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 

 riot depend chiefly upon a difference in virulence of 



