[Illustration: FIG. 220.--LOCATING A FOREIGN BODY IN THE BRAIN.]
In Fig. 220 is shown an X-Ray tube, as applied for locating a foreign body in the brain cavity, in which view the patient's head is interposed between the X-Ray tube and the fluorescing screen, or photographic plate, as the case may be; while Fig. 221 shows the application of the same devices to the body. In both these views the particular form of X-Ray apparatus is known as the "Fluorometer," made under the Dennis Patent, No. 581,540, April 27, 1897, and it is devised with reference to more accurately locating the foreign object by its shadow, for which purpose adjustable bracket-sights, seen in Fig. 221 on opposite sides of the body, are provided for bringing the X-Rays into proper alignment for projecting the shadow of the foreign body in true indicative position on the fluorescing screen, while a cross hatched grating behind the body, graduated in aliquot spaces of an inch, furnishes a measured field, and forms an easy and quick means of platting the position of said object. In the position of parts in the two figures the horizontal line, on which the foreign object lies, would be determined, but it would not indicate how deep in the object was, _i. e._, whether it was in the middle, or on one side. To determine this the fluorescing screen and grating are placed under the patient, and the X-Ray tube above, and the vertical line of the object is thus obtained. Both the vertical line and horizontal line having been obtained, it will be obvious that the foreign object will lie at the intersection of these two lines, which establishes for the surgeon its definite location.
[Illustration: FIG. 221.--X-RAY APPARATUS APPLIED TO THE BODY.]
It has been observed by Prof. Elihu Thomson, and also by Dr. Kolle, that the X-Rays are not absorbed and destroyed by the sensitive chemicals of a single photographic plate, but so potent and penetrating is their influence that the rays pass through and produce an image on a number of plates, placed one behind the other, thus affording means for multiplying the image at one exposure.
Among other uses of the X-Ray may be mentioned its capacity to detect spurious from genuine gems, the diamond giving a distinct color from its imitations, as do also most other precious stones.