Since the digestive tract is the most common source of intrinsic toxic materials it is natural to suppose that its disorders are very commonly due to these substances. As already stated disorders of the gastrointestinal tract cause the formation of toxic materials, which in turn perpetuate the initial disorder and add new clinical features to it. For example, constipation may Cause intestinal stasis; this allows the formation of some poisonous diamin from the absorption of which various symptoms result; this in turn aggravates the constipation until such a time arrives that some intestinal stimulant is formed, for many of the intestinal auto-toxins cause diarrhea, and the noxious mass is expelled from the body. Art may interfere and curtail the process by the administration of some drug which anticipates the intestinal purge. From a review of the individual substances described in Part II, it seems very probable that many of the evanescent symptoms of ill-health, such as occasional diarrhea, neuralgic and rheumatic pains, somnolence and lethargy, disturbed vision, subjective symptoms of varied nature, and transient disorders of the urinary tract - all of which are frequently associated with digestive disturbances - are the direct result of the absorption of some of these materials. As yet we do not know the various combinations into which they enter, or the changes in toxicity which they undergo in different associations, and there are doubtless many substances of whose existence we are unaware and whose chemical formulae have not yet been computed. As already noted, indol and other sub-oxidation products may be formed whenever there is lack of digestive fluids or faulty elimination of the excreta, and this may explain the remarkable clinical results which frequently follow the exhibition of sodium bicarbonate, diastase, malt, and other of the so-called "digestants." It would be interesting to dwell upon the philosophy of their actions, but we must be content with offering the view that this class of medicines shows the truth of the theories of auto-intoxication, for they attain results by stimulating the natural digestive functions, more completely oxidizing food materials, thereby preventing the formation of sub-oxids.