68 LABORATORY BACTERIOLOGY 



104. The Preparation of Acid Glycerin Agar. — Add 5 % 



glycerin to acid agar before sterilizing it. 



105. The Preparation of Acid Glycerin Bouillon. — This is 

 prepared either as ordinary bouillon (12), or as sugar- free 

 bouillon (59), with the omission of the alkali and the addition 

 of 5 % c. p. glycerin. 



106. The Preparation of Blood Serum. — When a small quan- 

 tity 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 drqwn off with a sterile pipette, 

 and distributed in small sterile test tubes (5-7 c.c. 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 steriHzer, 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 slaughter-house. 

 In this case it is often necessary to sterilize the liquid serum after 

 it has been distributed in tubes. This can be done in a water 

 bath at 62" C. for 2 hours each day for four consecutive days. 



107. The Preparation of Loeffler's Blood Serum. — This con- 

 sists of I part neutral bouillon (prepared from meat), contain- 

 ing 1% grape sugar, 3 parts liquid blood serum. Mix and 

 distribute in sterile test tubes, incline and solidify the same as 

 .blood serum. The temperature should be about 75° C, and 

 the exposure will be necessarily longer than for the pure blood 

 serum. When it is to be used for the cultivation of diphtheria 

 organism, it can be set at a much higher temperature (80° to 

 100° C). Label and store. 



For other methods and special media, see text-books. 



