MEDICAL PHOTOGRAPHY Every year sees the wider application of photography to medical science. At the present day photomicrography and radiography are of the very greatest importance, the first making it possible to obtain a permanent and exact record of the normal and abnormal appearance of the tissues, of the blood corpuscles, and of those blood-parasites and bacteria which are the cause of various diseases ; while the second assists in the diagnosing of fractures of the bones, the presence of foreign bodies within the thoracic and abdominal regions, and calculi in the kidney, etc., etc. Radiography is fully treated under the heading of " X-Ray Photo graphy," but the application of photomicro graphy to medical research calls for some consideration here. The microscope must have centring sub-stage, and should also have a good mechanical stage fitted with vernier scales which act as " finders." The most useful objectives will be, for medium and high power work, ct ith, -1-th, and nth in. oil immer sion; while for large sections and low-power work generally, a a in., i in., and y in. The selection of eyepieces will be governed by the type and quality of the objectives. It is most important that both eyepieces and objectives be kept perfectly clean and free from dust, dust on the lenses of the eyepiece giving rise to the appear ance of out-of-focus marks on the negative. The sub-stage condenser must also be carefully cleaned from time to time. As it is important to bring out as much detail as possible in the resulting negative, and all pathological and bacteriological preparations are stained with one or more stains, it is absolutely necessary not only to use carefully and thickly backed orthochromatic plates, but also suitable com pensating filters, that the maximum amount of detail, coupled with sufficient contrast, may be obtained. While visual observation of the
subject, with the compensating filter placed immediately behind the sub-stage condenser, will serve as a rough guide to the amount of detail and contrast likely to be obtained, unless the dyes used for the filter are spectroscopically true, and the photographic plate properly orthochromatised, the photographic result will not be as satisfactory as the visual examination promised. Long experience has shown that the most satisfactory results, as regards both the quality and resolution of the image, are to be obtained with a camera extension of io in. from the eyepiece of the microscope to the focusing screen of the camera. In photographing such subjects as skin eruptions and rashes, careful attention must be paid to the colour of the eruption. For instance, a pink, yellow, or red rash will show up much better if photographed with an ordinary plate of medium speed, than with an orthochromatic plate, for the simple reason that the ordinary plate being less sensitive to these colours, they will be rendered darker, and, therefore, more conspicuous, than if photographed on an orthochromatic plate. To photograph culture tubes of bacteria that have been inoculated by " stab " or " streak," place the tube in a large water bath or lantern alum trough filled with water. This will be found to do away with the unpleasant, bright, vertical reflections down the front and sides of the culture tube, and to facilitate the successful photographing of the growth within the tube.