226 MICRO-ORGANISMS IN WATER 



of microbes.- Miquel points out how rapid and enor- 

 mous the multiplication is which takes place in the first 

 instance, and how, when once the maximum has been 

 reached, the decline as rapidly follows, becoming, how- 

 ever, less marked as the age of the sample increases. 

 In fact, Miquel goes so far as to say that a spring-water 

 may be characterised by the power of rapid multipli- 

 cation possessed by the bacteria present, as well as by 

 the rapid decline in their numbers subsequently ex- 

 hibited. 



The following diagram, on the other hand, repre- 

 sents the phenomenon of multiplication exhibited by 

 the micro-organisms in waters containing a large initial 

 number of bacteria. 



In this figure the scale employed is much larger, 

 and the Dhuis spring-water is introduced in order to 

 illustrate, by comparison, how greatly inferior is the 

 power of multiplication possessed by the bacteria in the 

 rivers Marne and Seine and in the Ourcq canal-water. 

 As regards the Seine water collected at Ivry (above 

 Paris), Miquel states that at times during the summer 

 months it contains relatively few organisms compared 

 with its bacterial contents at other periods, and that 

 the multiplication exhibited in such cases resembles 

 that observed in spring waters. When, however, the 

 river-water contains as many as 20,000 to 30,000 

 microbes in 1 c.c, this power of rapid multiplication 

 disappears (see foot-note, p. 220). In the diagram the 

 Seine water is relatively pure, and the bacteria present 

 behave, to a certain extent, like those in spring-water, 

 only the multiplication 'is neither so rapid nor so exten- 

 sive. The river Marne exhibits first a rise in the num- 

 bers present, then a decrease, followed by a subsequent 

 increase, a phenomenon which is not unfrequently met 

 with in the multiplication of bacteria in water. The 



