MEMORANDA, 259 
8. One ounce of chloroform ; 
9. One of F.F. aqua ammonie ; 
10. Some fragments of thick plate (mirror) glass 1 inch 
square, or 1 by 2 inches; and finally, 
11. An ounce of “ dentist’s silex,’”” and— 
12. Thin French letter paper, of which 500 or more leaves 
are required 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 
instruments 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 neces- 
sary, 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 mani- 
pulation it should be fastened upon a piece of glass with 
isinglass—or what is better, upon thin paper well glued with 
the same substance upon glass; and a piece of thick paper or 
visiting card, perforated with a free aperture for the object, 
must be attached to the first paper. This is the guard, 
down to which the specimen must be ground with oil; and 
its thickness and the disposal of the object require the exercise 
of good judgment. Hot water will release everything; and 
chloroform remove the grease from the specimen; which, 
like that ground with water, is ready for the second part of 
the process. 
2d. Carefully cover the surface of a piece of the plate glass 
with thin French letter paper; next apply a paper guard, as 
before stated, but not thicker, for teeth and bone, than 
stoth inch; then trace a few lines with a lead pencil upon 
the first paper in the little space left in the guard so that the 
increasing transparency of a specimen being prepared may be 
appreciated ; and finally moisten the “space” with isinglass 
to the extent of the object, which must be delicately brushed 
over on the ground surface and at the edges with tolerably 
thin isinglass before it is cemented in its place. Gentle 
pressure should now be employed, and maintained with a wire 
spring, or thread wound round about. 
In two or three hours the second side may be ground in 
oil; silex may be employed at first, or even a file; but these 
means must not be persevered in, and the operation must be 
completed upon the bare hone. When the second side shall 
have been wiped with chloroform it may be polished with a 
