642 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
This is laid, with the specimen projecting into the central cell D, in a 
shallow longitudinal groove A cut just deep enough to enable the 
specimen to revolve without touching the cover-glass, a hole having 
also been cut for the reception of the rubber plug. The projection of 
this plug above the surface allows the whole arrangement to revolve by 
the mere movement of the finger. When the cover-glass has been 
placed in position the whole can be finished off with paper in the usual 
way. A neater appearance is obtained by mounting two specimens in each 
slip, one on either side of the cell.” 
Cleaning Cover-glasses.* — Herr E. Funck says that cover-glasses 
are most advantageously cleaned by uniting chemical and mechanical 
action. The dirty cover-glasses are soaked for some time in turpentine 
oil and then removed to a vessel containing some 30 com. of hydrochloric 
acid to which two or three pinches of potassium chlorate have been 
added. They are then heated in a water-bath until all colour has 
disappeared. The glasses are then washed with hot water and next 
placed in a mixture of equal parts of powdered soda, talc, and fine 
sawdust made into a thick soft paste with water. The mixture and the 
glasses are then heated for half an hour in a water-bath. After this 
the cover-glasses are again washed with hot water, to which a few 
centimetres of weak hydrochloric or acetic acid have been added. Lastly 
the glasses are washed with hot water or ether alcohol and dried with 
a soft cloth. They are now perfectly clean, and there is no necessity 
for heating them on the iron plate. 
Uses of Formaldehyd.j — Herr F. Cohn's experiments with formal- 
dehyd are confirmatory of previous observations showing that in weak 
aqueous solution and in vapour it kills bacteria, both in the vegetative 
and spore conditions. Hence it is extremely useful for sterilizing, dis- 
infecting, &c., and is suitable for the preservation of preparations. 
Against mould fungi its action is not invariable, and requires occasionally 
to be used in somewhat large quantity. 
Changes caused in Nervous Tissue by Hardening Reagents.f — 
Prof. H. H. Donaldson has made a number of experiments and observa- 
tions with the object of determining what changes are induced by the 
hardening reagents generally employed. He finds that a sheep’s brain 
under the influence of solutions of bichromate of potash increases in 
weight and volume ; this is due to the taking up of the solution, and it 
is made greater by freshness, absence of pressure, and low percentage 
of salts in the solution ; it is made less by a temperature of 38°. The 
general action of alcohol is to decrease the weight and volume of the 
sheep’s brain, and the higher the percentage of alcohol the more rapid 
and great is the loss in weight ; this loss is due to the decrease in the 
volume of the specimen by shrinkage, extraction of solids, and replace- 
ment of water by the alcohol of a less specific gravity. 
Alcohol of 50 per cent., a saturated solution of sodium chloride, or 
a mixture of bichromate of potash and alcohol disturb the normal weight 
but slightly. 
* Centralbl. f. Bakteriol. u. Parasitenk., xvi. (1894) pp. 113-4. 
f Jahresbericht d. Schles. Gesellscli. f. Vaterl. Gultur, ii. Abth. Bot. Section, 
(1893) pp. 23-31. X Journal of Morphology, ix. (1894) pp. 123-66. 
