PLATE-CULTIVATIONS. 7 I 



distributed throughout the gelatine. Any violent 

 shaking, and consequent formation of bubbles, 

 must be carefully avoided. From the so-called 

 "original" inoculate in the same manner afresh 

 tube of liquefied gelatine, introducing into it 

 three droplets with a sterilised ose. This tube is 

 then called the " first attenuation," or No. i. After 

 treating No. i as has been already described in the 

 case of the original, the same process is repeated 

 with a third tube, which is inoculated in the same 

 way from No. i. This is the "second attenua- 

 tion" or No. 2, and in some cases a " third atten- 

 uation " is carried out from No. 2. The last tube 

 must be inoculated in different ways, according to 

 experience for different micro-organisms. Some- 

 times a sufficient separation of the micro-organisms 

 is attained by inoculating the- last tube with a fine 

 straight needle dipped from one into the other 

 from three to five times. 



The next process consists in pouring out the 



gelatine on a glass plate and allowing it to solidify. 



Preparation of the Gelatine-plates. The 



directions to be observed in pouring out the gelatine 



are as follows : 



Place the box containing sterilised plates horizon- 

 tally, and so that the cover projects beyond the edge 

 of the table ; remove the cover, and withdraw a 

 plate with sterilised forceps ; hold it between the 

 finger and thumb by opposite margins, rapidly 

 transfer it to the filter paper under the bell-glass, and 



