PROCEEDINGS OF SECTION I. 697 



80 far had tlie teaching of the earlier physicians been forgotten 

 that Professor Koch opened his Nobel lecture in December, 1905, with 

 the following words : — " Only 20 years ago tuberculosis, even in its 

 most dangerous form — pulmonary phthisis — was not considered 

 infectious." 



Koch's discovery of the tubercle bacillus settled the matter finally. 

 It is now universally acknowledged that the tubercle bacillus is the 

 sole cause of consumption ; without the bacillus there can be no con- 

 sumption. 



THE SOIL. 



Lest I should overstate the danger of contracting consumption 

 in which we all stand, let me say at once that the tubercle bacillus will 

 not easily grow unless planted in suitable soil. The human subject, 

 debilitated by illness or overwork, by cares and disappointments, or 

 by a faulty mode of living, is the soil on which it best grows. Dark, 

 ill-ventilated, and small dwellings in a crowded neighborhood are the 

 nurseries in which it flourishes. If a man leads a healthy life he will 

 not easily be a prey to consumption. 



HOW THE DISEASE IS SPREAD. 



I would like to give you a clear idea of the way in which consump- 

 tion is spread. I think I cannot do so better than by placing before 

 you a magnified image of a tiny speck of expectoration taken from a 

 tuberculous patient (Plate I., fig. 1). 



You see there are a number of little rod-shaped bodies, stained a 

 red color. These are the tubercle bacilli, and there are a great many 

 of them. 



The actual volume of this little portion of expectoration which 

 you see here, greatly magnified, is a little more than three one- 

 hundredths part of a cubic millimetre, and if you count the number of 

 bacilli in the picture before you you will find that there are 144 of them. 

 If we assume that the amount of expectoration coughed up by this 

 patient in 12 hours was a half Htre (which is not an unusual amount), 

 then in a whole day (of 24 hours) this patient will have thrown out 

 more than four and a half billion tubercle germs. Further, since 1,000 

 tubercle germs measure about four millimetres, if we imagine all the 

 germs coughed up by this patient in a day to be arranged end to end, 

 to make one continuous filament, they would form a thread 11|^ miles 

 in length. 



Think of it, more than 11 miles of living tubercle bacilli in a day. 

 Now the man who was producing these miles of germs travelled to 

 Adelaide from his home, which is about 200 miles away in the country. 

 When I saw him at his lodging he spat indiscriminately upon the floor 

 of the room. He did not stay long in the same house, and he distributed 

 germs wherever he went. This man was a public danger, and I had 

 no power to detain him. When we know that consumption is an 

 infectious disease, which can only be contracted by contact with tubercle 



