EXPERIMENT STATION BULLETINS. 



317 



absolute tests that were carried out and the seventeen positive results that wore 

 obtained, the proportion of milks from the Hackney District containing tubercle bacilli 

 was found to be 22 per cent. 



I am, yours faithfully, 



ALLAN MACFADYEAN, M. D., Director." 



The writer has subjected fifty specimens of milk secured from difi'erent parts of 

 the State of Michifi'an to inoculation tests for tubercle bacilli. Sixteen, of these 

 samples came from cows whicli reacted to tuberculin. Jn only one case did the milk 

 set up tuberculosis in the guinea pigs and this milk came from one of the sixteen 

 known tuberculous animals. Periodical tests were made of the milk from the 

 tuberculous cows at the College, resulting in only one sample of tuberculous milk. 

 This sample came from a cow two or three days before she died of tuberculosis, but 

 which at previous tests for tubcicle bacilli in her ifiilk had given negative results. 

 Upon the examination of her udder after death, there were signs of incipient tubercu- 

 losis. This work would indicate that in all probability the presence of tubercle bacilli 

 in milk is not a common occurrence in the State of Michigan, but, although rare, it by 

 no means bespeaks indill'erence to the dissemination of this disease through the milk 

 supply. As long as this experiment station had milking cows which had responde-l to 

 tuberculin in its possession, occasional tests were made of the milk from these 

 cows. Thirteen cows have entered into these tests, but none of them have ever given 

 signs of possessing tuberculous lulders, with the exception of the one named above. 

 All but four liave been slaughtered up to the time of writing and careful post-mortem 

 examinations were imable to detect anything of a tuberculous nature in the udder. 



An experiment was undertaken at this laboratory to study the distribution of 

 tubercle bacilli in milk and its products. Inasmuch as there was no milk containing 

 tubercle bacilli from a naturally infected source, it became necessary to render the 

 milk tuberculous by artificial means. To accomplish this, lung tissue was secured 

 from a tuberculous cow which had run down very rapidly with the disease and had 

 been killed. The lungs were a solid mass of hard tubercles, with here and there a 

 tubercle containing creamy pus. About six pounds of this tissue was chopped very 

 fine, then transferred to a meat press. In the meat press some water was added to 

 it to moisten it and then pressure was applied. Together with the water, there was 

 obtained about one pound of juice from tliis mass. This extracted juice was added 

 to 120 povmds of morning's milk and thoroughly mixed. The microscopic examination 

 of the expressed juice revealed numerovis tubercle bacilli and upon an examination of 

 the milk after the addition of the expressed juice, a marked diminution was notice- 

 able. The milk was then passed through, after being mixed with the expressed juice, 

 a Mikado Separator. A microscopic examination was made of the slime, skimmed 

 milk, cream, butter made from the cream, and the buttermilk. An attempt was made 

 to estimate the relative number of tubercle bacilli in these difi'erent products. To do 

 this, a small platiniun loop was used, and as nearly as could be estimated, definite 

 quantities were taken from each of the products. Twelve cover-slips were made from 

 each product and eacli cover-slip was allowed fifteen minutes' time in counting tubercle 

 bacilli found in the specimen. The figures in the following table represent the number 

 of tubercle bacilli counted in each specimen during the alloted time. While this table 

 may not represent the exact proportion existing, it doubtless approximates the truth : 



^ 



Fxpresspd tissue juice 



-Alilk after juice was adfleri 



Slime after passing separator 



Skimmed milk after ])assiiiK separator 



Cream after passing separator 



Hutter made from i^ream 



Buttermilk from butter 



282 

 5 

 6 

 6 

 

 

 



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P. I 



^ i 



o I 



o 



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369 

 12 

 57 

 

 4 

 

 2 





 ID 



s 



O 



327 

 15 

 6 

 

 1 

 

 6 



a 

 o 



S 



'a 



a. 



240 

 16 

 

 6 

 

 

 



196 

 

 27 

 2 

 1 

 2 

 3 



390 

 

 27 

 

 4 

 1 

 o 



132 

 14 

 12 

 2 

 1 

 2 

 3 



be 



is 



138 177 



11 

 102 

 4 

 

 

 5 



01 

 24 1 

 2I 

 6{ 

 61 

 61 



300 

 4 

 12 

 1 

 4 

 4 

 



522 

 4 

 27 

 3 

 2 

 2 

 



S. 



^ 



288 3360 



2 83 



69' 369 



13i 38 



23 



4i 21 



3, 29 



