262 PRACTICAL MICROSCOPY. 



mended from extract of logwood, the latter being a very 

 variable article. 



For double staining, which is more generally useful than 

 the method just described, many formulae have been given, 

 the process having originated with Mr. G. D. Beatty, of 

 Baltimore, U. S. A. 



Perhaps the best paper in this country upon the subject 

 is that which appeared in the pages of ' Science-Gossip/ 

 for January 1880; but even the process therein described 

 is in several points open to modification and improve- 

 ment. 



Mr. A. J. Doherty, in a paper to ' The Northern Micro- 

 scopist/* describes at some length the method of staining in 

 carmine and green. The art consists of five stages or pro- 

 cesses i, decolorising the sections ; 2, washing the same ; 

 3, preparing for staining ; 4, staining in carmine ; 5, staining 

 in green. 



After bleaching and thoroughly washing to eliminate all 

 the chemicals, as already described, in order to obtain deep 

 colours, the sections must be steeped in a mordant com- 

 posed of a 10 per cent, solution of alum and water for 

 twenty-four hours, at the end of which time they will be 

 ready to be placed in the first staining fluid, the formula 

 for which is as follows : 



Carmine 15 grains. 



Ammonia 15 grains. 



Water 2 oz. 



The carmine is to be dissolved in the ammonia over the 

 flame of a spirit-lamp, the water added next, and the fluid 

 filtered before it is used. 



Immerse the sections in this stain for six or eight hours, 

 then take them out, and wash them in not more than two 



* June 1881. 



