CH. IX} 



MO UN TIN(,' PR /: I'ARATH INS 



253 



what sticky, then warm the cover gently and put it on the cell, crystals down. 

 Press on the cover all around the edge ( 347) seal, label and catalog. 



A preparation of mammalian red blood corpuscles may be satisfactorily 

 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-spcctroscopic work (\ 232). 



FIG. 198. Turn-Table for sealing cover-glasses and making shallow 

 mounting cells. ( Cut loaned by the Bausch & Lomb Opt. Co.). 



'}, 346. Preparation of Mounting Cells. (A) Thin cells. These are most 

 conveniently made of some of the cements used in microscopy. Shellac is 

 one of the best and most generally applicable. To prepare a shellac cell place 

 the slide on a turn-table (Fig. 198) and center 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 bfnsh lightly on the slide just over the 

 guide ring selected. An even ring of 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 dries. 



(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. 



