Medical microscopy : a guide to the use of the microscope in medical practice / Frank J. Wethered.

  • Wethered, Frank Joesph, 1860-1928.
Date:
1898, ©1892
Catalogue details

Licence: Public Domain Mark

Credit: Medical microscopy : a guide to the use of the microscope in medical practice / Frank J. Wethered. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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    of doubtful diagnosis, and for their sure detection a special illumination is absolutely necessary. The diaphragm is made of several different patterns. The most ordinary form consists of a wheel of dia- phragms of various sizes, and should be examined to see whether the apertures are concentric with the axis of the instrument. Another form consists of small blocks in which the openings are pierced, all fitting into a common receptacle, which is inserted below the stage. The most important feature is that the diaphragm must be placed i7nmediately beneath the object, in order to secure the best results. There are several more complicated forms, such as the iris, but for a description of them the reader is referred to larger treatises on microscopy. Although the choice of a stand is of no mean im- portance, the chief point is of course the selection of the objectives. For ordinary histological work, an inch lens and a quarter-inch is sufficient, but if it be intended to under- take the examination of sputum, etc., a twelfth-oil-immer- sion is necessary, as the micro-organisms cannot be seen with any certainty without this power. According to the Continental systems, the first named lenses are represented by Nos. 3 and 7 of Hartnach, or A and D of Zeiss. It should be borne in mind that the term one-inch objective, etc., indicates only that such a lens should possess the same magnifying power as a single lens of one- inch focus, and that it does not refer to the distance which the front of the lens focuses from the object, this varying greatly with the different makers. The qualities of a good objective are:—defining