(_b_) We come now to the prophylaxis which is to be adopted in the intervals of the paroxysms when neuralgia has been actually set up. This consists essentially in three things: (1) Physiological rest, as perfect as possible, of the affected parts; (2) protection from cold; (3) protection from sunlight; (4) avoidance of injurious mental emotions. (1) The maintenance of physiological rest, to the greatest extent that is possible, is an absolute necessity, if we would shield a nerve, which has lately been attacked with neuralgia, from fresh paroxysms. The most evident illustrations of this fact are afforded by those neuralgic affections in which it is most difficult to adopt this precaution. Thus the greatest embarrassment from this cause is met with in the case of sciatica; a mild case is often converted into one of great severity and intractability because the patient, in the early stages, either cannot or will not maintain the recumbent posture. So, too, though in less marked degree, the cure of cervico-brachial neuralgia is often greatly impeded by the difficulty of maintaining complete rest of the limb. Again, in neuralgia affecting the third division of the fifth, the movements of mastication and of speech are a terrible hinderance to the progress of recovery; and it often becomes necessary, in severe cases, to prescribe absolute silence, and even to feed the patient exclusively with such liquid or semi-liquid food as shall require no efforts of chewing. (2) Preservation from external cold is highly important. When a nerve of the arm, or leg, or trunk, is affected, warm flannel under-clothing ought immediately to be adopted. The patient who has been suffering from cervico-occipital neuralgia should for some time, in anything but quite summer weather, never go out without wearing a warm comforter round the neck. The sufferer from facial neuralgia should for some time after the cessation of actual attacks never face wind without wearing a thick veil. (3) Exposure to bright light must be scrupulously avoided by sufferers from ophthalmic neuralgia. The affection known as "snow-blindness" is really a neuralgia, with vaso-motor complications, produced by the glare of light reflected from snow; and one of the severest attacks of neuralgia which I personally ever experienced was provoked in this way. Even the comparatively slighter, but for an Englishman unusual, glare of sunlight which one meets with during the first days of a Continental holiday, in wandering about towns made up of clean white stone or whitewashed houses, is enough to provoke an attack, unless the eyes are carefully guarded with colored glasses.