.342 THE SENSORIAL FUMCTIONS. 



sense of touch depends are, first, an abundant provi- 

 sion of soft papillae supplied with numerous nerves ; 

 secondly, a certain degree of fineness in the cuticle; 

 thirdly, a soft cushion of cellular substance beneath 

 the skin ; fourthly, a hard resisting basis, such as 

 that which is provided in the nails of the 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 perceptions conveyed. 

 In forming an estimate of the degree of perfection 

 in which the sense is exercised in any particular 

 animal, we must, accordingly, take into account 

 the mobility, the capability of flexion, and the figure 

 of the parts employed as organs of touch. 



As touch is the most important of all the senses, 

 inasmuch as it is the foundation of all our know- 

 ledge 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 impres- 

 sions from the contact of external bodies, and of 

 perceiving variations of temperature, is probably 

 possessed by all animals, a small number only are 

 provided with organs specially appropriated 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 in- 

 sensible covering of shell. The integuments of 

 Insects, especially those of the Coleoptera, are in 

 general too rigid to receive any fine impressions 



