1094 



THE SENSES 



the brain seems to connect the arrival of sensory impulses from the 

 internal organs, which have few sensory fibres, and these perhaps not 

 often stimulated, with excitation in a related cutaneous region, from 

 which it is constantly receiving sensory impressions. The fact already 

 mentioned (p. 892), that in disease of internal organs the pain is re- 

 ferred to some portion of the skin, ma)' be thus explained. 



An attempt has been made to explain certain illusions of touch 

 on the theory that just as an object is recognized as single by the eye 

 when its images fallen corresponding points of the two retinae (p. 1037), 

 so an object is recognized as single by the fingers when it comes into 

 contact with corresponding points or rather areas of the skin. These 

 are the areas which experience has taught us are in contact with an 

 object when it is held in the natural way. When now a single object is 

 made, by placing the fingers in an unnatural position, to touch areas 

 which could ordinarily be touched at the same time only by two or 

 by three objects, we experience the sensation of contact with two or with 

 three objects. 



Fig. 467. Illusion of Touch of 

 Aristotle. A small object placed 

 between the index and middle 

 fingers, crossed as shown, is felt 

 as two objects (Wassenaar). 



Fig. 468. An Object placed in contact with 

 the Index, Middle and Ring Fingers, 

 crossed as shown, is felt as three objects 

 (Wassenaar). 



It is through the localization of touch sensations that the size and 

 form of objects in contact with the skin are perceived in the absence 

 of other than the cutaneous sensations, and especially in the absence 

 of visual and muscular sensations (stereognosis). 



Muscular Sensations (Muscular Sense), etc. Sometimes, although 

 rather loosely, grouped together as muscular sensations, are a number 

 of forms of sensation of which our knowledge is much less accurate 

 than it is in the case of the fundamental skin sensations. Among 

 these may be mentioned especially (i) the sensations by which the 

 position in space of the body as a whole or of particular parts is recog- 

 nized in the absence of visual sensations; (2) the sensations associated 

 with movements, passive as well as active ; (3) the sensations associated 



