OF MICROSCOPIC OBJECTS. 149 
If the bone is not sufficiently hard in its nature to bear 
the above method of handling whilst grinding and polishing 
—as some are far more brittle than others—as thin a section 
as possible must first be cut with the saw, and one surface 
eround and polished. The piece must then be dried and 
united to the glass by heated balsam in the same manner 
as shells, &c. After which the superabundance of balsam 
must be removed from the glass; then rub downuponthe stone 
and strop as before. Great care must be taken that the canals 
be not filled during the process with the dust of the bone, 
or of the polishing material. Dr. Beale, in the journal of 
_ the Q. M. C. takes occasion to say “that he cannot admit 
that the best way of preparing such sections is by grinding 
down, since it is too liable to fill the canals with débris.” He 
recommends that a fresh bone be taken—and a small slice 
cut off by a strong sharp knife. This is then to be im- 
mersed in carmine dissolved in ammonia—the ammonia 
being first neutralized by acetic acid. The walls of the 
vessels which penetrate the lacwne and canaliculi are by 
this means stained crimson, and thus the true structure of 
bone is rendered visible. When the polishing is completed 
the whole slide must be immersed in chloroform, ether, or 
some other spirit, to release and cleanse the section, when 
it may be mounted as the one above mentioned. 
Some have recommended a strong solution of isinglass to 
affix the half-ground teeth or bones to the glass as causing 
them to adhere very firmly and requiring no heat, and also 
being readily detached when finished. 
The reason why the sections of bone are usually mounted 
dry is that the lacune, bone cells, and canaliculi (re- 
sembling minute canals) show their forms, &c., very per- 
fectly in this state, as they are hollow and contain air, 
whereas if they become filled with liquid or balsam—which 
does sometimes occur—they become almost indistinguishable. 
There are some dark specimens, however, where the cells are 
already filled with other matter, and it is well to mount these 
with balsam and so gain a greater degree of transparency. 
