CH. X] MOUNTING MICROSCOPIC OBJECTS 323 



(3) In some resinous medium like Canada balsam, damar, etc 



501. Mounting dry or in air. The object should be thoroughly 

 dry. If any moisture remains it is liable to cloud the cover-glass, and 

 the specimen may deteriorate. As the specimen must be sealed, it 

 is necessary to prepare a cell slightly deeper than the object is thick. 

 This is to support the cover-glass, and also to prevent the running in 

 by capillarity of the sealing mixture. 



Order of procedure in mounting objects dry or in air. 



1. A cell of some kind is prepared. It should be slightly deeper 

 than the object is thick ( 503). 



2. The object is thoroughly dried (desiccated) either in dry air or by 

 the aid of gentle heat. 



3. If practicable the object is mounted on the cover-glass; if not it 

 is placed in the bottom of the cell. 



4. The slide is warmed till the cement forming the cell wall is 

 somewhat sticky, or a very thin coat of fresh cement is added; the 

 cover is warmed and put on the cell and pressed down all around till 

 a shining ring indicates its adherence. 



5. The cover-glass is sealed. 



6. The slide is labeled. 



7. The preparation is catalogued and safely stored. 



502. Example of mounting dry, or in air. Prepare a shallow 

 cell and dry it ( 503). Select a clean cover-glass slightly larger than 

 the cell. Pour upon the cover a drop of 10% solution of salicylic 

 acid in 95 % alcohol. Let it dry spontaneously. Warm the slide till 

 the cement ring or cell is somewhat sticky; then warm the cover 

 gently and put it on the cell, crystals down. Press on the cover all 

 around the edge, seal, label, and catalogue. 



A preparation of mammalian red blood corpuscles may be satis- 

 factorily made by spreading a very thin layer of fresh blood on a 

 cover with the end of a slide. After it is dry, warm gently to remove 

 the last traces of moisture and mount blood side down, precisely as for 

 the crystals. One can get the blood as directed for the Micro-spectro- 

 scopic work (413). 



