138 ANNUAL EEPOETS OF DEPARTMENT OF AGRICULTURE. 



independently and in cooperation with other divisions of the bureau, 

 regarding infectious diseases of animals, and the provision of facili- 

 ties required by the other divisions for making tests and studies on 

 large animals under farm and field conditions. 



During a considerable portion of the year the regular work of 

 the station was handicapped because the services of a part of the 

 small technical staff were needed in the bureau's campaign against 

 foot-and-mouth disease. In addition to this, unexpected work was 

 laid upon the station in the form of tests with material suspected 

 to be infected with the virus of foot-and-mouth disease from various 

 portions of the country. 



As the work for and in cooperation with other divisions of the 

 bureau has already been presented, this part of the report will be 

 confined almost entirely to the independent work of the station. 



TUBERCULOSIS INVESTIGATIONS. 



Studies on tuberculosis, which have been in progress for a number 

 of years and are being c(mtinued, justify several conclusions, as 

 follows : 



(1) That the propagation of tuberculosis among cattle depends 

 more largely on actual contact between tuberculous and healthy cat- 

 tle than on any other possible cause of infection. 



(2) That no wide separation between stables and pens occupied 

 by tuberculous and healthy herds of cattle is necessary to protect 

 the latter against infectious material discharged by the former. 



(3) That, in the preparation of stables which have been occupied 

 by tuberculous cattle and are subsequently to be occupied by healthy 

 cattle or other animals, a thorough cleaning is a factor of possibly 

 even greater importance than the use of disinfectants. 



(4) That tuberculosis among hogs depends almost exclusively on 

 the direct exposure of hogs to tuberculous cattle and to material de- 

 rived from such cattle, and only very slightly on the exposure of 

 healthy to tuberculous hogs. 



A detailed account of the experiments on which these conclusions 

 are based can not be given in this report, but the following brief 

 statement may give some idea of their character. 



No case of tuberculosis that can not be accounted for as the result 

 of direct contact between healthy and tuberculous cattle has devel- 

 oped among the cattle at the station for more than a dozen years, 

 notwithstanding that several groups of tuberculous cattle and an 

 equal or larger number of groups of nontuberculous cattle have been 

 maintained year after year on an area measuring less than 50 acres. 

 Contrary to this, several cases of tuberculosis have arisen from posi- 

 tively known but seemingly slight contact between healthy and tuber- 

 culous animals. For example, in two instances bulls which were 

 permitted to serve tuberculous cows on neutral ground — that is, on 

 ground neither in their own pens nor in the pens occupied by the 

 tuberculous cows — ^became affected with tuberculosis. Excepting at 

 the time of service these bulls were carefully protected against all 

 exposure to tubercle bacilli. 



An avenue less than 2 rods wide between two parallel stables, one 

 occupied by a herd of tuberculous and the other by a herd of healthy 



