CHAPTER II 

 MOUNTING OF SPECIMENS 



THE preparation of objects or specimens for 

 observation by means of the microscope is termed 

 mounting. This operation consists in placing the 

 specimen upon a glass slide, surrounding it with a 

 suitable mounting medium and covering it with a 

 thin piece of glass known as a cover-slip or cover-glass. 

 The slides employed are usually 25 by 75 millimeters 

 in size and should be clear of flaws. 



The purpose of the mounting medium is three- 

 iold; first, to correct excessive differences in refractive 

 index between the specimen and the air; second, to 

 fix the specimen in place; third, to preserve the 

 specimen for future use. Comparatively few vege- 

 table materials can be examined satisfactorily without 

 the use of mounting media. To obtain clear views, 

 contrast is necessary; and this can only be obtained 

 through the use of mounting media of suitable refract- 

 ive index. The refractive indices of specimen and 

 mounting medium should be neither too near nor 

 too far apart and the ideal mounting medium is 

 between these extremes. 



The cover-slip serves to fix the specimen in place, 

 checks excessive evaporation of the mounting medium, 

 prevents dust from lodging upon the specimen and 

 protects the lenses of the microscope. It is essential 

 that slides and cover-slips be thoroughly cleaned 



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