EXPERIMENTS WITH WHITE RATS 21 



stained films frequently appeared to be almost purely Gram-positive 

 rods of the B. acidophilus type. (See Table 5 and Chart 5.) 



The rise in the acidophilus curve is slightly more marked even when 

 two grams of dextrin are fed than during the administration of the 

 same amounts of lactose, the maximum in the former instance being 

 reached on the eighth day. In other words, dextrin has shown itself 

 to be at least as effective in simplifying the intestinal flora as lactose. 



Several of the dextrin-fed rats were killed for the purpose of making 

 bacteriological* examinations df different sections of the intestine. 

 B. acidophilus was present throughout the intestine, even as high as the 

 duodenum. With the exception of a few Gram-negative rods and strep- 

 tococci, it was practically the only organism found above the ileo- 

 caecal valve; whereas below this level it was strongly predominant. 

 (See Table 6 and Chart 6.) Gas-forming bacteria appeared to be 

 almost entirely eliminated. 



The results obtained thus far demonstrate conclusively that both 

 lactose and dextrin, when fed in sufficient quantities to albino rats, have 

 a most pronounced influence on the character of the intestinal flora, 

 transforming it from the ordinary complex type to one in which the 

 dominant organism is B. acidophilus. 



When smaller amounts of lactose or dextrin than two grams were fed 

 daily the transformations were less profound. Thus, one gram en- 

 couraged the development of B. acidophilus to only about 50 per cent 

 of the total fecal flora, as will be seen in subsequent pages (35-40). 



Glucose, maltose and sucrose. — None of these sugars, when fed in the 

 same manner and in the same amounts as the lactose and dextrin, 

 exerted any transforming influence upon the intestinal flora. This was 

 clearly brought out in the agar plates, the Veillon tubes and the Gram- 

 stained slides. Throughout these feeding experiments the flora pre- 

 sented the same character as when the rats were kept on the "normal 

 balanced" diet of bread and meat. A total of six rats was employed, 

 two for each sugar. (See Table 7 and Charts 7, 9 and 11.) 



Bacteriological examinations of the different levels of the intestine 

 gave negative results also. B. acidophilus was absent from the small 

 intestine, and was found below the ileo-caecal valve in numbers only 

 that are normally met with in rats subsisting on the basal diet. (See 

 Table 8 and Charts 8, 10 and 12.) 



The above results are in harmony with those of Hull and Rettger 

 (1914b, 1917). 



ADMINISTRATION OF LIVING SUSPENSIONS OF 

 B. ACIDOPHILUS 



All of the strains of B. acidophilus that were employed in these 

 experiments were isolated from the feces of albino rats during periods of 

 lactose or dextrin feeding. Typical colonies of this organism were 



