We have now followed every nutrient and food-accessory from the moment of its entry to its exit from the body, and so far as our knowledge permits, have accounted for its decomposition and the disposition of its end-products. The problem is, however, not nearly so simple as this survey would appear to set forth. We have taken notice of the fact that in addition to the dissolving operations of the digestive ferments, a precisely analogous process is effected by bacteria. The results of these two agencies are capable of being estimated with some degree of accuracy, because their products are for the most part tangible and accessible, but the problem is still further complicated by the undoubted existence of autolysis, a digestive action in the tissues themselves, and, in certain circumstances, by the formation of by-products in the alimentary canal, due to putrefaction or other decomposition of the food substances themselves. This last series of changes is effected by the bacteria normally present in the digestive tube, and the view has been advanced, especially by Combe, that the absorption of these by-products is responsible for the condition now so well known as intestinal auto-intoxication. A brief description of the arguments for and against the existence of this condition will enable us with greater precision to estimate the respective advantages of the various dietetic theories we are about to discuss.

Although the theory owes its inception to Bouchard in 1882, glimmerings of it may be discovered in the writings of others many years prior to this date. It first took solid form in 1868, when Senator directed attention to intoxications the cause of which, he said, resided in the intestines - a more correct view than that of Bouchard, who believed that they were due to dilatation of the stomach. Since that time the literature on the subject has been immense, and every one who has read Combe's well-known treatise must reckon with this latest factor in the production of chronic disease.

As the process takes place to a certain extent in every one, it may be looked upon as normal, and only when it has an ultimate sinister effect on the health can it be pronounced malign. When this occurs, either serious mistakes in diet - generally in the way of excess - have been allowed to take place, or else there has been a marked weakening of the natural defences of the body. It is usual to aver that excessive ingestion of protein food is the cause of offence to the system, but this is held only because we are much better acquainted with the chemical decompositions arising from the albuminous molecule than with those of others. Fatty acids producing "acidosis " may accumulate in the blood from the partial oxidation of fats; the fermentations of carbohydrates are apt to give rise to lactic, succinic, butyric, and other acids, which may injuriously influence the blood just as much by diminishing its alkalinity. From daily observations in practice one can hardly escape the conclusion that rheumatism - at least of the muscular variety - can arise from excessive quantities of acid in the body. I have repeatedly seen arthritis produced by indulgence in a dish like stewed rhubarb or stewed plums, and whatever be the explanation, it is closely bound up with the ingestion of more acid than the system can tolerate. The function of the kidneys is to eliminate excess of acid from the alkaline blood, and if they fail in this duty, then auto-intoxication must arise, because the blood is not alkaline enough to absorb carbonic acid from the tissues. We cannot afford to lose sight of these facts, in view of some of the after-effects of the administration of soured milk.