BACILLUS TYPHOSUS. 437 
Aqua dest. ; : : By oy ‘ . 1000 
Gelatin . “ e : y : . é 20 
Mannite (grape-sugar) . ‘ : ‘ F 10 
Sodium chloride. ; : P : 2 5 
Potassium chloride . : ‘ é - 2 5 
Boil, filter, add 2 per cent. agar and 10 ce. of normal sodic 
hydrate solution ; boil, filter, and sterilize. 
In making up the medium for work the only varia- 
tion was that the agar was added when the gelatin was 
put in in the original recipe, and the gelatin was 
added after the first filtration. 
The Capaldi medium is usually employed for surface 
cultures, but can be inoculated while melted’ in the 
tubes. Plates may be made beforehand, so that they 
are ready for use when the specimen comes in. As 
these plates are to be kept at 37° C., the difficulties in 
regard to temperature are avoided; but, unlike the 
Elsner plates, other organisms beside the colon and 
typhoid develop and may cause some confusion. In 
inaking the plates one or two are inoculated by gently 
carrying across their surface a platinum loop of feces 
“or urine. Others are then inoculated with a loop of 
urine or much diluted feces. In this way we are apt 
to have some plates with just the right amount of 
colonies. ; 
Appearance of the Colonies. Capaldi thus describes 
the differentiation: Typhoid: Small, gleaming, transpa- 
rent, almost colorless colonies (by reflected light, blue). 
Colon: Large, milky colonies (reflected light, brown). 
In using the medium it was found that even ina 
pure plate of typhoid the colonies vary much in size 
and appearance, while different typhoids show indi- 
vidual differences in growth. In general, a medium- 
sized, gray-white colony, with a few refractive granules, 
