38 BACTERIA 



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. 



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, and in point of fact, as regards distance, this may 

 be so. But until he has seen for himself what *' the gather- 

 ing-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 trafific, of cattle and 

 sheep — all these points must 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 col- 

 lection 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. 

 On receipt of such a sample of water the examination must be 

 immediately proceeded with, in order to avoid, as far as possi- 

 ble, the fallacies arising from the rapid multiplication of germs. 

 Even in almost pure water, at the ordinary temperature of a 

 room, Frankland found organisms multiplied as follows : 



No. of Germs 

 Hours. per cc. 



o 1,073 



6 6,028 



24 7,262 



48 48, lOO 



