OF MICROSCOPIC OBJECTS. 55 
is to be placed, but not to cover a greater surface than the 
object will totally hide from sight. This drop of gum must 
be allowed to dry, which will take a few minutes. Breathe 
then upon it two or three times, holding the slide not far 
from the mouth, which will render the surface adhesive. 
Then draw a camel-hair pencil through the lips, so as to 
moisten it slightly (when anything small will adhere to 
it quite firmly enough), touch the object and place it 
upon the gum in the desired position. This must be done 
immediately to ensure perfect stability, otherwise the gum 
will become at least partially dry and only retain the object 
imperfectly. 
When, however, the objects are so minute that it would 
be impossible to deposit atoms of gum small enough for 
each one to cover, a different method of proceeding must be 
adopted. In this case a small portion of the same gum 
solution should be placed upon the slide, and by means of 
any small instrument—a long needle will serve the purpose 
very well—spread over the surface which will be required. 
The quantity thus extended will be very small, but by 
breathing upon it may be prevented drying whilst being 
dispersed. This, like the forementioned, should be then 
allowed to dry; and whilst the objects are being placed on 
the prepared surface, breathing upon it as before will restore 
the power of adherence. A small patch of gold-size—or 
gum dammar solution which has been allowed to become 
“tackey”’—is very useful in many cases. 
When gum or other liquid cement has been used to fix 
the objects to the glass, the thin covers must not be applied 
until the slide has been thoroughly dried, and all fear of 
dampness arising from the use of the solution done away 
with. Warmth may be safely applied for the purpose, as 
objects fastened by this method are seldom, if ever found to 
be loosened by it. As objects are met with of every thick- 
ness, the cells will be required of different depths. There 
is no difficulty in accommodating ourselves in this—the 
deeper cells may be readily cut out of thick leather, card, or 
