president's address — SECTION I, 247 



and powdered sputum from four to seven days (in the dark 22 days), 

 in cloth fibres five to 10 days, and in street dust three to eight days (28). 

 It is strongly influenced by drying and by light, and it is probably 

 these factors rather than exposure to the air that causes its slow 

 decease, (e) 



The general principles of the dispersal of bacteria by coughing, 

 etc., apply to the bacillus of tuberculosis as to other bacteria. Fliigge 

 is rather incUned to belittle the danger of infection, as he says that if 

 a patient coughs into the hand or into a handkerchief, there is little 

 danger of infecting other people if the latter are over a yard away. 

 Then he lays down a general rule that workers in a workroom are quite 

 safe from infection by their confreres if that space is maintained, that 

 is to say, if each worker occupies one square metre of floor space, and 

 if the consumptive coughs into his hand or into a handkerchief. As 

 a rule a worker has both hands occupied while working, and cannot 

 be expected to liberate a hand or find a handkerchief when a sudden 

 fit of coughing seizes him. Laschschenko (27) found that while the 

 coarser particles might be caught in the hand, the finer ones remained 

 suspended, and could be detected at the ceiling of a room, 10 yards 

 from the individual who had emitted them. Heymann (12), after 

 showing that these fine particles can bring about tuberculosis in a 

 guinea-pig, asks if a man has not a far greater chance of contracting 

 the disease than an animal which breathes so feebly as the guinea-pig ? 

 The question is pertinent, but let us first consider the matter. 



The air which is exhaled during respiration is warm, and rises 

 above the head. The same would happen if the cough or sneeze were 

 directed outwards and forwards. But the sneeze is invariably directed 

 downwards, and so also is the deep cough. The warm air, with the 

 accompanying spray droplets, will, therefore, be sent towards the ground 

 and, being given out with some force, will be mixed with the surround- 



albuminoids. and the physical properties of the milk generally, may be altered as 

 little as possible. The commercial pasteuriser aims at avoiding the formation of 

 a skin or film of dried milk, to kill the bacteria in which an exposure to a higher 

 temperature or at a low temperature for a longer time is necessary. In America, 

 Theobald Smith (29) found an exposure for 1.5-20 minutes at 00° C. was enough 

 to kill Bac. tuherrMosis in milk ; Russell and Hastings (30) recommended the longer 

 limit. In Theo. Smith's experiments, the bacteria in the " skin " were virulent 

 after an hour's heating at 00°. In Sweden, Barthel and Stenstrom (31) determined 

 that an exposure of I'o to 2 minutes at 80° was ample, provided that a suitable 

 apparatus was employed. This time and temperature appear to be generally 

 employed in Denmark. The exposure which I have cpioted gives the limits with 

 the suitable times between which pasteurisation occurs. 



(e) Not only does it persist under adverse conditions longer than the less 

 robust bacteria, but it is also more slowly affected by disinfectants. In this con- 

 nection Steinitz (28), from a consideration of his experiments, suggests that sputum- 

 bearing material should be boiled, burnt, or soaked in mercuric chloride solution 

 (1-1000) for five hoiu-s. In the cases of rooms or clothes, the parts which have 

 been visibly contaminated should be moistened with mercuric chloride solution 

 (2-1000), and the other parts disinfected by means of formalin vapor, giving an 

 exposure of from three to seven hours with vapor of double concentration, i.e., 

 using 2 '5 grams of formaldehyde for everj' cubic metre of space. 



