tZQ CLASS REFTILIA. 



remarkable for their extreme tenacity of life, and the long 

 duration of their fibrous irritability after life is extinguished. 



The weakness of respiration diminishes the activity of the 

 nutritive system in reptiles, because the one is alwaj-s in 

 relation with the other. Accordingly, these animals eat but 

 little, and digest slowly. 



The small quantity which reptiles eat, is another reason for 

 the slowness of their growth, and the length of their existence ; 

 and the same character is also connected with the inactivity 

 of their senses. Their organs of sensation seem scarcely 

 developed. Their touch is very obtuse, in consequence of the 

 density and hardness of their skin. The sense of taste cannot 

 be otherwise than dull, because the tongue is either cartila- 

 ginous, or covered with a thick and viscous humour. The 

 smallness of the organs of smelling, indicate the weakness of 

 that sense. That of hearing appears to be less imperfect, 

 though its organ in reptiles is destitute of many useful parts, 

 such as the cochlea, the conch, and the meatus externus. 

 Even the tympanum is usually covered with skin, scales, or 

 muscles. Sight is the m.ost perfect sense in reptiles. They 

 have, for the most part, very large eyes, a contractile pupil, 

 like that of cats (especially the geckos, which appear to see 

 clearly by night), and a nictitating membrane, the same as in 

 birds. This indicates a great sensibility in this organ in these 

 two classes of animals, and the necessity under which they 

 labour, of having the intensity of the light moderated in its 

 action on their eyes. Nevertheless, the Cecilia, a genus of 

 serpents approaching the batracians, have excessively small 

 eyes concealed under the skin. The brain of reptiles is 

 remarkably small, and does not even completely fill the 

 cavity of the cranium, though that is far from being capacious. 



We shall now consider the nature of those localities in 

 which the reptile races most generally abound. 



Though shaded and humid tracts of land, and slimy 



