ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
833 
(6) Miscellaneous. 
Microchemical Reactions of Tannin.* — Mr. S. Le JVL Moore dis- 
tinguishes three kinds of tannin in plants, known by their different 
reactions with Nessler’s fluid, viz. : — (1) tannin giving an immediate 
brown precipitate, occasionally with brown-pink tendency ; (2) tannin 
giving a yellow colour, quickly becoming red-brown, and, finally, a cold- 
brown precipitate ; (3) tannin giving a yellow colour, the yellow 
substance readily diffusing through the cell-walls into the surrounding 
fluid, thus leaving the cells colourless after a varying lapse of time. In 
addition to the functions hitherto ascribed to tannin, the author believes 
that it may have a more general relation to the turgescence of the cell ; 
and that tannin is also most likely used up in the lignification of the 
cell-wall. 
Cleansing Used Slides and Cover-glasses. | — Dr. F. Knauer says 
that the slides and cover-glasses of old preparations may be made as 
good as new by the following method, which he has adopted for some 
time past. 60-80 (say) slides are placed in a vessel holding about half 
a litre of 10 per cent, lysol solution and boiled for twenty to thirty 
minutes. The still seething vessel is then placed straight away under a 
strong current of running water until it streams back quite clear, after 
which the glasses are taken out and dried on a clean cloth. If the 
preparations be of comparatively recent date a 5 per cent, solution is 
quite sufficient. 
Dr. J. B. Nias J says : — “ Bacteriologists and others who find them- 
selves with accumulations of Microscope slides may be glad of the 
following hint for cleaning them. It is not given in any text-book that 
I can discover. Instead of warming the slides one by one over a flame, 
pushing off the cover, and then scraping away the balsam and cleaning 
with alcohol, I put all my slides together into a saucepan with a lump 
of washing soda, and boil them. The heat of boiling is enough to soften 
most cements and all ordinary resins used for mounting, and I then fish 
out the slides one by one, push off the cover-glasses, and put them back. 
The action of the soda is to convert the balsam or other resin into a 
grumous mass, which is easily wiped off with a little rinsing. Cover- 
glasses can also be recovered for future use in the same way, if desired. 
I think this method may be of service to laboratory attendants. Neither 
do I find anything on the surface of new covers and slides which will 
resist the action of hot water and soda ; and so I prefer this way to 
the use of strong sulphuric acid and alcohol, or the other methods given 
in the text-books. The exact quantity of soda to be used is immaterial ; 
a piece about the size of a mandarin orange to half a pint of water 
will do.” 
Method for the Estimation of the actual number of Tubercle 
Bacilli in Phthisical Sputum. § — Dr. G. H. F. Nuttall describes with 
great lucidity a method which he has devised for estimating the actual 
number of tubercle bacilli in sputum. Naturally enough the procedure 
* Journ. Linn. Soc., xxvii. (1891) pp. 527-38. 
f Centralbl. f. Bakteriol. u. Parasitenk , x. (1891) pp. 8-9. 
X Lancet, 1891, p. 1414. 
Johns Hopkins Hospital Bulletin, No. 13, 1891 (5 figs.). 
