ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 463 



Soluble Prussian Blue.* — M. C. E. Guignet gives the two following 

 methods for making soluble prussian blue for injection purposes. 



(1) Ordinary soluble prussian blue. To a boiling solution of 110 

 grams of ferridcyanide of potash, are gradually added 70 grams of 

 crystallized iron sulphate. After boiling two hours it is filtered, and the 

 filtrate washed with fresh water until the washings are strongly blue. 

 The blue is then dried at 100° C. 



Thus made the blue is of an extremely rich colour, and will take up 

 a large quantity of gelatin without precipitating it. 



(2) Pure prussian blue soluble in water. A saturated solution of 

 oxalic acid is mixed to a pasty consistence with an excess of pure 

 prussian blue. The liquid is filtered and allowed to stand for two 

 months until all the blue is precipitated. It is then filtered and washed 

 with weak spirit in order to remove any oxalic acid. When dried the 

 blue dissolves easily in water. 



A similar result may be at once obtained by precipitating the oxalic 

 solution with 95 per cent, alcohol, or with a concentrated solution of 

 sodium sulphate, and then washing the precipitate with weak spirit. 



The author adds that molybdic acid will dissolve ordinary prussian 

 blue in large quantities. A mixture of the blue and the acid are heated 

 together, and after filtering, a deep blue liquid is obtained, which does 

 not alter in boiling, or precipitate on the addition of gelatin, and when 

 cold sets to a transparent mass of a dark blue colour. The molybdic 

 solution is precipitated by sulphuric, nitric acids, &c. The molybdate 

 and tungstate of ammonia also dissolve prussian blue. 



Vital Reaction of Methyl-blue.t — Dr. Max Joseph has tested 

 Ehrlich's method on Heteropods, and found that the clear intra vitam 

 stain could not be satisfactorily fixed. He remarks that the commercial 

 methyl-blue is unfit for use, and that only the chemically pure article 

 will give the results obtained by Ehrlich. Instead of a saturated solu- 

 tion, the author recommends the strength originally employed by Ehrlich, 

 1/4 gram dye in 100 grams of physiological salt solution. 



The best stain was reached about six hours after injection in the 

 body-cavity. 



Process of Staining Sections simplified by mixing the staining 

 fluids with turpentine.! — According to Dr. Kiikenthal's experiments, 

 a large number of colouring substances admit of being mixed with 

 turpentine, and serial sections may be stained in a short time by such 

 a combination. Methyl-green, methyl-blue, gentian-violet, safranin, 

 Bismarck-brown, eosin, fuchsin, tropaeolin, and malachite-green may be 

 used in this way. 



The dry colouring substance is dissolved in absolute alcohol, and the 

 solution dropped into turpentine until the mixture has any intensity of 

 colour desired. 



Meyer's § carmine solution. — Absolute alcohol, 100 ccm. ; pulverized 

 carmine, 3 gr. ; hydrochloric acid (neutralized with ammonia), 25 drops. 



* Journ. cle Micrographie, xiii. (1889) pp. 94-.^. 



t Anat. Anzeig., 1888, p. 420. J Amer. Naturalist, 1888, p. 1140. 



§ Tlie carmine is boiled in the alcohol and then the acid added. The solution is 

 then filtered, hot, and enough ammonia added to neutralize. After filtering agaio^ 

 the solution is mixed with turpentine and absolute alcohol. 



