BACILLUS OF TUBERCULOSIS. 281 
attention may be drawn to the fact that rooms which 
have been recently occupied by consumptives are not 
infrequently the means of producing infection (as has 
been clinically and experimentally demonstrated) from 
the deposition of tuberculous dust on furniture, walls, 
floors, etc. Fliigge has recently drawn attention to the 
fact that in coughing, sneezing, etc., very fine parti- 
cles of throat secretion are thrown out and carried by 
air currents many feet from the patient and remain 
suspended in the air for a considerable time. This 
is another means of infection, but probably an in- 
frequent one. We have now to encourage us a mass 
of facts which go to show that when the sputa is care- 
fully looked after there is very little danger of the 
infection of others except by close personal contact. 
Individual Susceptibility. It is believed by many 
that in demonstrating the possibility of infection in 
pulmonary tuberculosis its occurrence is sufficiently 
explained; but they leave out another and most impor- 
tant factor in the production of an infectious disease 
—individual susceptibility. That this susceptibility, 
or ‘‘ predisposition,’’ as it is improperly called, may 
be either inherited or acquired is now an accepted 
fact in medicine. It is even thought that the phys- 
ical signs and characters—the phthisical habit—which 
indicate this susceptibility can be externally recog- 
nized. Whatever may be the opinion with regard to 
these outward signs, there is no doubt that personal 
susceptibility is of the greatest importance in the pro- 
duction of this disease. Unquestionably, vast differ- 
ences exist in different individuals in the intensity 
of the tubercular process in the lung. That this does 
not depend chiefly upon a difference in virulence of 
