DISTRIBUTION AND HABITAT OF THE BACTERIA. 721 



it, should be removed as quickly and completely as 

 possible from the dwellings and from the neighbourhood 

 of susceptible individuals. This aim will be best fulfilled Their prompt 

 by a system of drainage which is at the same time com- 

 bined with a constant and sufficient supply of pure water, 

 thus rendering the carrying out of cleanliness easier. 

 The system of removal of refuse by means of pails seems 

 less satisfactory, especially when by this means the 

 excrement and the infective agents in it are thrown on 

 gardens or fields in the neighbourhood of dwellings, thus 

 leading to the preservation of the germs, and therefore 

 probably to their re-introduction into the dwellings. 

 The system of cesspools, by storing up the masses for a 

 longer time, affords a better guarantee than the pail 

 system for the death of the infective bacteria before they 

 reach the ground. A decided disadvantage of the two Disadvan- 

 last-mentioned methods as compared with the drainage ^her 

 system is, that there is always a danger of infective germs methods, 

 spreading in some way or other to the surroundings of 

 man, from dried masses in the exit-tube ; while in the 

 former system the water-closets and pipes leading there- 

 from can be readily kept in a clean and moist condition. 

 And further, stagnant gutters, dirty courts, &c., with 

 their multifarious dangers of infection, can only be effec- 

 tively dealt with by flushing with water and by drainage. 

 The question as to the hygienic value of the methods of 

 cleansing towns must therefore be reconsidered from the 

 points of view shortly indicated above; we must also 

 trace out more accurately the fate of the pathogenic 

 agents in each of the systems employed, and of course 

 we must also carefully weigh other interests before 

 coming to a final conclusion as to the value of any given 

 system. At all events the most important hygienic Necessity for 

 points of view from which these matters have up to the 

 present been considered are incorrect, because the view 

 has been acted on that especially good nutrient materials 

 for pathogenic bacteria are present in the refuse materials, 

 and that it is necessary to keep the soil free from these 

 substances, and to remove them from human dwellings, 

 in order to prevent a development of disease germs in 



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