356 ELEMENTARY PHYSIOLOGY less. 



can be distinguished by the tongue, if only one-twenty- 

 fourth of an inch ai)ai-t ; by the tips of the fingers if 

 one-twelftli of an inch distant ; vvliile they may be one 

 inch distant on the cheek or forehead, and even three 

 inches on the back, and still give rise to only one 

 sensation. 



Lastly, can we find any correspondence between the 

 various forms of end organ which have been described and 

 the various sensations felt in the skin ? The epicritic 

 sense of pressure is felt in many parts of the skin by 

 tactile corpuscles (Fig. 109). This is especially the case 

 where there are no hairs as on the palms of the hands. 

 The nerve-endings attached to the small hairs serve the 

 same function elsewhere. End-bulbs probably acquaint 

 us with " cold." We are uncertain as to the corresponding 

 organs for " heat." 



6. The Muscular Sense. — What is termed the 

 muscular sense is less vaguely localised than the 

 sensations referred to above in Section 2 (p. 343), 

 though its place is still incapable of being very accur- 

 ately defined. This muscular sensation is largely 

 the feeling of resistance which arises when any kind 

 of obstacle is opposed to the movement of the body, or 

 of any part of it ; and it is something quite different from 

 the feeling of contact or even of pressure. 



Lay one hand flat on its back upon a table, and rest a 

 disc of cardboai'd a couple of inches in diameter upon the 

 ends of the outstretched fingers ; the only result will be a 

 sensation of contact — the pressure of so light a body 

 being inappreciable. But put a two-pound weight upon 

 the cardboard, and the sensation of contact will pass into 

 what appears to be a very different feeling, viz., that of 

 pressure. Up to this moment the fingers and arm 

 have rested upon the table ; but now let the hand be 

 raised from the table, and another new feeling will make 

 its appearance — that of resistance to effort. This 



