at process, so well known in all clew-following,
elimination, comes in.

A patient comes in with pain-lines written all over his face. To put it
very roughly--has he cancer of the stomach? Pneumonia? Brain tumor? If
there be no play of the muscles distending and contracting the nostrils
with each expiration, no increased rapidity of breathing, no gasp when a
full breath is drawn, and no deep red fever blush on the cheeks, we
mentally eliminate pneumonia. The absence of these nasal signs throws us
back toward cancer or some other painful affection of the alimentary
canal. If the pain-lines about the mouth are of recent formation, and
have not graved themselves into the furrows of the forehead above and
between the eyebrows; if the color, instead of ashy, be clear and red,
we throw out cancer and think of colic, ulcer, hyperacidity, or some
milder form of alimentary disease.

If, on the other hand, the pain-lines are heaviest about the brows, the
eyes, and the forehead, with only a sympathetic droop or twist of the
corners of the mouth, if the nostrils are not at all distorted or too
movable, if there is no fever flush and little wasting, and on turning
to the eyes we find a difference between the pupils, or a wide
distention or pin-point-like contraction of both or a slight squint, the
picture of brain tumor would rise in the mind. Once started upon any one
of these clews, then a hundred other data would be quickly looked for
and asked after, and ultimately, assisted by a thorough and exhaustive
examination with the instruments of precision and the tests in the
laboratory, a conclusion is arrived at. This, of course, is but the
roughest and crudest outline suggestive of the method of procedure.

Probably not more than once in three times will the first clew that we
start on prove to be the right one; but the moment that we find this
barred, we take up the next most probable, and in this manner hit upon
the true scent.

As to the cause and rationale of these pain-lines, only the barest
outlines can be given. Take the mouth for an example. When all is going
well in the alimentary canal, without pain, without hunger, and both
absorption of food and elimination of waste are proceeding normally, the
tissues about the mouth, like those of the rest of the body, are apt to
be plump and full; the muscles which open the aperture, having fulfilled
their duty and received their regular wages, are quietly at rest; those
that clos