ments on monkeys showed that in health these animals have the power of very quickly ridding themselves of this variety of bacteria. Experiments now under way with a microorganism described by myself and Dr. Kendall as B. infantilis and found very abundantly in some of the digestive diseases of children, show the same thing to hold true.
The fact that B. bulgaricus does not readily gain a dominant position in the digestive tract in man or in the monkey has an obvious bearing on the results to be expected from its therapeutic use. If it be indeed true that B. bulgaricus is capable by its presence in the intestinal tract of inhibiting undesirable types of bacteria and especially the microorganisms concerned with intestinal putrefaction, then it must be equally true that the difficulty in obtaining a dominant and permanent foothold in the intestinal tract is a fact with which we must reckon in any estimate of the results likely to be obtained through the administration of these organisms. The moderate representation of B. bulgaricus in the large intestine after the free administration of lacto-bacilline is surely something very different from what has been already frequently pictured by the enthusiastic upholders of the use of this form of fermented milk in the treatment of diseases of the digestive tract.
I think it has been assumed with far too little reason that the dominant presence of foreign microorganisms of the lactic acid group is necessarily a desirable thing. If it could be shown that lactic acid bacilli, such as B. bulgaricus or certain varieties of B. acidi lactici, have the faculty of replacing undesirable forms of microorganisms such as the bacilli of typhoid or of paratyphoid fever or putrefactive microorganisms, such as B. proteus vulgarus or B. ærogenes capsulatus, this would undoubtedly be cause for congratulation, especially if it could be shown at the same time that the normal flora of the digestive tract remained unchanged. I do not deny the possibility that this selective kind of anti-bacterial action may some day be proved to exist. I desire merely to point out that at present I know of no facts to justify tis in believing that such antagonistic action as the lactic acid bacteria may possess is directed solely against the disease-inciting invaders of the digestive tract. If it should prove true that the antagonism exerted by the lactic acid bacilli against injurious invaders is also exerted against the obligate bacterial inhabitants of the alimentary canal, such as B. coli communis and B. lactis ærogenes, I am by no means convinced that this could be regarded as a point in favor of the prolonged therapeutic use of lactic acid bacilli. If, as appears to be true, these obligate inhabitants of the digestive tract are especially adapted to the normal conditions of secretion and digestion in the human intestine and tend to be suppressed in some serious conditions of the digestive tract (while their reappearance and reestablishment in abundant numbers
