justifiable expectation that the tumor disease might be controlled as
are many of the parasitic diseases, but the hypothesis awaits the
demonstration of its correctness. Despite the study of tumors which is
being actively pursued in many places and by the most skilled
investigators, no parasites have been found in animal tumors; the
objects previously described as parasites have been found not to be
such. It is difficult to bring in accord with the parasitic theory the
great variation in tumor structure, the relation of certain tumors, as
the malignant tumors of the breast and uterus, with the age of the
bearer, the congenital tumors which develop in intra-uterine life, and
there are many other conditions which oppose the theory.

The traumatic[2] theory. There is much in favor of this. In a certain
number of cases tumors do develop at the site of injuries. The
coincidence of injury and tumor is apt to be overestimated because of
the strong tendency to connect succeeding events. Tumors are not most
common on those parts of the body which are most exposed to injury.
They are rare, for instance, on the hands and feet, and very rarely do
they appear at the site of wounds caused by surgical operations. For
those tumors which develop in intra-uterine life it is difficult to
assign injury as a cause. There does, however, seem to be a relation
between tumors and injuries of a certain character. The natives of
Cashmere use in winter for purposes of heat a small charcoal stove
which they bind on the front of the body; burns often result and
tumors not infrequently develop at the site of such burns. Injuries of
tissue which are produced by the X-ray not infrequently result in
tumor formation and years may elapse between the receipt of the injury
and the development of the tumor. These X-ray injuries are of a
peculiar character, their nature but imperfectly understood, and the
injured tissues seem to have lost the capacity for perfect repair.