BACILLUS TYPHOSUS. 437 



Aqua dest t . 1000 



Gelatin 20 



Mannite (grape-sugar) . . . . . 10 



Sodium chloride ...... 5 



Potassium chloride ...... 5 



Boil, filter, add 2 per cent, agar and 10 c.c. 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 

 Eisner plates, other organisms beside the colon and 

 typhoid develop and may cause some confusion. In 

 making 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 in a 

 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, 



