BUREAU OF ANIMAL INDUSTRY. 155 



way to infect a cow with this disease is to permit her to ingest abor- 

 tion bacilli. Service by an infected bull has failed to transfer the 

 disease in our tests. While the unguarded and i)romiscuous use of 

 infected bulls is not recommended, the results of our experiments give 

 no indication that the bull, if kept in a special pen and permitted to 

 serve cows only on neutral ground, plays any part in the spread of 

 infectious abortion disease. It therefore appears that bulls owned 

 by associations, provided the precautions indicated are observed, are 

 safe in this respect. 



Some attention has been given also to the influence of abortion 

 disease on the fertility of the bull, but no conclusive results have yet 

 been obtained. 



As abortion among hogs, due either to the same bacillus that attacks 

 cattle or to other causes, is evidently increasing in frequency in 

 several portions of the country, work on this subject has been under- 

 taken and will be continued. 



TUBERCULOSIS AND MISCELLANEOUS WORK. 



Nothing radically new regarding tuberculosis was developed dur- 

 ing the year. Several investigations which have been in progress 

 several years have been continued and are nearing completion. 



The tests for potency and purity of tuberculins manufactured and 

 sold under Government license proved all the tested products to be 

 satisfactory. There seems to be a general tendency for commercial 

 tuberculin to be superpotent rather than subpotent. While this is 

 a better condition than the reverse would be, a definite, unvarying 

 potency is preferable. 



In view of the finding of tubercle bacilli in cream cheese a few 

 years ago, tests of this product have been continued. During the 

 year 100 samples were tested, with negative results in all cases, thus 

 indicating that the bureau's previous work has led manufacturers to 

 adopt effective means to prevent contamination. 



lests with milk from the local supply show that raw market milk 

 occasionally is contaminated with the abortion bacillus and more 

 rarely with the tubercle bacillus. A comparison between guinea pigs 

 injected respectively with commercial!}' pasteurized and raw market 

 milk shows that a very much larger proportion die from the latter 

 than from the former. Such results show conclusively that com- 

 mercial pasteurization, though still lacking official supervision, is a 

 commendable public-health measure. 



A large number of small experiment animals were raised at a cost 

 much lower than current market values. Various tests were made 

 with pathological material suspected to contain the virus of infectious 

 diseases. Biological products of various kinds Avere supplied the 

 other laboratories of the bureau. Every available portion of the 

 station's land was kept under intensive cultivation to obtain forage 

 for tlie experiment animals. 



EXPERIMENTS IN LIVESTOCK PRODUCTION IN CANE-SUGAR 



AND COTTON DISTRICTS. 



At the Iberia Experiment Farm, Jeanerette, La., experiments and 

 demonstrations with horses, mules, beef cattle, dairy cattle, and hogs 

 are conducted for the purpose of bringing before the farmers the 



