TOUCH. 271 



human fingers; and lastly, it is requisite that the organ be 

 so constructed as to be capable of being readily applied, in 

 a variety of directions, to the unequal surfaces of bodies; for 

 the closer the contact, the more accurate will be the percep- 

 tions conveyed. In forming an estimate of the degree of 

 perfection in which this sense is exercised in any particular 

 animal, we must, accordingly, take into account the mobili- 

 ty, the capability of flexion, and the figure of the parts em- 

 ployed as organs of touch. 



As touch is the most important of all the senses, inasmuch 

 as it is the foundation of all our knowledge of the material 

 world, so its relative degrees of perfection establish marked 

 differences in the intellectual sagacity of the several tribes^, 

 and have a considerable influence on the assignment of their 

 proper station in the scale of animals. 



Although the power of receiving obscure impressions 

 from the contact of external bodies, and of perceiving varia- 

 tions of temperature, is probably possessed by all animals, 

 a small number only are provided with organs specially ap- 

 propriated for conveying the more delicate sensations of 

 touch. The greater part of the surface of the body in the 

 testaceous Mollusca is protected by a hard and insensible 

 covering of shell. The integuments of Insects, especially 

 those of the Coleoptera, are in general too rigid to receive 

 any fine impressions from the bodies which may come in 

 contact with them; and the same observation applies, with 

 even greater force, to the Crustacea. The scales of Fishes,, 

 and of Reptiles, the solid incasements 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 ani- 

 mals having a soft and flexible integument, such as all the 

 naked Zoophytes, Worms, and Mollusca, 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 



