134 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
(5) Mounting-, including Slides, Preservative Fluids, &c. 
Fixatives.* — Dr. O. vom Rath recommends six fixatives. The first 
is picric-osmio-acetic acid: — 1000 ecm. saturated filtered solution of 
picric acid in distilled water, 1 grm. crystallised osmic acid, and 4 ccm. 
acetic acid. The second is picric-osmio-platinum chloride-acetic acid : — 
200 ccm. concentrated aqueous solution of picric acid, 25 ccm. 2 per cent, 
aqueous osmic acid, 1 grm. platinum chloride dissolved in 10 ccm. water, 
and 2 ccm. glacial acetic acid. After this fixative the objects are to be 
treated with wood-vinegar, or 20 per cent, tannin solution, and with 
gradations of alcohol. Thirdly, vom Rath recommends picric-platinum 
chloride-acetic acid for cells with much fat, yolk, or similar contents : — 
200 ccm. saturated aqueous solution of picric acid, 1 grm. platinum chlo- 
ride in 10 ccm. distilled water, and 2 ccm. glacial acetic acid. TLe 
fourth mixture is picro-corrosive-acetic acid ; the fifth picro-corrosive 
osmic acid or picro-corrosive-osmio-acetic acid. For collecting, when 
picric acid is apt to get spilt on hands and clothes, the author recom- 
mends the following : — 200 ccm. absolute alcohol, 1 grm. corrosive sub- 
limate, 2 ccm. glacial acetic acid. 
Canada Balsam.! — According to Herr G. Marpmann, Canada balsam 
is frequently adulterated with other resinous substances, the mixture 
often being quite useless for microscopical purposes on account of its 
drying too slowly, becoming cloudy or crystalline. Pure Canada balsam 
is a bright yellow, clear, slightly opalescent substance, soluble in 
chloroform and xylol ; forming cloudy solutions with alcohol, acetone, 
and benzine, because a part remains undissolved. When dry it forms 
a perfectly transparent hard layer, and does not become cloudy or 
crystalline. 
The author then goes through, in considerable detail, numerous 
t sts for detecting impurities in and adulterations of Canada balsam. 
These tests are far too numerous to mention', but the method seems, 
though tedious, easy, and for those requiring a perfectly pure and trust- 
worthy mounting medium, useful. 
Mounting Marine Animals as Transparent Lantern Slides. J — • 
Dr. H. C. Sorby finds that the methods which give good results vary 
much in the case of different animals. Some must be arranged on the 
glass and* dried quickly soon after having been caught, whereas others, 
such as jelly-fishes, must be treated over and over again with moderately 
strong alcohol to dissolve out all the salts. In some cases various staining 
materials must be used to bring out the structure, and some should be 
decalcified. Usually the animals are killed by keeping them for a short 
time in diluted alcohol, and then arranged on the glass after as much of 
the alcohol as will drain out is lost. They are dried in a current of air. 
In some cases they must be thoroughly soaked with clear gum before 
becoming quite dry. Finally, when quite dry, they are mounted in 
Canada balsam, and the edges of the cover- glass very completely bound 
round. 
• 
* Anat. Anzeig., xi. (1895) pp. 280-8. 
f Zeittchr. f. Angewandte Mikr., i. (1895) pp. 8-11, 38-46. 
j Rep. Brit. Ass., 1895, p. 730. 
