In any department of knowledge worthy of the name of science I think it will be admitted that one of the most important elements is terminology. The accurate (and adequate) expression of facts by appropriate words is a prime essential in the advancement of knowledge; the absence or imperfection of such is one of the greatest hindrances to progress. And perhaps no more forcible example of this can be adduced than the case of psychiatry, that sphere of knowledge in which all who are members of this Association are supposed to be more or less expert students. I doubt if any branch of science has suffered more than our own from the disability of an imperfect terminology, a point which it is hardly necessary to argue. I may, however, by way of illustration remind you of the numerous schemes of classification of insanity which have from time to time appeared, a matter with respect to which every writer on the subject seems to have done that which was right in his own eyes. But what would be thought of any science—say botany, chemistry, or zoology—if a new system of classification, and even new terms for genera and species, were to be brought out with the same frequency, or anything like the same frequency, as in the case of insanity? Can anything be more bewildering to anyone commencing the study of insanity than to take up book after book and find each writer adopting a different classification, and grouping cases under one heading or category which the next authority he takes up places under another and quite different one? Surely there ought to be, in the first place, agreement amongst authorities as to the meanings of terms, and in the next place at least some permanent basis of classification which all can accept, capable, no doubt, of expansion and modification with the advance of knowledge, but not liable to continual changes, not to say upheavals, in its fundamental structure.