120 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Staining Solutions made with Carmine, Cochineal, and Hsematin.* 
— Dr. P. Mayer, who has been at some pains to investigate the origin of 
cochineal and the composition of carmine, finds that carminic acid is not 
the sole staining principle, but that this acid must be considered in 
conjunction with alumina and also with calcium. 
The practical outcome of his investigations and experiments are 
formula} for staining solutions having a fixed composition and giving a 
definite result. Of these we may mention the following : — 
Carmalum. — Carminic acid, 1 grm. ; alum, 10 grm. ; distilled water, 
200 ccm. The solution is made with the aid of heat and the clear 
supernatant fluid or the filtrate used. The solution will keep if a few 
crystals of thymol be added, or if 1 per cent, salicylic acid or 5 per 
cent, salicylate of soda be used. 
Paracarmin. — Carminic acid, 1 grm-. ; chloride of aluminium, 1/2 grm. ; 
chloride of calcium, 4 grm. ; 70 per cent, alcohol, 100 ccm. The solu- 
tion is made cold or by the aid of heat, and after having stood is filtered. 
There is no necessity to differentiate the stain with acidulated 
alcohol, although this may be done. 
A staining solution made with cochineal, and having similar but less 
efficient properties to the foregoing : — Cochineal, 5 grm. ; chloride of 
calcium, 5 grm.; chloride of aluminium, 0*5 grm.; nitric acid (sp. gr. 
1 • 20), 8 drops ; 50 per cent, alcohol, 100 ccm. The cochineal is to be 
finely powdered and mixed with the salts in a mortar. The spirit and 
acid are then added, and the mixture heated to boiling. It is allowed 
to stand for some days and filtered. 
The author concludes by referring to lisemacalcium, a solution 
devised by him some time back. I He finds that it tends to throw 
down a deposit and decompose after a time, but this may be prevented 
by preparing the solution in two flasks, one containing the spirit, the 
acid, and the calcium chloride ; the other the hasmatin and the 
aluminium chloride. The two solutions are mixed when required for 
use. 
Demonstrating Cholera Vibrio.j: — Dr. L. Heim gives the following 
as a very practicable procedure for demonstrating the presence of the 
cholera vibrio. From the evacuation or from the intestinal contents 
a flakelet of mucus should be taken, and having been spread out on a 
cover-glass, stained with fuchsin and examined with an oil-immersion 
for vibrios. At the same time another little flake of mucus is to be 
placed on a cover-glass, and a drop of bouillon added thereto. The 
cover is then fitted over a hollow-ground slide, and the margins 
vaselined to make a hanging drop cultivation. Two other particles are 
to be distributed, one in a test-tube filled with bouillon, the other in a 
test-tube containing gelatin. From the latter plate cultivations, after 
some attenuations, may be obtained. Even if the usual indispensable 
apparatus be wanting, the suspected material may be inoculated on 
bouillon or a 2 per cent, pepton solution, and a plate culture made from 
the gelatin solution, the latter serving for further inoculations. This 
procedure is to be repeated during the next 24 hours, during which the 
* Mittheil. Zool. Station zu Neapel, x. (1892) pp. 480-501. 
t See this Journal, 1891, p. 831. 
1 Centialbl. f. Bakteriol. u. Parasitenk., xii. (1892) p. 353. 
