INVERTEBRATA, CRYPTOQAMIA, MICROSCOPY, ETC. 501 



metliod in elucidating the characters of various inflamed membranes, 

 and into the pathological questions connected therewith, which are 

 beyond our province. 



Preparation of Ranvier's Picrocarmine.*— The preparation of 

 this staining agent is, Mr. S. H. Gage says, somewhat diificult, owing 

 to the fact that the right proportions and the precise operations for 

 its manufacture have not been definitely determined. Ranvier's direc- 

 tions are, to add an ammouiacal solution of carmine to a saturated 

 solution of picric acid, until saturation. Four-fifths of this mixture 

 is then evaporated in an oven, allowed to cool, then well filtered and 

 the filtrate evaporated to dryness. When wanted for use the dry 

 powder is dissolved in water, in the proportion of one part by weight 

 of picrocarmine to 100 parts by weight of water. It is very difficult 

 to decide when the mixture of carmine and picric acid solutions 

 becomes saturated, and the simple watery solution soon becomes 

 mouldy. 



Some experiments were made in the anatomical laboratory of the 

 Cornell University, U.S., to determine definitely, if possible, the pro- 

 cess of making a solution that would keep for any length of time. 



1. It was found that equal parts by weight of picric acid and 

 carmine gave the best results. 



2. The picric acid should be dissolved in one hundred times its 

 weight of water, using heat if necessary. 



3. The carmine should be dissolved in fifty times its weight of 

 strong ammonia. 



4. Mix the two solutions. It seems to make no difference in tho 

 result which solution is poured into the other. 



5. Use porcelain evaporators and glass funnels. 



The best results were obtained wlicn the solutions wei'e made at 

 the ordinary temperature of the laboratory, 17° C, and tlien evapor- 

 ated three-fourths at a temperature of 40^-45° C. The solution 

 should bo allowed to cool, and filtered through two thicknesses of 

 filter paper. The filtered liquid is then evaporated to dryness at 

 40° C, or at the ordinary temperature. 



If the preparation has been successful the residue dissolved in one 

 hundred times its weight of water sliould give a clear solution, after 

 filtering. Make 50 c.c. of such a solution and filter it through two 

 thicknesses of filter paper and a fine cotton filter moistened well and 

 crowded into the neck of tlie funneh Filter the solution four or five 

 times through tho same filter, and a clear solution will probably bo 

 obtained. In case a clear solution cannot be obtained by repeated 

 filtering, the whole of the powder may bo dissolved in the proportion 

 given above and allowed to stand a few days in a tall narrow vessel. 

 If tho finely suspended particles settle, the top will bo clear and may 

 be decanted; but if the fluid reiuuins cloudy, a quantity of annnonia 

 equal to that originally used should be ailded to it, and the evapora- 

 tion of tluee-fourtlis should be repeated with the subsequent filtration 

 and evaporation to dryness. Usually, however, if the method given 



♦ ' Am. ai. Micr. J. mm.,* i. (1880) j). 22. 



