148 MOUNTING AND LABELING. \_CH. VII- 



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

 traces of moisture and mount precisely as for the crystals. One can get 

 the blood as directed for the Micro-spectroscopic work (§ 201). 



Fig. 125. Turn-Table for scaling cover-glasses, and making shallow mounting 



cells. ( Queen & Co. ) 



§ 233. Preparation of Mounting Cells. — ( A ) Thin Cells. These 

 are most conveniently made of some of the microscopical cements. 

 Shellac is one of the best and most generally applicable (§316). To 

 prepare a shellac cell place the slide on a turn-table ( Fig. 125) and cen- 

 ter it, that is, get the center of the slide over the center of the turn-table. 

 Select a guide ring on the turn-table which is a little smaller than the 

 cover-glass to be used, take the brush from the shellac, being sure that 

 there is not enough cement adhering to it to drop. Whirl the turn-table 

 and hold the brush lightly on the slide just over the guide ring selected. 

 An even ring of the cement should result. If it is uneven, the cement 

 is too thick or too thin, or too much was on the brush. After a ring is 

 thus prepared remove the slide and allow the cement to dry spontane- 

 ously, or heat the slide in some way. Before the slide is used for 

 mounting, the cement should be so dry when it is cold that it does not 

 dent when the finger nail is applied to it. 



A cell of considerable depth may be made with the shellac by adding 

 successive layers as the previous one drys. 



(B) Deep Cells are sometimes made by building up cement cells, but 

 more frequently, paper, wax, glass, hard rubber, or some metal is used 

 for the main part of the cell. Paper rings, block tin or lead rings are 

 easily cut out with gun punches. These rings are fastened to the slide 

 by using some cement like the shellac. 



§ 234. Sealing the Cover-Glass for Dry Objects Mounted in 

 Cells. — When an object is mounted in a cell, the slide is warmed until 

 the cement is slightly sticky, or a very thin coat of fresh cement is put 

 on. The cover-glass is warmed slightly also, both to make it stick to 

 the cell more easily, and to expel any remaining moisture from the ob- 

 ject. When the cover is put on it is pressed down all around over the 



