INTRODUCTION. 9 



Alum Cochineal is made by soaking 7 parts of crushed 

 cochineal insects and 7 parts of alum in 700 of water for 

 twenty-four hours. Then boil until the amount is reduced 

 to 400 parts. Allow to stand twenty-four hours, filter, 

 and add a little thymol to keep it from spoiling. This 

 stain has the advantage of not overstaining specimens. 

 Objects may be left in it from twelve to twenty-four hours. 



Grenadier's Borax Carmine. Two grams of carmine 

 are dissolved in a solution of 4 grams of borax in 100 cc 

 of water. Then 100 cc of 70% alcohol are added, the 

 whole allowed to stand twenty-four hours, then filtered. 

 A convenient method of use is to add about 1 part of 

 the stain to 25 of acid alcohol (100 cc of 70% alcohol 

 plus 5 drops of hydrochloric acid). After staining, place 

 the specimen for a few minutes in 70% alcohol to which 

 a little ammonia has been added. 



Picrosulphuric Acid is used for killing many animals 

 without distortion. It is made by dissolving picric acid in 

 water until no more will be taken up, and then adding to 

 100 parts of the solution 2 parts of sulphuric acid. It 

 is allowed to stand a day, is filtered, and is prepared for 

 use by adding 3 parts of water to 1 of the stock solution. 

 Specimens killed in this fluid are stained yellow, and 

 should be washed in several changes of water before 

 being placed in alcohol or formol. It takes from one to 

 three hours to kill. 



Further directions for the preservation of material and 

 for microscopic study and preparation may be found in 

 the various histologies (Stohr, Bohm and Davidoff, etc.) 

 and in Lee's " Microtomist's Vade Mecum" (Philadel- 

 phia). Recent methods and improvements are described 

 in the Journal of Applied Microscopy (Rochester) and the 

 Journal of the Royal Microscopical Society (London). 



