CUTANEOUS SENSATIONS. 285 



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 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 the object is 

 very heavy or very hot, it may cause pain. 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 experiments show that several sensations are in- 

 volved in the handling of objects, and that the knowledge so 

 gained is complex. 



The sensations from the objects resting on the skin of the 

 passive hand may, probably, all be referred to impressions 

 made on nerve endings in the skin, and are called Cutaneous 

 Sensations. They include : (1) the Pressure Sense, or Touch 

 proper, (2) the Temperature Sense, and (3) Pain. 



In lifting the object muscles are employed, and the sensa- 

 tion thus obtained is called the Muscular Sense. 



Before taking up these sensations singly, let us review a 

 few features of the nervous mechanism concerned. 



Nerve Endings in the Skin. We have learned that 

 the skin consists of two layers, the epidermis and the dermis. 

 We need now to recall those conical elevations of the dermis 

 that we call papillae. In these papillae are certain important 

 nerve endings. Since the sensory nerve impulses pass from 

 without inward, it would be more appropriate to speak of 

 the outer extremities of these nerves as their beginnings, or 

 origins, rather than as " endings." Still, as they are peculiar, 

 and are commonly termed endings, we may follow the ordinary 

 usage. 



There are several kinds of nerve endings in the skin and 



