34 BACTERIA IN WATER 



bacteriological cleanliness in all our manipulations. This means that 

 we must use only sterilised vessels or flasks for collecting the sample, 

 and in the manipulation required we must be extremely careful to 

 avoid any pollution of air or any addition to the organisms of the 

 water from unsterilised apparatus. A flask polluted in only the 

 most infinitesimal degree will entirely vitiate all results. Vessels 

 may be sterilised by heating at 150 C. for two or three hours. If 

 this is impracticable the vessel may be washed with pure sulphuric 

 acid, and then thoroughly rinsed out in the water which is to be 

 examined. 



Accompanying the sample should be a more or less full statement 

 of its source. There can be no doubt that, in addition to a chemical 

 and bacteriological report of a water, there should also be made a 

 careful examination of its source. This may appear to take the 

 bacteriologist far afield, but until he has seen for himself what " the 

 gathering ground " is like, and from what sources come the feeding 

 streams, he cannot judge the water as fairly as he should be able to 

 do. The configuration of the gathering ground, its subsoil, its 

 geology, its rainfall, its relation to the slopes which it drains, the 

 nature of its surface, the course of its feeders, and the absence or 

 presence of cultivated areas, of roads, of houses, of farms, of human 

 traffic, of cattle and sheep all these points should be noted, and 

 their influence, direct or indirect upon the water, carefully borne in 

 mind. 



When the sample has been duly collected, sealed, and a label 

 affixed bearing the date, time, and conditions of collection and full 

 address, it should be transmitted with the least possible delay to the 

 laboratory. Frequently it is desirable to pack the bottles in a small 

 ice-case for transit. Miquel, Pakes, and others have constructed 

 special forms of packing-cases, and these have their advantages. 

 But the ordinary bottle of water may be quite satisfactorily con- 

 veyed, as a rule, packed in sawdust and ice. On receipt of such a 

 sample of water the examination must be immediately proceeded 

 with, in order to avoid, as far as possible, the fallacies arising from 

 the rapid multiplication of germs. 



Multiplication of Bacteria in Water. In almost pure water, at the 

 ordinary temperature of a room, Frankland found that organisms 

 multiplied as follows : 



No. of Germs. 

 Hours. per c.c. 



. . 1,073 



6 ... 6,028 



24 . . * 7,262 



48 . . 48,100 



Another series of observations revealed the same sort of rapid 



