662 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1910. 



culosis occurs only in quite isolated cases, the patients being of Euro- 

 pean or coast origin. At the present time the lowest figure for some 

 regions in Australia is about 7 deaths per 10.000. But this figure 

 is also reached in some sections of our own country, as for example, in 

 the district of Osterode in the Province of Allenstein. 



Such low death rates have only been observed during the last few 

 years, and this leads me to the most notable phenomenon in the epi- 

 demiology of tuberculosis, to which I would especially invite your 

 attention, namely, the almost universal marked decrease in pulmonary 

 consumption which has become evident during the last 30 or 40 years. 



The lowering of the death rate began first in England, and it also 

 happened that the English hygienist Farr was the first who was 

 struck by this and who called attention to it. In our own country 

 Hirsch, the author of the well-known Handbook of Historico-geo- 

 graphical Pathology, was the first to mention it. 



This remarkable phenomenon was at first received with great scep- 

 ticism, and it was alleged that there were either errors in the statistics 

 or that it depended upon the decrease in the general death rate which 

 had been previously noted, though not to the same degree. But as 

 the decrease in pulmonary consumption was shown to occur almost 

 universally and also continued, there remained nothing to do but to 

 acknowledge it as a fact and to find an explanation therefor. 



In order to give an idea of the decrease of consumption, the course 

 of the death rate from that disease in the Kingdom of Prussia may 

 serve as a specially characteristic example. 



It is shown graphically by a curve in Table 2. Up to the year 

 1886 the figures representing the mortality remain with irregular, but 

 not marked variations a little above 30, then begins a decrease which 

 has kept up with but little variation to the present time. In the year 

 1908 the figure fell to 16.24, a decrease of nearly 50 per cent. 



For the German Empire the statistical records do not go back far 

 enough to demonstrate the reduction in consumption in a similar 

 manner. Yet the curve for all Germany resembles, as far as it goes, 

 that for Prussia ; it is somewhat higher, because the States of southern 

 German}' are not as favorably situated as Prussia with regard to the 

 disease. 



The significance of this reduction in consumption will be noted 

 when we observe that if the same relations prevailed now as 30 } T ears 

 ago about 100,000 more persons would die annually of consumption 

 than is now actually the case. It is therefore very important for us 

 to ascertain the causes for this decrease, in order to know whether it 

 is subject to any influence under our control; whether it would be 

 possible, were it arrested, to overcome the obstacle, also whether it 

 would be practicable to hasten its decline beyond the present rate. 



