84 



MICRO-ORGANISMS AND DISEASE [chap. 



The gelatine is then used for making plate-cultivations in 

 the ordinary plates, or is set as a thin film on the inside of 

 the flask. The writer uses a glass tube four to six inches 

 long, half an inch wide, containing in the middle a cotton- 

 wool or glass-wool plug about one and a half to two inches 

 long; at each end the tube is plugged with a small cotton- 

 wool plug. One end is drawn out in the shape of a large 



Fig. 14. — Plate-cultivation in which the surface of the Gelatine set in 

 A Plate-dish had been exposed for Three Minutes to Air in Oxford 

 Street. Natural size of the colonies. 



canula ; the whole is sterilised. When used the plugs of 

 the ends are removed, the canula end is joined to an as- 

 pirator and air is drawn through ; at the end of the experi- 

 ment the ends are again plugged. In order to use it after- 

 wards for plate-cultivations, the plugs of the ends are 

 removed, the central plug is then pushed out by means 

 of a thin glass rod, placed in liquefied nutrient gelatine 



