The Microscope. 53 



SELECTIONS. 



A FEW HINTS ON HARDENING JMBEDDING, CUTTING, 

 STAINING AND MOUNTING SPECIMENS. 



BY GEO. DUFFIELD, M. D., DETROIT, MICH. 



The rule I follow in the hardening of specimens is briefly 

 this : I cut the original specimen into pieces, not exceeding three- 

 quarters of a cubic inch, and put them in alcohol to remain 

 there from six to eight days ; they are then placed in 95 per 

 cent, alcohol for a day or two, until they have become firm, 

 which is easily seen by pressing them with the fingers. 



As soon as the specimen has become firm, a cork cut square 

 or rectangular, with smooth surface, is prepared. The specimen 

 is noted and numbered in a book, kept for that purpose, and 

 the same number is put upon the side of the cork, opposite 

 which the specimen is to be placed. The specimen is secured 

 to the cork in this wise : A thick solution of powdered gum 

 acacia is made ; a thin film is put on the cork. The specimen 

 having been previously washed in water and dried, is placed 

 upon the gummed cork and gently pressed down so as to expel 

 all air-bubbles that might be between the specimen and the 

 cork. Let the specimen stand a few moments in the air, then 

 put a teasing needle into the cork, and submerge the cork and 

 specimen, keeping the specimen " butter side up," in alcohol. 

 Allow it to remain this way for four or five minutes until the 

 gum becomes set, then remove the specimen from the alcohol, 

 and with a knife remove the gum from the sides of the speci- 

 men. Then drop it, " butter side down," into a wide-mouthed 

 jar, containing 60 per cent, solution of alcohol, and let it remain 

 for six to twelve hours, after which it will be ready for cutting. 



There is a new method of imbedding, far superior to albu- 

 men or paraffin methods, which I can recommend from per- 

 sonal experience. It is called the celloidin method. The 

 celloidin is manufactured by Shering of Berlin, and is for sale 

 by Messrs. Bachrach Bros., of Baltimore, Md. Celloidin is a 

 pure pyroxline, free from all organic constituents, and makes a 

 clear solution, free from all sediment, when dissolved in equal 

 parts of 95 per cent, alcohol and sulphuric ether. By this 



