In the observations which I am about to address to you, I purpose to set forth by illustrations the character and course of a form of mental derangement which has its special cause, certain characteristic features, and a definite course, almost invariably from bad to worse. I speak of that kind of insanity which is brought on by self-abuse. In doing this, however, I have another object in view; I am anxious to use my exposition in order to exemplify a new and practical classification of insanity which has been proposed and sketched out by Dr. Skae.