v.] METHODS OF INOCULATION. 31 



afterwards well supplied with moisture : ;' the sterile 



nourishing material (broth, aqueous humour, hydrocele fluid, 

 blood serum, liquefied gelatine mixture, liquefied ^gar-Agar 

 mixture, &c.) is then deposited by means of a capillary pipette 

 on to the centre of the cover-glass ; then the point of a capillary 

 pipette or needle containing the material it is desired to sow is 

 rapidly plunged into the drop of the nourishing material (or if 

 this is solidified is deposited in lines or points on the drop of 

 nourishing material), the cover-glass inverted and placed on to 

 the glass ring : the layer of olive oil keeps the edges of the 

 cover-glass air-tight on the glass ring. This cell is then placed 

 into the incubator 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-organ isms. Most water 

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

 experiment by Burden 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 (o) 

 microscopic specimens to be examined fresh ; (6) 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. Spill ers purple, gentian violet, 



1 Report* oftJie Medical Officer of the Priry Council, 1870. 



