TOUCH. 343 



from the bodies which may come in contact with 

 them ; and the same observation apphes, with even 

 greater force, to the Crustacea. The scales of 

 Fishes, and of Reptiles, the solid encasements of 

 the Chelonia, the plumage of Birds, the dense 

 coating of the Armadillo, the thick hides of the 

 Rhinoceros, and other Pachydermata, are evidently 

 incompatible with any delicacy of touch. This 

 nicer faculty of discrimination can be enjoyed only 

 by animals having a soft and flexible integument, 

 such as all the naked Zoophytes, Worms and Mol- 

 lusca, among the lower orders, and Serpents, among 

 the higher. The flexibility of the body or limbs is 

 another condition which is extremely necessary 

 towards procuring extensive and correct notions of 

 the relative positions of external objects. It is es- 

 sential therefore that those instruments which are 

 more particularly intended as organs of touch, 

 should possess this property. 



It will not be necessary to enter into a minute 

 description of these organs, because they have, for 

 the most part, been already noticed as instruments 

 of motion or prehension ; for the sense of touch is 

 in general exercised more particularly by the same 

 parts which perform this latter function. Thus the 

 tentacula of the various tribes of Polypi, of Acti- 

 niae, and of Annelida, are organs both of prehension 

 and of touch. The tubular feet of the Asteriasand 

 Echinus are subservient both to the sense of touch, 

 and to the faculty of progressive motion. The feet 

 of Insects and of Crustacea are well calculated, 

 indeed, by their jointed structure, for being applied 

 to the surfaces, and different sides of bodies ; but 

 they are scarcely ever employed in this capacity ; 



