412 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
lated, and by which the pressure can be measured and maintained for 
any length of time. The essential part is a three-necked Woulff ’s bottle, 
and the most convenient size is one of 8 oz. By one of the necks com- 
pressed air is introduced by a syringe. By another the pressure is 
transmitted to a bottle containing the fluid to be injected. Into the 
third fits a graduated manometer tube, the lower end of which dips into a 
layer of mercury at the bottom of the vessel, and is so arranged that the 
zero is flush with the mercurial level, and the mercury inside the mano- 
meter is brought to the same level by sucking out some air. The pressure 
is obtained by injecting air by means of some form of syringe, e. g. a 
Higginson, an aspirator or injection syringe. In the glass tube which 
leads into the bottle is placed a three-way stopcock, and this is a 
necessity for regulating the inflow and the outflow of air, and also for 
reducing or removing the pressure altogether. Two other stopcocks, 
one on the tube leading from the bottle and the other on the injecting 
bottle, are also desirable. The manometer may be graduated in atmo- 
spheres or in millimetres, &c., of mercury. 
(5) Mounting 1 , including" Slides, Preservative Fluids, &c. 
Chloral for Mounting Microscopical Preparations.* — M. A. 
Geoffroy recommends the following process especially for preparations 
of starch- grains, the lower Fungi, Algee, &c. Three or four grs. of the 
purest gelatin are dissolved in 100 ccm. of a 10 per cent, solution of chloral 
hydrate ; or the concentration may be varied according as a greater or 
less clarifying of the preparation is needed. This is applied in the 
same way as ordinary glycerin, but it is not necessary to remove the 
fluid entirely from the edge of the cover-glass. After a short time 
the gelatin hardens round the cover-glass in such a way that the pre- 
paration can be fixed in an alcoholic solution of shellac. Preparations 
made in this way and stained with carmine or iodine-green retain their 
colour for a very long time, while other stainings are more evanescent. 
Keeping Paraffin Sections Flat.f — After pieces of tissue have been 
hardened, says Mr. N. Walker, they are to be saturated with toluol, 
chloroform or the like, and then imbedded in parafiin of about 50° 
melting-point. The difficulty then arises of keeping the sections spread 
out flat and smooth on the slide. The preparations flatten out quickly 
if they are dropped into warm water, the temperature of which is just 
below the melting point of the parafiin. The slide is then put under- 
neath, the section lifted out of the water and dried in an incubator 
at 30°. The section will be found to have adhered firmly to the slide. 
The paraffin is then dissolved out in benzol, and the latter having been 
washed off with alcohol, the preparation is stained in the usual manner. 
Influence of the Composition of the Glass of the Slide and Cover- 
glass on the Preservation of Microscopic Objects.^ — Ilerr R. Weber 
remarks that it is a matter of common observation that objects mounted 
* Joum. de Bot. (Morot), vii. (1893) pp. 55-6. 
t Monatshefte f. Prakt. Dermatologie, xvi. (1893) p. 113. See Centralbl. f. 
Bakteriol. u. Parasitenk., xiii. (1893) p. 344. 
X Ber. Deutsch. Chcm. Ges., xxv. (1892) pp. 2374-7. 
