424 LETTER TO THE TDIE8. 



be permitted to give some account of it in the ' Times/ 

 The address, a copy of which has been courteously sent 

 to me by its author, is entitled ' The Etiology of 

 Tubercular Disease.' Koch first made himself known, 

 and famous, by the penetration, skill, and thoroughness 

 of his researches on the contagium. of anthrax, or splenic 

 fever. By a process of inoculation and infection he 

 traced this terrible parasite through all its stages of 

 development and through its various modes of action. 

 This masterly investigation caused the young physician 

 to be transferred from a modest country practice in the 

 neighbourhood of Breslau to the post of Govern- 

 ment Adviser in the Imperial Health Department of 

 Berlin. 



From this department has lately issued a most im- 

 portant series of investigations on the etiology of in- 

 fective disorders. Koch's last inquiry deals with a 

 disease which, in point of mortality, stands at the 

 head of them all. l If,' he says, ' the seriousness of a 

 malady be measured by the number of its victims, 

 then the most dreaded pests which have hitherto 

 ravaged the world plague and cholera included 

 must stand far behind the one now under consider- 

 ation.' Then follows the startling statement that one- 

 seventh of the deaths of the human race are due to 

 tubercular disease. Prior to Koch it had been placed 

 beyond doubt that the disease was communicable ; and 

 the aim of the Berlin physician has been to determine 

 the precise character of the contagium which previous 

 experiments on inoculation and inhalation had proved 

 to be capable of indefinite transfer and reproduction. 

 He subjected the diseased organs of a great number of 

 men and animals to microscopic examination, and found, 

 in all cases, the tubercles infested by a minute, rod- 

 ehaped parasite, which, by means of a special dye, he 



