BACTERIAL METABOLISM WITHIN THE BODY 695 



able at that time [1886], a series of investigations appeared which 

 added many detached facts to the problem of intestinal bacteriology. 



The discovery of the dysentery bacillus in 1898, and of Bacillus 

 bifidus in 1900, marks the close of the older period of the study of in- 

 testinal bacteria. The greatly improved cultural methods, both aerobic 

 and anaerobic, which resulted in the isolation and identification of closely 

 related types of organisms, as the several types of dysentery bacilli, 

 focused attention upon the value of carbohydrates, or derivatives of 

 carbohydrates, for diagnostic purposes in bacteriology. The decade be- 

 tween 1895 and 1905 was particularly noteworthy for the numbers of 

 new types and kinds of bacteria, both aerobic and anaerobic, which were 

 detected by this procedure. 



The problem of the intestinal bacteria was restudied, by the author, 

 with the great advantage of reasonably accurate methods of bacterial and 

 chemical procedures in 1909. The relationship between diet and intestinal 

 flora was observed, and the general phenomena relating to the alterna- 

 tions in dominance of fermentative and putrefactive intestinal floras in 

 response to carbohydrate and protein regimens were elucidated at this 

 time. The first observations were made upon cats and monkeys. It was 

 found that both carnivorous and omnivorous animals responded to the 

 same dietary changes in a similar manner. 



The striking features were the dominance of an acidogenic intestinal 

 flora, similar to that of a nursling, upon a carbohydrate diet [glucose 

 added to milk], and the dominance of proteolytic bacteria in the ali- 

 mentary canal upon a purely protein diet. The urinary changes also 

 were significant. Upon a carbohydrate regimen the urinary products of 

 putrefaction, as indican and phenols, were greatly diminished, or absent. 

 This corresponded to the chemical activities of the nursling bacteria cul- 

 tivated outside the body. Such organisms do not form indol or phenol 

 in culture media. The return to a protein diet was followed very soon 

 by the appearance, or great increase, of the indolic and phenolic sub- 

 stances of the urine. The fecal bacteria from such diets were predomi- 

 nantly proteolytic and reproduced in culture medias under proper condi- 

 tions the antecedent substances from which indican and the ethereal 

 sulphates are derived. 



It would appear from these observations that there was a very definite 

 and controllable relationship between certain diets, the bacterial types of 

 intestinal flora, and the presence or absence of urinary putrefactive 

 products. These experiments were repeated, greatly amplified, and con- 

 firmed in a later series (Herter and Kendall). 



The following observers, Bahrdt and Beifeld, Sittler, Eettger and 

 Ilorton, Torrey, Hartje and Klotz, have since corroborated the principle of 

 the alternation of bacterial types in the alimentary canal in response to 

 definite dietary stimuli, and have extended the field by indicating the 



