Aug. 19, 1922 ] SECTION OF MICROBIOLOGY. [ MnlZ^YoT"... 



produced by a living being, which regenerates itself in the course of the 

 successive passages. 



It will be obvious, then, that this transmissibility in series eliminates 

 hypotheses 1 and 2. The authors who have put forward these hypotheses must 

 admit that the principle derived from the organism which is attacked by para- 

 sites (hypothesis 1), or from the foreign bacteria (hypothesis 2), plays solely 

 the role of a transformer— that is to say, it gives rise in the bacteria which 

 undergo the transmissible lysis to a special state of "autolysability." We 

 come now to the third hypothesis. Only Bordet and Ciuca have attempted to 

 give an explanation of this. For them the leucocytic principle would provoke 

 in the bacteria a "hereditary vitiation of nutritional nature." I must say that 

 I do not understand how a filtered liquid can transmit a hereditary property. 

 Besides, the whole theory of Bordet and Ciuca is based on an experience 

 entitled "leucocytic exudates," which I have elsewhere stated it is impossible 

 to repeat— a statement which has not been challenged by Bordet." The result 

 obtained by him in one experiment would appear to be purely accidental." 



But it is to no purpose to discuss here, point by point, the di£Ferent theories; 

 it is sufficient to show that they are contrary to the facts. Hypotheses 1 and 2 

 being eliminated, there only remain to consider hypotheses 3 and 4. 



Second Fact: The lytic enzymes emanate from material corpuscles which 

 traverse filters; these corpuscles multiply in the course of the bacteriolysis. 



Experiment A. 



hi a well-developed bacterial culture, showing a marked turbidity, let us add 

 a small quantity (say 1/10,000,000 c.cm.) of a filtrate containing the bacteriophagic 

 principle, shake, withdraw 1 20 c.cm. and spread it over the surface of an agar slope. 

 Thus we spread over the agar a great number of bacteria and a very small quantity of 

 bacteriophagic principle. After incubation (eighteen to t\venty-four hours at 37°) 

 we note that the surface of the agar shows a bacterial growth with a certain number 

 of circular bare spaces here and there, where the agar presents no trace of growth. 

 These vacant spaces once formed are unchangeable; they never spread, and they 

 are never invaded by the surrounding culture. 



It is the presence of these immutable bare spaces, which are perfectly 

 circular, that characterizes what we have named "bacteriophage." Before 

 concluding that any bacteriolytic phenomenon is bacteriophagic, it becomes 

 necessary to verify if it gives rise to such bare spaces on agar culture. If not, 

 the bacteriolysis is not of bacteriophagic nature. 



The number of spaces depends simply on the quantity of filtrate added to 

 the bacterial culture. If into various bacterial emulsions we introduce variable 

 quantities of the filtrate, the number of bare spaces is strictly proportional to 

 the quantity of filtrate added. On the other hand, the number of the bare 

 spaces is independent of the number of bacteria contained in the medium; 

 whether one introduces a given quantity of filtrate into a bacterial emulsion 

 containing one hundred millions or ten billions of bacteria per cubic centi- 

 metre, the number of bare spaces on the agar is practically always the same. 



The phenomenon of these vacant spaces is only comprehensible on the 



