174 



islands mast be attributed to a difFeieiice of virulence as to the 

 various strains. Big islands point to a strong" effect with regard to 

 the typhoidstrain ; small ones to a weaker effect. This has also been 

 proved by a slill to be published investigation of Dr. Kropvef,d in 

 our laboratory, about staphylococci-bacteriophagi. 



Bacleriophagus W i always gives both big and small islands with 

 regai-d to T W i. 



Small and big islands are cultured over separatly 9 times, small 

 islands always being used for the series of small ones, big islands 

 for (he seiies of big ones in this process. 



The last culture of both always gave a mixture of big and small 

 islands again. 



Finally we have tried both bacteriophagi W i big ^' and W i 

 small ^^ as to 4 typhoidstrains. 



With l)Oth bacteriophagusstrains we got exactly the same result 

 which is only following once. 



1. Clearing. 



2. Checking. 



3. Islandformation. 



Typhoid 9 ++4 + 



,. n +++ 



„ 27 



» Wi -1-+++ 



++++ 

 ++++ 



+ 



Amsterdam, May 1922. 



++++ very big islands. 

 -}-+++ big islands. 

 -| — I — I — \- very small islands. 

 -\ — I — \ — |- big and small islands. 



Lahoratoriam of Hygiene. 



