318 DISEASES OF THE PERIPHERAL NERVES. 



ralgia caused by malarial poisoning), the action affects the trunk rathei 

 than the peripheral termination. This view is favored first by the 

 exact limitation of the neuralgic pain to the peripheral expansions of 

 a single nerve, and the freedom of the parts immediately adjacent, if 

 these are supplied by other sensory nerves. This limitation would be 

 quite inexplicable if the irritation acted on the periphery. How should 

 we explain the constant freedom of the radial side of a finger, or the 

 supra-orbital region of one side, from the injury that so severely af- 

 fected the ulnar side of the same finger or the supra-orbital region of 

 the other side ? The view that neuralgia starts from the nerve-trunk 

 is also supported by the fact that no idea of the variety of the irrita- 

 tion accompanies the pain. It is well known that the cutaneous pa- 

 pillae connected with the terminations of the nerves are the chief 

 source of the sensation of pressure and temperature. If the neuralgic 

 pain were induced by the action of an imperceptible cause on the skin, 

 the patients would have some impression of the quality of this irrita- 

 tion ; they would complain of burning, piercing, or some other kind of 

 pain. But, on the contrary, if a very cold or very hot body be applied 

 to an exposed nerve-trunk, if we puncture or squeeze it, there is al- 

 ways the same sort of pain, just as in neuralgia ; and, from the pain, 

 the patient cannot tell what cause induced it. Finally, the want of 

 benefit, in most cases, from division of nerves, indicates that the seat 

 of the disease is to be sought for in the trunk or branches, not in the 

 peripheral expansions of nerves. We do not know what physical or 

 chemical changes of the nerves cause their morbid excitement in neu- 

 ralgia. We may even suspect that they do not consist in any very 

 evident deviations from the normal, for these remove the excitability, 

 but that injuries only act as causes of neuralgia, when they exercise a 

 comparatively slight irritation on the nerves. If we find a nerve, 

 which was affected with neuralgia, much changed at some point, we 

 may be sure that this was not the starting-point of the pain, but that 

 it originated from some point higher up, where no changes of structure 

 can be made out with the naked eye or with the microscope. 



The predisposition to neuralgia varies with the person. A morbid 

 increase of excitability of the entire nervous system, so-called nervous 

 debility, of which we shall speak hereafter, and which is seen more 

 frequently in women than in men, in bloodless and debilitated persons 

 than in the full-blooded and strong, appears to lead to the occurrence 

 of neuralgia in some persons more readily than in others. 



The exciting causes that is, the irritations which, by their action 

 on the nerve-trunk, induce the neuralgia are partly known, partly un- 

 known. We are not justified in distinguishing cases from unknown 

 causes as " genuine " or " pure " neuralgia. The pain caused in the 



