translucent to the rays. The picture
confirms the prior diagnosis of tuberculous disease, and shows that the
joint will have to be opened and treated for the disease. Deposits of
uric acid in gouty diseases of the joints will undoubtedly be shown by
these methods, but this will scarcely be of any help in the treatment.
Whether light will be thrown on other diseases of the joints is a
problem not yet solved.

Analogous to the bony tissues are the so-called ossified (really,
calcified) arteries. In the dead body, arteries filled with substances
opaque to the X rays, such as plaster of Paris or cinnabar mixtures,
have already been skiagraphed successfully. It is not at all improbable
that calcified arteries in the living subject may be equally well shown.
So, too, when we are able to skiagraph through thick tissues, we may be
able to show such deposits in the internal organs of the body. Stones in
various organs, such as the kidney, will be accessible to examination so
soon as our methods have improved sufficiently for us to skiagraph
through the thicker parts of the trunk. The presence of such stones in
the kidney is very often inferential, and it will be a great boon, both
to the surgeon and the patient, if we shall be able to demonstrate
positively their presence by skiagraphy. For the reason already given
(the pelvic bones which surround the bladder), it is doubtful whether we
can make use of it in stone in the bladder. Gall stones, being made not
of lime and other similar salts, as are stones in the kidney and
bladder, but of cholesterine, are, unfortunately, permeable to these
rays; and it is, therefore, doubtful whether the X rays will be of any
service to us in determining their presence.

The chief use of the method up to the present time, besides determining
the diseases, injuries, and abnormities of bone, has been in determining
with absolute accuracy the presence of foreign bodies, especially of
needles, bullets, or shot and glass. It is often extremely difficult to
decide whether a needle is actually present or not. There may be a
little prick of the skin, and no further positive evidence, as the
needle is often imperceptible to touch. The patient, when
cross-questioned, is frequently doubtful whether the needle has not
dropped on the floor; and it might be, in some cases, a serious question
whether an exploratory operation to find a possible needle might not do
more harm than the needle. Moreover, though ce