276 



THE SPECIAL SENSES. 



of sensation designated under the terms ''epicritic" and '^proto- 

 pathic." The afferent fibers that enter the cord through the 



Fig. 119. — Representation of the distribution of cold and warm spots on the vola" 

 surface of forearm in a space 2 cms. by 4 cms. The red dots represent the cold spots as 

 tested nt a temperature of 10° C. The black dots represent the warm spots as tested at a 

 temperature of 41° to 48° C. 



posterior roots of the spinal nerves and the sensory roots of the 

 cranial nerves may be classified as follows: 



Cutaneous sensory fibers 



Deep (or subcutaneous) sensory fibers 



Non-sensory afferent fibers (Propriocep- 

 tive) 



Heat. 



Cold. 



Pressure. 



Tactile discrimination. 



Pain. 



Pressure. 

 Pain. 



Position (muscle-sense). 



From muscles, ligaments, etc., 

 end in cerebellum. 



The Punctiform Distribution of the Cutaneous Senses. — A 



most interesting fact in regard to the cutaneous senses is that 

 they are not distributed uniformly over the whole skin, but are 

 present in discrete points or spots. This fact was first clearly 

 estabhshed by BHx,* although it was discovered independently 

 by Goldscheider and in this country by Donaldson. These ob- 



* Blix, "Zeitschrift f. Biologic," 20, 141, 1884; Donaldson, "Mind," 39, 1, 

 1885. See also Goldschieder, "Arcliiv f. Physiologic," 1885, suppl. volume. 



