nce may exert an
influence.

The question as to whether tumors are an increasing cause of disease
is equally difficult of solution. The mortality statistics, if taken
at their face value, show an enormous increase in frequency; but there
are many factors which must be considered and which render the
decision difficult and doubtful. Tumors are largely a prerogative of
age, and the increased duration of life which preventive medicine has
brought about brings more people into the age when tumors are more
common. Owing to the greater skill in the diagnosis of tumors,
especially those of the internal organs, they are now recognized more
frequently and more deaths are correctly ascribed to them. Deaths from
tumors were formerly often purposely concealed and attributed to some
other cause.

No age is immune to tumors. They may be present at birth or develop
shortly afterwards. The age from five to twenty years is the most free
from them, that from forty-five to sixty-five the most susceptible,
particularly to the more malignant forms.

A tumor is a local disease. The growing tissue of the tumor is the
disease, and it is evident that if the entire tumor were removed the
disease would be cured. This is the end sought by surgical
interference, but notwithstanding seemingly thorough removal, the
tumor often reappears after an interval of months or years. There are
many conditions which may render the complete removal of a tumor
difficult or impossible. It is often impossible to ascertain just how
far the tumor cells have invaded the neighboring structures; the
situation of the tumor may be such that an extended removal would
injure organs which are essential for life, or at the time of removal
the tumor cells may have been conveyed elsewhere by the blood or
lymphatic vessels.

Successful removal depends mainly upon the length of time the tumor
has been growing. At an early stage even the most malignant tumor may
be successfully removed. It is evident from this how disastrous may be
the neglect of proper surgical treatment of a tumor. The time may be
very short between the first evidence of the presence of a tumor and
the development of a condition which would render complete removal
impossible.

The effect of a tumor upon its bearer depends upon its character and
situation. Pain is very commonly present, and is due to the pressure
which the growing tumor exerts upon the sensory nerves. Pain may,
however, not be present or