ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
673 
(4) Photomicrography. 
Photomicrographical Apparatus.* — Prof. Martens has fitted up in 
the Konigliche Mechanisch-Technische Versuchsanstalt in Berlin a 
photomicrographical laboratory which is almost unique in the complete- 
ness of the arrangements for the illumination of opaque objects. 
The Microscope employed was made by the firm of Zeiss after Prof. 
Martens’ design. It stands on a slide movable in the direction of the 
optic axis, and is fixed to a cast-iron plate which rests on two fixed 
points and an adjusting screw, so that the optic axis of the Microscope 
can be suitably directed. Both the body-tube (50 mm. wide), and the 
movable stage, which is provided with a coarse- and fine-adjustment, are 
directly attached to the common support The extent of movement of 
the stage is considerable, in order to facilitate the examination of large 
objects. The stage is of the same form as that in Zeiss’ photographic 
instrument. By means of the usual spring clamp an object-holder can 
be attached to it, so that in the case of irregularly shaped objects the 
surface to be examined can be properly adjusted. For the illumination 
by reflected light several methods are adopted. For weak objectives 
either a plane parallel glass set at 45° in front of the objective is used, 
or a prism placed so far forward as to cover one-half of the aperture 
of the objective. Both arrangements are carried by an adjustable 
holder attached to the body-tube. For higher objectives illumination 
from above through the objective is employed. For this purpose the 
light from a side opening is directed by a prism through one half of the 
objective so as to fall upon the object which is examined by the other 
half of the objective. In this arrangement the Zeiss apocliromatics 
O’ 30 and 0*95 N.A. (16 mm. and 4 mm. focal length) are used. The 
prism-holder consists of a small box whioh can be displaced sideways so 
as to give the effect of oblique light, or be shifted quite to one side, when 
the objective can be used with its full aperture for illumination by 
transmitted light. For the adjustment of the prism at right angles to 
the optic axis of the illuminating apparatus, a piece is provided which is 
movable about the optic axis and carries both objectives. This holder 
with the apochromatics and special prism can be replaced by another 
with fixed prism into which Zeiss objectives A, B, and DD fit. 
Photomicrographical Apparatus of the Leipzig Anatomical 
School. j - — Prof. W. His describes the photomicrographical apparatus 
which he employs in his embryological and morphological researches. 
The apparatus is not intended for the more difficult problems of photo- 
micrographical technique, but to answer the more modest requirements 
demanded by work at comparatively low magnifications. The aim of 
the author was to produce, under moderate magnification (10 to 200 
times), large pictures which could be of service for precise measurements 
and plastic reconstructions. The work was simplified by dispensing 
with the glass negative and taking the photographs directly on East- 
mann’s silver bromide paper. The apparatus first used was arranged 
* Central-Ztg. f. Optik u. Meclianik, xiii. (1892) pp. 135-6. 
f His, W., ‘ Der Mikrophotographische Apparat der Leipziger Anatomie’ 
(Festschr. Albert Kolliker zum 26. Marz 1892), Leipzig, 1892, 22 pp., 3 pis. and 
2 woodcuts. 
1892. 2 z 
