ust as soon as the process has progressed far enough to lower the
resisting power below a certain level, some acute infection steps in and
mercifully ends the scene. This is peculiarly true of pneumonia in old
age.

To the medical profession to "die of old age" is practically equivalent
to dying of pneumonia. The disease is so mild in its symptoms and so
rapid in its course that it often utterly escapes recognition as such.

The old man complains of a little pain in his chest, a failure of
appetite, a sense of weakness and dizziness. He takes to his bed, within
forty-eight hours he becomes unconscious, and within twenty-four more he
is peacefully breathing his last. After death, two-thirds of the lung
will be found consolidated. So mild and rapid and painless is the
process that one physician-philosopher actually described pneumonia as
"the friend of old age."

When once the disease has obtained a foothold in the body its course,
like one of Napoleon's campaigns, is short, sharp, and decisive.
Beginning typically with a vigorous chill, sometimes so suddenly as to
wake the patient out of a sound sleep, followed by a stabbing pain in
the side, cough, high fever, rapid respiration, the sputum rusty or
orange-colored from leakage of blood from the congested lung, within
forty-eight hours the attacked area of the lung has become congested; in
forty-eight more, almost solidified by the thick, sticky exudate poured
out from the blood-vessels, which coagulates and clots in the air cells.
So complete is this solidification that sections of the attacked lung,
instead of floating in water as normal lung-tissue will, sink promptly.
The severe pain usually subsides soon, but the fever, rapid respiration,
flushed face, with or without delirium, will continue for from three to
seven or eight days. Then, as suddenly as the initial attack, comes a
plunge down of the temperature to normal. Pain and restlessness
disappear, the respiration drops from thirty-five or forty to fifteen or
twenty per minute, and the disease has practically ended by "_crisis_."
Naturally, after such a furious onslaught, the patient is apt to be
greatly weakened. He may have lost twenty or thirty pounds in the week
of the fever, and from one to three weeks more in bed may be necessary
for him to regain his strength. But the chief risk and danger are
usually over within a week or ten days at the outside.

Violent and serious as are the changes in the lung, it i