52 STUDYING MOLDS, YEASTS, AND ACTINOMYCETES 



Potato plugs may be prepared as for the growth of bacteria, but 

 they are not very useful. Carrot plugs, prepared in the same way, 

 are especially useful in studying spore formation in yeasts. Mois- 

 tened slices of bread are sometimes used, especially in the study of 

 Mucorales. Langeron and Milochevitch " proposed the use of mois- 

 tened grains of barley, w^heat, and rye for the cultivation of derma- 

 tophytes. Conant - found polished rice to be a more favorable me- 

 dium, especially for the development of macroconidia in the genus 

 Microsporum. One part of rice is added to three parts of water in 

 flasks and sterilized in flowing steam on two successive days. 



The restriction of the dermatophytoses to the skin, nails, and hair 

 has led to a widespread belief that the skin and its appendages con- 

 tain specific nutrients favorable to the dermatophytes. Hair, 

 feathers, leather, and horn have been used for the cultivation of these 

 fungi. Williams*^ has especially studied the growth of dermato- 

 phytes upon hair, using only hair and distilled water as a medium. 

 The various dermatophytes grew, but more slowly and scantily than 

 on Sabouraud's medium. Emmons " grow dermatophytes upon thin 

 shavings of horn in order to study the development of spores. David- 

 son, Gregory, and Birt '^ similarly observed the development of spores 

 of dermatophytes from the continued growth of fungi on the infected 

 hairs after removal from the patient. Memmesheimer ^^ has de- 

 scribed a medium prepared from skin and hair for the cultivation 

 of dermatophytes. The whole skin of guinea pigs is used. To pelts 

 75 to 80 grams in weight is added 20 ml. of 30 per cent potassium 

 hydroxide and 75 ml. of tap water. This is boiled for 30 to 45 min- 

 utes, almost completely dissolving the skin. The solution is neutral- 

 ized wdth hydrochloric acid and filtered, tap water is added to make 

 1 liter, and 40 grams of maltose and 18 grams of agar are added. 

 This medium is said to give a more rapid growth of dermatophytes 

 than the usual Sabouraud agar, and also to yield a higher percentage 

 of positive cultures from cases of dermatophytosis. 



The addition of serum or ascitic fluid to a medium stimulates and 

 improves the growth of some strains of Actinomyces bovis. Other 

 strains grow as well without this addition and it is not necessary for 

 the isolation of most fungi. New or recently isolated strains of 

 Blastomyces and Histoplasma when grown on blood agar at 37° C. 

 grow as budding cells similar to those seen in tissue, but these fungi 

 are probably more easily isolated on Sabouraud's agar medium. 



It is usually preferable to prepare media from natural materials 

 by making an aqueous solution of the nutritive constituents by in- 

 fusion or decoction. Such liquid media may then be solidified by 



