94 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
At present it is a short-tube lens, but bj slightly closing the lenses 
it could be made into an objective for the long tube. 
In conclusion let me ask yon to go back to the micrcscopy of 1879, 
and then you will be better able to appreciate the great advance that 
has taken place in the improvement of the optical portion of the 
Microscope during the past ten years. 
C3) Illuminatingr and other Apparatus. 
Improvement in Abbe’s Camera Lucida.* — Dr. H. W. Heinsius 
has devised the following alteration in Abbe’s camera, so that it can be 
readily removed from the eye-piece and replaced, and that without dis- 
turbing the coincidence of the two images. The special advantage of 
the arrangement is that it allows the details of the preparation to be 
directly inspected from time to time, an advantage which any one who 
has tried to draw with a camera of any sort will appreciate. 
A ring of blackened brass of the same dimensions as the lower part 
of the camera, is connected by means of a joint to the arm which 
carries the mirror, and at the place where this is screwed to the mount of 
the prism. The three binding screws 
pass through the new tube instead of 
the old one, and thus clamp the instru- 
ment to the Microscojie. One slight 
alteration is necessary in order to pre- 
vent the neutral-tint glasses from 
falling out when the camera is turned 
up. The frames of these glasses are 
turned so that the latter are pushed in 
at the front and not at the top. 
Breath - screen, j* — In snub-nr sed 
persons, says Dr. P. Schiemenz, the 
expired air tends to pass down parallel 
to the tube during a microscopical ex- 
amination. The deposit of moisture, 
especially in winter, is sometimes 
annoying, and to obviate this the 
author recommends the adoption of a 
screen. This (fig. 7) may be made of 
a piece of stiff j)aper, the principal part 
of which is marly circular (diameter 
about 8 cm.j. The smaller portion is 
pierced by two holes, through which 
passes a string by which the apparatus 
is attached to the Microscope-tube. 
This breath-screen can of course be easily fixed in or moved to any 
position. 
Siphon Apparatus for cultivating living organisms under the 
Microscope. ;|; — Dr. J. af Klercker describes an apparatus which he has 
used for some time for observing living organisms under the Micro- 
* ZeitscLr. f. Wiss. Mikr., Ai. (1889) pp. 36-7. 
t T. c., pp. 37-8 (1 fig.). X T. c., pp. 145-9 (3 figs.). 
