DISCUSSION UPON THE DISSEMINATION 

 OF TUBERCULOSIS 



IN HIS OPENING ADDRESS 



Sir PHILIP SYDNEY JONES, M.D., said :— 



The importance of this subject could not well be exaggerated,, 

 tuberculosis being the most widespread, the most disabling and the 

 most fatal of all diseases to which man and animals are subject. 

 He thought that the purpose of the discussion would be best served 

 if he mentioned in brief outline (time would not permit him to do 

 more) (a) the conditions which determine the production of tuber- 

 culosis, (b) the sources from which the infective germ — the tubercle 

 bacillus — is derived, (c) the paths of infection or channels through 

 which the germ enters the body of man and animals, and finally 

 (d) the preventive measures which these considerations suggest. 

 He hoped that those who followed him would take up and elaborate 

 such of the points as may seem to them desirable. First, then, as 

 to the conditions which give rise to tuberculosis — the factors which 

 determine its occurrence. They are at least three — the implanta- 

 tion of the bacillus, the susceptibility of the individual, and the 

 environment. These factors may be conveniently spoken of as 

 the seed, the soil, and the sm-roundings. It is true, of com^se, that 

 the presence of the bacillus tuberculosis is the essential factor — where 

 there is no tubercle bacillus there is no tuberculosis — but the other 

 two factors are of almost equal importance. It is possible that a 

 large dose of very virulent tubercle bacilli alone may give rise to 

 an attack of tuberculosis, but in the large majority of cases there 

 can, I think, be no doubt that the other two factors are present 

 also. Just as in the growth of any plant there must be the proper 

 seed, the suitable soil, and the appropriate environment — the sun, 

 the rain and the wind — so in the production of tuberculosis there 

 must be the specific bacillus, the favourable soil, and the appro- 

 priate surroundings. A few words must be said on each of these 

 factors. 



The bacillus of tubercle is a microscopic vegetable growth 

 which has no habitat outside the bodies of men and animals. It 

 never arises de novo, but is always derived from some pre-existing 

 case of tuberculosis. Freely exposed to direct sunlight its vitality 

 is quickly destroyed, but in a dark, dirty, badly-ventilated room, 

 especially if the air of the apartment is tainted with the exhalations 

 of a number of persons, it may retain its vitality for weeks and 

 even months. The sources from which tubercle bacilli may be 

 derived are the expectoration, the droplets ejected in coughing or 



