Insanity results from a disease of the brain. Although after death, in many cases, no appreciable structural lesion can be detected in the cerebral mass, it would be illogical for us to conclude that the sentient organ has not been physically affected. Derangement of mind is but the effect of physical disease, and, like all other diseases, it has an early as well as an advanced stage. Medical men have not paid sufficient attention to the premonitory indications of mental alienation. Having erected an arbitrary standard of derangement in their own minds, they have been disposed to consider no deviation from mental soundness as insanity, unless it exhibited the symptoms which their preconceived ideas had led them to suppose necessary, in order to constitute that disease. They have argued as if insanity were a specific disease invariably manifesting the same phenomena, and in this way definitions have been framed, by which the soundness of the intellect has been tested. It is hardly necessary to say how fallacious all such tests must be. The brain, like every other organ, is liable to a variety of diseases, in all of which the mental faculties are more or less affected. The danger of attempting to erect an arbitrary standard of insanity is this: it induces us to overlook the incipient symptoms of mental derangement, and to consider no deviation from soundness of intellect as insanity which does not come within the scope of our definition. The early symptoms of mental aberration are as much an evidence of the presence of insanity, as when the disease is more advanced, and the indications become so apparent that no one hesitates in pronouncing the individual mad. Medical men who have maintained that the act of suicide is not invariably the result of insanity have argued as if the mental ailment was always self-evident and easily detected; whereas, those who have had any experience in the matter know full well, that occasionally there are no diseases more difficult of detection than those which relate to a morbid condition of the mind. If an act of suicide has been committed, and the individual at the moment of perpetrating it did not manifest evident symptoms of insanity, the conclusion drawn is, that he was perfectly sane at the time. That the facts of the case do not warrant this inference must be apparent to those who consider the subject in an enlarged point of view. If we examine attentively the majority of cases of suicide, we shall find that the unfortunate persons have laboured, either for some time previously or at the very moment, under depression of spirits, anxiety of mind, and other symptoms of cerebral derangement. Very few cases of suicide take place in which you cannot trace the existence of previous mental depression, produced either by physical or moral agents. It may be said that lowness of spirits is not insanity; certainly not, according to the _legal_ definition of the term; but