Upon reflection it will at once be seen that from these experimental data showing the ready penetrability of the infantile mucous membrane, another logical deduction follows: If even non-virulent anthrax bacilli introduced per stomach gain ready access to the circulation of the new-born, then it must be possible for all the bacteria of milk to do the same, and we may therefore expect that the accidental presence of pathogenic bacteria in the milk fed to infants will exercise a damaging influence on the infant organism. In considering their pathogenic possibilities the amount of the infectious germs which enter the system must, of course, be a matter of some importance. Under certain conditions, however, even a few germs may be sufficient to excite disease, for in the intestines, especially in the cæcum, they find an excellent place of incubation where they can multiply. A milk very poor in disease germs may thus lead to a virulent infection. In breast-fed infants the danger of introducing disease germs, excepting tubercle bacilli, of which I shall speak later, is not very great, for it is very unusual for living germs derived from the interior of the body to appear in the milk. The germs which can be found, even in perfectly fresh milk, are derived from the surface of the body, or from the mouths of the lacteals, or possibly even from the glandular epithelium, as researches conducted by myself, assisted by Mr. Rösler, have shown. But in _artificially nourished infants_ the matter is altogether different. It would be a miracle if, after all the manipulations to which the milk supplied to our large cities is subjected, it did not occasionally contain disease germs derived from the milker or from other persons who have handled the milk. If, by the time the milk reaches the city, the proliferation of these pathogenic micro-organisms has already gone on to a considerable extent, then usually the milk will contain a number of poisonous substances in addition to the micro-organisms. Some of these germs are killed by the scalding to which the milk is usually subjected before feeding, and the virulence of the rest is much diminished, so that in boiled milk practically no danger is to be apprehended from the micro-organisms. We are not at all sure, however, that we have made the toxins innocuous by this boiling, and probably a great many cases of intestinal catarrh in artificially nourished children are due, not to a parasitic, but to a toxic infection.