CULTURE METHODS 61 



2. Pour the contents of the tubes into Petri-dishes, and add 

 sterilized liquefied blood serum heated to 40 C., mixing it thoroughly 

 with the agar medium. (This method is specially adapted for the 

 growth of Diphtheria bacilli and gonococci.) 



CXIII. AGAR STROKE CULTURE PLATE METHOD. 



1. Liquefy some tubes of agar-agar, pour into Petri-dishes, and 

 allow to solidify. 



2. Dip a sterilized platinum wire in the suspected material, raise 

 the lid of the Petri-dish obliquely, and make several strokes with the 

 platinum wire across the surface of the agar-agar. Instead of using 

 dishes, take six or eight tubes of sterilized oblique surface agar-agar, 

 and make strokes on the surface of the medium. (The above methods 

 are only used when a quick diagnosis is necessary.) 



CXIV. ESMARCH'S ROLL CULTURE METHOD. 



1. Take three large wide-mouthed test-tubes containing 10 c.c. of 

 sterilized nutrient gelatine. 



2. Liquefy the gelatine, and inoculate with the material under 

 investigation, making the usual dilution, O 1 2 . 



3. Push the cotton plugs well down, cut off any ends, and put on 

 an india-rubber cap. 



4. Cool the gelatine by twisting the tube round and round on 

 its own axis in ice-water, when the gelatine will adhere to the inner 

 walls of the tube in a thin film. Before putting the tube in the ice- 

 water, roll the gelatine round the periphery of the internal portion of 

 the cotton plug ; by this means the centre of the plug remains free 

 from gelatine, otherwise an air-tight cavity results. 



5. To remove a colony from a roll culture, place the tube under 

 a low power lens (see special apparatus, Fig. 12), select the colony, 

 colour the outside of the tube over the colony, and then remove to 

 other media, etc., with a bent platinum wire, the stain outside acting 

 as a guide. 



CXV. BOOKER'S ROLL CULTURE METHOD. 



A much better method than the preceding, though depending 

 upon the same principles, is that recommended by Booker. 



1. Place a block of ice of convenient size in a dish, resting upon 

 a towel (which prevents it slipping). 



