EPIDEMIOLOGY OF TUBERCULOSIS. 



By Robert Koch. 



(A lecture given before the Academy of Sciences of Berlin at its session of 

 Apr. 7, 1910. )* 



Iiwestigations into the epidemiology of tuberculosis have brought 

 out some facts of interest and also of practical importance which will 

 be the subject of the present paper. 



First some preliminary remarks concerning the character of the 

 investigations. They are in all essential respects statistical. If at- 

 tempt had been made to cover the entire field, insurmountable diffi- 

 culties would have been encountered. 



Tuberculosis, as is well known, manifests itself in the most varied 

 ways, frequently occurring in such insignificant and latent forms that 

 no sharp distinction can be made between those affected and healthy 

 persons. For that reason it was necessary to limit the present dis- 

 cussion to a form that is sufficiently well marked and also diagnosed 

 with certainty. These conditions are best fulfilled by tuberculosis of 

 the lungs, the so-called pulmonary consumption. This form is also 

 to be recommended for such investigations because it is by far the 

 most frequent, the one chiefly concerned in disseminating tuber- 

 culosis and therefore the most important in medical practice. 



A still further limitation must be made. Owing to the long dura- 

 tion of pulmonary consumption and the difficulty of making sharp 

 distinctions as to its beginning, we must disregard the statistics of 

 illness from this disease and consider only the statistics of death. 

 In these we have original data that are, to a certain extent, trust- 

 worthy, and that may serve as a basis for investigation. 



It is true that this trustworthiness could only be absolutely as- 

 sured if in every case of death by pulmonary consumption the diag- 

 nosis were confirmed by an autopsy made by a competent expert, 



1 According to a manuscript kindly placed at the disposal of the editor of the Zeit- 

 schrift fiir Hygiene und Infections-krankheiten after the death of the author. Translated 

 from Zeitschrift fur Hygiene, Leipzig, 1910, vol. 67, Part 1, pp. 1-18. 



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