284 
REPTILES. 
what like fishes, being destitute of feet, with their bodies com¬ 
pressed behind ; others are provided with fins, which are, how¬ 
ever, devoid of cartilaginous or bony filaments for their sup¬ 
port, as in fishes. Their teeth are more suited for retaining 
their food, than for the process of mastication. Some of the 
genera subsist on vegetable food, but the greater number feed 
on animal substance. • Their meals are seldom, but they con¬ 
sume a large proportion at a time. 
The circulation of reptiles is but imperfect, as only a portion 
of the blood is aerated that flows from the heart, and that part, 
instead of taking a direct course to the various organs, is again 
incorporated with the circulating fluid. The organs by which 
the blood is exposed to the air, are by means of lungs situated in 
the abdominal cavity. The lobes of these organs are unequal 
in size, having cells of much larger dimensions than in warm¬ 
blooded animals. 
The motions of this class are principally confined to crawling 
and swimming. Some species leap, and others run with con¬ 
siderable rapidity: but the prevailing habits of the tribe are 
sluggishness, and obtuseness of sensation. 
The brain of reptiles is small. The nerves are solid in their 
texture. They exhibit sensation after the brain has been re¬ 
moved, and in some instances, even after decapitation. The 
heart has been known to pulsate after its removal from the body 
for hours. 
The senses of reptiles are five, but all imperfect. The scales 
or plates by which many are covered, render their feeling of 
touch obtuse; and those which have a smooth skin are only en¬ 
veloped in it like a bag ; as exemplified in frogs and their con¬ 
geners. The eye, in serpents and other tribes, is immoveable, 
and covered by a corneous membrane; while others appear 
blind. The cochlea is represented by a small bone under the 
tympanum. The nostrils are much contracted, so that their 
sense of smell must be imperfect •, and as they swallow their 
food without mastication, it indicates a want of delicacy in 
taste; besides, their tongue is soft and flexible, only fitted for 
holding their food. None of the reptiles have fleshy lips; some 
of the tortoises are provided with a horny bill like that of 
a bird. 
Reptiles all produce their young by means of eggs ; these are 
