CHAPTER XIV 



The Microscope 



THE microscope is an important instrument in mvcologic work. A be- 

 ginner should become familiar with the various parts and learn the 

 few necessary details of its proper care. The oil immersion objective is only 

 occasionally necessary, as in the examination of scales from a lesion sus- 

 pected of being erythrasma. The low power objective is useful in locating 

 the most desirable field for examination. A trained observer may detect 

 fungi by their appearance under low magnification (approximately X 100). 

 For finer details and for confirmation of the original observation, study of 

 the material under the high dry objective ( above X 400 ) is usually profita- 

 ble. We have found a third objective giving an intermediate magnification 

 (about X 200) useful for the closer examination of many slides. This has a 

 larger field and a greater depth of focus than the ordinary high dry objec- 

 tive; at this power, identification of structure is readily attained. If the prep- 

 aration is flooded with solvent, some of it is almost certain to run over onto 

 the stage of the microscope. If the slide is then removed and the stage 

 washed with a damp cloth, no harm will result. Unless the solvent is 

 removed, the stage will become tarnished and discolored. If the objective 

 accidentally touches the solvent, the solution should be wiped off promptly 

 with a wet microscope paper; otherwise vision is interfered with. Only soft 

 lens paper, especially made for the purpose, should be used to clean the 

 lenses in the eyepiece and objective. The beginner often makes the mis- 

 take of opening the diaphragm too far, allowing an overabundance of light 

 to pass through. Since the material is usually unstained, the light must be 

 subdued in order that fungous elements may be visible. 



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