308 



PRACTICAL MICROSCOPY. 



jelly, and very satisfactorily illustrates the general prac- 

 tice, though of course it is not all objects which will bear 

 boiling. 



An instrument called Smith's mounting machine, and 

 shown in Fig. 252, is very useful when mounting large and 

 elastic substances in glycerine jelly, as by it any degree of 

 pressure may be exerted upon the covering glass. 



The method of using this instrument may be explained by 

 mounting a lichen section (Figs. 253 or 254) in Deane's 



medium. The section having 

 been cut as thinly as possible, 

 it is to be soaked for a day 

 or more in some of the me- 

 dium diluted with just enough 

 water to render it fluid ; it is 

 then to be placed upon a 

 slip, the cover superposed and 



FIG. 253. 



FIG. 254. 



placed in the mounting instrument, a gentle pressure 

 being exerted by means of the screw ; the slide must 

 now be warmed over the lamp, and a drop of the medium 

 placed at the edge of the cover, when it will be drawn 

 under by capillary attraction. This is a very clean 



