MUSCLE SENSE 



327 



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THE SENSE OF TOUCH 



The skin and the mucous membrane of the mouth constitute 

 the organ of the special sense of touch (all mucous membranes 

 are sensitive to temperature and pain, but only that of the mouth 

 is sensitive to touch). 



The special nerve endings are situated in the deeper layers, in- 

 cluding the hair follicles, and the papillae. Upon their number 

 and nearness to the surface depends the 

 acuteness of this sense. An area covered 

 by thick layers of epidermis is not so 

 sensitive as one where it is thin; and vice 

 versa. 



There are several forms of nerve end- 

 ings: tactile cells, for common sensations, 

 found throughout the skin in the deeper 

 layers, hair follicles, and papillae; touch cor- 

 puscles, also in the papillae and especially 

 numerous in the palm and finger tips, where 

 sensation is particularly acute; other forms 

 in muscles and tendons; others still, for the 

 perception of heat and cold or temperature 

 sense, etc., etc. These all belong to the 



sensory nerves of the cerebro-spinal nerve 



^^ 

 system. 



The sense of touch includes many va- & 



rieties of impressions by means of which FIG. 207. TOUCH-COR- 

 . , P ,. . PUSCLE OF MEISSNER AND 



we may judge of surroundings, and gain WAGNER. 



the necessary knowledge concerning the b. Papilla of cutis. d. 

 external world whereby we can adjust our- N-ve-fiber *? 

 selves to its conditions. Several of these touch-corpuscles, g. Cells 



,,,.., of Malpighian layer. 



are included in the term muscle sensa- (From Stirling.} 

 tions"; they constitute the muscle sense. 



By this we become aware of many things, as the direction of 

 movements of our own bodies, whether active or passive; of the 

 postures of the body or its parts; (this knowledge we apply to 

 the maintenance of balance). Also, by muscle sense we estimate 

 the degree of force felt by the impact of a moving body, or of a 

 blow received or given (this last is closely related to the apprecia- 



