230 Bulletin 158 



one of thecowsof the University dairy, two species of micrococci 

 and one of a streptococcus were found to persist for several 

 months. The examinations made at different times showed first 

 one and then the other species to predominate in numbers. 

 After about ei^ht months, however, the micrococcus disappeared 

 from one quarter, leaving the streptococcus only, but the micro- 

 coccus remained in the other quarters. In another animal a 

 staphylococcus has persisted in the fore milk for over eight 

 months. The fact to be emphasized is that certain species of 

 bacteria sometimes do persist in the milk ducts. 



The question has often been asked if the bacteria which cause 

 the taint in the milk do not pass through the tissues of the ani- 

 mal from the intestinal tract to the udder. This question has 

 doubtless been suggested by the fact that frequently after the 

 cows begin to drink from stagnant pools, the taints and " gassy " 

 curds begin to appear. The frequent detection in the milk of 

 flavors and odors characteristic of vegetables which the cows have 

 eaten, such as garlic or turnip, ma}" have suggested that bacteria 

 could in like manner pass into the milk. The belief centered in 

 the affirmative answer to this question is so strongly entertained 

 by some dairymen that a word of explanation seems necessar3\ 



Some of the early hypotheses regarding bacteria in the animal 

 body might be construed to mean that such a procedure w^as pos- 

 sible, but the fact is now well established, supported by the 

 results of many investigations, that bacteria do not pass from the 

 digestive tract to the various glands of the body so long as the 

 animal is in a perfectly healthy condition. This does not imply 

 that such a passage does not under certain abnormal conditions 

 take place, but that it is a common or even a rare normal occurrence, 

 must in the light of our present knowledge, be unhesitatingly 

 denied. The occurrence of tubercle or anthrax bacilli in the milk 

 is not an analogous case, for in these diseases, the bacteria are 

 already within the animal body where they can be carried to vari- 

 ous parts by the blood and lymph in their respective vessels. 



In order to bring positive evidence to support this reply, two 

 experiments were made to test the power of bacteria to pass from 

 the intestine to the udder. The fore milk of two cows was 

 carefuUv examined and the normal bacterial content determined. 



