154 INFECTIONS CAUSED BY MOLDS 



the fungi in cultures; and made important contributions to the ther- 

 apy of dermatophytosis. His classification of the dermatophytes was 

 based on clinical manifestations for the separation of genera and 

 largely upon the characteristics of the colony for specific separation. 

 The three principal genera which he recognized can be defined in 

 mycological terms and this modification of Sabouraud's classifica- 

 tion will be followed here. His dependence upon colonial appearance 

 to determine species led to an excessive splitting of species and his 

 disregard of earlier specific names makes some of his names invalid. 

 Discussions of the dermatophytes will be found in many other publi- 

 cations.- *'' ^' «' ^°' ^5' ^'> 



Because of the complexity of the subject it will be necessary to 

 consider the important species of dermatophytes separately. We 

 shall therefore depart from the usual order followed elsewhere in this 

 book and discuss first the morphological and physiological features 

 which relate the dermatophytes to each other and the taxonomic 

 position they occupy. 



Cultural Characters. The identification of the various species of 

 dermatophytes is made very largely by the appearance of the colonies. 

 Since this is subject to some variation with the composition of the 

 medium, Sabouraud insisted that cultures should be made upon his 

 proof agar. Since the ingredients he used are no longer available or 

 were impure products, substitutes have been required. Plaut and 

 Griitz offered several alternative formulas which they claimed served 

 in place of Sabouraud's medium. Weidman also proposed some satis- 

 factory substitutes. A satisfactory medium which is constant in 

 composition, simple to prepare, and gives satisfactory colony char- 

 acteristics is described on page 55. It contains 1 per cent neopep- 

 tone and 2 per cent glucose. 



The colonies may be smooth and waxy if no aerial mycelium is 

 formed, or have a chalky surface, or velvety or woolly texture, de- 

 pending upon the abundance and height of the aerial mycelium. 

 They may be yellow or rose or violet in color, but most species are 

 yellowish or white. They may be irregularly folded to form cerebri- 

 form masses, regularly folded in radial patterns, or they may lack 

 folds. 



These characters are not constant. Pigment production may be 

 lost rapidly on subcultivation, and the texture of the colony is fre- 

 quently altered by the gradual or sudden appearance of an abundance 

 of sterile aerial mycelium, at first as localized tufts on various parts 

 of the colony, but rapidly growing over the whole colony. This is a 

 type of mutation which occurs regularly in some species of derma- 



