PHOTOGRAPHING BACTERIA, 111 
DESCRIPTION OF APPARATUS FOR PHOTOMICROGRAPHY BY OIL 
LIGHT. 
The apparatus consists of a camera, hung in a vertical position, of a 
microscope with substage condensers, suitable objectives and projection 
oculars, and a Laverne tri-wick, oil stereopticon with the projection objec- 
tive removed. 
The Light.—After trying all kinds of lamps, I found that the best illu- 
mination could be obtained by using a tri-wick stereopticon with the pro- 
jection objective removed, the middle wick only being lighted. The large 
four-inch condensers serve to concentrate the light, while the double lantern 
body prevents the radiation of heat to the microscope and shuts off all radiat- 
ing light. Consequently the microscope does not become heated, and if the 
room isdarkened the absence of extraneous light greatly aids in focussing on 
the camera screen. The oil light itself is quite yellow and so nearly mono- 
chromatic that with orthochromatic plates a color screen is seldom, if ever, 
required. After experimenting by taking photographs with and without a 
screen, I have found no particular difference in result even when photo- 
graphing difficult bacteria, and now seldom use one. If a screen is used a 
solution of bichromate of potash and sulphate of copper in dilute ammonia 
water placed in a trough between the lantern and mici oscope gives excellent 
results and does not materially lengthen the time of exposure. The lantern 
is placed about twelve inches in front of the microscope and with its central 
long axis in a plane which extends through the centre of the microscope 
mirror, the substage condenser, the objective, ocular and centre of camera. 
Microscope.—The microscope is used in the upright position. I have 
used this position rather than the horizontal for several reasons. The 
microscope is used on the work-table in an upright position, and in working 
when an object is found which it is desired to photograph, the microscope 
without changing adjustments has only to be carried to the photomicro- 
' graphic apparatus, placed in position, correct adjustments of light made, the 
camera racked into contact and the exposure made. With a conveniently 
placed dark room the whole operation will occupy but a few minutes. The 
upright position is necessitated when liquid preparations, as colonies of 
bacteria floating on liquefied gelatin, are to be photographed, or when the 
microscope is used for clinical photomicrography, as in photographing uri- 
nary deposits in urine, blood corpuscles in Thoma blood counter, ete. In 
bacteriological work where the bacteria are stained on the cover and after 
mounting the balsam is not quite dry, the cover is apt to slip if the micro- 
scope is used horizontally, but this doesnot occur with the microscope placed 
vertically. The horizontal position and long extension of camera is neces- 
sary for certain work, particularly where large pictures (7.e., over four 
inches in diameter) have to be taken, or where it is desired to obtain high am- 
plification by extension of camera rather than by high eyepiecing, or in 
photographing test diatoms with very high amplifications. For practical 
work, however, up to amplifications of one thousand diameters, and for 
photographs for illustration or reproduction, which are seldom required of 
over three and one-half or four inches in diameter, the upright position is 
much to be preferred on account of its ease of application and its practical 
advantages. 
Camera.—The upright position of the microscope necessitates a similar 
position for the camera. To allow easy working, the camera is hung on a 
rack-work attached to a rigid upright. The upright is placed to the right of 
the microscope so that it will be out of the way while working. 
Both the upper and the lower ends of the camera are movable on the 
rack-work. The upper end, which carries the screen and plate-holder, is 
movable, in order that different amplifications within limits can be gotten 
with the same objective. The lower end is movable that it may be racked 
