102 PSYCHOBIOLOGY 



tive process is maintained. Whether afferent terminals belong to the 

 central system may be chemically stimulated is an open question. As to 

 the stimulation of afferent visceral terminals in connection with tissues in 

 the skin, blood vessels and glands, and the specific effect thereof, we have 

 yet all to learn. 



REFERRED PAIN. 



In certain pathological conditions of the visceral organs, the pain which 

 is felt is falsely localized in the skin. This association of skin areas with 

 visceral regions is definite and specific, and by the exact area of the skin 

 which seems sore (although the skin is really normal), it is possible to 

 diagnose the exact visceral region affected. The linkage of skin and vis- 

 cera is doubtless through associative neurons located in the spinal ganglia. 

 Such neurons have been discovered, and probably join cell-bodies of vis- 

 ceral neurons with cell-bodies of somatic neurons. In this way it would 

 be possible for currents entering through the visceral channels to be 

 switched off to the somatic neurons and continue upwards over that route, 

 although the transfer does not occur unless there is pathological irritation. 



REFERENCES ON THE VISCERAL DIVISION OF THE NERVOUS SYSTEM. 



Langley, The Sympathetic and Other Related Systems of Nerves. Schafer's Text- 

 Book of Physiology, Vol. II. 



Starling, Physiology, Chapter VII, § XVIII. 



Howell, Physiology, Chapter XII. 



Herz, The Sensibility of the Alimentary Canal. London: Frowde, 191 1. 



Cannon, Bodily Changes in Pain, Hunger, Fear, and Rage. 



Cannon and Washburn, An Explanation of Hunger, American Journal of Physiology, 

 1912, Vol. XXIX, pp. 441-454. 



Carlson, The Control of Hunger in Health and Disease. 



Luciani, Human Physiology, Vol. Ill, Chapter VI. 



Herrick, An Introduction to Neurology, Chapters XVI, XVII. 



