ngular and incredible
things about the cancer process: that a cancer starting, say, in the
pancreas, and spreading to the brain, will there pile up a mass--not of
brain-cells, or even of connective tissue-cells--but of gland-cells,
resembling crudely the organ in which it was born. So far will this
resemblance go that a secondary cancer of the pancreas found in the lung
will yield on analysis large amounts of trypsin, the digestive ferment
of the pancreas. Similarly a cancer of the rectum, invading the liver,
will there pile up in the midst of the liver-tissue abortive attempts at
building up glands of intestinal mucous membrane.

This fundamental and vital difference between the two processes is
further illustrated by this fact: While an ordinary infection may be
transferred from one individual to another, not merely of the same
species, but of half a dozen different species, with perfect certainty,
and for any number of successive generations, no case of cancer has ever
yet been known to be transferred from one human being to another. In
other words, the cancer-cell appears utterly unable to live in any other
body except the one in which it originated.

So confident have surgeons and pathologists become of this that a score
of instances are on record where physicians and pathologists, among them
the famous surgeon-pathologist, Senn, of Chicago, only a few years ago,
have voluntarily ingrafted portions of cancerous tissue from patients
into their own arms, with absolutely no resulting growth. In fact, the
cancer-cell behaves like every other cell of the normal body, in that,
though portions of it can be grafted into appropriate places in the
bodies of other human beings and live for a period of days, or even
months, they ultimately are completely absorbed and disappear. The only
apparent exception is the epithelium of the skin, which can be used in
grafting or skinning over a wide raw surface in another individual.
However, even here the probability appears to be that the taking root of
the foreign cells is only temporary, and makes a preliminary covering or
protection for the surface until the patient's own skin-cells can
multiply fast and far enough to take its place.

A similarly reassuring result has been obtained in animals. Not a single
authenticated case is on record of the transference of a human cancer to
one of the lower animals; and of all the thousands and thousands of
experiments that have been made in a