BACILLUS TYPHOSUS. 421 



Because of the variations in the morphology and 

 physiology of this organism, and because of the diffi- 

 culty experienced in eiforts to reproduce in lower ani- 

 mals the conditions found in the human subject, our 

 knowledge of typhoid fever, though fairly accurate in 

 many respects, is, nevertheless, in certain essential de- 

 tails relating to its causation, very far from satisfying. 



A number of other organisms appear botanically to 

 be closely related to the typhoid bacillus, and under the 

 available culture methods for studying them they so 

 closely simulate it that the difficulty of identifying this 

 organism is sometimes very great. In addition the 

 variability constantly seen in pure cultures of the typhoid 

 bacillus itself in no way renders the task more simple. 



For example, the morphology of the typhoid ba- 

 cillus is conspicuously inconsistent; its growth on potato 

 which was formerly considered unique, may, with the 

 same stock, at one time be the typical invisible develop- 

 ment, at another it is easily to be seen with the naked 

 eye ; and the change of reaction which it is said to pro- 

 duce in bouillon is sometimes much more intense than 

 at others. The idol-producing function, hitherto re- 

 garded as absent from this organism, is now known to 

 be occasionally demonstrable by ordinary methods, and 

 frequently by special methods of cultivation. (Peckham, 

 /. c.) The only properties exhibited by it under the usual 

 conditions of cultivation that may be said to be constant 

 are its motility ; its inability to cause gaseous fermenta- 

 tion of glucose, lactose, or saccharose ; its incapacity for 

 coagulating milk ; and its growth on gelatin plates ; but 

 there are other bacilli which possess these same charac- 

 teristics to a degree that renders their differentiation 



