CHAPTER XIX. 



THE SPECIAL SENSES -TOUCH AND TEMPERATURE 



SENSE. 



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 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. 



Cutaneous Sensations. The sensations from the ob- 

 jects resting on the skin of the passive hand may, proba- 

 bly, all be referred to impressions made on nerve endings 

 in the skin, and are called cutaneous sensations. They 

 include: (i) the pressure 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. We need now 

 to recall those conical elevations of the dermis that we caU 



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