739. Photographing A Bacteria Slide

Photographing A Bacteria Slide. The photographing of bacteria is quite distinctive from the ordinary use of the microscope, and this class of work is mainly interesting to physicians and those interested in medical research. The two-thirds and one-sixth objectives, with their proper eye-pieces, are capable of giving satisfactory photographs of animal tissues, both normal and diseased. The high-power 1-12 oil-immersion objective, with its magnification of one thousand diameters, with either No. 1 or No. 2 eye-piece, is almost universally adopted by the scientific world as being sufficiently high to show very clearly the minute forms, such as blood and pus corpuscles, germs, bacteria and cell structure. For bacteriological work the slides are usually stained with methyl-blue and carbol-fuchsine. These stained slides necessitate the use of the color-screen during exposure.

740. To begin focusing and finding the field, the two-thirds objective should be used and the preliminary focusing should be done without the camera attachment. The method of focusing is the same as previously given, excepting that more care must be given. Every movement must be made quietly and deliberately.

741. After placing the slide upon the stage of the microscope, the field is found with a two-thirds objective, having the Abbe condenser wide open. When the field is found, before changing to a higher-power objective, first, with the coarse adjustment, slightly raise the microscope tube from the slide. Remove the two-thirds and insert the one-twelfth objective. As all three objectives are attached to the revolving nose-piece, all that is required is to turn the objective into position, when you are again ready for focusing.

742. Proceed by placing a drop of cedar oil upon the cover-glass of the slide. With the coarse adjustment lower the 1-12 objective until it comes in immersed contact with the slide; then, observing the image through the eye-piece, finish focusing with the fine adjustment, moving the slide about on the stage until a satisfactory field is found. With this obtained, slightly raise the objective from the slide. This is done to avoid any possibility of the objective and slide coming in contact while attaching the camera.

743. With the microscope raised, proceed to attach the camera to the barrel. Insert the ground-glass and again place another drop of cedar oil on the slide, then lower the objective until it becomes immersed in the oil. Now, covering the head and camera with the focusing cloth (see Fig. 1, Illustration No. 126), observe the image upon the ground-glass. Use the hand-focusing glass and focus with the fine adjustment of the microscope, until the image becomes perfectly sharp. Then very carefully remove the ground-glass without disturbing the instrument a particle and insert the plate-holder, when you are ready to make the exposure.

744. Before drawing the slide, place the cardboard between the light and stage of the instrument, so as to cut off all illumination. With this done, draw your slide and, after pausing for a few moments until everything is perfectly quiet, gently withdraw the cardboard, thereby making the exposure. When the exposure is completed, again replace the cardboard, thus cutting off the illumination. Follow this immediately by re-inserting the slide in the plate-holder.