GENERAL SENSIBILITY. 529 



the institution with which she was connected. " It is true of many 

 totally blind that, if a number of balls of worsted of various 

 colors are given them, and they are obliged to notice them care- 

 fully in order to use them in their proper places in work, they 

 will rarely make a mistake. So we may give them pieces of silk, 

 with the same result ; but this does not prove that, having been 

 told the colors in one material or fabric, they will recognize them 

 in any other. 



" We have no evidence that there is any inherent property in 

 the color red, or blue, or yellow, which will enable the most sensi- 

 tive touch to detect each in all materials offered." 



Sense of Pressure. When objects are laid upon the hand there 

 is a sensation produced, which is that of pressure, and by the exer- 

 cise of this sense we are able to distinguish differences in the 

 weights of objects. This is true of other portions of the body as 

 well as of the hand. Sense of pressure and tactile sensibility are 

 not identical ; indeed, portions of the body in which the latter is 

 very acute are nevertheless very insensitive to pressure. Thus the 

 tactile sensibility of the tip of the tongue is very highly devel- 

 oped, but its sense of pressure is very deficient. Kirkes says that 

 with the tip of the tongue one cannot detect the radial pulse. 

 While there is a marked difference between the tongue and 

 the finger in their ability to distinguish the pulse-beats, still the 

 writer is positive that the statement that these cannot be felt by 

 the tongue is not true for all individuals. 



It is to be borne in mind that in the investigation of the sense 

 of pressure the muscles must not be brought into play, otherwise 

 a new factor is involved the muscular sense. 



Muscular Sense. This sense is brought into action in lifting 

 weights, and the estimation of the weight of an object depends 

 upon the amount of nervous energy (efferent impulses) necessary 

 to accomplish the result. Some authorities regard it as a modifica- 

 tion of the sense of pressure ; but the two senses are undoubtedly 

 distinct. 



Sense of Temperature. By this sense the difference in tem- 

 perature of bodies is recognized, and it is a well-known fact that 

 the various portions of the body are endowed with different 

 degrees of sensibility in this regard : The hand will bear a degree 

 of heat which would cause great pain to some other parts of the 

 body. The sense of temperature and that of touch are entirely 

 distinct, and this fact may readily be demonstrated by pressing 

 firmly on a sensitive nerve* until the part to which it is distributed 

 is almost devoid of the sense of touch, when it will be found that 

 the sense of temperature is unaffected. 



Not only is the sense of temperature distinct from other sensa- 

 tion, but even this is so subdivided that there are heat spots and 

 cold spots that is, portions of the skin which are excited by heat 



34 



