jj6 Methods of Microscopical Research [October, 



changes it to deep purple. Still more important is the fact that 

 salts soluble in alcohol give a blue-gray, green-gray or blue-black 

 precipitate. For' example, if a piece of cloth that has been dyed 

 in cochineal and washed, be treated with an alcoholic solution of 

 a ferric or a calcic salt, it will assume a more or less deep blue 



As the salts present in the living organism are seldom, if ever, 

 fully removed by preservative fluids, but in some cases even in- 

 creased, it will often happen that an object, though stained in the 

 red fluid, comes out blue, precisely as when stained with hema- 

 toxylin. Such a result cannot, however, be obtained in the pres- 

 ence of acids, nor in the absence of inorganic salts ; under these 

 conditions the color is always red. It is not possible, therefore, 

 to know what color an object will ultimately present. 



Very often the different tissues of one and the same object 

 present unlike colors. In the embryos of Lumbricus, Kleinen- 

 berg found the walls of the blood vessels red, their contents dark 

 blue. Glandular tissues, or their contents, arc frequently stained 

 gray-green. 



Objects treated with chromic or picric solutions, or with alco- 

 hol, usually stain without difficulty; but osmic acid preparations 

 should be bleached before staining. Cochineal does not color so 

 intensely as hematoxylin, and hence the latter often gives more 

 satisfactory results in the case of large objects stained in toto. 



As before pointed out, alcohol causes the salts contained in sea 

 water to be precipitated, thus forming a crust on the exterior of 

 the animal which interferes with the staining process. It is there- 

 fore necessary to treat marine animals that have been preserved 

 in strong alcohol, with acid alcohol (i-io parts hydrochloric acid 

 to iooo parts 70 per cent, alcohol), and then carefully wash in 

 pure 70 per cent, alcohol before staining with cochineal. 



?. Picro-carmine.—K very excellent picro-carmine is prepared 

 by Dr. Mayer in the following manner: 



To a mixture of powdered carmine (2 g.) with water (25 cenr), 

 while heating over a water bath, add sufficient ammonia to dis- 

 solve the carmine. The solution may then be left open for a few 

 weeks (Mayer) in order that the ammonia may evaporate ; or the 

 evaporation may be accelerated by heating (Hoyer). So long as 

 any ammonia remains, large bubbles will form while boiling, but 

 as soon as the free ammonia has been expelled, the bubbles will 



