170 MOUNTING AND LABELING [CH. VII 



In all of these different methods, unless glycerin of increasing strengths has 

 been used to prepare the tissue, the fixing agent is washed away with water before 

 the object is finally and permanently mounted in either of the media. 



For glycerin jelly no cell is necessary unless the object has a considerable 

 thickness. 



$ 251. Order of Procedure in Mounting Objects in Glycerin. 



1. A cell must be prepared on the slide if the object is of considerable thick- 

 ness ( 248, 249). 



2. A suitably prepared object ( 250) is placed on the center of a clean slide, 

 and if no cell is required a centering card is used to facilitate the centering 



(Fig. 138)- 



3. A drop of pure glycerin is put upon the object, or if a cell is used, enough 

 to fill the cell. 



4. In putting on the cover-glass it is grasped with fine forceps and the under 

 side breathed on to slightly moisten it so that the glycerin will adhere, then one 

 edge of the cover is put on the cell or slide and the cover gradually lowered upon 

 the object (Fig. 136). The cover is then gently pressed down. If a cell is used, a 

 a fresh coat of cement is added before mounting ($ 249). 



FIG. 139. Slide and cover-glass showing method of 

 anchoring a cover-glass with a glycerin preparation when 

 no cell is used. A cover-glass so anchored is not liable to 

 move when the cover is being sealed ($ 253). 



FIG. 140. Glass slide with cover-glass, a drop of re- 

 agent and a bit of absorbent paper to show method of irri- 

 gation (\262, 263}. 



5. The cover-glass is sealed (\ 249). 



6. The slide is labeled ( \ 308). 



7. The preparation is cataloged and safely stored ( 309, 311). 



$ 252. Order of Procedure in Mounting Objects in Glycerin Jelly. 



1. Unless the object is quite thick no cell is necessary with glycerin jelly. 



2. A slide is gently warmed and placed on the centering card (Fig. 138) and 

 a drop of warmed glycerin jelly is put on its center. The suitably prepared object 

 is then arranged in the center of the slide. 



3. A drop of the warm glycerin jelly is then put on the object, or if a cell is 

 used it is filled with the medium. 



4. The cover-glass is grasped with fine forceps, the lower side breathed on 

 and then gradually lowered upon the object (Fig. 136) and gently pressed down. 



5. After mounting, the preparation is left flat in some cool place till the 

 glycerin jelly sets, then the superfluous amount is scraped and wiped away and 

 the cover-glass sealed with shellac ($ 253). 



6. The slide is labeled (308). 



7. The preparation is cataloged and safely stored (\ 309, 311). 



\ 253. Sealing the Cover-Glass when no Cell is used. (A) For glycerin 

 mounted specimens. The superfluous glycerin is wiped away as carefully as possi- 

 ble with a moist cloth, then four minute drops of cement are placed at the edge of 

 the cover (Fig. 139), and allowed to harden for half an hour or more. These will 



