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 
(B&. coli) and placed in the incubator. The next morning the 
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 exception that the 
bouillon should have a reaction of + 2.5. 
‘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 exception that it is titrated to a reaction of + 2.5, 
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 to 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. 
1 Smith, Journal of Experimental Medicine, Vol. II (1897), p. 543. 
