714 
SUMMARY OF CURRENT RESEARCHES, ETC. 
with the cover-glass in the shallow chamber. To make a good air-tight 
contact with the slide, grasp the syringe with the left hand and allow 
the lower side of the latter to hold the washers firmly to the slide. 
The hole drilled in the syringe is to act as a trap or valve, and is to be 
tightly covered with the first finger of the left hand (keeping the latter 
in position, grasping the syringe and holding the washers to the slide) 
at each downward stroke of the piston, and uncovered at each upward 
stroke. This is, of course, done to prevent the entrance of air to the 
vacuum chamber beneath after it has once been exhausted. I have 
found that three or four strokes are sufficient to bring all the bubbles 
to the surface of the mounting fluid and cause them to burst.” 
New Fixing Fluid for Animal Tissues.* — Dr. G. Mann has obtained 
good results (minimum shrinkage, distinctness of cell-outline, admirable 
fixing of cell-plasma and nuclei) by using the following mixture : — 
Absolute alcohol, 100 ccm. ; picric acid, 4 grm. ; corrosive sublimate, 
15 grm. ; tannic acid, 6-8 grm. 
In order to obtain good results it is essential to use only living 
tissue ; to have thin pieces ( * 5-1 cm.) ; to have an amount of fluid 
twenty times the bulk of the tissue ; to go through an elaborate series of 
washing and alcohol transferences ; to add chloroform very gradually ; 
to saturate the chloroform gradually with solid paraffin, first at the 
ordinary temperature, then at 25° C., and lastly at 52° 0., keeping the 
bottle well stoppered ; to allow the chloroform to evaporate gradually, 
avoiding accelerating devices which cause shrinkage, and so on. For 
minuter details of a method which has certainly yielded good results 
reference should be made to the original paper. 
C6) Miscellaneous. 
Apparatus for Observing Movements in Plants.f — Dr. F. Noll 
describes a modification of the stroboscope (zoetrope), by means of 
which the movements of a seedling plant which elevates itself by means 
of geotropism can be demonstrated, and exhibited in the lecture-room. 
The instrument may also be applied to the observation of the move- 
ments of tendrils, the periodical movements of foliar organs, &c. 
Determination of Diastase in Leaves and Stems.f — M. St. Jentys 
explains the failure of Wortmann to find diastase in the aqueous extract 
of leaves and stems on the following grounds : — It is probable that the 
diastase is formed only in small quantities, as it is required for the con- 
version of starch into sugar. The presence of tannin in the aqueous 
extract causes, the precipitation of the starch, which is then only with 
great difficulty acted upon by diastase ; it also precipitates the diastase 
itself. Finally, diastase possesses only a very feeble power of diffusion ; 
and therefore, when contained within cells, passes into the solution only 
after the complete destruction of the cell-walls, and in company with 
the tannins which then precipitate it. 
* Anat. Anzeig., viii. (1893) pp. 441-3. 
f Verhandl. Naturh. Yer. Preuss. Rheinland, xlix. (1892) pp. 37-41. 
t Verhandl. Akad. Wiss. Krakau, xxiv. (1893) 47 pp. See Bot. Centralbl., liv. 
(1893) p. 193. 
