392 THE ORGANS OF SPECIAL SENSE 



ceous glands. They are arranged in the form of a 

 wreath. 



5. Corpuscles of Vater or Pacini. They are oval- 

 shaped structures situated along the course of afferent 

 nerves distributed to the skin on the palms of the 

 hands and soles of the feet, external genital organs, 

 joints, etc. They consist, when examined under 

 the microscope, of bulbs composed of granular pro- 

 toplasm surrounded by layers of connective tissue, 

 and are joined by the axis-cylinder of the afferent 

 nerve. 



The sense of touch is the sensation conveyed to 

 the brain by an object we touch coming in contact 

 with the end-organs in the skin and mucous mem- 

 branes. By this sense we are enabled to touch and 

 be touched by objects and determine their size 

 and weight; quality, whether hard or soft, rough 

 or smooth, sharp or dull, etc.; also the temperature 

 of a body or surface coming in contact with the 

 skin and mucous membranes, whether it is hot or 

 cold. 



The Skin. The skin possesses (1) touch sense and 

 (2) temperature sense. The touch sense is subdivided 

 into (a) pressure sense and (6) place sense. 



The touch sense is stimulated by mechanical pressure 

 coming in contact with the end-organs in the skin 

 and mucous membrane. 



Touch Spots. The areas of the skin and membrane, 

 which when stimulated by an object, as pin, knife, 

 etc., give rise to the sensation of touch, are not 

 general throughout the surface of the skin, but are 

 localized spots in the skin (these areas are called 

 touch spots) with intervals which are insensitive to 

 stimuli. 



The greater number of touch spots in a given area 

 the greater is the acuteness of the touch. These spots 

 are more numerous in the hands and in the neighbor- 

 hood of hair follicles. The skin of the index finger 



