?264 REPORT OF THE LEPROSY COMMISSION:
showing any signs of proliferation. They are in fact true
parasites. Animals, such as guinea-pigs, are infected with the
greatest ease. Again, the tubercle bacillus, as Cornet6 has
shown, is widely distributed throughout space without any loss
of vigour. À priori one would be inclined to assume that
tuberculosis must be a highly contagious disease. But ex-
perience teaches beyond doubt that of healthy individuals
living in the immediate neighbourhood of phthisical patients,
by no means all become affected; "in fact perhaps only
slightly more than would become affected if the opportunity
for infection were less."7 The disposition of an individual is
of the highest importance in bringing about a tubercular infec-
tion. In fact, as Flügge says, "the disposition actually gov-
erns the mode of diffusion of tuberculosis." And that in
tuberculosis the danger of infection is so small is chiefly ex-
plained by the fact that the existence of the bacillus, and its
introduction into the human body, are not sufficient to bring
about the infection without the necessary individual disposi-
tion.
The causes and nature of such disposition may be unknown,
but that it exists no one denies, and its bearing on contagion is
evident. The experiments of Monti, Leo, Charrin, Roger, and
E. Klein8 have thrown much light on the nature of disposition
and susceptibility. These will be more fully alluded to in
Chapter VI. The greater the prominence given to this dis-
position, the less the absolute influence of contagion becomes.
"We notice the best example of an individual disposition in
tuberculosis, where the greater or smaller collection of resistent
germs around the human body has, as we know from experience,
a subordinate importance in the diffusion of the disease. It has
become an almost general practice in tuberculosis to counteract
(6) G. Cornet: Ueber Tuberculose. Leipzig; and footnote on page 287.
(7) C. Flügge: loc. cit., page 219.
(8) Nineteenth Annual Report of the Local Government Board, 1889-90, Sup-
plement, page 217.