1893.] THE MICROSCOPE. 33 



QUESTIONS ANSWERED, 



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

 tions relating 10 microscopy , whether asked by professionals or amateurs. Persons of all 

 grades of experience, from the beginner uptuard, are ivflcovie to the benifits >f tins depart- 

 ment. The questions are number id for future i eference. 



12Q. Hoiv are jjiicrotome knives to be kept in sharp condi- 

 tion? — R. 



The knife must be carefully honed on a perfectly even and flat 

 oil-stone. The process is similar to that of honing a razor. This 

 sharpening should be done habitually after using the knife, and be- 

 fore it is laid away. The stone should be very fine, and one too 

 hard for a barber's hone. " because it cuts too slowly, " is just the 

 sort of a stone to put a very fine, smooth edge on a microtome 

 knife. If the knife has been nicked it should be sent to the cut- 

 ler to be ground to a smooth, straight edge, and be honed as if it 

 were a razor. A piece of good calfskin glued to a flat wooden 

 back may be used as a strop to keep the edge keen, at intervals 

 during the cutting of sections. 



JJO. How are vegetable sections to be preserved ivhile await- 

 ing opportunity to mount them? — R. 



They are best preserved in alcohol, especially if they are to be 

 mounted in balsam. If intended for glycerin or glycerin jellv, 

 preserve them in glycerin and water, equal parts, with a little 

 camphor or carbolic acid added, to prevent mould. Sections 

 preserved in this latter fluid may be mounted in balsam if the 

 glycerin be carefully removed by soaking them in several 

 waters. 



JJi. Will vegetable stains fade out if exposed to sun- 

 light?— R. 



Sunlight is a very powerful bleacher, and unnecessary exposure 

 in it should be avoided. Vegetable sections stained in carmine, 

 picro-carmine, or logwood may be regarded as permanent. Sec- 

 tions stained in the aniline dyes are not permanent, as a rule, and 

 will quickly fade in sunlight. 



i ?2 . In double-staining a section should a lio-ht or dark stain 

 be used first? — R. 



That depends upon the chemical characteristics of the staining 

 fluid, not upon the hue. Some aniline dyes may be used together, 

 as safranine and methyl green. The following double stains 

 should be used separately and in the order named : carmine and 

 logwood, logwood and eosin, picro-carmine and aniline green 

 or blue, carmine and indigo-carmine. Picro-carmine, rosein and 

 indigo-green, used in this order, will produce a triple staining in 

 suitable objects. 



