XMII SENSATION TOUCH TASTE 197 



together as one-twenty-fourth of an inch. On the check the 

 points arc usually still felt as one when they are as much as an 

 inch apart, and on the back of the body even when they are 

 three inches apart. The sense of touch is therefore least 

 delicate on the back. 



Temperature Sensations. Besides the sensation of 

 touch which arises from the contact of a body with or from 

 pressure on the skin, we may have sensations of another kind, 

 sensations of warmth or of cold. In such cases it is the change 

 of temperature of the skin caused by the hot or cold body which 

 gives rise to the sensation. If one hand is cooled by being 

 placed in ice-cold water, and the other hand warmed by being 

 placed in hot water, lukewarm water will then feel warm to 

 one hand and cold to the other. The change of temperature 

 acts on the endings of the sensory nerves. It is only through 

 the peculiar end organs of the nerves that these sensations can 

 be excited by changes in temperature, for cold or heat applied 

 directly to the nerve leads only to pain. The sense of warmth 

 varies in delicacy in different parts of the body. It is delicate 

 on the palms of the hands, and, unlike the sense of touch, 

 particularly so on the cheeks. This is why a washerwoman 

 holds her iron near her cheek to tell if it is too hot. 



Muscular Sensations. If the hand is resting on the 

 table and a weight is placed in the palm, we experience a 

 sensation of touch, we feel the pressure of the weight, and 

 from the amount of this pressure we can, without moving the 

 hand, form an idea of the weight of the body. But we can 

 form a much better judgment as to the weight of the body if 

 instead of keeping the hand still on the table we raise and lower 

 the hand so as to lift the body up and down. We then form 

 our judgment by sensations which are in some way connected 

 with the contraction of the muscles by which the weight is 

 poised, and hence are called muscular sensations. 



Taste. The organ of the sense of taste is the mucous 

 membrane of the mouth, especially that of the tongue and 

 palate. The tongue is composed of a mass of striated 

 muscular fibres, running in various directions, covered by 

 mucous membrane. This mucous membrane consists of an 

 outer epithelium formed like the epidermis of several layers of 

 cells, and beneath this of a vascular connective tissue layer 



