2 REPTILIA. 



In cold or temperate climates almost all of them pass the win- 

 ter in a state of torpor. Their brain, which is proportionally 

 very small, is not so essentially requisite to the exercise of 

 their animal and vital faculties, as to the members of the two 

 first classes ; their sensations seem to be less referred to a 

 common centre, for they continue to live and to exhibit volun- 

 tary motions, long after losing their brain, and even after the 

 loss of their head. A communication with the nervous sys- 

 tem is also much less necessary to the contraction of their 

 fibres, and their muscles preserve their irritability after being 

 severed from the body much longer than those of the pre- 

 ceding classes ; their heart continues to pulsate for hours 

 after it has been torn away, nor does its loss prevent the body 

 from moving for a long time. The cerebellum of several has 

 been observed to be extremely small, a fact which tallies with 

 their slight propensity to motion. 



The smallncss of the pulmonary vessels permits reptiles to 

 suspend the process of respiration without arresting the course 

 of the blood ; thus they dive with more facility, and remain 

 longer under water than either the Mammalia or Birds. The 

 cells of their lungs, being less numerous, because they have 

 fewer vessels to lodge on their parietes, are much wider, and 

 the organs themselves sometimes resemble simple sacs with 

 scarcely any appearance of cells. 



Although some of them are incapable of producing audible 

 sounds, tliey are all provided with a trachea and larynx. 



Their blood not being warm, there was no necessity for 

 teguments capable of retaining heat, so that they are covered 

 with scales or simply with a naked skin. 



The females have a double ovary and two oviducts; the 

 males of several genera have a forked or double penis, those 

 of the last order, the Batrachians, have none. 



No reptile hatches its eggs, and in several genera of the 

 Batrachise, they are fecundated after their exclusion from the 

 female, in which case the egg is enveloped by a membrane 

 only. The young of this latter order, on quitting the egg, 

 have the form and branchiaB of Fishes, and some of its genera 



