454 HILDA HEMPL HELLER 



1902) he gives other formulae; several are given by Fred. Anker- 

 schmitt used physiological salt solution containing cubes of 

 potato to enrich spUtters of hemicellulose. Choukevitch em- 

 ployed 1 per cent pepton broth with 5 per cent starch for starch 

 sphtting organisms. Sihcate jelly as a substrate for such of these 

 organisms as will not grow on agar is described by Omeliansky 

 (1899) and formulae for similar jelhes are given by Fred and by 

 Kiister. 



III. Symbionts have been used to enrich certain types of anaer- 

 obes. Sturges and Rettger found that B. putrificus flourished 

 best in the presence oiBact. coli, and used the latter as a symbiont 

 for the former. Rhein used Bad. faecalis-alcaligenes as a sym- 

 biont for anaerobes, cultivating them in the presence of air : this 

 organism has several advantages. Wilson and Stere describe a 

 cocco-bacillus which is an excellent anaerobe symbiont. 



IV. Another resource is to test the resistance of the desired spe- 

 cies to unfavorable circumstances. Thus McCoy and Bengtson of 

 United States Public Health Laboratory isolated many strains of 

 tetanus with great ease by heating toxic strains at 70° for a half 

 hour and inoculating the spores in veal agar dilution shakes. 

 This technique is adverse for an anaerobe, but B. tetani appears 

 to be hardy enough to withstand it. Modified highly acid or 

 alkaline media, or media poor in protein may be used for such pur- 

 poses. A pure strain of the desired organism is invaluable in test- 

 ing out media of this sort. 



V. Aniline dyes may be used to eliminate certain species of or- 

 ganisms and the possibiUties which they offer are almost unlimited. 



VI. Selective temperatures may be employed for enrichment of 

 various organisms. B. hotulinus was long thought to produce 

 toxin at low temperatures only, because the contaminating or- 

 ganisms in the cultures outgrew it at 37°. Thermophilic organ- 

 isms are of various types, and are discussed by Bergey. iSIajor 

 W. J. Tulloch tells me that the flora obtained by incubating a 

 mixture of anaerobes in meat medium at 42° is quite different 

 from that obtained at 37°, slender, oval end-sporing organisms 

 predominating. It is probable that anaerobic organisms will be 

 found that grow at much higher temperatures than at 42°. 



