76 MILK HYGIENE 



tion. Through the discovery of the prevalence of feed- 

 ing tuberculosis in swine, horses and cattle, veterina- 

 rians have emphasized the great danger that may come 

 to man by the use of meat and, especially, of the raw 

 milk of tuberculous animals. Many physicians have 

 taken the same ground, while others would minimize 

 this danger to a great degree, or combat its existence 

 entirely, by pointing out the great infrequency of 

 primary intestinal. tuberculosis iu man, and they claim 

 that tuberculosis of man, almost without exception, 

 begins in the lungs and is an infection by inhalation. 

 There is still disagreement on this subject. It cannot be 

 denied that there is a remarkable difference between 

 the prevalence of feeding tuberculosis of calves and pigs 

 on the one side, and the prevalence of the unmistakable 

 feeding tuberculosis of man. 



Since avian tuberculosis has been shown to differ 

 from tuberculosis of mammals, and since tuberculosis 

 of dogs is not transmissible to rabbits, but evokes only 

 a temporary local process (Jensen), it has become neces- 

 sary to consider the differences between tubercle bacUli 

 from different sources and, especially, to study experi- 

 mentally the relation of cattle tuberculosis to tubercu- 

 losis of man. Of investigations undertaken in this line, 

 those of Th. Smith and Frothingham are valuable 

 because they show a certain difference ia the bacilli of 

 cattle from those of man and prove that tubercle bacilli 

 of man possess but slight virulence for cattle. This 

 question has become especially interesting since the 

 tuberculosis congress in London in 1901, when Koch 

 gave the results of experiments that he had conducted 

 in connection with Schiitz and, on "the basis of these, he 

 believed he could afifirm that tuberculosis of man is not 

 transmissible to cattle and, on the other hand, that 

 tuberculosis of cattle is probably not transferred to 



