238 IMPORTANT VARIETIES OF FISSION- FUNGI. 



from the preliminary culture, almost with absolute cer- 

 tainty many coli forms are obtained, but also, according 

 to most of the critical writers, much fewer typhoid bac- 

 teria than were in the original fluid (Losener). 



2. The direct preparation of plates from gelatin which con- 

 tains materials interfering with growth : phenol, hydrochloric 

 acid, methyl violet, potato juice, etc. Losener, who has 

 tested all these methods, recommends the following as the 

 only useful one : Plates are prepared directly upon gelatin 

 containing 0.03 to 0.05% phenol. The plates are best pre- 

 pared, according to Kruse, by inoculation upon the surface 

 (Tech. Appendix). Upon this carbol-gelatin the colonies 

 of Bact. typhi and coli grow in the usual manner ; many 

 others, especially liquefying varieties, are, on the contrary, 

 greatly retarded. From all colonies resembling typhoid 

 inoculations are made into liquefied 2% grape-sugar agar 

 (about a dozen tubes) and the shake cultures thus pre- 

 pared are placed in the incubator. The tubes in which 

 there is no fermentation are studied further, as indicated 

 on page 239. 



Almost simultaneously with Losener, Eisner studied, in 

 Koch's Institute, the methods for the ready demonstration 

 of typhoid bacteria by means of special nutrient media, and 

 instead of the potato-gelatin of Holz, 1 which had given 

 unsatisfactory results in the hands of many writers, he 

 recommended a new feebly acid potato-gelatin containing 

 \% iodid of potassium. (See Tech. Appendix.) (Z. H. 

 xxi, 25.) 



According to Eisner, scarcely any bacteria except Bact. 

 typhi and coli grow upon his nutrient medium, the lique- 

 fying varieties not at all. Bact. coli grows very well, and 

 after twenty-four hours presents already perfectly developed 

 colonies. 



In contrast to this, the Bact. typhi grows very slowly; 

 after twenty-four hours the colonies are scarcely visible 

 with low magnification, and after forty-eight hours they 

 appear as small, clearly shining colonies, like water drop- 



1 According to Holz, if carbolic acid is added to potato-gelatin, even 

 the typhoid bacteria grow in a non -characteristic manner; if the addi- 

 tion is omitted, then very many liquefying germs are not at all dis- 

 turbed in their growth. 



