CLASS III. REPTILIA: ORDEE 1. CIIELONIA. 
355 
The Reptilia comprise four orders very distinct in some respects, though united in others : the 
Chelonia, or Tortoises ; the Loricata, or Crocodiles ; the Sauria, or Lizards ; and the Ophidia, 
or Serpents. These are generally regarded with little favor by mankind, but their natural history 
is nevertheless fall of interest. With the exception of a few tortoises they are all carnivorous 
animals. They have all a slow circulation ; their blood is cold, that is, but little above the tem- 
perature of the surrounding medium ; the amount of their aggregate muscular energy is less than in 
the mammalia ; their movements are generally crawling and swimming ; and though some of them 
leap and run with celerity on certain occasions, their habits are generally sluggish, their digestion 
slow, their sensations obtuse, and in cold or temperate climates they pass nearly the whole 
winter in a state of lethargy ; they continue to Hve and to execute voluntary movements for a 
considerable time after having been deprived of the brain, and even when the head is severed 
from the body. Their heart pulsates, in some cases, for many hours after it has been detached, 
and its loss does not deprive the body of mobility for a still longer period. Their blood not being 
warm, they do not requu-e teguments capable of retaining heat ; they are according^ covered 
with shells, scales, or naked skin. No reptile incubates its eggs. In certain genera of batrachians 
