of the lactic acid bacilli it is claimed that they drive out other forms of bacteria from the large intestine the chief seat of intestinal putrefaction. It is desirable that we should soberly consider the known facts relating to this question. I think it safe to say that the ability of lactic acid forms to replace or dominate other types of bacteria in the large intestine is much exaggerated. I have devoted some study to this question, especially in the case of the B. bulgaricus employed in the production of lacto-bacilline. This organism, owing to its large size, morphology and cultural peculiarities is easily recognized and is cultivable, from the intestinal contents. When given to human beings in the large numbers present in lacto-bacilline it can after a few days' administration be cultivated without difficulty from the movements. Even when large quantities of the fermented milk have been taken I have not found that it becomes the dominant organism, although it may be present in moderate numbers. On stopping the administration of the lacto-bacilline, the B. bulgaricus generally disappears in the course of a few days, showing that it has not permanently established itself within the intestinal tract. There may be exceptions to this statement, but I have not yet met with any. These clinical results are quite in accord with those obtained by Dr. Kendall and myself in experiments upon a monkey fed for two weeks on lacto-bacilline exclusively. At the end of this period, when the movements were showing the regular presence of B. bulgaricus in relatively moderate numbers, the animal was killed and the digestive tract examined with care at all its levels. The lactic acid organisms were found in greatest abundance in the small intestine. In the lowest portion of the small intestine a notable falling off was observed and other types of bacteria were prominent. In the large intestine the numbers were only moderate as compared with other varieties of bacteria, thus clearly showing that in this instance, at least, the B. bulgaricus was very far from dominating other associated types of bacteria. I consider this fact noteworthy, as the experiment was carried out under conditions highly favorable to the establishment of the lactic acid bacilli in the digestive tract. The large number of microorganisms given and the relatively short extent of the digestive tract in the monkey should, it would seem, provide conditions for the adaptation of the organisms throughout the alimentary canal.
It is probable that the experience Just recounted with regard to lactic acid bacilli is not at all exceptional, or in other words that foreign bacteria in general find it difficult to gain a permanent footing in the digestive tract. The literature of experimental bacteriology shows this to be the case. Personal experiments made with a highly fermentative putrefactive organism—B. ærogenes capsulatus (B. welchii or B. perfringens of the French writers)—in feeding experi-
