30 MICRO-ORGANISMS AND DISEASE [chap. 



and dissolved, then boiled, and either kept in the flask as 

 stock or decanted into sterile test-tubes to the amount of 

 5-10 cc, plugged with sterile cotton-wool. These are 

 steamed (see below) on two successive days, each time for 

 twenty minutes. 



This nutrient broth, with 5-8 per cent, pure glycerin 

 represents glycerin broth. 



3. Buchner's Fluid. — 10 parts of Liebig's extract, and 8 

 parts of peptone, in 1,000 parts of water. 



4. Hydrocele Fluid (Koch). — A new or well sterilised 

 trocar and cannula are used for the tapping ; to the cannula 

 is fixed an india-rubber tube that has been soaking in strong 

 carbolic acid solution for forty-eight hours. The distal end 

 of the tube is introduced carefully and rapidly into the neck 

 of a sterilised flask plugged with sterile cotton-wool, and the 

 fluid thus allowed to flow into the flask to about two-thirds 

 of its volume. This fluid is then decanted into sterile test- 

 tubes (plugged with sterile cotton-wool), each tube receiving 

 about S to 10 ccm. The tubes are then exposed in the incu- 

 bator to a temperature of from 55° to 60° C. for two to 

 three hours on two or three consecutive days. 



Ascites fluid is obtained in the same way. 



5. Blood Serum (Koch). — A glass cannula and india- 

 rubber tubing are soaked for forty-eight hours in strong 

 carbolic acid ; the cannula is tied into the carotid artery of 

 a healthy horse, and the arterial blood, after opening the 

 clip at the proximal end of the artery, is allowed to flow 

 into sterile flasks, or cylinders with stoppers. After letting 

 the blood stand for 24 to 48 hours in a refrigerator or in an 

 ice-box, the serum is taken off" by means of large sterile 

 glass pipettes and introduced into sterile test-tubes, each 

 receiving about 5 to 10 ccm. The test-tubes, plugged with 

 sterile cotton-wool, are then exposed in the incubator to a 



