TUBERCULAR DISEASE. 197 



was sufficient to account for the prevalence of the 

 disease. Indeed the wonder was, not that so many 

 suffered, but that more did not suffer from a disease, 

 the germs of which were to be found on every hand. 

 This was the position taken up by some immediately 

 after Koch's discovery, but already opinion on the 

 subject is toning down, and at present there are 

 very few who do not admit the existence of a pre- 

 disposition to tubercular disease, which is hereditarily 

 transmitted. 



It has been proved conclusively that tubercular 

 disease can be conveyed from individual to individual, 

 apparently regardless of temperament or diathesis, 

 by the introduction of the tubercle bacillus into the 

 system, but that there exists a diathesis which pre- 

 disposes the owner to the attack of this particular 

 disease germ, there can be no possible doubt. That 

 this peculiar constitutional state is a degeneration, 

 that it is, like every other degeneration, hereditary, 

 and that it is frequently associated, both in individual 

 and family, with other degenerate conditions, such 

 as idiocy, insanity, deaf-mutism, cancer, drunkenness, 

 epilepsy, and crime, it is now my business to prove. 



It is impossible to guess to what this great discovery 

 of Koch's may lead in the near future. Since the 

 bacillus can be cultivated outside the body in arti- 

 ficial media, there is no reason why, by varying the 

 conditions under which it is so cultivated, the germ 

 itself should not be altered in character and rendered 

 less virulent. This might lead to protective inocula- 



