117 



an iijterpretation of the self-pniification of water can hardly lie 

 afforded without reckoning with the bacteriophage. 



If a special inquiry in this direction were to show tliat bacterio- 

 jihages play a more piotuinent part in the process of self-purification 

 than has hitherto been assumed, we should not only have to revise 

 and modify our conceptions of and our insight into this self-puri- 

 fication of water and our views concerning the action of sand-filters 

 and oxidation-beds, but also a broad field would be opened up for 

 studying the biological cleansing of sewage. 



Like many others 1 also became convinced by my experimentation 

 in India of the prominent part played by protozoa in the destruc- 

 tion of micro-organisms in the surface-water. 



For this reason I deemed it a matter of importance to ascertain : 



n. whether in surface-water, e. g. that in and aiiout Leyden, bac- 

 teriophage could be found, and whether the self-puritication of that 

 water was in any way due to bacteriophages that might occur in it. 



b. whether in surface-water, polluted intentionally with a profusion 

 of pathogenic micro-organisms, and allowed, to pui'ify itself, bac- 

 teriophages are to be observed thai may have annihilated the germs. 



c. the influence which is played on ilie piiritic-ation by substances 

 that kill the protozoa but do not injure the bacteriophages. 



d. whether protozoa aud bacteriophages combined may accelerate 

 the process of self-purification. 



To this end the following experiments were performed: 



On the 2^^ of June 100 c.c. of various samples of Leyden water 

 were mixed every time with a concentrated broth. The mixture 

 stood during 24 hours at 37° C. and was then filtered first through 

 rock-meal and subsequently through a '•bougie". The filtrate was 

 mixed in quantities of 0,5; 0,2; 0,1; and 0,05 c.c. with broth, which 

 was afterwards inoculated with an 18-hour-old Flexner-culture. For 

 an examination for bacteriophage a smear-culture was made on 

 agartnbes of the luoth thus prepared. After an incubation of 24 

 hours at 37° C. an estimination was made for "phages'. 



The result is that frotn the examined waters bacteriophages can 

 be isolated that react especially to Flexner but also have an action 

 on other intestinal bacteria. 



Thus tiie isolated bacteriophages annihilate all the Flexner, Y, 

 and Shiga Kruse stocks of our collection. 



They also have an action on bacillus faecalis alcaligenes, on a 

 proteus and a proteus X 19, but do not act upon Typhus, Para- 

 typhus A. and B. or Enteridite Gartner, neither on two coli-stocks 

 of our collection. 



