REPTILIA. 5 
CLASS III. REPTILIA. 
We have now arrived at a class of animals, in the production of which 
nature has seemed to deviate from her usual plan of beauty and utility, as 
all the orders, comprising the series, with the exception of the first, are 
calculated to create in man feelings of the deepest disgust, aversion, and 
often terror. The grotesque forms, in which ugliness and deformity mani- 
fest themselves in multifarious variety, the utter uselessness of all, save the 
exception just named, and the venomous and dangerous character of many, 
have caused them in all ages to be regarded by man as symbols of moral 
degradation and types of all evil. We instinctively shrink from contact 
with them, and start with a shudder when one is suddenly and unexpectedly 
revealed to our sight. It is difficult to define or describe that emotion of 
dread which one experiences when the cold and slimy snake glides along at 
his feet, with its forked tongue and menacing hiss. Even the touch of the 
harmless toad will produce sensations of the most disagreeable character, 
The animals of this class have the heart so constructed, that at its several 
contractions it sends only a portion of the blood into the lungs, the re- 
mainder returning into the general circulation without being subjected to 
respiration. “As respiration imparts warmth to the blood, reptiles are con- 
sequently cold-blooded, and their aggregate muscular energy is less than in 
the mammalia, and much Jess than in birds. Wence their meyements ean 
scarcely be performed otherwise than by crawling or swimming ; and though 
several of them leap and run with celerity on certain occasions, their habits 
are generally sluggish, their digestion excessively slow, their sensations ob- 
tuse, and, in cold or temperate climates, they pass nearly the whole winter 
in a state of lethargy. Their proportionally very diminutive brain is less 
necessary than in the two preceding classes for the exercise of their animal 
and vital functions ; their sensations seem to be less referable to a common 
centre; they contrive to live and to execute voluntary movements for a con- 
siderable time after having been deprived of the brain, and even when the 
head is severed. Their heart pulsates for many hours after it has been 
detached, and its loss does not deprive the body of mobility for a still longer 
period. The smallness of the pulmonary vessels enables them to suspend 
respiration without arresting the course of the blood, and thus to remain 
submerged for a longer time than mammalia or birds.” 
As the amount of respiration in this class is not fixed, as in the mammalia 
and birds, but varies according to the relative proportion of the diameter of 
the pulmonary artery, as compared with that of the aorta, some respire 
