OP MICROSCOPIC OBJECTS. 54 



is to be placed, but not to cover a greater surface than the 

 object will totally hide from sight. This drop of gum musl 

 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 



