224 PRINCIPLES OF PHYSIOLOGY 



particles. In the skin there are plexuses of 

 fine nerve fibres, running even among the 

 cells of the epidermis, which receive delicate 

 pressures, as in touch. These pressures are 

 also detected by nerve fibres connected with 

 specialized structures formed mainly of epider- 

 mic cells, such as touch bodies, tactile cor- 

 puscles, and Paccinian bodies. No special 

 terminal organs for temperature have been 

 discovered in the skin, but there are points in 

 the skin sensitive to heat, others to cold, and 

 both distinguishable from those devoted to 

 pressure. It would seem there are also pain 

 spots. There appear to be even different 

 systems of sensibility in the skin. If a sensory 

 nerve to an area of skin is divided, sensibility 

 may return if the ends unite. The sensations 

 that return first have been termed prolo- 

 pathic, and depend on heat, cold, and pain 

 spots. But another order of sensations return 

 later, and seem to depend on tactile sensations 

 and a finer sense of sensibility to pain. This 

 kind of sensibility has been called epicritic. 

 It follows, then, that when we bring the 

 finger flat against a surface we stimulate 



