1 8 Journal of Comparative Neurology. 



tex. He does not believe that the sensation of itching origin- 

 ates in the tactile corpuscles, although readily admitting that 

 these bodies are the media of peripheral expression for the sen- 

 sation. Certain analogies between itching and pain, touch and 

 temperature sense, indicate a cerebral origin for all forms of 

 peripheral sensorial impressions. He finds support for the the- 

 ory in the pain of the hypochondriac and the hysterical, the 

 itching of hypnotic suggestion, of neurasthenia and the 

 itching aura in certain cases of epilepsy, etc. 



But we have already seen that the evidence is far from con- 

 vincing for the existence of special nerves for pain and must return 

 toGoldscheider's paper in i8gi^ where, in discussing the summa- 

 tion phenomena of pain, he suggests that the secondary sensation 

 is a summation phenomenon which probably takes place in the cell- 

 ular elements scattered through the nerve tract. The cells store 

 the energy which goes to them while that which passes directly 

 along the fibres reaches the brain first. Subsequent accessions 

 break down the cellular resistance and thus an explosive incre- 

 mental stimulus reaches consciousness as pain. A single sensa- 

 tion if excessive may produce the like effect. Now accepting 

 the accumulating evidence of a special cellular course for exces- 

 sive stimuli we may inquire how simple pleasurable sensations 

 are produced. .Several hints are at our disposal. Many of these 

 pleasures are accompanied by a peculiar nervous diffusion, as in 

 tickling and the genial effect of warmth. This effect is known 

 as irradiation and is also characteristic of higher states of pleas- 

 urable feeling. Both pain and pleasure depend on exalted 

 stimuli, but the reaction of the system toward the stmuli 

 largely determines their pleasurableness or painfulness. The 

 same excitation may excite one or the other feeling at different 

 times. Attention has thus a powerful but not regulatable in- 

 fluence. In the higher spheres of pleasure-pain this influence 

 is more marked. This irradiation has a great tendency to in- 

 volve vaso-motor channels, as we have seen above, while the sum- 

 mation processes of pain awaken various reflexes in their path 



'Dubois Reymond's Archiv, 164. 



