suited for experimental investigation; they are
determined by observation."[1]

[1] Lancet, London, October 7, 1911.

No "serum," no drug, no curative agency of any kind, has thus far been
discovered upon which the slightest dependence may be placed. The
only measure of relieve which medical science can now suggest is early
and complete extirpation. Of what proportion of cases even this
insures immunity we cannot tell.

Without decrying what has been done in the laboratory, may it not be
that we have gone in that direction as far as there is any hope for
success, and that all effort should now be directed TO THE DISCOVERY
OF THE CAUSE OF MALIGNANT DISEASE IN HUMAN BEINGS? That great secret
still eludes us, but until we can penetrate that mystery, it is
difficult to perceive how we may hope to prevent the increasing
prevalence of the great destroyer . Yet there is one method of
investigation which (speaking from a study of cancer statistics for
more than twenty-five years) seems to me to offer, more than all
others, a reasonable hope of ultimate success. It is independent of
all sacrifice of animal life. It involves, however, an expenditure
far greater than is possible for any private investigator, and
probably only by the co-operation of the Government can it be
undertaken with any chance of success. Yet, if Society can once be
aroused to a recognition of the need for the completest possible
investigation concerning malignant disease, and particularly the
reasons for its differing prevalence among people of different
nationalities, habits, and general environment, that inquiry will take
place, even though it cost the price of a battleship.

The subject is so vast and involved that it cannot be discussed with
any approach to completeness in a single essay. Suppose, however,
that we glance at the theory which regards cancer as due to a microbe
which in some mysterious ways gains admission into the human body,
lying for a time dormant, but liable under appropriate stimulation to
be awakened into malignant activity. We know at the outset that if
any such germ of disease exists, it has thus far escaped visual
recognition. No human eye can be said with certainty to have seen it,
even when aided by the most powerful microscope; but this may be due
to the fact that, like the germ of certain other diseases, it is so
minute that it lies beyond the range of human vision. There are,
however, certain facts pertaining t