So far as my researches extend little attention has been paid to the subject of this paper. Yet I think it would be rash to assume that what is unrecorded is necessarily rare, even in days when so much more is put into print than any of us can either read or mark, much less digest, and when the number of writers seems in danger of exceeding the number of readers. Insanity, in some degree, as a sequela of surgical operation, though certainly rare, is, I believe, less uncommon than usually supposed, and it is chiefly in the hope of eliciting additional information from others that I venture to record my own small experience. On two subjects medical science has still an infinite deal to learn: first, the influence of disease on the mind; secondly, the influence of mind on disease. In attempting to contribute a little to the first-mentioned subject, I can really deal only with a subdivision of it, viz., the effects that may be produced on the mind by surgical measures undertaken for the relief of disease.