(10) Secondary affections (_a_) of secreting glands, or (_b_) vaso-motor nerves; or (_c_) of nutrition of tissues; or secondary localized paralyses of muscles, or localized anæsthesia of a somewhat decided though not complete kind, as described in Chapter II.; any one or any number of these various complications may be present. I must insist that the above picture includes only the essentials for a diagnosis of neuralgia; if the painful affection will not answer to the conditions therein included, we have no right to call it a neuralgia--it belongs, for every practical purpose, to some other category of disease. Let me add one more essential characteristic, which is, that the pain begins and assumes its characteristic type before any other of the phenomena appear, with the single and partial exception of anæsthesia. There are some special modes of diagnosis of the varieties of neuralgia, developed of late years, that require notice here; they are chiefly the result of the researches of Moriz Benedikt. As regards the quality of the pain, Benedikt says that the curve of intensity has an intimate relation to the _locus in quo_ of the neuralgia (_i. e._, whether in the periphery, trunk, or roots). An inflammatory irritation set up at the periphery of a nerve (by a joint-inflammation, for instance) produces a continuous pain; the same kind of irritation, attacking a nerve-trunk (_e. g._, in the bony canals), produces a paroxysmal pain; an inflammation spreading from the vertebræ to the nerve-roots or the cord-centres produces momentary lancinating pains. The latter characteristic he supposes to be especially characteristic of the centrally-produced neuralgias; and I may observe, as so far confirmatory of this idea, that this is especially the character of the pains in locomotor ataxy. There are sundry special cases to be considered, however: thus, Benedikt himself remarks that the pain set up by the pressure of a pulsating aneurism is, from the nature of things, lancinating from moment to moment. Eulenburg,[32] moreover, says that Benedikt's tests of the locality of the primary mischief only hold good under the following circumstances: (1) When the irritability and the exhaustibility of the nerves are in a normal condition during the neuralgia; (2) when the irritation that calls forth the paroxysm is either identical with the original cause of the disease, or at least operates upon the same spot. The two conditions, however, do not concur. The irritability and exhaustibility may be sometimes excessive in neuralgias, sometimes normal, and perhaps, in certain cases, beneath the normal standard; by which means the form of the curve of intensity must be considerably modified. Moreover, the irritation that provokes an attack may from the periphery attack the primary seat of the disease, even when this is central, on account (says Eulenburg) of exaggerated conductivity of the nerves (his second