36 BACTERIA IN WATER 



sorts of vegetable detritus. Many of these organisms are held 

 responsible for certain disagreeable tastes and odours. The colour 

 of a water may also be due to similar causes. Dr Garrett, of 

 Cheltenham, has recorded the occurrence of redness of water owing 

 to a growth of Orenothrix polyspora, and many other similar cases 

 make it evident that not unfrequently great changes may be produced 

 in water by contained microscopic vegetation. 



With the exception of water from springs and deep wells, all 

 unfiltered natural waters contain numbers of bacteria.* The actual 

 number roughly depends, as we have seen, upon the amount of 

 organic pabulum present, and upon certain physical conditions of 

 the water. In some species multiplication does not appear to 

 depend on the presence of much organic matter, and, indeed, some 

 bacteria can live and multiply in almost pure water ; e.g., Micrococcus 

 aquatilis and Bacillus erythrosporus. Again, others depend not upon 

 the quantity of organic matter, but upon its quality. And frequently 

 in a water of a high degree of organic pollution it will be found that 

 bacteria have been restrained in their development by the competi- 

 tion of other species monopolising the pabulum. It will be necessary 

 to deal with the subject under the two subdivisions of (1) quantity 

 and (2) quality of bacteria found in water. 



Quantity of Bacteria in Water 



Percy Frankland has quoted in his book -f- a number of records 

 of the quantity of organisms found in various waters. These tables 

 give the returns for the rivers Seine (Miquel), Ehone, Sadne (Eoux), 

 Spree (Frank), Isar (Prausnitz), Limmat (Schlatter), Ehine (Moers), 

 etc. Here it is unnecessary to do more than give typical illustra- 

 tions, and for comparative purposes English rivers may be taken. 

 Prof. Frankland himself collected water from the river Thames 

 at various times and seasons, and some of his results were as 

 follow : — 



* Bacteria, of course, exist in the water of the sea. Near land, as might be 

 expected, the number is greatest, and diminishes rapidly further out to sea. 

 Currents sometimes bring them to the surface from a depth of 596 fathoms 

 (Fischer). At a depth of 100-200 fathoms bacteria have been found in large 

 numbers. The comparative paucity at the surface is due to the germicidal effect 

 of sunlight. Ocean bacteria vary widely in size and shape. Apparently, typical 

 cocci and bacilli are never met with on the high seas. Spirilla and zoogloea 

 masses are common. Most sea bacteria are motile and furnished with flagella • 

 some are anaerobes. ' 



f Micro-organisms in Water (1894), pp. 89-116. 



