

 swallow the air, as it were, the 

 ribs being immovable; there is 

 no natural division between the 

 chest and the abdomen, and respi- 

 ration is not regular; in serjH-nts 

 one lung is rudimentary (Fig. 288). 

 468. All reptiles are cold- 

 blooded animals, and the tem- 

 perature of their bodies rises and 

 falls with that of the surrounding 

 medium. A heat of from 40 to 50 6 

 (Centigrade scale) is quickly fatal 

 to most of them, and the effects of 

 cold are well known, for during 

 winter most reptiles eat no food, and 

 do not even digest what happens 

 to be in their stomachs ; the respiration becomes slower, and 

 their whole state resembles hybernation. 



469. Like birds, they lay eggs, and their young do not 

 suckle ; they have no mamma3 ; but there is this peculiarity, 

 which also happens in some fishes, that in some the young are 

 hatched before being born, as in the viper; and such animals 

 are called ovoviviparotts. 



The young reptile, on quitting the egg presents nothing 

 anormal; it resembles its parent in its mode of respiration, 

 general structure of the body, and external form. 



470, Reptiles generally abandon their eggs when laid, 

 and the young are developed by the heat of the external 

 atmosphere; but there is one remarkable exception in the 

 great Indian serpent, called python, which hatches its eggs, 

 during which period its own temperature will rise to 40. 



* Heart and large vessels of the Crocodile : v, v, veins which bring back 

 blood from different parts of the body to the right auricle (od) ; vt, the 

 two ventricles, internally separated by a partition ; up, the two pulmonary 

 arteries proceeding from the right ventricle to the lungs ; a, a vessel pro- 

 ceeding from the same ventricle to the descending aorta; vp, pulmonary 

 veins carrying the arterial blood from the lungs to the left auricle (og), from 

 whence it passes into the left ventricle, and thus enters the aorta (ao) and 

 into the two arteries (cc) which proceed to the head, &c. [The letters ao 

 in the above figure have been inadvertently placed on the. right auricle 

 as well as on the descending aorta. B. E.] 



