fection could be prevented, the element of heredity could be
practically disregarded.

We are inclined to regard even the well-marked tendency of tuberculosis
to attack a considerable number of the members of a given family to be
due largely, in the first place, to direct infection; secondly, to the
fact that that family were all submitted to the same unfavorable
environment in the matter of food, of housing, of overwork, or of the
New England conscience, with its deadly belief that "Satan finds some
mischief still for idle hands to do."

Upon direct pathological grounds nothing is more definitely proven than
that the actual inheritance of tuberculosis, in the sense of its
transmission from a consumptive mother to the unborn child, is one of
the rarest of occurrences. On the other hand, the feeling is general
that, inasmuch as probably four-fifths of us are repeatedly exposed to
the infection of tuberculosis and throw it off without developing a
systemic attack of the disease, the development of a generalized
infection, such as we term consumption, is in itself a sign of a
resisting power below the average. Should such an individual as this
become a parent, the strong probability is that his children--unless, as
fortunately often happens, their other parent should be as far above the
average of vigor and resisting power--would not be likely to inherit
more vigor than that possessed by their ancestry. So that upon _a
priori_ grounds we should expect to find that the children born of
tuberculous parents would be more susceptible to the infection to which
they are so sure to be exposed than the average of the race. So that the
marriage of consumptives should, unquestionably, upon racial grounds, be
discouraged except after they have made a complete recovery and remained
well at least five years.

To sum up: while the earlier steps of civilization unquestionably
provide that environment which is necessary for the development of
tuberculosis, the later stages, with their greatly increased power over
the forces of nature, their higher intelligence and their broader
humanity, not merely have it in their power to destroy it, but are
already well on the way to do so.

CHAPTER VIII

THE GREAT SCOURGE

Not only have most diseases a living cause, and a consequent natural
history and course, but they have a special method of attack, which
looks almost like a preference. It seems little wonder that the
terror-stricken