v.] METHODS OF INOCULATION. 49 



and exposed there to the desired temperature. Microscopic 

 examination is carried out from time to time to watch the 

 progress made. This can be done with high powers, since 

 the growth is taking place on the lower surface of the 

 cover-glass. 



Although contamination with air-organisms is not excluded, 

 still it is possible by making several specimens at the same 

 time and operating rapidly, to obtain pure cultures. This 

 glass cell can be also watched on a warm stage, or in a Klebs' 

 warm chamber. 



M. Nachet of Paris has designed a glass cell, in which the 

 drop of nourishing material is deposited on to the bottom of 

 the cell, the glass slip being here replaced by a very thin 

 glass ; but then there is a peculiar arrangement in the micro- 

 scope, by which the lower surface of the glass cell, i.e. the one 

 nearest to the growth, is directly subjected to microscopic 

 observation. 



After what has been said above about inoculation of solid 

 and fluid nourishing media with solid matter, it is not 

 necessary to dwell specially on the method of inoculation 

 with earth or similar substances. 



3. Examination of Water for Micro-organisms. Most 

 water contains bacteria of some kind, as has been shown by 

 direct experiment by Burdon-Sanderson. 1 If any sample of 

 water is to be examined for micro-organisms, particularly 

 bacterial forms, it is allowed to stand for a few hours, till 

 most of the particulate matter is settled, and then with 

 a capillary pipette a little of the fluid and sediment is drawn 

 out and used for (a) microscopic specimens to be examined 

 fresh ; (b) microscopic specimens prepared after the Weigert- 

 Koch method, i.e. by spreading out on a cover-glass a thin 

 layer, drying it. staining it with suitable aniline dyes, e.g. 

 1 Reports of the Medical Officer of the Privy Council, 1870. 



