86 THE STORY OF THE BACTERIA. 



spread is these discharges from the bowels, 

 containing the living, virulent typhoid bacilli. 



Here, we have an essentially similar con- 

 dition of affairs to that in tuberculosis, namely, 

 bacteria of a particular species causing a dis- 

 ease which, without them, could not or does 

 not, so far as we know, exist, and after in- 

 ducing the disease in an individual, being 

 discharged alive and virulent from the body. 

 Here, as in tuberculosis, although the mode of 

 infection is somewhat different, if all the dis- 

 charges from persons suffering from the dis- 

 ease could be immediately destroyed by car- 

 bolic acid or corrosive sublimate, all danger of 

 infection, so far as we know, would be removed. 

 Typhoid fever is thus a preventable disease. 



So far as we know, typhoid fever affects 

 man alone, and he alone forms the source of 

 infection. But, unfortunately, the bacteria are 

 not generally destroyed, and the house-mates 

 of the patient, or those who use the same water 

 supply, or are dependent upon the same food 

 sources, or subject to a connecting and defec- 

 tive sewage system, now and then are liable, 

 through food, or water, or air, to take into the 



