ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 811 
1/8 in. Binding posts are riveted to the brass for connection with a 
battery. 
In order to apply this instrument, a sufficient quantity of the fluid 
containing the bacteria should be used to fill the cell and grooves. A 
cover-glass is placed over the cell and its contents. Two small clean 
sponges, saturated with either the fluid or distilled water, are then placed 
Fig. 87. 
underneath the platinum points and in contact with the fluid in the grooves. 
The bacteria are now ready for observation, the electricity is turned on, 
and the quantity noted by the milli-ampere meter to stop all sign of 
germ life. They can now be cultivated on gelatin in the ordinary way 
should it be desired to determine whether or not their vitality has been 
entirely destroyed. 
Other uses for the slide will readily occur to one working in this 
field : for example, the effect of electricity on the blood and different 
tissues. 
I have found this instrument very satisfactory, not only as an 
easy, but as a quick way of finding out the amount of electricity required 
to destroy micro-organisms.” 
New Apparatus for drawing Low Magnifications.* — Dr. L. 
Edinger has devised a simple form of apparatus for drawing low magnifi- 
cations' (fig. 88), in which the image is projected directly upon the 
paper and a perfectly free movement is given to the object which lies 
horizontally on a stage. 
The apparatus has the following construction. On a polished 
wooden base, which serves as drawing board, rises a wooden upright 
which supports a horizontal tube, closed in front by a condensing lens 
and behind by a mirror set at 45°. The rays of a lamp are concentrated 
by the lens upon the mirror. Through an opening beneath the mirror 
the light falls downwards upon an object-stage which is adjustable in 
height. Beneath the object-stage is a lens, supported in au adjustable 
holder, which produces on the base-plate an objective image of prepara- 
tions which are placed on the object-stage. According to the adjust- 
ment of lens and drawing-board it is possible to take magnifications 
from 2 to 20. The apparatus, however, is supplied with three lenses, 
* Zeitachr. f. Wiss. Mikr., viii. (1891) pp. 179-81. 
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