TOUCH AND SENSATION. 57 



touch the skin without our being instantly made 

 aware of its presence and properties. 



While, however, sensation is common to the 

 whole surface of the body, there are parts of the 

 skin more immediately destined by Nature for the 

 exercise of Touch, and for the better appreciation 

 of all the qualities of which it is cognizant. Such 

 are the hands and tongue in man, the proboscis in 

 the elephant, the tail in some of the monkey tribe, 

 and the tenticula in fishes. Now, in accordance 

 with the explanation given of the dependence of 

 sensation upon nervous endowment, it is remark- 

 able that all the parts destined for this special ex- 

 ercise of Touch receive the most abundant sup- 

 ply of sensitive nerves. Thus the nerves going to 

 the hand and arm, the most perfect instruments of 

 Touch and Sensation in man, are at their dorsal 

 roots five times larger than those which are destined 

 for its motion; and, in like manner, the nerve sup- 

 plying the tactile extremity of the proboscis of the 

 elephant exceeds in size the united volume of all 

 its muscular nerves. On the other hand, in animals 

 covered with hair or feathers, whose Touch and 

 Sensation are comparatively defective, the muscular 

 nerves far exceed in size those of Sensation ; and 

 wherever Nature has endowed any particular part 

 with high sensitive powers, she is invariably found 

 to have distributed to that part, and to it alone, a 

 proportionally higher nervous endowment. In man, 

 the innumerable nervous papillae destined for the 

 exercise of Touch may be distinctly seen in parallel 

 irregular rows on the fingers and palm of the hand, 

 and everybody knows how acute the sense is in 

 these parts. In fishes, on the other hand, no nervous 

 papillae can be detected on the surface of the skin; 

 but many of them have tentacula or projections 

 generally about the mouth, for the special purpose 

 of exercising Touch, and these are always plentifully 

 supplied with branches from the fifth pair of nerves. 



