THE BACTERIOPHAGE CORPUSCLE 85 



Identical experiments have been performed with bacteriophage 

 principles active for B. coli, for B. typhosus, and for B. pestis* 



With B. coli, the last active dilution, for the race under investigation 

 was 10-^ This dilution divided among 10 tubes of suspension caused 

 bacteriophagy in 8, the other 2 remaining unattacked. 



And, finally, the dilution 10"^ of the bacteriophage principle acting 

 upon B. pestis, distributed among 10 suspensions of this organism caused 

 bacteriophagy in 5, the other 5 remaining turbid. Control tests showed 

 that the turbid tubes did not contain a trace of the bacteriophage 

 principle, even after repeated filtrations. 



We have then, a definite proof that the bacteriophage exists in the 

 form of corpuscles. 



If further proof of the corpuscular nature of the bacteriophage is 

 desirable, it has certainly been provided by the very beautiful demon- 

 stration presented by Eijkman at the meeting of the Society of Bacteriol- 

 ogists of Holland. His experiment was based upon the well recognized 

 fact that if a drop of a liquid, which contains a substance in solution, is 

 allowed to evaporate slowly, when it is completely dry the substance 

 present will be found evenly distributed over the entire surface previ- 

 ously occupied by the drop; while, on the contrary, if the substance in 

 the liquid is insoluble, in the form of corpuscles, as the drying proceeds 

 the phenomenon of capillarity becomes operative and the corpuscles 

 are attracted toward the periphery, so that when the evaporation is 

 finished, the substance will be found in a circle indicating the circum- 

 ference of the area previously occupied by the drop. 



Eijkman placed on an agar plate a very dilute suspension of bacterio- 

 phage corpuscles, and allowed the fluid to evaporate slowly. When 

 desiccation was finished he covered the surface of the plate with a sus- 

 pension of the susceptible bacterium. After incubation, the plate 

 revealed an appropriate number of plaques, and these were arranged in 

 a circle, representing the contour of the drop of fluid which had been 

 originally placed on the agar. Thus, making application of the phe- 

 nomenon of capillarity, Eijkman has afforded further proof of the cor- 

 puscular nature of the active principle in a bacteriophage filtrate. 



From the fact of the corpuscular nature, it becomes evident that the 

 important thing permitting bacteriophagy to take place is not the con- 

 centration of the bacteriophage principle in the suspension, but the 



* The bacteriophage filtrates utilized in these experiments were from suspen- 

 sions of 200 million bacteria per cubic centimeter rendered limpid by bacteri- 

 ophagy. 



