536 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
just at a level. After from 12 to 24 hours the two liquids will be of 
the same strength. The tissue can then be taken out and placed in the 
infiltrating bath at once. 
This method for hardening has been tried in the botanical laboratory 
at Cornell University on nearly all kinds of plant-tissue, and in every 
case it was found to be successful. For the most delicate tissues, \shere 
slow hardening is desired, 5 per cent, alcohol can be placed in the dehy- 
drating tube and thick chamois skin used for a diaphragm, and for some 
of the more delicate algas it has been found advisable to use as low as 
1 per cent, alcohol in the tube. The strength of the alcohol in the jar 
can be kept up by adding to it from time to time some calcium chloride. 
This will not injure the alcohol in the least. 
The jar should be tall enough to allow the cover to be kept on while 
the tubes are in position, and thus prevent evaporation of the alcohol. 
An apparatus of such a form, having thirteen dehydrating tubes, has been 
in constant use in the botanical department for a year without changing 
the alcohol, and is yet in good working order. 
Experiments have been made with one of smaller size, and it is found 
that all hardening agents, such as picric, chromic, acetic, or osmic acid, 
can be used in it with equal success. 
The advantages claimed for the apparatus are these : — Not more 
than 24 hours is necessary for dehydrating and hardening nearly all 
kinds of plant-tissue. The apparatus does away with the transferring 
of the tissue from bottles containing alcohol of different strengths, and 
as no sudden transition from solutions of different strengths occurs, the 
tissue is less liable to shrink. The simplicity of the apparatus places it 
in the reach of all. 
Many different materials may be used for a diaphragm, and almost 
any desired speed of dehydrating obtained. The apparatus can also be 
made of any size to adapt it for private or general laboratory work. 
It would seem that such an apparatus would work equally well for 
animal tissue, but as yet I have not been able to make an extended trial 
of it ; however, in the case of some insects hardened in it, it was found 
to be admirably adapted to the purpose.” 
Method for fixing Preparations treated by Sublimate or Silver 
(Golgi’s Method).* — Sig. A. Obregia gives a method for rendering pre- 
parations treated by Golgi’s sublimate or silver procedure so per- 
manent that they may be afterwards stained and protected with a cover- 
glass. 
The sublimate or silver preparations are sectioned without any im- 
bedding or after having been imbedded in paraffin or celloidin. In the 
latter case care must be taken not to use alcohol weaker than 94 or 95 per 
cent., at any rate for the silver preparations. The sections are then 
transferred from absolute alcohol to the following mixture : — 1 per cent, 
gold chloride solution, 8-10 drops; absolute alcohol, 10 ccm., which 
should have been made half an hour previously and exposed to diffuse 
light. After the sections are deposited therein the vessel containing 
them is placed in the dark. The silver is gradually replaced by gold, and 
* Virchow’s Archiv, cxxii. (18C0) pp. 387 et seq. See Zeitschr. f. Wise. Mikr., 
viii. (1890, pp. 97-8. 
