598 PATHOGENIC MICROORGANISMS 



that in 1894 the deaths in Germany from all other infectious diseases 

 amounted to 116,705, those from tuberculosis alone to 123,904. Similar 

 statistics might be chosen from the health reports of any large city. 

 While the disease is less common in rural districts than in large towns, 

 the difference is not so striking as is generally supposed. 



Kober 32 states that, owing to active measures of prevention, the 

 death rate from tuberculosis has been reduced from 326 per 100,000 in 

 1888 to 147.6 in 1913, which he says means that, if the former rate of 

 mortality had been continued "the number of deaths from this disease 

 last year (1914) would have been 322,027, instead of 143,000," meaning 

 the saving of over 179,000 lives. 



Although there has been much discussion concerning the different 

 methods of infection, there seems to be very little doubt at the present 

 time that inhalation is the most common means of human infection. 

 In coughing, expectoration and sneezing, small droplets of fluid in 

 which all kinds of microorganisms are found, are sprayed into the air, 

 and these may be deposited upon the mucous membranes of people 

 in close contact with the disease. The striking distance of such droplet 

 infection is not very large, but is, as Kober points out, particularly 

 dangerous because the bacilli thus enter the respiratory passages 

 directly from body to body. In addition to this, the tubercle bacilli 

 may remain alive in dust sufficiently dry to be blown about by draughts 

 and winds. Although the bacilli are not spore bearers, their acid-fast 

 nature renders them somewhat more resistant to desiccation and sun- 

 light than are most other germs. 



Next to direct inhalation, the most frequent method of transmission 

 is probably through the digestive tract. Such infection may take place 

 by direct contamination of food from the expectoration and saliva of 

 consumptives or by indirect infection of food, and milk, through the 

 agency of fingers, flies, etc. 



Milk Infection. The question of intestinal infection, however, is 

 particularly important in connection with transmission of bovine tuber- 

 culosis to man through the agency of infected milk. The general public 

 has probably very little idea of the frequency of tuberculosis in cattle. 

 In a community supervised more closely than usual, the work of Public 

 Health Service bacteriologists in Washington, revealed 6.72 per cent of 

 samples of market milk infected with tubercle bacilli. This percentage 

 is probably very much lower than that which would naturally be found 

 in districts with a less well-developed dairy supervision, and in some 



82 Kober, Kep. No. 309, U. S. P. H. S. Keports, October, 1915. 



