428 INNERVATION. [CHAP. XIV. 



much with differences in the mobility of such parts. In general, 

 touch is most acute in regions best suited, by their structure, for 

 easy and diversified contact with external substances; for the 

 power of nicely determining the position, direction, and amount of 

 pressure upon the organ of touch, is essential to the perfection of 

 the sense. The will can not only excite and check the contrac- 

 tions of the muscles, but is able to regulate their force and duration 

 with wonderful precision; for, by the muscular sense, as stated in a 

 previous chapter, the mind is able to appreciate the state of con- 

 traction of a muscle by impressions originating in the nerves sup- 

 plied to its fibres. This power, both of recognizing and governing 

 the muscular movements, is from our earliest infancy brought into 

 association with the impressions derived from the tactile organ, 

 and made accessory to its function ; and the perfection to which 

 habit, in numerous instances, brings the sense of touch, is chiefly 

 due to an improved capacity it confers, of appreciating the impres- 

 sions made on the organ, in connexion with niceties of muscular 

 movement. 



In animals, as in man, we may notice the local concentration of the sense 

 in general obedience to this relation of mobility. In monkeys the fingers are 

 highly endowed with it, and the papilla there developed closely resemble 

 those on the human hand. The prehensile tails of certain tribes possess great 

 mobility, can readily be applied all round an object, and are largely supplied 

 with nerves and papillae. In addition to this, there is an absence of hair from 

 that surface adapted for contact with bodies. In some ant-eaters the tail is 

 highly tactile, and likewise in the chameleon. 



In the canine and feline races the sense of touch resides in the paws, which 

 present a large papillary structure ; in the lips, where the whiskers are de- 

 veloped ; and in the tongue. In ruminants and solipeds it has its special seat 

 in the lips, which are long, very moveable, and largely supplied with sensitive 

 and motor nerves. The upper lip of the rhinoceros is an excellent example 

 of these conditions ; and, still more so, the snout of the tapir and the trunk 

 of the elephant, where the integuments about the orifice of the nostrils are 

 endowed with exquisite powers both of sense and motion. 



But nowhere, perhaps, is the sense of touch more acute than in the mem- 

 branous expansions of the wings of bats, whereby they are enabled to traverse 

 dark and tortuous passages, in rapid flight, without injury. Spallanzani 

 blinded them with a view of determining whether sight conferred any part of 

 this singular power, but found that this mutilation interfered in no respect 

 with the faculty. They were still able to fly in the space between suspended 

 threads without touching them. He could not conceive it possible that so 

 wonderful an endowment could depend on any exaltation of mere touch, and 

 he resorted to the supposition of the existence of a sixth sense, possessed of 

 some unknown mode of action. But Cuvier, with more sagacity, has referred 

 it to an eminent sensibility of the nerves, which are profusely expanded over 

 the web of the wings. This membrane seems admirably calculated to receive 



