15 



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 (i e.. through milk J, the tuber- 

 culous 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 

 suffeiing fi-om ' 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 Avith the disease. This explains 

 at once the contradictions in the statements of various authors, who have made 

 feeding experiments with the milk from cows suffering from ' perlsucht.' If infec 

 tion from tuberculous animals does not appear to be frequent, it must by no mcaas 

 be underrated." 



Tliis caiitiou is one which was necessary at the time it was written, 

 and its repetition is as necessary now. as ever. What conchisions 

 may be readied in regard to its extreme, importance, are well shown 

 by the statistics collected and presented by Dr. Brush before the New 

 York Academy of Medicine, on April 29, 1889 {Boston Med. and 

 Surg. Journal, cxx. p. 467 et seq.). In this paper the siuthor states 

 that after several years of close study 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 conclusion that the only 

 constantly associated factor is found in the in-bred bovine species. 

 If a community was closely connected with in-bred dairy cattle, 

 tuberculosis prevailed, and, vice versa, if there were no in-bred dair}' 

 cattle there was no tuberculosis. In the discussion following this 

 paper many objections were raised. Dr. Brush went on to say that 

 he believed that the disease was originally derived from the bovine 

 species. He did not believe that less than fifty per cent, of all dairy 

 cattle were affected by it, while the statistics he had qnoted showed 

 that wherever there was a race of people without cattle phthisis was 

 unknown. He believed, furthermore, that if all the cattle in this 

 country were to be killed, the disease would finally die out entirely 

 here. 



Such statements as these are a revelation to the generality of practi- 

 tioners, and may seem to be somewhat forced, but they certainly 

 indicate, together with the statistics upon which they are based, the 

 existence of a greater danger than has been fairly realized. That the 

 danger from the consumption of milk coming from cows affected with 

 tuberculosis has been understood by individuals at least, and that, 

 too, before the auuoiuicement of Koch's discovery, is very well shown 

 by extracts from a letter which I take the liberty of quoting here. 

 The gentleman writing it is a veterinaria'i in practice in Providence, 

 R. I., and the observations were made and the advice given more 

 than ten years ago. That portion of his letter bearing upon the 

 subject in hand is as follows : 



