260 MEMORANDA. 
bit of silk upon the finger; and after spontaneous separation 
from the paper in hot water the specimen ought to be well 
washed on both sides with a camel’s-hair pencil and soap 
water, dropped into cold water, and thence extracted to dry. 
After immersion in chloroform for a moment, and examination 
for the removal of possibly adherent particles, the section 
may be declared suitable for mounting. 
Before proceeding to this step, a few precautions are neces- 
sary about particular sections. Transverse sections of teeth 
or bone should be dried, after the preliminary washing, 
between glass, in order to avoid the disadvantage of warp- 
ing. Very porous parts, such as cancellated bone, or fragile 
bodies, such as the poison fang of serpents, require that the 
whole structure, or the canals, be saturated with glue and 
dried. Sections may now be cut with a saw, ground in oil, 
and cemented to the holding-glass subsequent to immersion in 
chloroform. 
Mounting —Spread a sufficient quantity of old Canada 
balsam, or of that thickened by heat (not boiling), upon a slide, 
and,when cold, place the section upon it. Have ready a spatula 
bearing a quantity of equally inspissated balsam warmed 
uatil it flows, with which cover the specimen, and then 
immediately warm the slide, being careful to employ the least 
possible heat. Now carefully depress the section, and with- 
draw every air bubble with a stout needle set in a handle 
towards the ends of the slide: put on the cover glass, slightly 
warmed, not flat, but allowing one edge to touch the balsam 
first, press out superfluous balsam, and the specimen is safe. 
The slide may now be cleaned with a warm knife, spirits of 
wine, and ammonia. 
This communication would be incomplete without some 
very important hints concerning “ cover glass.” It is easy to 
clean small covers, but very thin glasses or large ones, one or 
two inches in length, are not so safely handled. All danger of 
breaking is, however, avoided by placing a cover upon a large 
clean slide, and wiping one side only with a bit of men damp 
with aqua ammonie, and then with a dry piece. The other side 
may be cleaned after the mounting. 
In the next place, all preparers are aware of the difficulty 
attending the use and application of large covers. I beg 
leave to assure the inexpert that the following method will 
ensure success. Having prepared the cover glass, and super- 
imposed it, let it first be gently pressed downwards at many 
points, with the flat end of a lead pencil; it will be found, 
however, almost impossible to flatten it without breaking, 
consequently too much balsam will overlie and underlie the 
