436 THE POPULAR SCIENCE MONTHLY 



nerves." When a viseus is the seat of origin of pain the impulses which 

 ascend its sympathetic nerves excite the centers of sensory nerves in 

 the spinal cord. 



The theory which I have attempted to outline in this article is laid 

 on the same basis, somewhat broadened. All pain is " referred " — to 

 the right spot, if its source be in the skin; because the skin is elabo- 

 rately supplied with place-defining nerves — to an organ or part, skin, 

 muscle, joint, which the ego, during the progress of self-investigation, 

 has discovered in the same segment of the body, if its source be in a 

 viseus. 



The body is permeated with a felt-work of nerves, unprovided with 

 specialized nerve-endings, conveying no definite information, and in 

 consequence without precise distribution in the seat of consciousness. 

 This non-specialized system which binds the various parts of the body 

 together is the mechanism through which the caliber of blood-vessels, 

 erection of hairs, secretion of glands, contraction of the walls of ducts 

 and of the intestines, and many other domestic adjustments are effected. 

 It is also the medium through which the gray matter of the cerebro- 

 spinal axis is affected sympathetically with damage to the tissues. The 

 resultant altered conductivity of the gray matter leads to modification 

 of the only kind of impulses with which consciousness is concerned — 

 impulses which inform. We infer that the damage which is giving 

 rise to a feeling of pain is in the part from which the modified impulses 

 come. 



When attempting to formulate the theory of pain it is necessary to 

 discard the prejudice that there need be a proportional relation be- 

 tween the intensity of pain and the magnitude of the physiological 

 changes which condition it. A heavy blow hurts more than a light one. 

 Yet a change which could not be detected by any piece of apparatus 

 in use in a physiological laboratory, if it affect the nerve-tissue of a 

 tooth, may give rise to more pain than is caused by a crushed limb. 



Another prejudice, from which it is difficult to shake free, attributes 

 to the mind an innate knowledge of the topography of the body; an 

 innate knowledge, that is to say, of the distribution of its news-agents, 

 the sensory endings of nerves. 



Thirdly, it is necessary to remember, when investigating the ma- 

 chine, that the machine is the man. It is not sufficient to design a 

 scheme of telephone wires requiring for its use a listening ear at its 

 center, the brain. The ear is a part of the machine. There is no need 

 to picture a system of pain nerves, carrying news of damage to an at- 

 tentive mind. A departure from the normal in the functioning of the 

 sensory apparatus is pain. 



