1990 Journal of Applied Microscopy 



The most satisfactory mounting fluid for general purposes is five per cent, 

 formalin, but for many vertebrate eggs a fifteen per cent, solution is necessarj'. 

 Only boiled or distilled water should be used in making up the mounting for- 

 malin, otherwise air bubbles are liable to be present after the mount is sealed. 



The mounting fluid thus prepared should be placed in a jar or pan, and the 

 specimens fixed to the glass, laid therein, so that the cover may be placed and 

 the air completely excluded. The mount is then ready to be raised horizontally 

 from the pan, and the superfluous fluid around the edge of the crystal absorbed 

 with filter paper. A thick solution of balsam dissolved in toluene is then 

 dropped around the edge of the cover, cementing it to the base. The balsam 

 will harden in from two to six weeks, according to the size of the specimen, so 

 that the mount may be handled in any manner. 



I have used in these mounts crystals 



varying in diameter from one to ten 



inches, and of a depth from one-eighth 



inch to two inches. If the crystals are 



Fig. 2.— a, Square base glass ; /■, balsam ^^^ ground SO as to fit accurately to the 



cement ; c, watch crystal cover. , , , i i • • 



base, the edges must be dipped m a ten 



per cent, solution of gelatin before being applied. 



I have made durable mounts in the last 18 month of sections of the brain, 

 series of the vertebrate brains, dissected eyes and ears, series of fish and frog 

 eggs showing all stages of segmentation, series of vertebrate embryos, and 

 dissections of various systems of the Achordates. 



Labels and letters may be attached with warm gelatin solution to any por- 

 tion of the specimens before immersing them in the mounting fluid. Water- 

 proof ink must of course be used in writing. 



A dry mount similar to the one above described serves admirably for dis- 

 playing insects. In this case a warm ten per cent, solution of gelatin should be 

 used to cement the crystal to the base. Alvin Davison. 



Lafayette College. 



The Microscopical Exhibit at the New York Botanical Garden. 



A popular feature of the display intended for public instruction at the museum 

 of the New York Botanical Garden is the permanent microscopical exhibit, made 

 possible by the use of twenty-four microscopes of special design provided through 

 the generosity of Mr. William E. Dodge. 



The Leitz stand V is used in the construction of these instruments. The 

 foot is removed and the base of the supporting column is fastened into a hard- 

 wood block GxQxiys in. This wooden base is blackened and has beveled edges. 

 The whole instrument, with the exception of the upper part of the draw-tube, is 

 then enclosed in a plate-glass case as indicated in the accompanying figure, the 

 outside measurements of the case being Sj4 x 4^ x 4^ in. 



The glass plates forming the sides of the case are inserted in grooves on the 

 wooden base and are held together at the top by a metal collar. Cement was at 



