440 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
of potassium in a 4 per 1000 solution. Immersion in chloride of 
palladium may be continued for two or three days or even weeks without 
danger, and even with advantage, if the solution be renewed ; but im- 
mersion in iodide of potassium must not be for more than one or two 
hours. Those who have used these reagents speak highly of them. 
Useful Modification of Gram’s Method.* — Dr. Eng. Bothin says 
that many of the well-known inconveniences incidental to Gram’s method 
may be obviated, and the staining of the bacteria much improved by 
washing the preparation, section or cover-glass, in anilin-oil-water after 
it is removed from the gentian-violet solution, and before it is immersed 
in the iodine solution. 
Genevan Reagent. j — Under this name (react if genevois ) Prof. R. 
Chodat recommends a double staiuing reagent which he finds useful in 
the differentiation of vegetable tissues. It consists of a slightly alcoholic 
and ammoniacal solution of congo-red (2 per cent.) and chrysoidin (2 per 
mille). The section is first decolorized by eau de Javelle, and then 
immersed in this reagent for a few seconds, when a beautiful double or 
triple staining is obtained. The cellulose membranes are coloured rose, 
while the lignified or cutinized cells take a yellow tint varying 
according to the degree of hardening of the membranes. 
( 5) Mounting-, including Slides, Preservative Fluids, &c- 
Fixation and Preservation of Compressed Objects. $ — Mr. N. A. 
Cobb suggests the following method for fixing, staining, and mounting 
compressed objects. The object— e. g. a dipterous larva or a Nema- 
tode — is compressed between two small cover-glasses of the same size ; 
the amount of compression must be regulated by means of two hairs, or, 
better, two pieces of spun glass. The animal should be laid on one 
of the covers in a drop of water too small to entirely fill the space 
between the covers. When the other cover is laid on and the object 
is correctly compressed and arranged, the covers must be fixed in place. 
This is done by moving the two covers to the edge of the slide by 
means of a needle, and touching first one side of the pair, then the 
other side, with the wrick of a wax taper or candle which has just been 
extinguished. The melted wax serves to cement the covers together, 
and they may be afterwards handled without much risk. 
The covers, thus united, must be allowed to lie until all or nearly 
all the water between them has evaporated. To further treat the animal, 
take an elongated piece of quill or other similar elastic non-metallic 
substance, and make in it two cuts in such a w r ay as to convert the quill 
into a compressing machine ; into the compressorium so made insert the 
covers. To fix the object, take hold of the quill and place one edge of 
the covers in the fixing fluid, which will run in by capillary attraction. 
The author recommends that the whole apparatus be made so small as 
to be readily introduced into the object-box of his differentiator. 
* Centralbl. f. Bakteriol. u. Parasitenk., xi. (1892) pp. 231-2. 
f Arch. Sci. Phys. et Nat., xxvi. (1891) p. 500. 
J Proc. Linn. Soc. N.S.W., vi. (1891) pp. 143-6 (3 figs.). 
