2 CLASS REPTILIA. 



that reptiles have cold blood, and that their muscular 

 power is less, upon the whole, than that of quadru- 

 peds, and a fortiori than that of birds. Accordingly, 

 they do not often perform any movements, but 

 those of creeping, and of swimming; and though 

 many of them leap, and run fast enough, on some 

 occasions, their general habits are lazy, their diges- 

 tion excessively slow, their sensations obtuse, and in 

 cold and temperate climates, they pass almost the 

 entire winter in a state of lethargy. Their brain, 

 proportionally smaller, is not so necessary to the 

 exercise of their animal and vital faculties, as it is in 

 the first two classes of the animal kingdom. Their 

 sensations appear less referable to a common centre. 

 They continue to live and exhibit voluntary motion, 

 after having lost the brain, and even after decapita- 

 tion, and that for a very considerable time. The 

 connexion with the nervous system is also much less 

 necessary to the contraction of their fibres, and. 

 their flesh, after having been separated from the rest 

 of the body, preserves its irritability much longer 

 than in the preceding classes. Their heart will beat 

 for several hours after it has been plucked out, and 

 its loss does not hinder the body from moving for a 

 long time. In many of them, it has been observed, 

 that the cerebellum is remarkably small, which 

 perfectly accords with their little propensity to 

 motion. 



The smallness of the pulmonary vessels permits 

 reptiles to suspend their respiration without arrest- 



