248 



Physiology. 



Since, however, food and drink naturally enter by the 

 throat and stomach, the mucous membrane of these 

 organs has become the spokesman of the body. 



What we learn by touching Objects. Let one person 

 rest the hand flat on the table, palm upward, and close the 



eyes. An object placed on the 

 palm, by another person, may give 

 rise to various sensations, so that 

 it may be described as rough or 

 smooth, light or heavy, hot or 

 cold, wet or dry, etc. If now the 

 thumb and fingers are raised and 

 applied to the object, more definite 

 information will be gained as to its 

 shape, size, surface, etc. Now 

 raise the object in the hand, and 

 further appreciation will be gained 

 as to its weight. These experi- 

 ments show that several sensations are involved in the 

 handling of objects, and that the knowledge so gained is 

 complex. 



Cutaneous Sensations. The sensations from objects 

 resting on the skin of the hand may all be referred to im- 

 pressions made on nerve endings in the skin, and are 

 called cutaneous sensations. They include: (i) the pres- 

 sure sense, or touch proper, (2) the temperature sense, and 

 (3) pain. 



Nerve Endings in the Skin. The skin consists of two 

 layers, the epidermis and the dermis (see Figs. 64 and 65). 

 In the papillas of the dermis are nerve endings called 

 touch corpuscles (see Fig. 95). 



Nerve 



Fig. 95. Papilla of Skin with 

 Touch Corpuscle. 



