RESPIRATION IN REPTILES. 149 



the different orders, or tribes, we shall find a great di- 

 versity in the situation, forms, and structures of these dif- 

 ferent parts. In the reptiles, as the Frog and Snake, 

 the epiglottis is wanting, the food being carried over the 

 aperture of the trachea by the tongue. 



The lungs of reptiles are large sacks situated on each 

 side of the chest, into which the bronchia lead. 



The mechanism by which the air is taken into the 

 lungs in these animals, is exceedingly curious, and quite 

 peculiar to this tribe, it having been for a long time a 

 subject of controversy among naturalists, how these crea- 

 tures breathed. 



Respiration of the Frog. As an example of the man- 

 ner in which breathing is carried on among reptiles, con- 

 sisting of the Chamelion, Lizards, Snakes, and others, 

 we will describe that of the Frog, a race well known to 

 all our readers. Mr. Bell, in his anatomy, has described 

 this process at length ; but the following extract is suffi- 

 cient for this work. 



On watching a Frog ever so carefully, when it is still 

 and quiet, we can scarcely discover any signs of respir- 

 ation, since it never opens its mouth to receive the air, 

 and there is no motion of the sides to indicate that it 

 breathes. Yet on any sudden alarm, we see the animal 

 blowing itself up, as if by some internal power, while at 

 the same time its mouth remains entirely closed. We 

 may perceive, however, that its throat is in motion, as 

 if the reptile was so careful of its mouthful of air, as to 

 transfer it backwards and forwards between its mouth 

 and lungs. But if we direct our attention to the nostrils, 

 we may observe in them at twirling motion at each 

 movement of the bag under the throat ; for it is through 

 the nostrils that respiration is carried on in this animal, 

 there being no other communication between the lungs 

 and the air. 



The jaws are never opened but for eating, which is 

 only for the instant that it darts out its tongue, and as 

 quickly returns it with an insect. The throat, and sides 

 of the mouth, form a kind of bellows, to which the nos- 

 trils are the inlet ; and it is by the contraction of this 

 13* 



