224 MICRO-ORGANISMS IN WATER 



micro-organisms, and that it has never before been in- 

 habited by such living matters ; it is. only reasonable to 

 infer, therefore, that those of its ingredients which are 

 capable of nourishing the particular micro-organisms 

 which flourish in it are wholly untouched, whilst in the 

 case of the river-waters the most available food supply 

 must have been largely explored by the numerous 

 generations of micro-organisms which have inhabited 

 them. Also far fewer varieties of micro-organisms are 

 found in this deep-well water than in the case of the 

 river-waters, hence those forms which are present will 

 have a more undisputed field for multiplication in the 

 absence of competing forms. This would also explain 

 the greater capacity for multiplication which is exhi- 

 bited by the filtered river-waters as compared with the 

 water in its raw condition, a large number of varieties 

 having been eliminated in the treatment which the 

 water has undergone at the waterworks during storage 

 and sand-filtration. 



This remarkable phenomenon of bacterial multipli- 

 cation, generally taking place more abundantly in pure 

 or in waters containing a small number of microbes to 

 start with than in impure or waters containing a large 

 initial number, has been made the subject of some highly 

 interesting and suggestive investigations by Miquel. 1 



Thus a sample of the Yanne spring-water, in which 

 only 150 micro-organisms were present in 1 c.c. at the 

 time of collection, on being kept for twenty-four hours 

 at 20 C., contained as many as from 30,000 to 40,000, 

 whilst a sample of the Ourcq canal-water, which is 

 highly polluted and very rich in bacterial life to begin 

 with, on standing for a similar length of time, exhibited 

 no increase in the numbers present. 



1 Manuel pratique ft Analyse bacteriologique des Eaux, Paris, 1891, 

 p. 140. 



