Complete.

I AM persuaded myself that all madness, or nearly all, takes its rise in some part of the apparatus connected with the digestive organs, most probably in the liver. That the brain is usually supposed to be the seat of madness has arisen from two causes: first, because the brain is universally considered the organ of thought; on which account, any disease which disturbs the thinking principle is naturally held to be seated there: secondly, because in dissections of lunatics some lesion or disorganization of the brain has been generally found. Now, as to the first argument, I am of opinion that the brain has been considered the organ of thought chiefly in consequence of the strong direction of the attention to the head arising out of the circumstance that four of the senses, but especially that the two most intellectual of the senses, have their organs seated in that part of our structure. But if we must use the phrase “organ of thought” at all, on many grounds I should be disposed to say that the brain and the stomach apparatus through their reciprocal action and reaction jointly make up the compound organ of thought. Secondly, as to the post-mortem appearances in the brains of lunatics, no fact is better ascertained in modern pathology than the metastasis, or translation to some near or remote organ, of a disease which had primarily affected the liver—generally from sympathy, as it is called, but sometimes, in the case of neighboring organs, from absolute pressure when the liver is enlarged. In such cases the sympathetic disorder, which at first is only apparent, soon becomes real, and unrealizes the original one. The brain and the lungs are in all cases of diseased liver, I believe, liable beyond any other organs to this morbid sympathy; and supposing a peculiar mode of diseased liver to be the origin of madness, this particular mode we may assume to have as one part of its peculiarity a more uniform determination than other modes to this general tendency of the liver to generate a secondary disease in the brain. Admitting all this, however, it will be alleged that it merely weakens or destroys the objections to such a theory; but what is the positive argument in its behalf? I answer—my own long experience, and, latterly, my own experiments directed to this very question, under the use of opium. For some years opium had simply affected the tone of my stomach, but as this went off, and the stomach, by medicine and exercise, etc., began to recover its strength, I observed that the liver began to suffer. Under the affection of this organ I was sensible that the genial spirits decayed far more rapidly and deeply; and that with this decay the intellectual faculties had a much closer sympathy. Upon this I tried some scores of experiments, raising and lowering alternately, for periods of forty-eight, sixty, seventy-two, or eighty-four hours, the quantity of opium. The result I may perhaps describe more particularly elsewhere—in substance it amounted to this, that as the opium began to take effect, the whole living principle of the intellectual motions began to lose its elasticity, and, as it were, to petrify; I began to comprehend the tendency of madness to eddy about one idea, and the loss of power to abstract—to hold abstractions steadily before me—or to exercise many other intellectual acts, was in due proportion to the degree in which the biliary system seemed to suffer. It is impossible in a short compass to describe all that took place; it is sufficient to say that the power of the biliary functions to affect and to modify the power of thinking according to the degree in which they were themselves affected, and in a way far different from the action of good or bad spirits, was prodigious, and gave me a full revelation of the way in which insanity begins to collect and form itself. During all this time my head was unaffected. And I am now more than ever disposed to think that some affection of the liver is in most cases the sole proximate cause, or, if not, an indispensable previous condition of madness.