350 BACTERIOLOGY. 



Because of the variations in the morphology and cul- 

 tural peculiarities of this organism, and because of the 

 difficulty experienced in efforts to reproduce in lower 

 animals the conditions found in the human subject, 

 typhoid fever is bacteriologically one of the most unsat- 

 isfactory of the infectious diseases. 



There are a number of other organisms which botan- 

 ioally appear to be nearly related to the typhoid bacillus, 

 and which, with our present methods for studying them, 

 so closely simulate it, that the difficulty of identifying 

 this organism is sometimes very great. In addition to 

 this, 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 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 invis- 

 ible 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 indol- 

 producing function, hitherto regarded as absent from 

 this organism, is now known to be occasionally demon- 

 strable by ordinary methods, and frequently demonstra- 

 ble by special methods of cultivation. (Peckham, I. c. ) 



The only properties possessed by it that may be said 

 to be constant are its motility, its inability to cause gas- 

 eous fermentation of glucose, lactose, or saccharose, its 

 incapacity for coagulating milk, and its growth on 

 gelatin plates; but there are other organisms which 

 approach these same characteristics to a degree that 

 renders their differentiation from the typhoid organisms 



