NEW YORK MILK COMMITTEE 187 



and that it is the only known infectious disease from which no 

 vertebrate species is immune. Although tuberculosis has re- 

 ceived more attention than any other disease from investiga- 

 tors in pathology, bacteriology, and hygiene, our knowledge of 

 it is in some respects extremely rudimentary. As he observes, 

 we know so little about its period of incubation that we are 

 unable to determine whether those are right who believe that 

 tuberculosis arises from infection that may enter the body at 

 any time of life, or those who believe that it almost constantly 

 develops from latent tubercle bacilli taken into the body dur- 

 ing the milk-drinking period of life. This is perhaps the crux 

 of the whole tuberculosis problem, and it ought probably to be 

 accorded more weight by those who are inclined to attribute 

 all tuberculosis to discovered exposure to human infection. 



On the question of infectivity and hereditary influence the 

 report contains some valuable remarks. We know, Dr. 

 Schroeder says, that the revelations of post mortem examina- 

 tions prompt the conclusion that few persons escape the tu- 

 bercle bacillus, while it is agreed that tuberculosis develops with 

 peculiar frequency when the drain on the mental and physical 

 forces is greatest rather than during periods following excep- 

 tional exposure to infection. But we know further, says this 

 authority, that the children of tuberculous parents succumb 

 to tuberculosis not necessarily as children more commonly 

 than those of healthy parents. This is a disputed conclusion. 

 With regard to infectivity Dr. Schroeder thinks that tubercu- 

 losis is not so common amongst persons unusually exposed to 

 infection as we might expect; and that men with tuberculous 

 wives and women with tuberculous husbands, when their family 

 records as regards tuberculosis are clean, contract the disease 

 so rarely that their presumably intense exposure cannot be 

 said to infect them more frequently than persons in general 

 become infected. The tubercle bacillus is, he believes, peculiar 

 in that it is prone to remain alive and virulent for long periods 

 in circumscribed, closed tuberculous lesions and that it may re- 

 main in the body indefinitely without causing conditions which 

 may be identified as tuberculosis. Finally, he argues that tu- 

 bercle bacilli in dairy products are either in a fresh or well- 

 preserved state, and that they are directly introduced into the 

 body with the use of indespensable articles of food, while tuber- 



