302 On the Sense of Feeling-, 



thick, serrated, and resisting. Where it covers the bone, as upon the 

 head, it is thinner, but strongly adherent. In them the vascular network 

 is not strikingly developed, and the pigment is almost fluid. 



The shell of these animals must be considered as formed by the cutis j 

 and the thin plates which peel off, and form the tortoise-shell of commerce, 

 as the representative of the epidermis. There have not been discovered 

 any vestiges of a cryptic or phaneric system. 



The beautiful forms into which the plates forming the covering of the 

 tortoise family are thrown, are familiar many of them to us all ; but they are 

 delineated in a manner which seems to equal nature under her most favour- 

 able circumstauces, in the magnificent plates of Mr. Thomas Bell. 



In the class of reptiles we find upon the whole a very inconsiderable 

 advance in the perfection of the organs of tact and touch, compared with 

 what we shall see in the higher classes. Their organs would seem to be 

 in a sort of transition state, many of them possessing the smooth and 

 flexible integument usually accompanying perfection of tact, while the 

 forms of others are so constructed, as to make the most of such an organ ; 

 the two advantages not being, however, combined in any great degree in 

 the same animal. 



In the lower and amphibious reptiles, as the frog, &c. the skin we have 

 seen to be delicate and polished, and apparently very fit to exercise the 

 sense of touch. The anterior extremity of their trunk is, however, never 

 elongated into a snout ; and although the posterior becomes occasionally a 

 tail, it is commonly stiff and rigid, and useful chiefly as an organ of loco- 

 motion, a use to which the extremities seem almost entirely to be applied. 



In the Pipa, however, the fringes which skirt the extremity of the digits 

 are, it is probable, organs of touch. 



The shape and flexibility of the serpents would render their whole 

 bodies an admirable organ of touch, but that their cutis is thick and scaly, 

 and almost incapable of receiving impressions. 



Such of the saurians as want the hind legs, are but little removed from 

 the serpents ; and even where the digits exist, and are long and mobile, 

 they are used rather as organs of locomotion. 



The cameleons and geckos, possessing thin skins, long digits, and long 

 prehensile tails, are probably superior in respect of this organ to most of 

 their associates. The tail of the cameleon is remarkable for its length, 

 and is one of the points of declination from the lizard to the serpent type. 



In the crocodiles and tortoises the sense of tact is probably feeble. 



Speaking generally, although in the class reptiles we find an obvious 

 modification of the type, preparing, as it were, for the development of the 

 sense ; yet the requisite supply of nerves, and thinness of the cuticle, are 

 deficient. 



Leaving the reptiles, we next arrive at the birds; and the principal 

 tegumental difference between the two classes consists in the possession of 



