FLEMMING'S SOLUTION 23 



may then be cut directly after freezing. The staining properties 

 of tissues hardened in this fluid are well preserved. The speci- 

 mens may be kept in it indefinitely. 



PICRIC ALCOHOL (GAGE) 



Picric acid 2 grams. 



Alcohol 500 c.c. 



Water 500 c.c. 



This is an excellent fixing agent for most tissues. Hardening 

 is completed in one to three days. 



OSMIC ACID is sold in hermetically sealed capsules. It is used 

 in one per cent, solution in distilled water, The solution should be 

 freshly made when possible. It deteriorates in the light, and must 

 be kept in a dark closet. Its vapor is very irritating. The use- 

 fulness of osmic acid depends largely upon its property of staining 

 fat black. It is often employed in pathology. In histology it is 

 most valuable for nervous tissues. It stains the medullary sheaths 

 of medullated nerve-fibers black. The pieces of tissue must be not 

 more than four millimeters thick, as osmic acid has very feeble 

 penetrating power. They are left in the solution twenty -four 

 hours, washed thoroughly, and transferred to eighty per cent, 

 alcohol. In preparing specimens for microscopical study, it is best 

 to avoid using turpentine or xylol, which dissolve the stained fat, 

 if that is to be preserved. 



FLEMMING'S SOLUTION 



Two per cent, osmic acid solution 4 parts. 



One per cent, chromic acid solution 15 parts. 



Glacial acetic acid 1 part. 



The pieces of tissue should be four millimeters or less in thick- 

 ness. They are left in the fluid twenty-four hours, and, after 

 thorough washing, are transferred to alcohol. This fluid is 

 designed to preserve the karyokinetic figures, using safranin or 

 hasmatoxylin to stain them. It is also admirable to fix cellular 

 structures in general, and it stains fat black as well as osmic acid 

 alone. 



Another formula proposed by Flemming for fixing the karyo- 

 kinetic figures consists of 



Chromic acid 2 grams. 



Glacial acetic acid 1 c.c. 



Water . 100.0 c.c. 



