g2 THE MICROSCOPICAL NEWS. 
PREPARING BaciLLus Tusercutosis.—Prof. J. Brun proposes 
the following “ameliorations” to Koch and Ehrlich’s processes :— 
1st. Not to coagulate the albumen by heat, avoiding desiccation 
at more than 80° C. At 100° or 120° C. the bacteria are contracted. 
2nd. To render the organic matter transparent by acetic acid :— 
Concentrated nitric acid 5 parts, glacial acetic acid 10 parts, water 
55 parts. 
3rd. To neutralize the nitric acid which, remaining to a greater 
or less extent in the organic layer, at length decolorizes the bacteria 
and renders them invisible. For this purpose is to be used a con- 
centrated aqueous solution of aniline which neutralizes all the acid 
not removed by repeated washings. 
4th. To avoid Canada balsam, the index of which (1.53) is too 
high, and to take a neutral liquid having the same index as the 
albuminoid substances (1.37) :—Very white gelatine 14 parts, 
salicylic acid ‘25, distilled water 88. This has an index of 1.356 
for the yellow rays. | Castor-oil can also be used, though its index 
is 1.46. 
It is better to leave the field uncoloured than to colour it an 
orange-brown with vesuvine or other colouring matter, because the 
blue of the bacteria is rendered fainter by the complementary orange 
tint—f Rk. M.S. 
Mountine Mepia.—Prof. H. Hoyer has found excellent mount- 
ing media not only in L. Bach’s solution of gum arabic in liquor 
ammoniz aceti, but also in acetate of potash, as well as a third 
modification with glycerine and chloral. The two former are more 
particularly suitable for preparations stained with aniline colours, 
especially bacteria. The latter is suitable for sections hardened in 
chromic acid, alcohol, &c., and objects coloured with carmine or 
hzematoxylin. 
The solutions are thus prepared :—A high 60 c.cm. glass with a 
wide neck is filled two-thirds full with selected white gum arabic 
(in pieces, not powder), and then acetate of potash or ammonia is 
added, or a solution of chloral-hydrate (of several per cent.) to which 
5-10 per cent. of glycerine has been added. The gum with frequent 
shaking dissolves in a few days and forms a syrupy fluid, which is 
slowly filtered for twenty-four hours. The clear filtered fluid will 
keep a long time, but if spores of fungi begin to develop a little 
chloral can be added and the fluid refiltered.— 7. R. AZ. S. 
