On Preventive Inoculation. 



269 



pendence from seasonal or local changes, than is the case with the cholera 

 microbe. 



Outside the endemic area cholera remains in one and the same place 

 but for a few weeks, and in any given part of a town often for a few 

 days only. It is rare that it visits the same barrack more than once in 

 five, sometimes ten years, and when it occurs, a temporary evacuation 

 of the place puts a stop to the disease. 



The typhoid virus, on the contrary, sticks to an infected locality for 

 years, and causes a continuous incidence of the disease for which occa- 

 sionally nothing short of a complete desertion of the station is 

 effective. 



At the same time, while the cholera infection seems to be almost 

 exclusively confined to the water supply, in typhoid the improvement 

 of the water appears to leave intact a large number of other sources of 

 danger which up to the present have escaped detection. 



While thus differing in their life-history in nature, the bacilli of 

 cholera and typhoid present important common features in the manner 

 in which they behave in the human and animal body. 



The chief centre of infection in both instances is the intestinal canal, 

 the circulatory system remaining free from invasion. When inoculated 

 into animals, both microbes admit of the same kind of transformation 

 by passages from animal to animal ; and against both immunity can 

 be created in laboratory animals by the same preparation of virus as 

 used in the inoculations for cholera ; while, when examining the tissues 

 of immunised animals, the same modifications are detected in them as 

 those observed after the anti-cholera inoculation. 



These considerations have led us to expect from the typhoid inocula- 

 tion in man a similar protective effect to that observed in the inocula- 

 tion against cholera ; and seeing that the period of life during which the 

 newcomers to India remain susceptible to typhoid extends only over a 

 few years, it would seem that the application of the system, when 

 properly organised, is likely to prove of a very high practical value. 



Inoculation and General Sanitary Measures. 



The anti-cholera inoculation, the inoculation against plague, and that 

 against typhoid thus came to put themselves on the same line as 

 vaccination, and represent attempts at dealing with epidemics on a 

 plan differing from measures of general sanitation. During the last 

 few years the question has, therefore, been frequently debated as to 

 the relation in which the two stand to each other. 



It is scarcely necessary to say that inoculation cannot be substituted 

 for a good water supply, the draining, cleansing, or improvements in 

 the building of cities, or for the admission of a larger amount of light 

 and air into over-crowded localities, for all those measures to which the 



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