00 PRACTICAL MICROSCOPY. 



Among the more common objects floating in the air and gaining 

 access to reagents, to subsequently appear in our mounted specimens, 

 are the following: 



Fibres. Procure minute pieces of uncolored linen, cotton, wool, 

 and silk. With a needle in either hand, tease out or separate a few 

 fibres on slides, add a drop of water and cover.* 



Starch. Procure samples of wheat, corn, potato and arrow-root 

 starch, or scrape materials containing any one of these substances 



FIG. 22. EXTRANEOUS SUBSTANCES. 



A. Granules of potato starch. 



B. Corn starch. 



C. Wood fibres. The circular dots are peculiar to the tissue of cone-bearing trees. 



D. Spiral thread from a tea leaf. 



E. Fragment of feather. 



with a sharp knife. To a minute portion on the slide add a drop of 

 water, cover and examine L and H. 



Wood Shavings, Feathers, Minute Insects, Portions of Larger In- 



* These substances, as well as most of those which follow under the same 

 heading, may be mounted permanently as follows: Put the dry material in 

 clean turpentine for a day or two, to remove the contained air. Transfer to 

 the slide, tease, separate, or arrange the elements, after which wipe away the 

 turpentine with strips of blotting paper. Add a drop of dammar and place 

 the cover-glass thereon. The weight of the cover will be sufficient to press the 

 object flat, if it be properly teased or separated. Although I do not advise the 

 making of colored rings around cover -glasses, they may be formed after first 

 protecting the dammar with a ring of gelatin. Vide formulae. 



