ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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solution is dropped on the cover-slip, and the latter heated over a flame 
until it begins to vaporise. This should be done twice. 
The preparation having been allowed to cool for 1-2 minutes, is 
decolorised in 4-5 per cent, sulphuric acid, and contrast-stained for 
1-2 minutes in malachite-green or methylen-blue. 
Instead of Ziehl’s solution, anilin-oil fuchsin or gentian-violet may 
be used. In this latter case, Bismarck-brown or vesuvin should be 
used as contrast stain. 
Dahlia as a Stain for Bacteria in Celloidin Sections.* * * § — Mr. R. 
C. Reed recommends dahlia for staining bacteria in sections prepared 
by the celloidin method. The formula used is, saturated alcoholic solu- 
tion of dahlia 20 ccm., distilled water 100 ccm. The sections are over- 
stained (15-30 minutes), and then thoroughly washed with 95 per cent, 
alcohol, until the celloidin around the section appears colourless. They 
are then cleared up, for which purpose clove oil is preferred. 
This method is not, of course, suitable for bacteria which require 
special stains or treatment. 
Importance of Testing the Reaction of Sputum in Staining for 
Tubercle Bacilli. f — Dr. N. G. Ward points out the importance of test- 
ing the reaction of sputum, and if it be found acid, to render it alkaline 
before staining it. Any alkali may be used. The reason given by 
D. B. Kyle, who was the first to call attention to this fact, is that the 
capsule of the bacillus is permeable by an alkali, but not by an acid. 
In staining the sediment of urine, pus, or any secretion or fluid for 
tubercle bacilli, it is equally necessary to make sure it is alkaline before 
staining. 
(5) Mounting:, including 1 Slides, Preservative Fluids, &c. 
Gelatin as a Fixative. — Mr. H. H. Dixon has recently used as a 
fixative a dilute solution of gelatin in an aqueous solution of bichromate 
of potash. The solution should be quite fluid at 10° C. The ribbon 
of paraffin sections is laid on a drop of this solution on the slide. 
Wrinkles are removed by gently warming the slide. The superfluous 
fluid is then removed by means of blotting paper, and the gelatin 
allowed to dry and harden. During this process it should be exposed 
to a bright light, the action of the light rendering the fixative quite 
insoluble even in warm water, and so removing all danger of detach- 
ment from the slide. 
The bichromate has the further advantage of preventing the gelatin, 
after exposure to the light, from taking up the dyes used as stains. 
C6) Miscellaneous. 
Paste for Labels.^ — A paste for sticking labels on glass, porcelain, 
and metal, may be made of gummi arab. 15 • 0 parts, tragacanth pulv. 7 • 5, 
glycerini 45*0, thymoli 0*3, alcohol 3*75, water up to 120*0. The 
gum arabic is dissolved in 15 parts water, and the tragacanth rubbed up 
* Trans. Amer. Micr. Soc., xix. (1897) pp. 182-5. 
f Microscopical Bulletin, xv. (1898) pp. 1-2. 
j Ann. of Bot., xii. (1898) pp. 117-8. 
§ Photog. Zeitung. See Zeitschr. f. angew. Mikr., iii. (1898) p. 364. 
