140 THE BACTERIOPHAGE AND ITS BEHAVIOR 



B. Ten cubic centimeters of the Shiga suspension are inoculated with 

 1 cc. of the filtrate prepared from the feces from the same dysentery 

 patient, but collected 24 hours later, the patient now being convalescent. 

 Counts of this mixture give : 



When plated immediately, no plaques, or less than 100 corpuscles 

 per cubic centimeter. Thus, the filtrate contained less than 1000 per 

 cubic centimeter. 



After one and one-quarter hours the plating shows no plaques. 



After two and one-half hours there are 9 plaques, or 900 corpuscles 

 per cubic centimeter. 



After three and three-quarters hours, in a 1 : 10 dilution, there are 27 

 plaques, or 27,000 per cubic centimeter. 



After five hours, a 1:1000 dilution shows 13 plaques, representing 

 1,300,000 per cubic centimeter. 



In this last experiment (B) the corpuscles were present in the filtrate 

 in very small numbers, certainly less than 1000 per cubic centimeter, 

 that is, there were less than one-sixteenth as many as in the filtrate of 

 the first preparation (A). Nevertheless, the suspension was completely 

 dissolved in ten hours and the fluid remained sterile indefinitely. 



It is unnecessary to insert here the many experiments made for the 

 purpose of proving that the multipHcation of the bacteriophage cor- 

 puscles is always proportionate to their activity. All have given results 

 comparable to those presented above: The more active the bacterio- 

 phage the greater the multipHcation of corpuscles. We have already 

 seen in the preceding chapter that with a Shiga-bacteriophage of low 

 activity a single corpuscle yielded only 17 millions after 24 hours, while 

 under the same conditions, a single corpuscle of a very active race gave, 

 in the same length of time, 12,000 milfion per cubic centimeter. With 

 these two races the increase with the second is 700 times that of the 

 first. With the Staphylo-bacteriophage I have observed an increase 

 from 1 corpuscle to 780 millions with a race of average activity, and 

 from 1 to 98,000 milHons with a race that is very active. Here, with two 

 races acting under the same conditions one is 125 times more active 

 than the other. For but sUghtly active races figures still lower have 

 been observed. 



From these results it may be concluded that activity in the bacterio- 

 phage corresponds to the vigor with which it multipHes at the expense 

 of susceptible bacteria (d'Herelle^^^). 



This conclusion leads to an interesting deduction: the facts disclose a 

 curious coincidence, not without significance. What do we mean by the 



