BACTERIA IN WATER 53 



isolate anaerobic bacteria, and to furnish a complete report 

 these also must receive careful attention. 



The Bacteriology of Water. In many natural waters there 

 will be found varied contents even in regard to flora alone : 

 algce, diatoms, spirogyrcz, desmids, and all sorts of vegetable 

 detritus. Many of these organisms are held responsible for 

 divers disagreeable tastes and odours. The colour of a water 

 may also be due to similar causes. Dr. Garrett, of Chelten- 

 ham, has recorded the occurrence of redness of water owing 

 to a growth of Crenothrix 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 upon the amount of or- 

 ganic pabulum present, and upon certain physical conditions 

 of the water. As we have already seen, bacteria multiply with 

 enormous rapidity. In some species multiplication does not 

 appear to depend on the presence of much organic matter, 

 and, indeed, some can live and multiply in sterilised water: 

 Micrococcus aquatilis and Bacillus erythrosportis. Again, 

 others depend not upon the quantity of organic matter, but 

 upon its quality. And frequently in a water of a high de- 

 gree of organic pollution it will be found that bacteria have 

 been restrained in their development by the competition of 

 other species monopolising the pabulum. Probably at least 

 one hundred different species of non-pathogenic organisms 

 have been isolated from water. Some species are constantly 

 occurring, and are present in almost all natural waters. 

 Amongst such are B. liquefaciens, B. fluorescent liq., B. fluor- 

 escens non-liquefaciens, B. termo, B. aquatilis, B. ubiquitus, 

 and not a few micrococci, etc. Percy Frankland 1 collected 

 water from various quarters at various times and seasons, 

 and some of his results may here be added : 



1 Micro-organisms in Water (1894). 



