BACTERIOLOGY AND WATER 99 



livery. Dr. Koch, who personally superintended 

 this inquiry in Altona, traced another local out- 

 break of cholera in the city to the use of a 

 well-water obviously open to pollution, which 

 was used by about 270 persons. In one of the 

 houses employing this water, and in the immediate 

 vicinity of the well, a boy died of cholera on 

 January 23rd, and during the week following a 

 number of cases occurred amongst persons using 

 this source. On discovering the cholera bacilli 

 in this polluted water, its contamination was 

 placed beyond doubt, and five days after the 

 well was closed all cases ceased in the locality. 



There cannot be any longer a doubt as to 

 the value of sand-filtration as a means of water- 

 purification, but the responsibility which we have 

 seen attaches to this treatment of water cannot 

 be exaggerated, for whilst when efficiently pursued 

 it forms a most important barrier to the dis- 

 semination of disease germs, the slightest im- 

 perfection in its manipulation is a constant 

 menace during any epidemic. 



It is, as a rule, during the winter months that 

 the largest number of bacteria are present in 

 the filtered water, and it is therefore of especial 

 importance that during this season, when the raw 

 river water is generally richest in bacterial life, 

 and when, therefore, the filters are most taxed 



