126 ANNUAL REPORT OP THE Off. Doc. 



termed clinical observation. Numerous eases were recorded to 

 show thai people had become infected with tuberculosis from cattle, 



through wounds upon the hands. Some of these eases appear to 

 lack none of the accuracy of a deliberately planned scientitie experi 

 nieiit, the possible sources of error having been so carefully excluded. 

 There are also numerous cases of record which are believed to show 

 that tuberculosis has been conveyed through milk from cows to 

 children. Some of these observations appear to have been made 

 with such care and completeness as to exclude all probability of 

 error. For example, I am personally familiar with the following 

 case: A young couple shortly after marriage moved into an entirely 

 new house, in which their hist child was born. The parents were 

 thoroughly healthy, rugged people, entirely free from the slightest 

 suspicion of consumption and, so far as known, there was no taint 

 of consumption in the family of either. The single servant was a 

 healthy young person. The child, which was fed on the milk of one 

 cow, died of tuberculosis when about eight mouths old. Attention 

 was then directed to the cow and it was found that she was rather 

 extensively tuberculous. 



Those who oppose the view that tuberculosis may be transmitted 

 from the bovine to the human subject call attention to the possi 

 bility of error in all of the great number of observations similar to 

 the one that I have just given. Their criticism is that such observa- 

 tions do not prove that a child was infected through the milk unless 

 all other possible sources of infection are rigidly excluded. They 

 say that the child may have contracted tuberculosis from a human 

 subject through some unseen and unsuspected channel, that the 

 germ may have been brought into the house by the grocer's boy or 

 by the baker or upon the hem of the skirt of a visitor. Such possi- 

 bilities must be admtted, but it cannot destrov the conclusion that is 

 usually drawn from these observations. 



If we assume, merely for the sake of argument, that 10 per cent, 

 of the tuberculosis of childhood is derived from cattle, it should not 

 be in the least surprising, in view of the extent to which consump- 

 tion prevails, and in view of the long time usually required for its 

 development, the months or years that may elapse from the time 

 that the infection is acquired until the first symptoms of illness 

 appear, that the route of passage of infection from the cow to the 

 baby should be unrecognized and unobserved. That this observa- 

 tion should not be made is still less surprising in view of the fact 

 that for centuries tuberculosis has been passing from one person 

 to another, and is chiefly propagated in this way, but it is only in 

 the most recent times, that this essential fact has been recognized. 

 Even now, there are a few unconvinced persons who deny it. 



The recent great additions to our knowledge of the bacteriology 

 of tuberculosis, which have made it possible to distinguish the 

 bovine from the human type of tubercle bacillus, have made it pos 

 sible to obtain exact and convincing evidence as to whether the 

 bovine bacillus is capable of causing disease in the human subject. 

 Koch recognized this point, as Smith had before him, and suggested 

 that experiments be made to determine just how often people are 

 infected by the bovine bacillus, the possibility of which he did not 

 deny, although he regarded such infection as exceedingly rare. 

 Studies on this point have been made in nearly all civilized countries 



