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L. A. KOHN AND C. KRUMWIEDE, JR. 



volume of pentane. Close the bottle tightly with a rubber 

 stopper and shake for one-half hour in a shaking machine. The 

 container is then allowed to stand for one and one-half to two 

 hours at room temperature, the bottom fluid or sediment re- 

 moved with a pipette and plated. His results may be summa- 

 rized as follows: 



Thus, while one specimen positive on direct plating was 

 negative after shaking, 7, or 33 per cent of the total positives, 

 were positive only after shaking. 



These results were so favorable that we investigated the 

 method. Unless otherwise stated, we have followed the method 

 of Hall. 



Our first attempts were made with stools from typhoid carriers 

 and with greatly diluted broth cultures of recently isolated 

 typhoid strains. The shaking was for one-half hour, and after 

 shaking, the emulsions were allowed to stand for two hours 

 before plating on the Endo medium. The results may be 

 roughly illustrated by the following examples: 



MATERIAL 



Stool suspension 

 Stool suspension 



Stool suspension 



DIRECT PLATING 



Positive — 5 per cent typhoid 

 Positive 4,000 total colonies; 



75 per cent typhoid 

 Positive 5,000 total colonies; 



5 per cent typhoid 



AFTER SHAKING 



1 typhoid colony 



100 total colonies; 90 per 



cent typhoid 

 200 total colonies; 1 per 



cent typhoid 



Broth suspensions of several cultures (pure) yielding by direct 

 plating from 400 to 5000 colonies per plate, after shaking, and 

 then plating an equivalent amount of material, gave no colonies. 



While, with the one stool cited above, there was a relative 

 increase in the proportion of typhoid to total flora, it would 



