Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.

of this nerve, where it passes behind the neck of the thigh-bone after it has emerged from the pelvis. This is explained, perhaps, from the fact that at this spot the greater sciatic is more ex- posed than any other large nerve trunk in the human body. It is here liable to be exposed to severe or prolonged pressure in sitting and walking; to bruising and concussion; to irritation, as from severe toil, riding and walking; to chill and congestion, from cold, wet, or damp, or from sitting upon any cold seat, particularly after great heat or fatigue; any of which is suffi- cient to set up a morbid action that may amount to a neuralgia, a rheumatism, or an acute attack of sciatic inflammation. Now, some always regard this malady as a neuralgic or rheumatic affection ; and no doubt it does occasionally partake of the one or the other specific character, because of the existence of one or the other in the system at the same time. But sciatic neu- ralgia may appear occasionally as a mere symptom of some morbid irritation in the alimentary canal, or of some one of the inter-pelvic viscera, thus being only a reflex nervous action; then, after the cause is removed, the painful condition of the nerve appears to continue chronic, just as palsy of the limbs continues, after the lesion in the brain, that was the first cause of it, has been healed. It is all important to be able to distinguish the organic from the symptomatic sciatica. In tracing the cause of each particular case, the history of it becomes an important 'witness, not to be slightly questioned, because of the more prominent symptoms in all cases being so similar. Nevertheless, by care- ful analysis of the local and of the general symptoms, and by tracing the history of the precedent circumstances that are con- nected with the appearance of the pain, we shall find the ap- parent difficulties of the diagnosis to vanish as this investigation proceeds. The very first symptom, mark, of acute sciatica — which, indeed, is manifested very soon after the exposure of the patient — is a sense of weight of that leg, together with a feeling of coldness, numbness, or a want of sensibility ; and this is accom- panied, or perhaps soon followed, by rigors, and other very dis- 30*