ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
799 
therefore, be fixed at any particular stage, and the previously liquefied 
gelatin sets again, but without losing the appearance due to liquefaction. 
The bacteria look and stain just as well as they ever did, even when they 
have been exposed to the action of formalin vapour for some weeks. 
Test-tube puncture cultivations of liquefied species are also fixed by 
means of formalin. Thus puncture cultivations of cholera and Finkler- 
Prior spirilla can be preserved to show their characteristic funnel- 
shaped liquefaction. 
When Petri’s plates are used the method is carried out by inserting 
under the lid a layer of filter paper, upon which 10-15 drops of formalin 
are deposited ; the capsules are placed in a moist chamber also con- 
taining a dishlet with some damp cotton-wool. Test-tube puncture 
cultivations are treated by moistening the lower end of the cotton-wool 
plug with about 10 drops of formalin, and then placing the glass in a 
vertical position in a tall glass vessel, on the floor of which is placed 
some cotton-wool moistened with formalin (50-60 drops to 1000 com.). 
The glass is then closed. To obtain a good result it is necessary to 
use fresh undecomposed formalin. 
Sander — TJeber das Wachsthum von Tuberkelbacillen auf pflanzlicben Nahrboden. 
(On the Growth of Tubercle Bacilli on Vegetable Media.) 
Arch. f. Hygiene , XVI. p. 238. 
Schmidt, A. — Ueber die Benutzung verschiedener Sputa als Nahrboden und das 
Wachstum der Pneumokokken auf denselben. (On the use of various Sputa as 
Culture-media and the Growth of Pneumococci on them.) 
Centralbl. f. Klin. Med., 1893, pp. 625-8. 
(2) Preparing- Objects. 
Fixing Fluid for Animal Tissues.* — Dr. G. Mann recommends the 
following fluid for fixing animal tissues : — Absolute alcohol 100 ccm., 
picric acid 4 grm., corrosive sublimate 15 grm., tannic acid 6-8 grm. 
It is essential to use only living tissue, and the pieces should not exceed 
0*5-1 cm. in thickness and the amount of fluid used should be 20 
times the bulk of the specimen. The tissue must be immersed for 12-24 
hours, after which it is washed (a) twice in absolute alcohol for five 
hours each time, or (6) for two hours in running water, and then placed 
for 12 hours in 30 per cent, spirit containing enough tincture of iodine 
to give it a brown colour. Then for 12 hours more in 50 per cent, 
spirit containing potassium iodide. Transfer to 50 per cent, spirit for 
three hours, and next place for five hours in each of the following, 70, 
80, 85, 90 per cent, spirit. (If process a be employed it is necessary to 
immerse the sections before staining for five minutes in iodine-iodide 
solution.) Then transfer to absolute alcohol for six hours (twice). 
After this they may be saturated with chloroform and finally imbedded 
in paraffin. 
The advantages claimed for this method are that it causes less 
shrinkage than other methods; the cell outlines are well marked and 
the cell plasma and nuclei are very distinct. 
Preservation of Colours in Dragon-Flies.t — Prof. P. Stefanelli 
recommends a simple method of making dry preparations of Odonata. 
* Anat. Anzeig., viii. (1893) pp. 441-3. 
t Bull. Sue. Entomol. Ital., xxv. (1893) pp. 1-11, 
