BUREAU OF ANIMAL INDUSTRY. 135 



animals are intiCKluced from without but which are maintained by 

 raising the calves born in them. A number of young cattle are now 

 being held under observation with special regard to their later abor- 

 tion-disease history. 



Studies regarding the significance of the bull in the spread of 

 abortion disease have yielded only negative results, which, liow^ever, 

 should not be interpreted hastily as justifying the use of bulls from 

 infected herds or with those that have served promiscuously. 



An important fact about abortion disease, repeatedly confirmed 

 by experiment and observation, is that a large proportion of in- 

 fe.ted cows become more or less enduring carriers of abortion bacilli, 

 and though they may seem normal and free from manifest physical 

 signs of the disease they are a constant danger as a means of spread- 

 ing infection. 



A little work has been done with regard to the pathological sig- 

 nificance of the bacillus of infectious abortion disease of cattle for 

 hogs, and as this seems to be a subject of increasing economic im- 

 portance, moi*e work has been planned for the future. 



TUBERCULOSIS. 



The investigations on tuberculosis have been continued, and 

 though nothing essentially new has been discovered, previously re- 

 ported results have received additional confirmation. For example, 

 the evidence we now have shows conclusively that stables which have 

 harbored tuberculous cattle may be sufficiently cleaned, without the 

 use of chemical disinfectants, to make them safe for. healthy cattle. 

 It is not advocated that the use of chemical germicides should be 

 Jibandoned. but the results of the station's experiments indicate that 

 thorough cleaning is more effective than geiTnicides, if either is 

 used alone. The two used together, in the manner in which the sta- 

 tion uses them, the germicide as an adjunct to the cleaning and not 

 tlie cleaning; as an adjunct to the germicide, have a practically un- 

 failing efficiency. 



MISCELLANEOUS WORK. 



Tests for the detection of virulent tubercle bacilli in market cheese 

 have been continued and show that conditions leading to infection 

 previously found in some kinds of cheese have been corrected. 



In addition to periodic tests of the potency and freedom from in- 

 jurious agents of the tuberculin prepared and sold under Govern- 

 ment license, a considerable amount of work was done to devise an 

 improved method for standardizing tuberculin. It is too early to 

 re})ort results of the latter work. 



A large number of small experiment animals were raised at an 

 expenditure much lower than would have been required had they 

 been purchased. As in former years every available portion of the 

 station's land was kept under intense cultivation and a considerable 

 saving thus effected in expenditures for forage. 



