germs that normally
inhabit our throats, our intestines, or our immediate surroundings. The
ultimate foundation question of the science of bacteriology is, How did
the disease germs become disease germs? But the question is still
unanswered.

However, fortunately, here, as in other human affairs, imperfect as our
knowledge is, it is sufficient to serve as a guide for practical
conduct. Widely present as the pneumococcus is, we know well that it is
powerless for harm except in unhealthful surroundings. There is another
interesting feature of its life history which is of practical
importance, and that is, like many other bacilli it is increased in
virulence and infectiousness by passing through the body of a patient.
Flushed with victory over a weakened subject, it acquires courage to
attack a stronger. This is the reason why, in those comparatively
infrequent instances in which pneumonia runs through a family, it is the
strongest and most vigorous members of the family who are the last to be
attacked. It also explains one of the paradoxes of this disease, that,
while emphatically a disease of overcrowding and foul air, and attacking
chiefly weakened individuals, it is a veritable scourge of camps,
whether mining or military. When once three or four cases of pneumonia
have occurred in a mining camp, even though this consist almost
exclusively of vigorous men, most of them in the prime of life, it
acquires a virulence like that of a pestilence, so that, while
ordinarily not more than fifteen to twenty per cent of those attacked
die, death-rates of forty, fifty, and even seventy per cent are by no
means uncommon in mining camps. The fury and swiftness of this "miners'
pneumonia" is equally incredible. Strong, vigorous men are taken with a
chill while working in their sluicing ditches, are delirious before
night, and die within forty-eight hours. So widely known are these
facts, and so dreaded is the disease throughout the Far West and in
mountain regions generally, that there is a widespread belief that
pneumonia at high altitudes is particularly deadly.

I had occasion to interest myself in this question some years ago, and
by writing to colleagues practicing at high elevations and collecting
reports from the literature, especially of the surgeons of army posts in
mountain regions, was somewhat surprised to find that the mortality of
all cases occurring above five thousand feet elevation was almost
identical with that of