12 MATERIALS AND PROCESSES OF SLIDE-MAKING 



Solution B 



80% Alcohol 100 ml. 



Phenol 4 Gm. 



Ethyl ether 6 ml. 



Note: One part of A is mixed with three parts of B immediately before use. 



This is very nearly as good a general-purpose fixative as the mixture of Gilson 

 and has the advantage over Gilson's that objects fixed in it can be handled 

 with steel instruments before being washed. It is not desirable to leave spec- 

 imens in it too long (certainly not more than two or three days) and the fix- 

 ative should be washed out in 70 per cent alcohol. 



Removal of Fixatives. Under each of the formulae given above, it has 

 been indicated in what fluid the specimen should be washed to remove the 

 fixative. This simple washing, however, is not always sufficient in the case of 

 fixatives containing mercuric chloride or picric acid. Mercuric chloride occa- 

 sionally gives rise to long needlelike crystals in tissues. These may be prevented 

 by soaking the specimen, after it has been washed in running water over- 

 night, in: 



Lugol's Iodine: 



Mix 1 Gm. of potassium iodide with 0.5 Gm. of iodine. Add 2 or 3 ml. of 

 water and shake until dissolved. Then dilute to 50 ml. If diluted to 150 

 ml., this becomes "Gram's iodine." 



Note: Iodine is very soluble in strong solutions of potassium iodide and very 

 insoluble in weak solutions. 



After the pieces have been soaked in this solution overnight, they should be 

 transferred to either 70 per cent or 90 per cent alcohol in which they should 

 remain until no further color comes away. Specimens so treated never show 

 the fine needlelike crystals after mercuric fixation, but there is no reasonable 

 explanation of why this should be so. 



Tissues fixed in picric acid naturally are a bright yellow. All this bright 

 yellow color cannot be removed since some of it is due to the formation of 

 complexes with the proteins. However, there are two methods by which much 

 more of the yellow color can be removed than by washing in alcohol alone. 

 The first is to add a few grains of lithium carbonate to the 70 per cent alcohol 

 in which the specimen is being washed. The lithium salt appears to free some 

 of the bound picric acid. Another method, which is more troublesome but 

 much more satisfactory, is to transfer the specimen to: 



Lenoir's Fluid: 

 Water 70 ml. 



95% Alcohol 30 ml. 



Ammonium acetate 10 Gm. 



