378 BACTERIOLOGY. 



oughly cleansed with hot water is taken to the slaughter- 

 house and filled with freshly-shed blood from a calf or 

 sheep. The blood is received directly in the jar as it 

 spurts from the cut in the throat of the animal. After 

 the edge of the jar has been wiped it is covered with 

 the lid and set aside, where it may stand quietly until 

 the blood has thoroughly clotted. The jar is then car- 

 ried to the laboratory and placed in an ice-chest. If 

 the jar containing the blood is carried about before the 

 latter has clotted, very imperfect separation of the serum 

 will take place. It is well to inspect the blood in the 

 jar after it has been standing a few hours, and if the 

 clot is found adhering to the sides, to separate it by a 

 rod. The blood is allowed to remain twenty -four hours 

 on the ice, and then the serum which surrounds the clot 

 is siphoned off by a rubber tube and mixed with one- 

 third its quantity of nutrient beef broth, to which 1 

 per cent, glucose has been added. This constitutes the 

 Loffler blood-serum mixture. This is poured into tubes, 

 which should be about four inches in length and two- 

 thirds of an inch in diameter, having been previously 

 plugged witli cotton and sterilized by dry heat at 

 150 C. for one hour. Care should be taken in filling 

 the tubes to avoid the formation of air-bubbles, as they 

 leave a permanently uneven surface when the strum 

 has been coagulated by heat. To prevent this the end 

 of the pipette or funnel which contains the serum should 

 be inserted well into the test-tube. About 2 c.c. are 

 sufficient for each tube. The tubes, having been filled 

 to the required height, are now to be coagulated and 

 sterilized. They are placed slanted at the proper angle 

 and then kept for two hours at a temperature just below 

 95 C. For this purpose a Koch serum coagulator 



