well. Few cytologists use the same formulae, each usually wanting 

 his favorite formula, hence it is best to keep on hand certain stock 

 solutions, among which are small amounts of osmic acid and platinic 

 chloride. Below are listed certain fixatives containing one or both 

 of these reagents, also a list of stock solutions. The makeup of the 

 fixatives from the stock solutions is given in parts by volume, and the 

 amount desired by an investigator can be made up to the nearest mul- 

 tiple of the total parts indicated. 



Acetic acid, glacial 



Chromic acid, 1% 



Chromic acid, 1% in 



1% NaCl 



Formic acid 



Mercuric chloride, sat 



soln. in hot water 



STOCK SOLUTIONS 



Mercuric chloride, 0.5% 

 in 1% chromic acid 

 Osmic acid, 2% 

 Picric acid, sat. aq.soln. 

 Platinic chloride, 10% 

 Potassium dichromate, 10% 



FIXATIVES: 



Some of the fixatives listed here keep well and may be kept for 

 a long time. Those which deteriorate are noted. All of these form- 

 ulae are from Lee's Vade Mecum, unless otherwise stated. In making 

 osmic acid wash off the paper covering of the glass ampoule; rinse 

 in distilled water, and file a notch around the tube. Drop the am- 

 poule into a clean, glass stoppered bottle of a capacity greater 

 than the amount of osmic desired. The tube of osmic crystals may 

 now be broken open with a heavy glass rod. As many tubes as wanted 

 may be crushed inside the glass bottle but not over 200-300 c.c. of 

 2% should be kept in solution. 



All osmic acid and fixatives containing it should be kept in 

 dark bottles with well fitted glass stoppers. Osmic acid reduces 

 slowly in the light and at high temperatures; when it is issued it 

 should be in a brown bottle or the bottle should be covered with black 

 paper . 



When issuing fixatives the label should indicate definitely the 

 formula used, since there are 4 Flemming's and 3 Von Rath's solutions. 



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