110 
PRINCIPLES OF BACTERIOLOGY 
melted and cooled to 60° C.). Tube in Wassermann test 
tubes (4x3^ inch). 
(b) Prepare 1 per cent solution of China blue in dis¬ 
tilled water. 
(c) 0.4 c. c. of normal sodium hydroxide is added to 10 
c.c. of 1 per cent solution of China blue, and the mixture 
is heated in water-bath for ten minutes at 100° C. (the 
blue color now changes to brown). 
(d) 1.2 c.c. of this mixture is added to 100 c.c. of 
agar. 
(e) 0.1 per cent glucose and 1 per cent lactose are also 
added, and the mixture is heated for ten minutes in 
water-bath at 100° C. Cool to 60° C., and pour on the 
first layer (step A) the same amount as the latter. 
The changes caused by the different bacteria on this 
medium are shown in the following table. 
Bacillus 
Gas 
Bottom Layer 
Top Layer 
Typhoid 
No 
Black 
Pale blue 
Paratyphoid A 
Yes 
No change 
Pale blue 
Paratyphoid B 
Yes 
Black 
Colorless 
Colon 
Yes 
Black 
Deep blue 
Enteritidis 
Yes 
No change 
Colorless 
15. Cornstarch Medium 
This little-known medium is the best medium for 
gonococcus cultivation, also for pneumococcus and other 
bacteria which grow with difficulty. On this medium the 
gonococcus, which dies on all other media in four to five 
days, will live over four weeks, so that where cultivation 
and frequent transfers are to be made this medium will 
be found of greatest help. 
(a) 500 grams of lean beef are added to 1,500 c.c. of 
water, and put in a flask on ice overnight. 
