CHAPTER XVII. 



THE TYPHOID BACILLUS. 



The typhoid bacillus plays a most imporfcaafc part ia a 

 very large number of bacteriological examinations of 

 water, and it is therefore of great importance to learn 

 to recognise it with certainty. This^ however, is a 

 not very simple matter, as the characteristics of this 

 bacillus are very indefinite. 



Material may be probably procured in the following 

 manner, if a pure culture is not to be obtained. A 

 small portion of fresh excreta from a patient, in a 

 tolerably early stage of the disease, is obDained from a 

 hospital, and with it plate cultivations are made. 

 Typhoid bacilli cannot always be secured in this 

 manner, but in certain stages of the disease, they are 

 often present in great numbers in the excreta, in 

 which case they are certain to appear on the plate 

 cultures. Ordinary nutrient gelatine is used, and the 

 temperature should be kept at aboub 20° C. 



If, however, a pure culture of the typhoid bacillus 

 is to be procured, this may be used as the original 

 material for further investigations. The first thing to 

 do is to prepare plate cultures, in order to learn the 



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