122 TRANSFORMATION OF THE INTESTINAL FLORA 



interesting field of study, namely bacterial implantation within the 

 digestive tract for therapeutic purposes. 



According to MetchnikofF, the so-called lactic acid therapy consists 

 essentially in administering per os living cultures of lactic acid bacilli, 

 either in milk soured by them or as tabloids, or in pure culture together 

 with some fermentable carbohydrate. The lactic acid bacilli ferment 

 the carbohydrate in the alimentary canal, producing lactic acid and 

 thus exerting a direct influence on the bacterial processes, particularly 

 in the large intestine. Soured milk was considered to be of special merit 

 in this method of treatment, particularly milk which was rendered acid 

 with B. hulgaricus. 



So general has the use of soured milk and of B. bulgaricus products 

 become that the market is flooded with various commercial preparations, 

 in the form of powders, tablets or liquid cultures or suspensions which 

 contain as their active principle the organism which has been shown to 

 be the most important souring agent in the sour milk products of the 

 Orient, namely B. bulgaricus. Not only has it been claimed that 

 beneficial results are obtained by the ingestion of milk which has been 

 soured by B. hulgaricus, but that this organism itself, without the 

 addition of milk or lactose exerts the same favorable influence by 

 destroying or eliminating harmful bacteria from the intestinal tract, 

 and thus preventing auto-intoxication. 



Repeated attempts in the present investigation to establish B. bul- 

 garicus in the alimentary canal of albino rats and of man through the 

 administration per os of extremely large numbers of this organism 

 were entirely unsuccessful. At no time in the study was B. bulgaricus 

 recovered from the feces of man or the white rats or from any portion 

 of the digestive tract of the rats, irrespective of whether the organism 

 was fed alone or together with a utilizable carbohydrate. However, in 

 all of the subjects which received the suspension of B. bulgaricus in 

 connection with lactose or dextrin there followed a multiplication of 

 B. acidophilus, and to the same extent as when similar amounts of the 

 carbohydrates were fed without any addition of bacterial suspensions. 



These results are in harmony with those of the following observers. 

 Kulka (1914) demonstrated in his experiments upon man that the 

 "B. metchnikovi," when introduced per os, cannot be recovered from the 

 feces. Rahe (1915) failed to procure any evidence by feeding experi- 

 ments that B. bulgaricus is capable of surviving in the lower intestine of 

 man. Morse and Bowditch (1906) found that practically the same, 

 and in some instances better, results were obtained with pasteurized as 

 with raw acidified milk or buttermilk, and concluded that the action of 

 the lactic acid bacteria is unimportant. 



Although considerable doubt has been cast upon Metchnikoff's ex- 

 planation of the merits of sour milk therapy, the fundamental principle 

 of his arguments must in the main be accepted. That is, bacterial 

 implantation with the concomitant transformation of the intestinal 



