130 ANNUAL REPOETS OF DEPARTMENT OF AGRICULTURE. 



an abortion. It has been proved that the bacilli may persist indefi- 

 nitely in the udders of cows, and that their presence in this organ 

 is associated in a large proportion of cases with their occurrence in 

 the uterus and placenta at the time of parturition, even when the 

 latter event is wholly unattended with physically observable symptoms 

 of abortion disease. The only known and demonstrated sources of 

 abortion bacilli which can be held accountable for the perpetuation 

 and spread of the disease are the milk of cows with infected udders 

 and the material passed from the vagina by infected cows shortly 

 before, during, and shortly after either an abortion or a parturition. 

 By way of practical application of present knowledge of the disease 

 the bureau advises that healthy cattle should not bo exposed to the 

 raw milk of cows which react to abortion tests, and reacting cows 

 should invariably be removed to special maternity pens or stables 

 some time before they calve, and kept there until all discharges from 

 their vaginas have ceased. Cows which show even the remotest 

 symptoms of a possibly approaching abortion should immediatel}^ be 

 segregated. Abortion bacilli remain ahve and virulent for remarkably 

 long periods in aborted fetuses and afterbirth and discharges from 

 the uteruses of infected cows. 



TUBERCULOSIS. 



Repeated tests were made of the potency and rehability of tuber- 

 cuhn manufactured and sold under Govermnent licenses and permits. 

 The tests proved that most of this product now on the market is 

 satisfactory, and that the estabhshments which manufacture it may 

 be divided into two kinds — those which produce tubercuhn of con- 

 stant potency and those which produce tubercuhn of varying po- 

 tency. As would naturally be expected, the tubercuhn produced 

 by the latter at times is below a reasonable standard. 



Investigations on the control and eradication of tuberculosis among 

 food animals continue in progress. The results obtained again em- 

 phasize that this destructive disease would dechne materially in 

 frequency if relatively simple precautions against its spread were 

 more commonly and thoroughly understood and practiced by owners 

 of hve stock. The recurrence of the disease in cleaned herds, it 

 seems, must be charged to other causes than insufficient disinfection 

 of infected stables, as very Httle disinfection, in addition to thorough 

 cleaning, is required to make a stable from which tuberculous animals 

 have been removed safe for healthy animals. Thorough cleaning has 

 been shown to be of greater importance than the use of chemical 

 germicides. 



Studies regarding the possible spread of tuberculosis by small 

 rodents, such as rats and mice, are being continued, and are giving 

 interesting results which promise to be economically valuable. Mice 

 which have ingested tuberculous material are especially to be sus- 

 pected as possible spreaders of tuberculosis, as tubercle bacilli multi- 

 ply enormously in their bodies and are freely scattered with their 

 feces 



TUBERCLE BACILLI N MARKET CHEESE. 



Tests on the occurrence of tubercle baciUi in cheese have shown 

 that varieties of cheese which require some time to ripen before they 

 are marketed rarely contain virulent pathogenic bacteria, while soft 



