THE 



ANIMAL KINGDOM, 



Class REPTILIA. 



Reptiles have the heart disposed in such a 

 manner, as that, on each contraction, it sends into 

 the kings only a portion of the blood which it has 

 received from the various parts of the body, and the 

 rest of that fluid returns to the several parts, with- 

 out having passed through the lungs, and undergone 

 the action of respiration. 



From this it results, that the oxygen acts less on 

 the blood than in the mammifera. If the quantity 

 of respiration in the latter animals in which the 

 whole of the blood passes through the lungs, before 

 returning to the parts, be expressed by unity, the 

 quantity of respiration in the reptiles must be 

 expressed by a fraction of unity so much the smaller, 

 as the portion of the blood sent to the lungs on each 

 contraction of the heart, is less. 



As respiration communicates to the blood its heat, 

 and to the fibres their nervous irritability, so we find 



VOL. IX. B 



