BACILLUS TYPHOSUS. 431 
completely dissolved by a few minutes’ boiling. The 
medium is then titrated, to determine its reaction, 
phenolphthalein being used as the indicator. The 
requisite amount of normal hydrochloric acid or sodium 
hydrate solution is added to bring it to the desired 
reaction—i. e., a reaction indicating 2 per cent. of nor- 
mal acid. To clear the medium add one or two eggs, 
well beaten in 25 c.c. of water, boil for forty-five min- 
utes, and filter through a thin filter of absorbent cotton. 
_Add the glucose after clearing. The reaction of the 
medium is most important; it should never contain less 
than 2 per cent. of normal acid. 
The tube medium contains agar, 5 grammes; gelatin, 
80 grammes; sodium chloride, 5 grammes; meat ex- 
Fic, 54. 
| 
re 
Hiss’ plate media: Small light colony (¢) is composed of typhoid bacilli; 
large colony (c) of colon bacilli. (From Hiss.) 
tract, 5 grammes, and glucose, 10 grammes to the litre 
of water, and reacts to 1.5 per cent. acid by the indi- 
cator. The mode of preparation is the same as for the 
plate medium, care being taken always to add the 
