PROPERTIES OF THE BACTERIOPHAGE 



275 



Wollman^^^ has also found that the bacteriophage will pass through 

 open membranes and that it is retained by tight membranes. 



Prausnitz^^^ has gone a step further in solving this question of size. 

 Working with a Flexner-bacteriophage he has carried out filtrations 

 using as a measure of comparison colloids in which the size of the 

 granules has been determined. Making use of a series of Hahn mem- 

 branes, he compared the passage of bacteriophage corpuscles with that 

 of the granules of colloidal silver (0.001 per cent solution), of gelatin 

 (1 per cent) and of hemoglobin (1 per cent). 



His results are summarized in table 25. 



Before filtration 



Passed by filter No. 20J 



Passed by filter No. 50 . 



Passed by filter No. 100 



Passed by filter No. 200 



Passed by filter No. 400 



230,000 

 129, 000 



27,000 



2,500 











Slight re- 

 duction 

 1/10 



1/1000 



Traces 



Very slight 

 reduction 



Very slight 

 reduction 



Slight reduc- 

 tion 



Marked re- 

 duction 



Very strong 

 reduction 



No 

 No 

 No 

 No 

 No 



* By counting plaques. 



t Quantity present in the filtrate, determined colorimetrically. 

 t The numbers assigned to the Hahn filters represent the number of minutes 

 required for the filtration of 100 cc. of water. 



Prausnitz concluded that the diameter of the bacteriophage corpus- 

 cles is approximately that of the micella of the collargol used in his 

 experiment, about 20/x/x. 



By an entirely different procedure (refraction) von Angerer'^^ derived 

 results indicating that the diameter of the corpuscle must be about 



30mm. 



The figures obtained by Prausnitz and by von Angerer are, therefore, 

 remarkably near the same.* 



Levaditi and Nicolau have found, also by means of collodion mem- 



* For purposes of comparison, it may be said that the Asterococcus of pleuro- 

 pneumonia of cattle, the smallest organism visible under the microscope, has a 

 diameter of between 100 and 200juai- 



