64 STUDYING MOLDS, YEASTS, AND ACTINOMYCETES 



tose of Chanut and 1 per cent of the granulated peptone of Chassaing. 

 These were obtainable for many years from the Maison Cogit, 36 

 Boulevard St. Michel in Paris. Although the ingredients were of un- 

 known composition, they were constant and gave reproducible re- 

 sults. The difficulty in obtaining these ingredients in other parts of 

 the world has led to the development of substitute media which are 

 often also called Sabouraud's agar. Attempts to reproduce the cul- 

 tural characters of dermatophytes as described by Sabouraud on 

 these substitute media indicated that the peptone rather than the 

 sugar was the essential ingredient. For ordinary work a medium 

 containing 2 per cent glucose and 1 per cent Neopeptone (Difco) is 

 a satisfactory substitute for Sabouraud's agar. It may be adjusted 

 to pH 5.6 and is commonly called Sabouraud agar or Sabouraud 

 glucose agar. Pure glucose is more satisfactory than maltose for 

 most fungi; it is more constant in composition, cheaper, and not so 

 likely to change in sterilization. Usually a somewhat better growth 

 is obtained if tap water is used instead of distilled water. There are 

 very few molds, yeasts, or actinomycetes which will not grow 

 abundantly on this medium. It is widely used for saprophytic and 

 industrial fimgi as well as for medical work. 



The original formula for Sabouraud's agar presented in the pre- 

 ceding paragraph is that of Sabouraud's "proof" agar, originally in- 

 tended primarily for the isolation and identification of dermato- 

 phytes. Species of these fungi have been based largely upon the 

 color and texture of the colonies, which characters may vary mark- 

 edly with slight variations in the medium. In addition to his proof 

 agar, Sabouraud used a conservation agar for the continued cultiva- 

 tion of strains in a collection. He believed that medium was less 

 likely to give rise to pleomorphism in dermatophytes than the proof 

 agar. The conservation medium contained no sugar, only 3 per cent 

 of peptone. Some fungi are more difficult to transfer from this me- 

 dium because they produce fewer aerial hyphae and conidia. The 

 dermatophytes can often be kept safely on the glucose agar if they 

 are placed in the refrigerator (2° to 5° C.) immediately after reaching 

 full development (10 to 15 days) and stored there until the next 

 transfer. 



The impression that the pathogenic fungi are fastidious in their 

 nutritional requirements and will grow only on Sabouraud's medium 

 is erroneous. Most of them grow well on a variety of media and, on 

 the other hand, Sabouraud's medium is unsuitable for some patho- 

 gens such as Actinomyces bovis. In addition to being a good, easily 

 prepared medium, it is very useful in the identification of dermato- 



