There is no need to dilate at greater length upon the varieties in the symptoms of myalgia, according as it affects one or another part of the body. We must consider, briefly the different kinds of cause that produce it. The immediate source of the pain being, as we have seen, the sense of embarrassment in a muscle obliged to contract when unfit for the work, we have to ask what are the remoter causes that can produce this special unfitness for the work of contraction. They are three: (_a_) Overlabor pure and simple (_i. e._, in proportion to the existing bulk and quality of the muscle); (_b_) cold, and especially damp cold, producing a semi-paralyzing effect on the vaso-motor nerves, and causing congestion and sometimes a little effusion among the fibres or within the sheath of the muscle; (_c_) fatty degeneration of muscle which is exposed to inevitable and incessant work. Either of these conditions may so disable the muscle that its unavoidable contractions will set up the myalgic state. Undoubtedly however there is something further, in the shape of a natural predisposition not yet understood, which makes some patients so much more liable to suffer myalgic pain as a consequence of this sort of influences than other persons are. I am in no condition to decide what the nature of this predisposition is; I feel sure it is heightened by an inherited or acquired gouty taint, but I have seen it in people whom there is no reason to suspect of gouty tendencies. It appears to have no connection with true rheumatism. Still after all that can be said, myalgia remains a disease chiefly of local origin, and depending for nine-tenths of its causation upon a derangement between the balance of work and nutrition in the muscle. As regards the diagnosis of myalgia from neuralgia, which is a very important matter, the following are the main points that we should recollect: _Neuralgia._ _Myalgia._ Follows the distribution of a Attacks a limited patch or recognizable nerve or nerves. patches that can be identified with the tendon or aponeurosis of a muscle which, on inquiry, will be found to have been hardly worked. Goes along with an inherited or As often as not occurs in persons acquired nervous temperament, with no special neurotic which is obvious. tendency. Is much less aggravated, Is inevitably, and very severely, usually, by movement than aggravated by every movement of myalgia is. the part. Is at first accompanied by no Distinguished from the first, by local tenderness. localized tenderness on pressure as well as on movement.