20 MICRO-ORGANISMS AND DISEASE. [CHAP. 



in all other cases, sterilised by overheating) into flasks, and 

 treated in the same manner as the broth. 



An excellent fluid is beef broth with i per cent, of peptone, 

 the mixture is then made faintly alkaline, boiled and filtered 

 into sterile flasks, then well boiled to serve as stock, or to 

 be at once decanted into test-tubes. 



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 (by 

 over-heating) 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 5 to 8 ccm. The tubes are then exposed in 

 the incubator to a temperature of from 55 to 60 C. for 

 three to five hours on five or six consecutive days. 



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 

 12 to 24 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 

 8 ccm. The test-tubes, plugged with sterile cotton-wool, are 

 then exposed in the incubator to a temperature of 58 to 62* 

 C. in the same manner and for the same time as the 

 hydrocele fluid was. 



