UBIQUITY OF BACTERIOPHAGE 421 



In 3 specimens, 4 of the 12 colonies from each were susceptible; 

 In 7 specimens, 3 of the 12 colonies from each were susceptible; 

 In 4 specimens, 2 of the 12 colonies from each were susceptible; 

 In 2 specimens, none of the 12 colonies in either one was susceptible. 

 In the last two cases, — -those where all of the organisms proved to be 

 resistant, — I subjected the 12 colonies in each case to a series of trans- 

 fers in an acid medium, the acidity being at the limit for growth of the 

 organism at 41°C., and between each two passages I isolated colonies 

 on a 1 per cent glucose agar, according to the method of Roux, described 

 above. The sequence of cultures was, therefore, alternately, growth 

 in an acid medium, isolation on agar, growth in an acid medium, isola- 

 tion on agar, etc. At the 5th, 10th, 15th, 20th, and 25th isolations I 

 determined whether any of the colonies had lost their resistance, 

 whether they had become susceptible to the bacteriophage contained 

 in the filtrate made from the same specimen from which the 12 original 

 colonies had been isolated. With the two filtrates the results were : 

 Filtrate 1. 

 At the 5th passage, none of the colonies had become susceptible; 

 At the 10th passage, 1 of the colonies had become susceptible; 

 At the 15th passage, 1 of the colonies was still susceptible; 

 At the 20th passage, 4 of the colonies had become susceptible; 

 At the 25th passage, 5 of the colonies had become susceptible. 

 Filtrate 2. 

 At the 5th passage, 1 of the colonies had become susceptible; 

 At the 10th passage, 1 colony was still susceptible; 

 At the 15th passage, 1 colony was still susceptible; 

 At the 20th passage, 6 of the colonies had become susceptible ; 

 At the 25th passage, 7 of the colonies had become susceptible. 

 It is very probable that had the passages been continued other 

 colonies would have become susceptible, but this is of no consequence 

 for the matter with which we are at present concerned. 



In the course of these 17 examinations I also isolated certain colonies 

 which were colorless on Endo,- — -14 in all, which upon microscopic ex- 

 amination proved to be baciUi. Of the 14, 6 proved to be B. fecalis 

 alkaligenes, for they failed to ferment glucose. The identity of the others 

 was not determined. Of the 14 colonies 13 were susceptible to the action 

 of the bacteriophage present in the filtrate of the specimen which yielded 

 the colony. 



I have procured specimens from 6 other normal persons, and the 

 examinations were carried out in the same manner. Of the 12 colonies 

 isolated in each case from the specimen which furnished the filtrate; 



