Vol. 6, 1920 
ZOOLOGY: CHEPLIN AND RETTGER 
425 
further that larger amounts than 2 grams of lactose stimulate B. bifidus 
to increased activity, and that when as much as 3 grams of lactose is 
administered daily the Tissier organism assumes the chief role, thus 
supplanting B. acidophilus even. 
The addition of 1 cc. of B. acidophilus suspension (McFarland nephelom- 
eter turbidity scale of 5) to 1 gram of lactose or dextrin brought the B. 
acidophilus level to the same point as when 2 grams of either lactose or 
dextrin were fed. The simplification of flora was rapid and complete, 
and B. acidophilus persisted as the dominating type as long as the com- 
bined feeding of B. acidophilus and the carbohydrate continued. Further- 
more, the administration of 2 cc. daily of the B. acidophilus culture or 
suspension without the carbohydrates results in the intestinal implanta- 
tion of B. acidophilus and the complete suppression of the other bacterial 
types which are ordinarily present in the enteric tract of the white rat. 
The response of the different rats to the pure culture feeding was prac- 
tically the same in all of the subjects. It was of special interest to note, 
further, that the various curves which represent the development of B, 
acidophilus in the feces of the rats were of practically the same height and 
character, whether 2 grams of lactose or dextrin, or 1 gram of either of 
these carbohydrates together with 1 cc. of the B. acidophilus culture, or 
2 cc. of the culture alone were fed daily. 
Post-mortem examination of the different sections of the alimentary 
canal of rats harboring the simplified flora in the lower intestine revealed 
a general distribution of B. acidophilus throughout the length of the 
intestine. 
Since the bacteria within the digestive tract procure their pabulum 
directly or indirectly from the diet consumed by the host, it is but logical 
to assume that there must be a definite relationship between the chemical 
nature of the ingested food and the metabolic activities of the intestinal 
organisms. Many investigators have noted that marked changes in the 
intestinal flora follow sharp alterations in the diet, especially from a high 
protein to a high caloric diet and vice versa. However, the so-called 
"high calory diets" can at best accomplish a short-lived bacterial reforma- 
tion only, that is a change in metabolic activities of organisms already 
present from the putrefactive to the fermentative type. This shifting 
of bacterial metabolism is not necessarily accompanied by an elimination 
of undesirable bacteria from the alimentary tract. Lactose and dextrin, 
among the carbohydrates studied, alone have the property of stimulating 
the development of aciduric organisms. 
Repeated attempts in the present investigation to establish B. hul- 
garicus in the alimentary canal of albino rats through the administration 
of extremely large numbers (5 cc. of suspensions) of this organism were 
entirely unsuccessful. At no time was B. bulgaricus recovered from the 
