CUTANEOUS SENSATIONS 497 



THE HISTOLOGICAL CHARACTER OF THE ELEMENTS 

 INVOLVED IN CUTANEOUS SENSATIONS 



A very large number of different forms of sensory nerve-endings have 

 been described in relation to the skin. Their exact allocation among the 

 different cutaneous senses presents considerable difficulties. 



As regards touch, two kinds of elements are probably involved. In 

 the first'place, the most sensitive tactile apparatus are the follicles of the 

 shorT hairs. Around these follicles we find a sheaFof nerve fibres, some 

 of which end in the hair papilla and others form a ring near the level of 

 the openings of the sebaceous glands. The other tactile end- organ is 

 Meissner's corpuscle. The distribution of these in the skin is not, however, 

 dissimilar to that of the power of discrimination, with which they may be 

 specially connected. Other end-organs which are supposed to be stimulated 

 by changes of pressure, and therefore to be tactile, are the organs of Ruffini 

 which occur in the papillae of the palm and fingers, and, lying more deeply, 

 the elastic tissue spindles as well as the Golgi corpuscles and the Pacinian 

 corpuscles in the subcutaneous tissue. 



As regards pain, we known that in the cornea, which possesses only 

 the pain sense, the sensory nerve- endings are in the form of branches of 

 axis cylinders among the epithelial cells. Similar free nerve-endings occur 

 in the epidermis all over the body, and it is therefore imagined that these 

 have the special function of subserving the pain sense. We have at present 

 no evidence as to the histological character of the organs by which the 

 sensations of heat and cold are aroused. 



