Intoxication means the action on the living elements of the tissues of substances which affect the intimate vital chemistry of these elements. In this sense it has wide relations and is frequently an incident, but always an important incident, in a variety of diseases. Intoxication includes mere Poisoning, or the introduction of toxic substances from without, but that group of conditions does not concern us here. Again, almost all Infections are accompanied by intoxication, this being, in many cases, the most significant phenomenon of the disease. Excluding this group of conditions from our present review, there remain certain phenomena which are not the effect of poisons intruded as such nor of toxines produced in the body by infective agents. To this group the term Auto-intoxications is applied.

Auto-intoxication is a term whose use is by no means strictly defined. As it implies an intoxication of the body by itself, it may properly be limited to the production of poisons either in the metabolism of the tissues or in the course of processes which belong to the ordinary and normal functions of the body.

The elaboration of poisons in the regular metabolism of the tissues has been the subject of investigation by the French school and especially by Bouchard. The alkaloids thus produced are designated leucomaines, which are distinguished from alkaloids arising from putrescence of albuminous tissues or ptomaines. Extracts of normal tissues, more especially muscle and liver, afford poisons, which, introduced into animals, produce symptoms which may end in death. Again, it has been pointed out that the urine contains poisons, and that the amount and character of these poisons vary greatly under different circumstances. The amount is considerably increased, for example, in fatigue, a fact indicating that, in the action of the muscles, there is a considerable production of leucomaines. The toxicity of the urine, no doubt, has various sources, but its existence may serve to show that the blood contains, under normal conditions, poisonous matters.

The intestinal canal is, under normal conditions, the seat of a variety of fermentations - some of them connected with the ordinary processes of digestion, gastric or intestinal, some of them connected with the action of microbes which may have a useful effect in breaking up certain chemical combinations of the food, but which also produce various products of an offensive or injurious character. There must be variations in both forms of fermentation, and it may be presumed that defect in the proper digestive fermentations will ' give greater opportunity to the bacterial forms. The products of the bacterial fermentations are doubtless absorbed, and they frequently proclaim the fact by the evil odour of the breath and other exhalations. It must be regarded as undecided to what extent the-symptoms of dyspepsia are due to an auto-intoxication produced in the way indicated or by reflex nervous influences, but certainly the deranged chemical processes and the absorption of various products of putrefaction play some part in the symptomatology. It is stated that the toxicity of the urine is increased in the course of digestive disorders. Whilst dyspepsia or mere constipation may increase the products of ordinary putrid decomposition in the intestine, there may, in some cases, be extraordinary fermentations set up. Gastrointestinal catarrhs are sometimes accompanied by fever, and in this case there is either a very excessive absorption of the products of ordinary fermentation or the introduction of a special kind. Probably the latter is the case, and the condition passes beyond the strict limits of auto-intoxication. There are some who would include such cases in the term, and would even extend it to infections such as cholera, where a special microbe leads to the production of very specific poisons, but such an extension of the term is undesirable.

The liver has had an important part assigned to it in relation to gastro-intestinal auto-intoxication. By certain French writers it is asserted that the liver is the destroyer of toxic matters which -are normally absorbed from the intestine. As the alimentary canal is constantly the abode of foul materials, these cannot fail of absorption, and it is a function of the liver, in receiving all the blood coming from the intestine, to destroy the poisonous matters, and prevent their entrance into the general circulation. To what extent the liver exercises this function cannot be said, but the view is apt to receive too ready an assent from its apparent support of the popular view that derangements of the liver have to do with many of the lighter ailments of mankind. It is an exaggeration of this view to suggest that the symptoms of acute yellow atrophy (icterus gravis) are in large measure due to the alimentary poisons reaching the circulation, on account of the elimination of the function of the liver.