364 



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



that which we were employing. First, we determined that an 

 emulsion of typhoid in broth was not more susceptible to the 

 action of pentane than a similar emulsion in either a normal 

 stool suspension, or in the same suspension sterilized by steam- 

 ing for one-half hour. Thus : 



Summary of reactions of several strains: shaken ten minutes, stood one hour 



Direct plating After shaking 



In broth 2500 colonies 



In stool suspension 2500 colonies, 95 per cent typhoid 



In sterilized stool suspension 2500 



On attempting to find the approximate percentage of typhoid 

 bacilli which would survive shaking alone, we found wide varia- 

 tions between individual strains. With some, 250 colonies per 

 drop were completely lost on shaking; with others, the numerical 

 reduction varied from 40 to 98 per cent. With this reduction in 

 numbers, there was frequently a concomitant reduction in the 

 size of the colonies developing after shaking. It was thought 

 that the physical effect of shaking might be responsible, but on 

 shaking without pentane (with equivalent saline dilution) prac- 

 tically no reduction occurred, whereas, in this case, 5000 

 colonies per loop were killed by pentane. It was thought that 

 the bacilli might be contained within the supernatant pentane 

 rather than in the subjacent broth, but culture from the pentane 

 in two cases where the broth yielded from 3 to 25 colonies per 

 drop, showed it to be sterile. 



We then investigated more accurately the effect of standing 

 after shaking. The results with several strains were : 



* Strain (in other tests) shows unusual resistance to pentane. 



In a final series of stool examinations, small amounts of carrier 

 stool were added to normal stools so as to give mixtures poor in 



