File:A treatise on obstetrics for students and practitioners (1896) (14570782179).jpg

Identifier: treatiseonobstet00davi (find matches)
Title: A treatise on obstetrics for students and practitioners
Year: 1896 (1890s)
Authors: Davis, Edward Parker, 1856-
Subjects: Obstetrics Radiography in obstetrics Obstetrics Obstetrics
Publisher: Philadelphia and New York, Lea brothers & co.
Contributing Library: Francis A. Countway Library of Medicine
Digitizing Sponsor: Open Knowledge Commons

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des, one of which is a straight wire, the other aflat disk, preferably of platinum. The most efficient electrode for thispurpose is the cathode formed by platinum wire projecting into thebulb. When the current is so arranged that this electrode becomescathodal the surface of the tube is phosphorescent and gives forthabundant rays. If the object to be studied is placed from 12 to 18inches from the tube upon a photographic plate, perfectly sealed in apasteboard or wooden holder, the rays permeate the object and theplate-holders, throwing a shadow of the impermeable portions of theobject upon the photographic plate. For successful working of theapparatus a high vacuum must be present in the tube. Some thinkthat uranium glass is the best material for the construction of the tube,while it is generally agreed that the thinner the wall of the tube thebetter the results obtained. Different observations show that pene-trating power is sometimes gained by the use of a leaden diaphragm^ PLATE I.
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Pelvis and Foetal Skull, taken with Rbntgen Rays. THE DIAGNOSIS OF ADVANCED PREGNANCY. 51 and that results vary in proportion to the nearness of the object to thetube employed, the electromotive force, and the vacuum in the tube. The time necessary to procure a picture varies greatly. An hourhas been necessary in some cases, while from a few minutes to fifteenor twenty have given excellent results in others. The time requiredseems proportionate to the thickness of the object, the vacuum in thetube, and the electromotive force. The application of the plate to the patient is necessary in studyingthe trunk of the body ; thus, in observing the pregnant womb theplate in its holder should be bandaged upon the abdomen of the patient,as near to the foetus as possible. In ordinary positions and presenta-tions the plate should be applied to the left side of the mothers abdo-men, as near to the brim of the pelvis as possible. The patient shouldlie upon a suitable table or bed, her abdomen covere

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