THE RESPIRATORY ORGANS 335 



546. Within the last few years a great deal has been said and 

 written on tuberculosis. The general belief is that the microbe or 

 parasite that caused the disease in the human subject and the 

 domestic animal is one and the same. The late Professor Koch, 

 the discoverer of the tubercle bacillus, as well as of the diagnostic 

 agent tuberculin, however, startled the world in 1901, when he 

 made it known at the Congress on Tuberculosis, held in London, 

 that he had failed to infect animals with tuberculosis when they had 

 been inoculated with the human bacilli, and that, after various 

 experiments, he ' felt justified in maintaining that human tubercu- 

 losis differs from bovine, and cannot be transmitted to cattle.' 

 Although not an experimenter, I have for years thought and said 

 that there must be great difference between the two bacilli, and 

 the matter is still doubtful. My reason for holding this opinion is 

 that farmers, their families and servants — both male and female — 

 who work among and tend cattle so affected, and who daily drink 

 quantities of milk in a warm state, newly drawn from the udders of 

 tubercular cows, are healthy people, and, as a class, it would be 

 difficult to find another so free from consumption ; and although the 

 disease can be communicated from one cow to another living in close 

 habitation, yet I cannot favour the idea that it is transmittible to the 

 human subject by either drinking the milk or eating the flesh of 

 tubercular animals, as for ages past an indirect practical test has 

 been and is still carried on by these people drinking milk from 

 affected beasts without any ill-effect ; while I have seen butchers 

 who trade in these tubercular subjects eat the flesh of tubercular 

 carcasses, both raw and cooked, without taking any harm — in fact, 

 they are splendid specimens of healthy subjects. The active 

 immunity is possibly due to the opsonic condition of the blood of 

 these people, which prevents them taking the disease. 



547. With reference to the hereditary nature of the disease, 

 the late Professor Koch says : ' Though hereditary tuberculosis is 

 not absolutely non-existent, it is nevertheless extremely rare '; 

 and again he says : ' I should estimate the extent of infection by the 

 milk and flesh of tubercular cattle, and butter made from their milk, 



