ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
551 
(4) Photomicrography. 
Photographing Bacteria.*— Sir H. E. Koscoe and Mr. J. Lunt 
describe a method of photographing bacteria, which they say is very 
simple and requires no special 
apparatus or “ microscopic ac- 
cessories.” The arrangement 
of the apparatus is shown in 
fig. 63. 
A common duplex paraffin 
oil lamp was the source of 
illumination. As methyl- 
violet was the stain employed 
and as this transmitted actinic 
rays of light a screen was 
spectroscopically adjusted to 
the stain employed, and a 
weak solution of potassium 
bichromate was found to serve 
the purpose admirably. The 
stained bacteria appear black 
on a bright yellow back- 
ground. The photographic 
plates employed must, there- 
fore, be sensitive to yellow 
light. 
Abbe’s condenser was used, 
without diaphragm, and was 
focused rather farther from 
the object than for ocular ex- 
amination. A simple clip 
stage was employed without 
mechanical accessories. The 
microscopic preparations were 
ordinarily obtained from young 
pure cultures, thus securing 
cells full of protoplasm, which 
stain deeply, an essential for 
actinic contrast on the photo- 
graphic plate. Canada balsam 
in xylene was uniformly em- 
ployed as a mounting medium. 
The lenses used were Leitz’ 
1/12 oil-immersion for 740 
diameters, Zeiss’ D for 370, 
and Zeiss’ A for 100 and 50 
diameters. No eye-piece was 
used, nor was there any lens 
in the camera, which was con- 
nected to the tube of the Micro- 
scope by a horizontal dark box extension. Edwards’ isochromatic plates 
* Phil. Trans., 182 B (1892) pp. 642-4. 
