DISEASES OF UNCERTAIN OR VARIABLE SEAT - the somewhat indefinite heading of this chapter has been adopted from the classification of the Registrar-General, for the purpose of grouping together some diseases which, while they cannot be included among such as owe their origin to a;morbific or adventitious impregnation, at the same time cannot be readily classified under the diseases of particular organs, because of the varia ble nature of their cause and their seat. In the order which we have pre scribed to ourselves they must be considered here, because their symptoms are among the objective phenomena of disease, and each division presents one prominent feature common to the whole group.
In a strictly scientific point of view, it may be alleged that they ought to be studied simply as symptoms ; but for the purpose of diagnosis they must be considered in their relation to each other, as we shall thus be enabled to compare their extent and situation, and to ascertain with more exactness the deductions which they warrant with reference to internal organs. The classi fication which separates them from the deeper-seated disease is justified by the circumstance that they may be the only definite symptom of its presence ; they are the subject of complaint and the object of treatment, and it is only by inference that we are led to suspect the existence of anything more.
They also differ from mere symptoms in presenting decided and broadly marked characters, which are uniform and consistent, whatever be their situa tion or supposed cause. They do not necessarily accompany the more im portant lesions with which they are usually associated, but seem only to super vene under certain circumstances, of which the most important probably is an altered condition of the blood itself. Further, although they are most fre quently dependent on some form of organic lesion, yet occasionally the very same appearances may be observed when the disorder is solely in the circulat ing fluid itself, and thus they become allied with what we have called the chronic blood-ailments.
Our inquiry will here be limited to their distinguishing features, pointing out wherein they resemble or differ from each other in situation and appearance, and indicating only in a general manner their probable causes. The more nunnte examination of the disease with which they are allied must be deferred till we come to the consideration of those organs in which they are situated.