714 



BACTERIA IN AIR, SOIL, WATER, AND MILK 



obtaining markedly favorable results by feeding pure cultures of Bacillus 

 lactis aerogenes to infants suffering from fetid diarrhea. Similar ex- 

 periments * carried out with the "Welch bacillus (aerogenes capsulatus) 

 and Bacillus coli, however, had no such corroboratory results, since this 

 anaerobe possesses a considerable resistance against an acid reaction. 

 In considering the difficulties of the problems involved in this question, 



Fig. 166. — Bacillus bulgahicus. 



it occurred to Metchnikoff* that much of the practical failure of therapy, 

 based upon the principles stated above, might be referred to insufficient 

 powers of acid production on the part of Bacillus coli, Bacillus lactis 

 aerogenes, and other germs previously used. In searching for more pow- 

 erful acid producers, his attention was attracted to Bacillus bulgari- 



1 Tissier and Martelly, Ann. de I'inst. Pasteur, 1906. 



2 Metchnikoff, "Prolongation of Life," G. P. Putnam's Sons, N. Y.; also in " Bao- 

 t^riotMrapie," etc, " Bibliothfeque de tb^rapeytique," Gilbert and Carnot, Paris, 

 1909. 



