I would also go farther, and express the opinion that peripheral influences of an extremely powerful and continuous kind, where they occur with one of those critical periods of life at which the central nervous system is relatively weak and unstable, can occasionally set going a non-inflammatory centric atrophy which may localize itself in those nerves upon whose centres the morbific peripheral influence is perpetually pouring in. Even such influences as the psychical and emotional, be it remembered, must be considered peripheral--that is, they are external to the seat and centre of the neuralgia. And there are probably few practitioners of large experience who have not seen a patient or two in whom the concurrence of some unfortunate psychical with some other noxious peripheral influence, the whole taking place at some critical period of life (especially in the years between puberty and marriage), seems to have totally deranged the general balance of nervous forces, and induced morbid susceptibilities and morbid tendencies to some particular neurosis. It is a comparatively frequent thing, for example, to see an unsocial solitary life (leading to the habit of masturbation), joined with the bad influence of an unhealthy ambition, prompting to premature and false work in literature and art. The bad peripheral influence of constant fatigue of the eyes in study may so completely modify a young man's constitution as to make a wreck of him in a very few years, changing him from the state of habitual and conscious health to that of chronic neurosis of one sort or another. And, though it is doubtless on persons with congenital tendencies to nervous diseases that such a combination of bad influences produces its most serious effects, yet there unquestionably are a few persons in whom they appear to entirely generate the neurotic constitution. I have already touched upon the part that misdirected psychical influences, especially religious and other forms of emotional excitement, may play in this unfortunate perversion of the natural and healthy nervous functions, more especially in youth; and need only add, here, that perhaps the most fatal combination of all the bad influences is the melancholy union of highly-strained religious sentiment with peripheral sexual irritation, which is, unfortunately, a too common phenomenon under certain systems of education. The most frequent neurotic consequences of the class of influences which have now been referred to are probably neuralgia--in the form either of migraine, of nervous angina, or of sciatica--or else asthma.