ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
235 
is added as not to visibly alter the colour. Usually one drop of the 
acid to a Petri’s capsuleful of solution is sufficient. After some minutes 
tlie sections may be washed in tap water. When the preparations have 
been fixed by Benda’s method, caustic soda is used instead of oxalic acid. 
(3) Though thionin is a very instructive staining reagent, it is 
capricious, and does not last well as a rule. This untoward event is due, 
the authoress thinks, to the mounting medium. Colophonium or Canada 
balsam, applied by heating a little piece in the flame and using it while 
hot, is advised ; as by this device preparations will keep for at least a 
year without obvious alteration. Toluidin is also said to be a suitable 
medium for mounting sections stained with thionin. 
Modification of Van Ermengem’s Method for Staining Flagella.- 
— Dr. H. M. Gordon has stained the flagella of Micrococcus melitensis 
and Bacillus pestis by Pitfield’s and Van Ermengem’s methods, but the 
latter, with the following modifications, gives the best results. The re- 
ducing agent, i.e. the tannin and gallic acid solution, must be several 
weeks old. The specimens should be left double the prescribed time in 
the mordant, for from 1J-3 minutes in the first silver solution, from 
2-3 minutes in the reducing agent, and in the last silver solution until 
the film begins to darken. Sometimes good preparations are obtained 
by washing in distilled water between the baths, and sometimes it is 
advisable to reverse the order of the baths. 
Modification of Pitfield’s Method for Staining Flagella. f — Mr. B. 
Muir gives the following modification of Pitfield’s method for staining 
flagella. 
(A) The mordant. Filtered 10 per cent, aqueous solution of tannic 
acid, 10 ccm. ; saturated aqueous solution of sublimate 5 ccm. ; satu- 
rated aqueous solution of alum, 5 ccm. ; Ziehl-Nielsen phenol-fucbsin, 
5 ccm. The mixture is to be centrifuged or allowed to stand all night. 
The clear fluid is then pipetted off. It will keep for one or two weeks. 
(B) The stain. Saturated aqueous solution of alum, 10 ccm. ; satu- 
rated al cholic solution of gentian-violet, 2 ccm. The solution will keep 
for two or three days. 
To stain the film, flood the surface with the mordant, heat until 
vapour arises, and allow to steam for about one minute. Wash in run- 
ning water for about two minutes, and then dry over the flame. Flood 
the surface with the stain, heat, and wash as before. 
If black stained preparations be preferred, treat with Gram’s iodine 
solution for one minute, dry over the flame, and mount in balsam. 
The advantages claimed for this method over Van Ermengem’s are 
that it is more simple to work ; that it forms very little precipitate on 
the film ; and that the organisms and their flagella appear to retain their 
natural proportions. 
Sudan iii. in Botanical Microtechnique. — Dr. L. Buscalioni has 
investigated the staining reactions of Sudan iii. on vegetable tissue. 
Sudan iii., or Biebrich scarlet, is a brick-red powder, insoluble in water 
and alkalies, soluble in alcohol, chloroform, ether, fatty and ethereal 
* Lancet, 1899, i. pp. 688-9 (1 pi.). 
t Journ. Pathol, and Bacter;ol., v. (1898) pp. 374-6. Cf. this Journal, 1893. p. 133. 
j Malpighia, xii. (1899) pp. 421-40 ; Bot. Centralbl., lxxvi. (1898) pp. 398-9. 
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