CHAPTER XVIII 



The Direct Examination 



THE purpose is to determine the presence of fungous material. In many 

 instances this is sufficient to establish the diagnosis. With tinea versi- 

 color and a few other mycoses, this is the sole method of confirming the 

 clinical diagnosis. A positive result is much more valuable than a negative 

 one, since the latter is based only on a sample and this may fail to contain 

 fungous elements which are present elsewhere. Furthermore, treatment 

 decreases the amount of fungous material to be seen. 



The direct examination does not establish the identity of species except 

 in certain instances, which will be described later. The reason is that in the 

 filamentous stage usually observed, most fungi appear similar. 



1. SOLVENTS AND STAINS 



For ordinary routine use we have not found anything better than a 10 

 per cent solution of potassium or sodium hydroxide. With more concen- 

 trated solutions crystallization may occur, and this prevents or interferes 

 with the examination. Furthermore, the more caustic solutions are hard on 

 the hands. Other solutions which have been advocated include xylene, 

 sodium sulfite and chloral hydrate in acacia, but there are disadvantages in 

 the use of these and of other advocated solvents which we have tried. 



A solvent which may be used when time can be allowed for clearing of the 

 material and which offers a semipermanent specimen is an aqueous solution 

 containing 5 per cent potassium hydroxide and 25 per cent glycerin. With 

 this, little or no crystallization occurs and the material does not dry. In the 

 examination of pus, when for instance actinomycosis or blastomvcosis is 

 suspected, this solution is advantageous as a sob cut since the pus cells are 

 destroyed and the fungous material becomes more apparent. 



Stained slides are seldom practical for the routine demonstration of fungi 

 which cause superficial diseases. It is difficult to hold stain with potassium 



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