CHAPTER XXI. 



TOUCH, TEMPERATURE, MUSCULAR SENSE, 

 TASTE, SMELL. 



It was long known that sensations of touch were brought 

 about by the stimulation of sensory nerves and that the 

 section of such nerves destroyed the sensation, but it was 

 rather late before the special end organs of touch were dis- 

 covered. The first known end organs of touch were the 

 Pacinian corpuscles, discovered by Vater in 1741. The 

 touch corpuscles were not discovered until 1852, when they 

 were described by Wagner and Meissner. It was in 1846, 

 however, when E. H. Weber published his work that physi- 

 ologists arrived at the present conception of the sensation 

 of touch and temperature. 



THE ANATOMY OF THE END ORGANS OF TOUCH. 



Every part of the skin is sensitive, being supplied with 

 sensory nerves. Usually these nerve fibers end in plexuses, 

 the final terminations of which, in the form of little fibrils, 

 which have lost their medullary coat, end in the dermis, or 

 may reach even in among the cells of the Malpighian layer 

 of the epidermis and there terminate without any special 

 end organ. In those portions of the skin, however, where 

 the sensation of touch is specialized special end organs are 

 found. These are of several kinds: 



1. The Pacinian Corpuscles. These, as just stated, 

 were the first discovered, a fact due, no doubt, to their 

 relatively large size, ranging from a fifteenth to a tenth of 

 an inch in length. In the transparent omentum of the cat 

 they are readily recognized with the unaided eye as little 

 whitish translucent bodies. They are found in large num- 

 bers in the areolar tissue under the skin of the hand and 



(477) 



