use in the domain of
medicine. It is, therefore, with great pleasure that I accede to the
request of the editor of this Magazine to state briefly what has been
achieved in the department of medicine up to the present time.

The method of investigating the body by means of the X rays is very
simple, as is shown in Figure 1. The Crookes tube, actuated from a
storage battery or other source of electricity through a Ruhmkorff coil,
is placed on one side of the body. If need be, instead of using the
entire tube, the rays from the most effective portion of it only are
allowed to impinge upon the part of the body to be investigated, through
an opening in a disk of lead interposed between the Crookes tube and the
body. On the other side of the part to be investigated is placed a quick
photographic plate shut up in its plate-holder, and is exposed to the
rays emanating from the tube for a greater or less length of time. The
parts of the plate not protected by the body are acted upon by the rays,
through the lid of the plate-holder (to which the rays are pervious),
while the tissues of the body act, feebly or strongly, as the case may
be, as obstacles to the rays. Hence, the part of the plate thus
protected is less acted upon than the rest, and a shadow is produced
upon the plate. The soft tissues of the body form but a very slight
obstacle to the passage of the rays, and, hence, throw very faint
shadows on the plate. The more dense portions, presenting a greater
obstacle to the passage of the rays, throw deeper shadows; hence the
bones are seen as dark shadows, the soft parts as lighter ones. That the
flesh or soft parts are not wholly permeable to the rays is well shown
in the skiagraph--i.e., a "shadow picture"--of a foot. (Figure
2.) Where two toes overlap, it will be observed that there is a deeper
shadow, like the section of a biconvex lens.

[Illustration: FIGURE 2.--SKIAGRAPH OF A FOOT, SHOWING AN EXTRA BONE IN
THE GREAT TOE, WHICH WAS REMOVED BY PROFESSOR MOSETIG.

(From the "British Medical Journal.")]

When we attempt to skiagraph the thicker portions of the body, for
example, the shoulder, the thigh, or the trunk, even the parts
consisting only of flesh obstruct the rays to such an extent, by reason
of their thickness, that the shadows of the still more dense tissues,
like the thigh bone, the arm bone, or the bones of the trunk, cannot be
distinguished from the shadows of the thicker soft parts. Tesla
("Electrical