There is a constant endeavour in psychiatry, as in other branches of medical science, to distinguish between organic and functional disorder. Year by year, in most of these other branches, the organic group becomes larger, the functional group smaller. But unfortunately the same cannot be said for psychiatry. When all is said and done, the term “functional disease” is largely a cloak for ignorance. Where there is disease there must be something to show for it, but if the changes are so subtle as to escape detection, we at once label the condition “functional.” General paralysis was considered a functional disease until it was proved to have a very solid anatomo-pathological basis; indeed, until this proof was forthcoming it could hardly be said to exist as a definite entity at all. Until this process is extended to other forms of insanity, clear thinking in psychiatry is impossible. We are still far too prone to look only upon the mental side of the cases which come under our care, whereas we ought diligently to search for some physical causal factor that may be at work, and for corresponding physical changes that may give us a clue to such a factor.