78 EXPERBIEXT STATION. [Jan. 



lias 1)0011 carriod on to (lotcnnino to what oxtont Tinsterilizcfl, 

 mixed milk from herds of common dairy cattle, not tuberculin 

 tested, may be responsible for the transmission of bovine tuber- 

 culosis. The work is nearly completed and will appear as a 

 separate contribution to the report, or in bulletin form, at an 

 early date. 



The general plan of the experiment has been to make it of 

 a practical nature by carrying it out under conditions as nearly 

 like those as are found in the farmers' stables and herds, and at 

 the same time sufficiently guarded against error to give it a sci- 

 entific value in the determination of the relation of milk as an 

 agency for the transmission of the disease under ordinary farm 

 conditions. The investigation has its practical application in 

 the eradication of tuberculosis from herds by the use of tubercu- 

 lin as a diagnostic and by every other known means. If the 

 disease is to be stamj^ed out in a herd of cattle it is not alone 

 sufficient to discover and remove those animals already affected, 

 but also to discover and remove the source from which the infec- 

 tion comes. The exix^riences of the past of those who have tried 

 to rid a herd of tuberculosis by the use of tuberculin and by 

 slaughter of affected animals and disinfection of stables, have 

 shown that it is not easily accomplished, owing to the difficulty 

 of detecting the origin of the cases that are almost certain to 

 appear after diseased animals have been removed and the stable 

 thoroughly and effectively disinfected. It frequently happens 

 that after a variable period of several weeks to as many months 

 more indications of the existence of the disease are discovered 

 among the animals which necessitate the repetition of the tuber- 

 culin testing and disinfection. The possible source of reinfec- 

 tion has in some instances been directed to milk from infected 

 and non tuberculin-tested animals not showing marked physical 

 symptoms of tuberculosis, but excreting tubercle bacilli in their 

 milk. 



In the case of largo dairy herds or those of large public insti- 

 tutions, where sufficient milk is not produced by the herd at 

 all seasons to supply a trade or for home consumption, it fre- 

 quently happens that milk from untested cattle is purchased and 

 brought onto the farm, and possibly some remaining unsold or 

 unused is fed to calves or hogs and proves the source of the 



