42 LABORATORY BACTERIOLOGY 



muscle sugar. To eliminate this the following method has 

 been recommended.' Beef infusion is inoculated in the even- 

 ing with a rich fluid culture of some acid-producing organism 

 (i?. coH communis) and placed in the incubator. The next 

 morning 1;he white of an egg is added, and the infusion is 

 boiled and filtered. Peptone and salt are added as usual. 

 It is boiled, filtered again, distributed in tubes or flasks as 

 desired, and sterilized the same as bouillon (§ 12). 



63. Preparation of acid agar. This is prepared in the same 

 manner as ordinary agar (§ 18), with the omission of the sodium 

 hydrate in the bouillon from which it is made. 



64. Preparation of acid glycerin agar. Add 5 % glycerin to 

 acid agar before sterilizing it. 



65. Preparation of acid glycerin bouillon. This is prepared 

 either as ordinary bouillon (§ 12) or as sugar-free bouillon 

 (§ 62), with the omission of the alkali and the addition of 

 5 % c.p. glycerin. 



66. Preparation of blood serum. When a small quantity is 

 sufficient it can be obtained from a dog aseptically. The 

 animal is properly tied on the operating table, etherized, the 

 skin over the carotid or femoral artery is thoroughly dis- 

 infected and turned back, the artery exposed, a sterile glass 

 canula inserted, and the blood collected in a sterile flask by 

 means of a sterile rubber tube attached to the canula. After 

 the serum is formed it can be drawn off with a sterile pipette 

 and distributed in small sterile test tubes (5-7 cc. in each). 

 It is well to set the liquid serum in an incubator for a few 

 days to test its sterility. The tubes of liquid serum are inclined 

 (the same as agar) and placed in a blood-serum sterilizer, or 

 other chamber, in which the temperature can be raised to 70° 

 or 75° C. until the serum has set. Store in a cool place. 



If larger quantities of the blood are required, it is more con- 

 venient to collect it from bleeding animals in a slaughterhouse. 



^ Smith, y«/r«rt/ of ILxperiniental Medicine, Vol. II (1897), p. 543. 



