PART III. 

 HISTOLOGICAL TECHNIQUE. 



CHAPTER XXVI. 



PRACTICAL SUGGESTIONS FOR THE CARE AND USE OF 

 THE MICROSCOPE. MICROSCOPICAL TECHNIQUE. 



IN selecting a microscope the following considerations are of 

 importance : 



The stand should be supported on three points and rest firmly on 

 the table ; have a rack-and-pinion coarse adjustment, and a fine 

 adjustment free from all loss of motion. It is rarely used in an 

 inclined position, and a jointed stand is unnecessary. A triple 

 nose-piece, or revolver, is a great convenience, and an Abbe con- 

 denser with iris-diaphragm is almost indispensable. 



Three objectives are needed : a Leitz No. 3 or No. 4, No. 7, and 

 T Vth or y^th oil immersion, or their equivalents of other manu- 

 facture, are suitable powers for general use. Two oculars, No. 2 

 and No. 4, will answer. 



The microscope should be protected from direct sunlight and acid 

 fumes, and be kept in a dry, moderately cool place. "When not in 

 use it should be covered or placed in its case, to protect it from 

 dust. If the lenses become dirty, they may be wiped with a soft, 

 clean cloth or Japanese paper, either dry or moistened with water, 

 and followed by a dry cloth or paper. Balsam or cedar oil may be 

 removed with a cloth or soft paper moistened with xylol, after which 

 the parts should be carefully wiped dry. 



In making microchemical tests special care should be taken not 

 to let the reagents come in contact with the objectives. 



Objects should always be examined in a liquid, unless there is 

 some special reason for examining them in a dry state ; and should 

 be covered with a cover-glass, unless a cursory inspection with a 

 very low power is all that is required. 



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