GENERAL DISCUSSION AND SUMMARY 119 



experiments with white rats were reported which indicated that lactose 

 and dextrin exercise a marked transforming power on the intestinal 

 flora, bringing about a predominance of B. bifidus. These results are 

 in agreement with our own in principle, but differ in that they placed 

 chief emphasis upon the Tissier organism in their findings, whereas in 

 our experiments B. acidophilus played the role of primary importance. 



Hull and Rettger (1917), as the result of limited observations on 

 this particular carbohydrate, reported that the administration of dex- 

 trin to albino rats did not cause any noticeable increase in the numbers 

 of B. acidophilus. These findings are in disagreement with the results 

 of dextrin feeding in the present investigation, and may have been due 

 to the idiosyncrasies of the few rats that were used by Hull and Rettger 

 in the dextrin feeding experiments. 



Kendall's suggestion (1911) that the feeding of liberal amounts of 

 lactose to infants may cause an abnormal or excessive development of 

 B. welchii, and similar contentions of other observers, receive no support 

 whatever from the present studies. While there can be no doubt that 

 B. welchii ordinarily finds favorable conditions within the intestinal 

 tract of man and of the albino rat, the feeding of lactose has at no time 

 caused an increase in the numbers of this organism. On the contrary, 

 there was always a marked reduction, and at times complete elimina- 

 tion of not only B. welchii, but of B. coli as well. 



Following the administration of two grams of lactose or dextrin in 

 association with the basic diet, B. acidophilus made its appearance in 

 all parts of the intestine of white rats, even the duodenum. Whether 

 the presence of this organism in appreciable numbers in the small intes- 

 tine was due to the proliferation of bacilli already occurring there, or 

 to an upward movement of bacilli from the large intestine must of 

 course still remain undetermined. 



Maltose, saccharose and glucose appeared to exercise no transform- 

 ing influence on the types of bacteria present in the intestinal tract of 

 white rats. These results are in perfect agreement with those of Dis- 

 taso and Schiller (1914) and Hull and Rettger (1917). Torrey 

 (1919), however, claims to have obtained a moderate increase in the 

 numbers of B. acidophilus as a result of sucrose feeding in dogs. The 

 findings in the present investigation, which run almost parallel with 

 those encountered in the bacteriological examinations of the fecal 

 specimens of rats subsisting on the basal diet alone, emphasize the im- 

 portance of the selection of special carbohydrates (lactose and dextrin) 

 for favorable transformation of the intestinal flora, and not merely 

 a carbohydrate, as is so often recommended. 



The most plausible explanation of the favorable influence of lactose 

 and dextrin feeding on the implantation of B. acidophilus is one which 

 to a large extent rests upon the fact that they are not completely 

 destroyed before reaching the large intestine. There they establish an 

 optimum environment by serving as a readily available source of energy 



