CHAPTER XIII 



OBJECTS OF GENERAL INTEREST: CELL-MAKING, FLUID 

 MOUNTS, "INTOTO" PREPARATIONS, DRY MOUNTS, 



OPAQUE MOUNTS 



When objects of considerable thickness are to be mounted it 

 is sometimes necessary to resort to cells which will contain the 

 object and support the cover-glass. Fluid mounts and aqueous 

 media must occasionally be resorted to for delicate objects which 

 would be injuriously affected by alcohol, or which are unsuitable 

 for mounting in balsam. When such mounts are used, whether 

 in a cell or not, the cover-glass must ordinarily be sealed with a 

 cement if the preparation is to be permanent. In all cases where 

 it is at all practicable, balsam mounts are to be preferred for 

 permanent preparations. Glycerin is a convenient mounting 

 medium for many objects, especially for temporary mounts. It is 

 often used where such media as balsam would render the prepara- 

 tion too transparent; it is much more favorable, moreover, to the 

 preservation of color than are resinous media. For making cells 

 and sealing circular covers, a turntable (Fig. 36) is desirable, 

 although the work may be done by following a guide ring drawn 

 on paper and placed under the slide. 



I. TURNING CELLS 



Prepare 12 or 15 slides as follows: 1. Place a slide on a turn- 

 table and adjust it so that its center lies over the center of the 

 turntable. 



2. Dip a small camel's hair pencil into gold size, but do not 

 take up enough of the fluid to drop. 



3. Choose a guide ring on the turntable which is of slightly 

 smaller diameter than the cover-glass to be used, whirl the table 

 and hold the pencil lightly over the guide ring. The ring which 

 has been spun should be even. If it is not, practice turning rings 

 until satisfactory ones are made. If the gold size is old it is 

 probably too thick to make suitable rings. Pure linseed oil may 



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