THE EXAMINATION OF WATER 647 



(3) The flood conditions having passed away, the bacilli very 

 rapidly disappear from all waters. Consequently this 

 supports the suggestion that these organisms are especially 

 susceptible to natural forces inimical to bacteria. 



The Bacteriology of Water from a Shallow Well. 



(i) In common with most other water supplies, including rivers, 

 lakes, springs, &c., B. cloaca would appear to be the pre- 

 dominating organism in a well after prolonged drought. 



(2) Even a small downpour of rain, after a prolonged spell of dry 



weather, has a very marked influence in increasing the 

 number of fascal bacilli in wells situated in porous soils. 



(3) Early showers, following on a long period of hot weather, 



have caused an increase in the number of Coli communis in 

 this well. It is not by any means certain where these coli 

 come from, but it is unlikely that they come from the surface 

 of the ground, and probable that they remained alive in (he 

 lower layers of the soil, 



(4) After heavy downpours of rain, in consequence of which it is 



certain that surface contamination has penetrated deep into 

 the layers of the soil, a mixture of fjecal organisms is usually 

 found in the water obtained from wells. Coli communis 

 appears to be present after early rains, but disappears as the 

 rains become more plentiful. 



(5) Plentiful rains improve the quality of the subsoil water after 



the contaminated surface water has run off" the land. 



(6) Shallow wells are a most unsatisfactory source of water supply, 



especially if they are situated in a highly porous soil, and 

 unless the greatest possible care is exercised in protecting a 

 large space of ground in the immediate vicinity from all 

 chances of pollution. 



The Bacteriology of Hitman and Animal Fceces. 



(i) The flora of the intestinal tract of men and animals are subject 

 to very considerable changes due to influences which are at 

 present unknown. These influences have been proved to 

 operate over very wide areas. 



(2) Within certain very wide limits, these forces appear to affect 



man and animals equally, both as regards number and kind 

 of micro-organisms. 



(3) Under well-defined conditions, such as heavy rainfall, the 



water supplies contain the same organisms as the fasces of 

 man and animals at that particular time, but this similarity 

 of bacterial flora is also noted occasionallv when rain is 

 absent, and there is no apparent cause for it. The explana- 

 tion of this occurrence is at present unknown. 

 41 



