324 BOAKD OF AGRICULTURE. [Jan. 



begin in the lungs, it is to be supposed thtit the infection in 

 all these cases has taken place in the manner suggested, — 

 by the inhalation of phthisic sputum dried and made into 

 dust. The second principal source for the tubercle-bacilli 

 — viz., tuberculosis of the domestic animals — appears not 

 to have anything like the importance of the phthisic sputum. 

 The animals, as is well known, produce no sputum, so that 

 during their life no tubercle-bacilli get from them into the 

 outer world by means of the respiratory passages. Also in 

 the excrement of tuberculous animals the bacilli appear to 

 be only exceptionally present. On the contrary, it is a fact 

 that the milk of tuberculous animals can cause infection. 

 With the exception of this one way, therefore (^. e., 

 through milk) , the tuberculous virus can only have effect 

 after the death of the animal, and can only cause infection 

 by the eating of the meat. The same conditions hold for 

 the milk of cows suffering from ' perlsucht.' Before all 

 things, if infection is to take place, it is necessary that the 

 milk contain tubercle-bacilli ; but this appears to be the case 

 only when the milk-glands themselves are affected with the 

 disease." These were the opinions of Dr. Koch in 1882 

 (opinions, experiments and observations of other scientists 

 will appear further on in this paper). If infection from 

 tuberculous animals does not appear to be frequent, it must 

 by no means be underrated. 



In the statistics presented by Dr. Brush before the New 

 York Academy of Medicine, April, 1889, he says * that, after 

 close study for several years of the affection, including a 

 consideration of all accessible statistics, and the habits of the 

 people among whom it prevails, he has arrived at the con- 

 clusion that the only constantly associated factor is found in 

 the in-bred bovine species. In the discussions that followed 

 the paper, and the objections raised. Dr. Brush said that he 

 believed that the disease was originally derived from the 

 bovine spesies, and that not less than fifty per cent of all 

 dairy cattle were affected with it; and, as to the connection 

 with the human species, statistics showed that, wherever 

 there was a race of people without cattle, phthisis or tuber- 

 culosis was not known. 



* Boston " Medical and Surgical Journal," cxx., p. 467 et seq. 



