EXPERIMENTS WITH WHITE RATS 13 



In order to conserve space, quite a number of charts, curves and 

 photograpliic plates originally prepared for publication have been left 

 out of this book. Those which do appear have been selected because of 

 their representative character. The curves were plotted to show 

 average figures. 



Throughout the present treatise the generic term "Bacillus" has 

 been applied to the acidophilus and bulgaricus organisms. "Bacterium" 

 has the greater claim to recognition here, from the standpoint of both 

 motility and spore production. Furthermore, such usage would be in 

 harmony with the general recommendation of the Committee on Classifi- 

 cation of the Society of American Bacteriologists which, however, 

 recommends the use of the generic term "Lactobacillus" for the group 

 of milk-souring bacteria to which B. acidophilus and B. bulgaricus 

 belong. The term "Bacillus" has been retained because of its universal 

 use in connection with these two organisms by both bacteriologists and 

 men of the medical profession, and because of the lack of definite action 

 on the point at issue taken by organized societies. 



PRELIMINARY FEEDING EXPERIMENTS 



While chief emphasis was placed on the implantation of B. acidoph- 

 ilus in the intestine of the white rat, considerable attention was given 

 also to the influence of various carbohydrates on the intestinal flora, 

 both with and without the administration of suspensions of B. acidoph^ 

 ilus, and to the possibility of establishing B. bulgaricus in the digestive 

 tract. In every experiment the animals were first given a basal diet 

 which was found to encourage the development of the usual complex 

 flora without completely eliminating B. acidophilus, a normal inhabi- 

 tant of the alimentary tract of man and animals. This diet, consisting 

 of bread (ten grams) and chopped lean beef (three grams), encourages 

 to a certain extent the "putrefactive" and gas-producing types of 

 intestinal bacteria. It was consumed freely bj' the rats, and appeared 

 in every way to serve, for the relatively short periods in which it was 

 fed, as a complete and wholesome food. 



Tables 1 and 2 give the results of examinations of the intestinal 

 flora of rats receiving the basal or "normal balanced" diet alone. In 

 the first of these tables will be seen the relative numbers of B. acidoph- 

 ilus, gas production in the Veillon tubes, and the description of Gram- 

 stained films of the fecal suspensions, while the second table shows the 

 distribution of B. acidophilus and other types in the alimentary canal, 

 namely the duodenum, jejunum, ileum, caecum and the colon and rec- 

 tum. Few bacteria were found above the ileum. In the ileum, and to 

 a still greater extent in the large intestine, there were large numbers of 

 bacteria, with B. coli as the dominating organism. B. acidophilus was 

 found in the large intestine only, and even here it was comparatively 

 rare. (See Tables 1 and 2, and Charts 1 and 2.) 



