292 THE AMERICAN MONTHLY [Oct-, 



HEREDITY DOUBTED. 



The popular idea that tuberculosis is generally inherited 

 cannot, from a bacteriological standpoint, be subscribed 

 to. While we do not say that the direct transmission of 

 the disease from parent to offspring is impossible, yet we 

 do aflSrm that this is at least of comparatively infrequent 

 occurence. It is true that a specially vulnerable or in- 

 vulnerable type of tissue may be and is inherited, the 

 former rendering the individual prone to infection, the 

 latter conferring partial or complete immunity from in- 

 fection by the bacillus tuberculosis. In the one case the 

 seed, when sown, falling on good ground, bears fruit not 

 -au hundred, but many million fold ; in the other, falling 

 by the roadside or on stony ground, either fails of growth 

 altogether or develops to a limited extent only. 



HOW THE BACILLUP GROAVS. 



Having once gained access to vulnerable tissues whether 

 that vulnerability has been inherited or acquired, the 

 irritation set up by the growth and multiplication of the 

 bacilli, aided by the poisonous chemical products 

 elaborated in their cells and from the albuminoids in the 

 tissues of the host, little nodules or new growths are 

 developed which constitute the essential lesions of tuber- 

 culosis. These new growths or tubercles, as they are 

 called, have a tendency to undergo caseous degeneration 

 and break down, and the detritus, containing large num- 

 bers of the l)acilli, is thrown off with the ssputum incases 

 of pulmonary tuberculosis. If the sputum thus contami- 

 nated is allowed to soil the floor and become dry and 

 pulverized, the air of the room, laden with dust bearing 

 the spores of the bacilli, becomes a source of danger to 

 the non-tuberculous persons in the apartment, as well as 

 the patient himself, whose chances of recovery are dimin- 

 ished by reason of constant reinfection through germs 

 which nature has once expelled. 



