58 PRACTICAL BACTERIOLOGY 



swabbed out with a test-tube brush, using the cane handle form, as 

 wire handles are apt to go through the bottom of the tube. When 

 thoroughly cleansed, rinse with a warm 1 per cent, solution of 

 commercial hydrochloric acid (this is to remove the alkali), rinse 

 thoroughly in clean running water, and stand top down until the 

 water has drained from them. 



Fill the desired amount of media into the tubes from a small 

 Erlenmeyer flask, or use a funnel with a pinch-cock, prepared for the 

 purpose when exactitude is necessary, but for all practical purposes an 

 Erlenmeyer flask is sufficient. Care must be taken that none of the 

 material is dropped in the inside of the mouth of the test-tube, as it 

 will cause the cotton plugs to adhere. The filled tubes are plugged 

 with cotton wadding plugs, carefully rolled together before insertion, 

 and the tubes sterilized in the steam sterilizer for fifteen to twenty 

 minutes on each of three successive days. The old method of steriliz- 

 ing the tubes and cotton wadding before filling is no longer in vogue, 

 the discontinuous sterilization being sufficient. 



CVII. METHODS OF CULTIVATING BACTERIA. 



1. The platinum wires and loops, both before and after use, are 

 sterilized in the Bunsen flame, from above downwards, the wire being 

 held almost perpendicular in the flame, and the upper portion of the 

 glass or metal rod it is attached to passes several times directly 

 through the centre of the flame. 



2. Fluid cultures are inoculated with one platinum loop- full of a 

 pure culture. 



3. Gelatine and agar-agar stab cultures are made with the platinum 

 wire, making only one stab in each tube, reaching almost to the 

 bottom of the medium. 



4. A gar-gelatine and potato contact cultures are made with the 

 platinum loop, the material being spread over the surface of the 

 media. The agar and gelatine media being solidified obliquely, whilst 

 the potato surface is either oblique or flat, when the material can be 

 further spread with a potato-knife. 



CVIII. KOCH'S ORIGINAL PLATE CULTURE METHOD. 



FOR THE ISOLATION OF GERMS IN A PURE CULTURE. 



1. Take three tubes containing 10 c.c. of sterilized nutrient gela- 

 tine, and melt the medium by heating in the water-bath at 40 C. 



2. When the first tube has cooled to 30 C., remove the cotton 



