202 Modern Microscopy 



Chloride of barium.* Sulphate of iron.* Asparagine. 

 Chlorate of potash.* Tartrate of soda.* Quinidine. 

 Sulphate of copper.* Salicine. Santonine. 



Spermaceti (fuse). Stearine (fuse). Tartaric acid. 



Those marked * are more effective when crystallized in 

 gum or gelatine. 



Crystals of Silver. Clean a cover-glass and fasten it 

 to a slide with the breath ; make a 1 per cent, solution of 

 nitrate of silver, and place a drop of it in the centre of 

 the cover-glass. Now add a very small fragment of copper, 

 and put the slide away out of reach of dust until the 

 crystals have formed, and all moisture has evaporated. 

 Then make a shallow opaque cell, and place a small drop 

 of gum water in its centre. Take up the cover with a pair 

 of forceps, crystals uppermost, of course, and drop it into 

 the cell ; now take a needle-point, and carefully press on 

 the cover-glass between the crystals, until it lies quite flat, 

 and air-bubbles, if any, have exuded. Put the slide away 

 again until the gum has dried. Now put the slide into a 

 turn-table; run on a coat of shellac cement to the upper 

 surface of the cell. Allow this to become half dry, and then 

 apply a cover-glass. 



The following specimens from the vegetable kingdom 

 make fine polariscope objects : Starches, hairs, scales from 

 leaves, cotton and silk fibres, cuticles of leaves, and longi- 

 tudinal and transverse sections of stems. 



Starches can be obtained from most vegetable substances 

 by scraping the cut surface with a knife. Place the scrapings 

 in a bottle of water and shake well ; then strain through 

 muslin of sufficiently fine texture to allow the starch to 

 pass, but to retain the fibres. Now put the strained material 

 into a bottle, shake it up, and then allow to settle ; the 

 starch will fall to the bottom of the bottle in a few minutes. 

 T hen pour off the water ; add some more, and repeat the 

 process until all trace of cellular tissue is removed. When 

 the starch is quite clean, take up a little in a dipping-tube ; 

 apply a drop to a clean cover. See that it spreads evenly 



