422 THE BACTERIOPHAGE AND ITS BEHAVIOR 



In 2 cases, 4 of the 12 colonies were susceptible; 

 In 1 case, 2 of the 12 colonies were susceptible; 

 In 2 cases, 1 of the 12 colonies was susceptible; 

 In 1 case none of the colonies was susceptible. 

 In this last case I carried out a series of purifications, as in the two 

 negative instances reported above, and at the 10th passage 1 of the 

 12 colonies was found to be susceptible.* 



My first experiments upon the subject had shown that "the bacterio- 

 phage exists in the intestine, where it lives normally at the expense of 

 the B. coli."^^^ The experunents which I have made since have verified 

 this observation and permit me to affirm that the bacteriophage protobe 

 is always, in every individual, a normal inhabitant of the intestinal 

 tract, where it persists because of a symbiosis with the colon bacillus. 

 But in order to demonstrate its constant presence it is not sufficient 

 to combine any stool filtrate whatever with any strain of B. coli what- 

 ever. It is essential to adopt an adequate method, such as that which 

 has been described. 



Many authors have confirmed this observation that the bacterio- 

 phage is present in the intestinal contents of normal man. Dumas^^* 

 found the bacteriophage present in 5 of 8 healthy persons which he 

 examined. Debre and Haguenau"^ also found it in some individuals 

 who had no intestinal disturbance, as did Beckerich and Hauduroy'^^ 

 and da Costa Cruz.^^^ This last author examined the same healthy 

 person at 5 different times and on 3 occasions he found a bacteriophage. 

 These different authors did not demonstrate the bacteriophage 

 solely because of its virulence for B. coli, but because at the time of 

 examination the virulence of the bacteriophage in the individual ex- 

 amined extended to a dysentery or a paratyphoid bacillus. This occurs 

 very frequently, as I reported in some of my earlier studies. ^^^^ ^^^ 



Tomaselfi^^^ procured specimens of the stools of 10 normal persons, 

 and from his determinations, he reported the following virulences : 

 In 3 persons : 



B. dysenteriae Shiga + -1- + 

 B. typhosus (2 of 4 strains tested) + 

 B. paratyphosus B (4 of 4 strains tested) + 

 In 1 person: 



B. dysenteriae Shiga + 



B. typhosus (1 of 4 strains tested) + 



B. paratyphosus 5 (3 of 4 strains tested) + + + 



* The purifications were not continued, since what I wished to show had been 

 demonstrated at this point. 



