INTELLIGENCE OF BATEAOHIANS. 



13 



imperfect, the structure of the heart only presenting one ventricle ; 

 the "blood, returning after a partial regeneration in the lungs, 

 mingles with that which is not yet revivified : this mixed fluid 

 is launched out 

 into the economic 

 system of the 

 animal. Thus 

 Eeptiles and Ba- 

 trachians are said 

 to he cold-blooded 

 animals, more es- 

 pecially the for- 

 mer, in which the 

 respiratory organs, 

 which are a con- 

 stant source of in- 

 terior heat, are 

 only exercised 

 very feebly. 

 Owing to this low 

 temperature of their bodies, reptiles affect warm climates, where 

 the sun exercises its power with an intensity unknown in tem- 

 perate regions ; hence it is that they abound in the warm lati- 

 tudes of Asia, Africa, and America, whilst comparatively few are 

 found in Europe. This is also the cause of their becoming torpid 

 during the winter of our latitudes : not having sufficient heat in 

 themselves to produce reaction against the external cold, they fall 

 asleep for many m.onths, awakening only when the temperature 

 permits of their activity. Serpents, Lizards, Tortoises, Frogs, are 

 all subjected to this law of their being. Some hybernate upon the 

 earth, under heaps of stones, or in holes ; others in mud at the 

 bottom of ponds. The senses are very slightly developed in these 

 animals ; those of touch, taste, and smell, are very imperfect ; that 

 of hearing, though less obtuse, leaves much to be desired ; but 

 sight in them is very suitably exercised by the large eyes, with 

 contractile eyeballs, which enables certain reptiles — such, for 

 instance, as the Geckos, to distinguish objects in the dark. Most 

 Reptiles and Batrachians are almost devoid of voice : Serpents, 



Fig. 2. — Skeleton of a Frog. 



