PLATE- CULTIVATIONS. 7 5 



moved from the gelatine. It is, however, not easy 

 to be successful at first, but with practice this can 

 be accomplished with rapidity and precision. A 

 cover-glass-preparation is then made in the manner 

 already described, viz., by rubbing the extremity 

 of the needle on a perfectly clean cover-glass and 

 examining by Babes' rapid method, or by thinning 

 out the micro-organisms in a droplet of sterilised 

 water previously placed on the cover glass, drying, 

 passing three times through the flame, and staining 

 with a drop of fuchsine. 



Inoculations should be made in test-tubes of 

 nutrient gelatine and agar-agar, from the micro- 

 organisms transferred to the cover-glass before 

 it is dried and stained, from any remnants of the 

 colony which was examined, or from other colonies 

 bearing exactly similar appearances. In this way 

 pure cultivations are established, and the macro- 

 scopical appearances of the growth in test-tubes 

 can be studied. The plates should be replaced 

 in the damp chambers as soon as possible ; drying 

 of the gelatine, or contamination with micro- 

 organisms gravitating from the air during their 

 exposure, may spoil them for subsequent examina- 

 tion. Nutrient agar-agar can also be employed 

 for the preparation of plate- cultivations, but it is 

 much more difficult to obtain satisfactory results. 

 The test-tubes of nutrient agar-agar must be 

 placed in a beaker with water and heated until the 

 agar-agar is completely liquefied. The gas is then 



