320 BACTERIOLOGY. 



of the typhoid bacillus itself, in no way renders the 

 task more simple. 



For example, the morphology of the typhoid bacillus 

 is conspicuously inconstant ; its growth on potato, which 

 was formerly described as characteristic, may, with the 

 same organism, at one time appear as the typical invisible 

 development, at another time it may grow in a way 

 easily to be seen with the naked eye ; and the change of 

 reaction which it is said to produce in bouillon is some- 

 times much more intense than at others. 



The only properties possessed by it that may be said 

 to be constant are its motility, its inability to cause 

 fermentation of glucose, lactose, or saccharose, its 

 incapacity for coagulating milk, the absence of indol- 

 production, and its growth on gelatin plates ; but there 

 are other organisms which approach these same charac- 

 teristics to a degree that renders their differentiation 

 from the typhoid organism often a matter that requires 

 the careful application of all these different tests. 



These points should be borne in mind in the exami- 

 nation of drinking-water supposed to be contaminated 

 by typhoid dejections, for the organisms which most 

 nearly approach the typhoid bacillus in growth and 

 morphology are just those organisms which would 

 appear in water contaminated from cesspools, i. e., the 

 organisms constantly found in the normal intestinal 

 tract. Even in the stools of typhoid-fever patients 

 the presence of these normal inhabitants of the intes- 

 tinal tract renders the isolation of the typhoid organisms 

 somewhat troublesome, 



The spleen of a patient dead of typhoid fever is the 

 safest place from which to obtain cultures of this organ- 

 ism for study. But it must always be remembered that 



