led to the general conviction among experts that bacterial
diseases are preventable; and they already are to a large extent
prevented. The dangers of infection and the way to avoid it are
better understood than they used to be. It is barely twenty years
since people exposed themselves recklessly to the infection of
consumption and pneumonia in the belief that these diseases were
not "catching." Nowadays the troubles of consumptive patients are
greatly increased by the growing disposition to treat them as
lepers. No doubt there is a good deal of ignorant exaggeration
and cowardly refusal to face a human and necessary share of the
risk. That has always been the case. We now know that the
medieval horror of leprosy was out of all proportion to the
danger of infection, and was accompanied by apparent blindness to
the infectiousness of smallpox, which has since been worked up by
our disease terrorists into the position formerly held by
leprosy. But the scare of infection, though it sets even doctors
talking as if the only really scientific thing to do with a fever
patient is to throw him into the nearest ditch and pump carbolic
acid on him from a safe distance until he is ready to be cremated
on the spot, has led to much greater care and cleanliness. And
the net result has been a series of victories over disease.

Now let us suppose that in the early nineteenth century somebody
had come forward with a theory that typhus fever always begins in
the top joint of the little finger; and that if this joint be
amputated immediately after birth, typhus fever will disappear.
Had such a suggestion been adopted, the theory would have been
triumphantly confirmed; for as a matter of fact, typhus fever has
disappeared. On the other hand cancer and madness have increased
(statistically) to an appalling extent. The opponents of the