CHAPTER V 

 MICROSCOPY 



BY MORRIS MOORE 



To one acquainted with the cultural characteristics of various groups of 

 fungi, it is easy to recognize the larger groups, but for accurate diagnosis a 

 microscopic study of the morpholog}' of the organisms is necessary. The 

 fungus must be allowed to grow for a sufficient length of time to permit im- 

 portant morphologic characters to develop. If the organism is pathogenic, all 

 the precautions mentioned for transfer must be taken to insure that spores of 

 dangerous microbes are not detached to float in the air and perhaps inoculate 

 some one. The slide and cover should be thoroughly cleaned with acid alcohol 

 and passed through a flame to remove any traces of fat. In dislodging the 

 material to be studied, great care should be taken not to entangle unneces- 

 sarily the mycelium. With yeastlike fungi this latter step is simplified, since 

 it is necessary only to take a loopful of the culture without fear of entangling 

 the mycelium as may occur with filamentous forms. 



The mounting of the material should be done carefully. A drop of dis- 

 tilled water, alcohol, Amann's lactophenol preparation, or glycerin, either 

 with or without a stain, is placed in the center of the slide. The fungus is 

 then lifted carefully from the tube with a platinum or nichrome needle or 

 spatula, dislodged into the drop, or pushed oft* by another needle if not pulled 

 off by the surface tension of the mounting medium. Platinum is preferable to 

 nichrome because of its rapidity in cooling, but nichrome is a harder metal 

 and is better for thick, hard growths which resist elevation by the needle. The 

 material is spread out as gently as possible in the mounting medium and a 

 cover glass is lowered carefully on the preparation, avoiding the inclusion of 

 bubbles of air. Alcohol has the advantage of killing the organism, and, hav- 

 ing a low surface tension, does not dislodge spores badl3^ It also has a tend- 

 ency to form fewer air bubbles, but it soon dries out and must be replaced 

 quite promptly by Avater or water and glycerol (2 parts water and 1 part 

 glycerol). This is done by placing a drop on the slide next the cover glass 

 and allowing it to be drawn in under as the alcohol evaporates. Care must 

 be taken, if glycerol is used, that it does not wet the top of the cover glass, 

 as it will be difficult to remove later. The disadvantage in the use of glycerol 

 alone lies in the fact that yeastlike or even filamentous forms may be cleared 

 to such an extent that it is \ery difficult to make out the morphology of the 

 organism. To avoid this, various dyes, such as methylene blue, crystal violet, 

 or eosin, are incorporated either as an aqueous or alcoholic solution (usually 

 about 1%) in amount sufficient to produce the desired intensity. Water does 

 not evaporate rapidly, but, owing to its high surface tension, tends to tear 



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