1895 THE MICROSCOPE 173 



QUESTIONS ANSWERED, 



Note. — Dr. S. G. Shanks, of Albany, N. Y., kindly consents to receive all sorts of ques- 

 tions relating to microscopy , 7vkether asked by p> o/essionals or amateurs. Persons of au 

 g ades of experience , from the beginner upivard, are w<'lcome to the benefits of this depav 

 nient. The questions are numbered for future reference. 



232 Where can I get slides of common rocks, or hoiv can 1 make 

 them?— A. P. S. 



Rock sections can be obtained from dealers in microscopical 

 goods and material or may be ground as follows : 



Select a thin fragment of rock, rub one side flat with No. 70 

 emer}' and w^ater on an iron plate, smooth with flour emery. 

 Wash, dry, and cement the flat surface to a piece of glass, with 

 hard balsam, using a gentle heat. Grind the rock as before 

 until thin enough to transmit light through the translucent ele- 

 ments. Much care is necessary as the se3tion becomes thinner. 

 Finally dissolve the balsam cement with benzol or chloroform, 

 liberate the section, wash with care because many minerals are 

 extremely brittle, mount in balsam. A section can be made in 

 20 to 30 minutes if you are not in a hurry. 



233 What is Hollis' Glue .^— HoUis' Glue is a solution of shel- 

 lac in alcohol, i. e., shellac varnish. 



234 Will a few droits of glycerine prevent the cracking of shellac 

 cements f — If not, ichat will? — Glycerine is not suitable. Add ten 

 drojDS of castor oil or of Venice turpentine to each ounce of 

 shellac varnish. 



PRACTICAL SUGGESTIONS. 



By L. a. WILLSON, 

 cleveland, ohio. 



How To Obtain Free Trichina. — Place a portion of tl e 

 flesh containing encysted trichina in dilute hydrochloric Acid. 

 This acid dissolves the lime of the capsule and leaves the ani- 

 mals free. Then they ma,y be picked out with needles under a 

 dissecting scope or hand magnifier. Before placing the flesh in 

 the acid it should be well teased. After removal, the trichina 

 should be bleached in chlorinated soda. They may also be 

 stained. A section of a cat's tongue with stained trichina makes 

 an attractive slide. 



