Vol.. 6, 1920 
ZOOLOGY: CHEPLIN AND RETTGER 
705 
feces during the experimental periods. The transformation of the in- 
testinal flora from the usual mixed to the simple aciduric type cannot be 
ascribed, therefore, to increased acidity within the lumen of the intestine. 
The presence of a reducing substance in the feces of subjects receiving 
transforming amounts of lactose is further evidence in support of the view 
that the lactose is at least in part carried into the large intestine and helps 
to create in it an optimum environment for the development of B. acido- 
philus. 
Attempts to implant Bacillus hulgaricus in the intestine of man failed in 
every instance. The conclusions arrived at in the rat feeding experiments 
are borne out here. 
Seventeen human subjects were employed in a total of 45 experiments. 
All but two of these subjects were apparently normal individuals. No 
restrictions were made in the daily diets, which continued essentially 
the same as before the investigation. 
B. acidophilus milk possesses several advantages over ordinary sour and 
B. hulgaricus milk, aside from its property of transforming the intestinal 
flora. It is pleasing to the taste and smell. It does not become very 
acid or in any other way materially change its character even on long 
standing. The curd is soft and of a creamy consistency. The creamy 
appearance of the milk persists without appreciable wheying off. The 
product is prepared easily when proper precautions are taken. Pure 
strains of B. acidophilus must be employed which have been grown in 
milk sufficiently long to produce acidity and a soft curd within 24 hours 
when kept at a temperature of 35-37° C. 
The same methods were employed in the routine examination of the 
feces as in the earlier experiments with rats, namely, the preparation and 
use of whey agar plates, Veillon tubes and Gram-stained slides. The 
plates and the Veillon tubes were particularly valuable and are strongly 
commended for work of this kind. The Veillon tubes aided not only in 
the detection of B. acidophilus colonies, but served admirably as an index 
of the disappearance of B. coli and other gas-producing bacteria from the 
intestine. It soon became evident that as the aciduric type of organisms 
materially increased in numbers the volume of gas in the tubes corre- 
spondingly decreased. A so-called complete transformation of flora was 
evidenced by the crowding of the whey agar plates with small fluffy colo- 
nies, the absence of gas from the Veillon tubes, as well as complete pre- 
ponderance of the characteristic sea-urchin-like colonies throughout the 
tubes, and by the large numbers of Gram-positive rod-shaped organisms 
of the B. acidophilus type on the stained slides. 
A full account of the authors' studies on the transformation of intestinal 
flora and the implantation of Bacillus acidophilus is now in the Yale Uni- 
versity Press, and will appear in book form at an early date. 
