C. Johnston on Microscopical Preparations. 233 
11. An ounce of “ dentist’s silex,” a 
12. Thin French letter paper, of which 500 or more leaves are 
oe ag to fill up the space of an inch: I examine the object 
and decide upon the plane of the proposed section. 
Coarse approximative sections may be obtained with the saw 
or dividing file (excepting silicified substances), but these instru: 
ments are not applicable to longitudinal sections of small human 
or other teeth, small bones, &c. Take now the object in the 
fingers if sufficiently large, and grind it upon the coarse hone 
with water, to which add “silex” if necessary, until the surface 
coincides with the intended plane, Wash carefully: finish upon 
the finer hone; and polish upon soft linen stretched upon a 
smooth block, : 
._ If the object be too small to admit of immediate manipulation 
It should 
what is better, upon thin paper well glued with the same sub- 
With thin French letter - next apply a paper guard, as be- 
paper; next apply & pi a : 
fore stated, but not thicker, for teeth ae bone, than ;3sth inch; 
Q Yof a specimen being prepared may be appreciated ee 
ally moisten the “space” with isinglass to the extent ot the 
Semented in its place. Gentle pressure should now be employed, 
and maintained with a wire spring, or thread wound round about. 
'0rm. fo 
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Mountin g. 
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