686 REPTILIA. 
Reptiles possess five senses, but none of them in great perfection. Thus, 
their sense of touch is obtuse, from the scales, plates, or shells of some 
species; and even when the skin is naked, it is not adherent to the body, but 
envelopes it like a bag, as is seen in a frog. Sometimes, as in the serpents, 
their eyes have no eyelids, are often immoveable, and covered with a corne- 
ous substance ; in some, three eyelids are to be distinguished; while some 
again appear to be destitute of sight. They have no cochlea, and but a small 
bone under the tympanum. Their nostrils are small, and their sense of 
smell appears weak. Their taste is not delicate, for the greater number 
swallow the prey whole; and in those which have the tongue soft and flexi- 
ble, this organ serves chiefly for the seizrre of their food. Many species of 
reptiles have no ribs, as the frogs; among others, as the serpents, these ribs 
are free, and without a sternum; in the tortoises, they are all fixed together ; 
and in the lizard family, the ribs are disposed nearly as in the birds. The 
lungs are always included in the same cavity. The smallness of the pul- 
monary vessels permits reptiles to suspend their respiration without stop- 
ping the circulation of the blood; and thus they can remain for a long time 
under water with ease. The cells of their lungs are few in number, and 
generally large, and this organ has sometimes the form of simple sacs, 
scarcely cellular. They are provided with a trachea and larynx, although 
all have not the faculty of uttering sounds. No species of reptile is possess- 
ed of true fleshy lips. Some, as the tortoises, have a horny bill like a 
parrot; others have teeth of various forms, not serving, however, in general 
for the maceration of food, but for retaining their prey; while others, as 
certain serpents, have hollow fangs, which are erected when the animal 
opens its mouth to bite, and which insert an active poison into the wound 
made by these teeth. Reptiles have but one opening, for rejected solid and 
fluid matters, and for the organs of generation. The females have a double 
ovary and two oviducts, and, though oviparous, none of the species hateh 
their eggs. Those which couple, deposit eggs covered with a hard envelope; 
and the eggs of those species which do not, are soft and glaring. The 
greater part abandon their eggs after having deposited them in a convenient 
place; though some species carry them about with them. The voung, on 
quitting the ova, appear sometimes in the form which they preserve through 
life ; but im other cases they are, at this period of their existence, organized 
like fishes, are not fully developed till after a certain period, and undergo a 
complete metamorphosis. Such are the tadpoles of the frog. Many spe- 
cies of this class are used as articles of food in different countries. The use 
of others in the economy of nature, is apparent, in limiting the excessive 
reproduction of insects and worms; while they themselves, on the other 
hand, form the principal food of some families of birds. The poisonous spe- 
cies are not very numerous, and their range is daily diminishing, as cultiva: 
tion and population increase. 
