224 ANATOMY FOB, NUKSES. [CHAP. XIX. 



The power of discriminating between different pressures, 

 and also the power to localize impressions, varies in different 

 regions of the body. 



A careful study of the skin shows that the organs of touch 

 are separated from each other by an appreciable distance, so 

 that we may speak of " pressure points or areas " which are sepa- 

 rated from one another by points or areas which are insensitive 

 to pressure. 



Temperature, In addition to the end organs of the sense of 

 touch, there are also structures in the skin which are only 

 stimulated by changes in temperature. These structures are 

 of two kinds: stimulation of one causing the feeling of cold; 

 stimulation of the other, the feeling of heat. The distribution 

 of the end organs of the sense of heat and cold is punctiform 

 like the pressure sense, and we may therefore speak also of 

 "heat and cold" points, each of these points having its own 

 local sign. 



Pain. The nerve endings of the sense of pain are very 

 widely distributed throughout almost the whole body. 



Muscular sense. The end organs of the muscular sense are 

 situated in the tendons and between the fibres of the muscles. 

 They convey to us the sense of the tension and pressure under 

 which our muscles are placed, and from this we infer the position 

 of the various parts of the body. Thus their function is to aid 

 in coordinating muscular action, in preserving equilibrium, and 

 in estimating weight or resistance. 



Common sensation. Under this heading may be grouped a 

 number of sensations often of a very indefinite character. They 

 are the various obscure sensations proceeding from the viscera, 

 which may give us the feeling of well-being or of the reverse. 

 The sensations of hunger, of thirst, and possibly of fatigue 

 belong to this class. 



The sense of taste. The special organ of the sense of taste is 

 the tongue, which is a movable muscular organ covered with 

 mucous membrane. This mucous membrane closely resembles 

 the skin in structure, except that the papillae it contains are 

 more highly developed. The papillae project as minute 

 prominences and give the tongue its characteristic rough 

 appearance. 



Some of the papillae are simple and resemble those found in 



