Manual of Bacteriology And Pathology for Nurses

nterested in such laboratory technic are referred to the more pretentious works for physicians and medical students. Owing to their minute size, bacteria can only be examined by means of a high-power microscope, assisted by a device known as an oil-immersion lens, in which a drop of cedar oil is interposed between the lens and the cover-glass, beneath which is the object to be observed, the purpose of such device being to concentrate all of the rays of light emerging from the specimen observed. In addition there is needed an Abbe condenser, a device for concentrating the rays upon the object viewed. Being provided with the proper apparatus, the specimen may be examined in several ways. If the specimen be from a liquid culture, a drop may be taken on a platinum loop placed between a cover-glass and slideand examined with the oil-immersion lens. Or it may be examined by the hanging-drop method. In this method a slide is used in which a small depression is hollowed out. The drop of culture or pus to be examined is placed upon the cover-glass, which is then inverted over the depression, and the drop allowed to hang free in the space between the cover-glass and slide. By this means the movement of motile bacteria and agglutination, as in the Widal test, may be observed. By sealing the edges of the cover-glass, evaporation is prevented, and the specimen may be studied for days, and such processes as spore formation and fission observed. If it be desired to stai...