THE SEKSES. 661 



tact is replaced by one of pain. Further, in all highly sensitive parts, 

 the papillae are numerous and highly vascular, and the sensory nerves 

 are connected with special end-organs which have been described p. 99 

 et seq. 



The special endings of the nerves which have to do with touch may, 

 however, be here again xfnentioned. They are of two kinds, viz., (a) 

 touch corpuscles, which are found chiefly in the hands and feet, particu- 

 larly on the palmar surface of the hands and fingers, but also on the 

 under surface of the forearm, nipple, eyelids, lips, and genital organs. 

 Touch corpuscles are situated in the cutis vera. (b) end bulbs, which 

 are found in conjunctivas and other mucous membranes, the lips, genital 

 organs, tongue, rectum, and elsewhere, but not in the skin proper. As 

 regards the Pacinian corpuscles and similar end-organs, which are so 

 widely distributed, and which may be in some way connected with the 

 sensation, when they are found in the skin they are situated very deeply 

 in the cutis vera or in the subcutaneous tissue. They are extremely 

 numerous on the nerves of the palmar surface of the fingers. In all of 

 these endings, and in similar ones found in other animals-, the nerve 

 ends, as in axis cylinder, in a special development of the connective tis- 

 sue sheath. In addition to these special nerve-endings, nerve-fibres 

 appear to terminate everywhere in the skin between the cells of the 

 Maipighian stratum of the epidermis in the ends, and in certain animals 

 some of them appear to end in special and rather large cells. 



It is practically impossible to distinguish between what is called 

 mere contact and touch in which the element of pressure comes in. 

 The acuteness of the sense of touch depends very largely on the cutane- 

 ous circulation, which is of course largely influenced by external temper- 

 ature. Hence the numbness, familiar to every one, produced by the 

 application of cold to the skin. 



Acuteness of the Sense. The perfection of the sense of touch on 

 different parts of the surface is proportioned to the power which such 

 parts possess of distinguishing and isolating the sensations produced by 

 two points placed close together. This power depends, at least in part, 

 on the number of primitive nerve-fibres distributed to the part; for the 

 fewer the primitive fibres which an organ receives, the more likely is it 

 that several impressions on different contiguous points will act on only 

 one nervous fibre, and hence be confounded, and perhaps produce but 

 one sensation. Experiments have been made to determine the tactile 

 properties of different parts of the skin, as measured by this power of 

 distinguishing distances. These consist in touching the skin, while the 

 eyes are closed, with the points of a pair of compasses sheathed with 

 cork, and in ascertaining how close the points of compasses might be 

 brought to each other, and still be felt as two bodies. 



