106 Tuberculosis. 



gressive tuberculosis. Inhalation and feeding experiments showed 

 the slight virulence of the human tubercle bacillus for cattle. 



In the experiments of Nocard, Meyer, Calmette and Guerin 

 and Zwick, the inoculation of tubercle bacilli of bovine origin into 

 the milk ducts resulted in a tuberculosis of the udder with rapid 

 emaciation of the animal, terminating in death ; whereas the bacilli 

 of human origin produced only a passing inflammatory irritation, 

 and an interstitial atrophy of the udder. Calves which nursed on 

 these latter infected udders remained healthy (Zwick and Maier), 

 or on the other hand (in one case of Zwick) intestinal tuberculosis, 

 with tuberculosis of the mesenteric lymph glands, developed. At 

 autopsy undertaken 20 weeks after the infection, the udder of the 

 cow showed atrophy with miliary tuberculosis, without however 

 typical tuberculous changes in the regional lymph glands. 



From these results the conclusion may be drawn that tubercle 

 bacilli of human origin are only very slightly dangerous for cat- 

 tle. It should be considered however that occasionally after artifi- 

 cial infections the bacilli may persist in the infected region, with 

 or without marked local or at times even generalized changes. 

 Calves may develop intestinal tuberculosis or tuberculosis of the 

 mesenteric lymph glands as a result of ingesting a large amount of 

 tubercle bacilli of the human type. 



Almost the same relation exists in man towards the bacillus 

 of bovine tuberculosis. The principal dangers threatening man 

 are through the possibility of infection from affected human beings, 

 and less so to the possibility of infection with diseased products of 

 animal origin, as for instance milk. The possibility of tuberculosis 

 infection through animal products is presented with remarkable 

 frequency, as may be seen from the above statements; still the 

 rarity of infection with the bovine type is quite striking. 



Hogs which become readily infected with the bovine type are very frequently af- 

 fected by the ingestion of skimmed milk containing tubercle bacilli. 



In northern Germany some of the herds show an infection of 50-60, occasionally 

 even up to 90%. The experience at the tuberculosis eradication stations indicated that 

 by the elimination of cattle affected with open tuberculosis a marked reduction was 

 obtained in tuberculosis of hogs, and that this measure in association with pasteuriza- 

 tion of the skimmed milk, offers a certain remedy against the spread of tuberculosis of 

 hogs. 



The same opportunity which is afforded hogs to contract- 

 tubercle bacilli from the feeding of skimmed milk, would apply 

 to man. The relative infrequency of the infection of man with 

 the bovine type of tubercle bacillus is not the result of a milder 

 virulence of the bacilli but is due to the previous boiling of the 

 milk. Convincing observations have also been made on this point. 



However before entering into a discussion of these, it will be 

 advisable to illustrate further the possibility of infection for man 

 from the standpoint of the port of entry, and also show the relative 

 condition existing between the necessary infective quantity of 

 bacteria and the establishment of the disease. 



