98 MICRO-ORGANISMS IN WATER 



rain or snow has fallen the numbers show a decided 

 increase. This is especially exhibited in the experiments 

 of January 28 and 30 and February 6 and 15, the latter 

 experiment being particularly instructive in this respect, 

 as many as 24,000 micro-organisms being found at 

 Engstringen in 1 c.c. of water. At Dietikon, after a 

 How of 10 kilometres, the bacterial condition of the 

 water approaches very often to that of the river before 

 the influx of sewage. 



On April 26 and April 30 the flow of the river was 

 three times as rapid as usual, indicating a larger volume 

 of water passing along the river-bed. Thus the effect 

 of the sewage discharge was not bacterially so marked, 

 whilst the sedimentation of the micro-organisms in con- 

 sequence of the more rapid flow of the water was not 

 so complete, the number at Engstringen, in proportion 

 to those found at Wipkinger, being larger than usual. 



Thus, again, is shown the diminution in the number 

 of bacteria which takes place during the flow of a river, 

 the bacterial purification of the water through sedimen- 

 tation taking place in this instance without the assist- 

 ance of a lake-expansion, as in the case of the river 

 Spree at the Havel, but during the uninterrupted flow 

 of the river along its course. 



According to Moers,^ the Ehine at Muhlheim con- 

 tained in 1885 the following numbers of micro- 

 organisms in a c.c. : — 



Bacterial Cofidition of the Biver Bhine at Milhlheim (Moers) 



The river Main has been examined by Rosenberg^ 



^ * Die Brunnen der Stadt Muhlheim a. Eh. vom bakteriologischen 

 Standpunkte aus betrachtet,' Erganzungsheft z. Centralhlatt fur allgem. 

 Gesundheitspfiege. Bd. 2. Heft 2. 



^ Archivfilr Hygiene, p. 448, 1886. 



