BUREAU OP ANIMAL INDUSTRY. 133 



the principal facts that it has either discovered or proved to be true, 

 as follows: 



1. That infected cows often remain carriers of the bacillus of in- 

 fectious abortion disease long after they have ceased to manifest 

 symptoms of their infected condition. 



2. That cows which have never aborted and regularly produce 

 seemingly normal calves may be chronic carriers and disseminators 

 of abortion bacilli. 



3. That the habitat of the abortion bacillus in the bodies of infected 

 cows that are apparently healthy is the udder. 



4. That the infection in an infected udder may be limited to a 

 single quarter, or may exist in two, three, or all quarters. 



5. That both the milk and the blood serum of cows with infected 

 udders invariably agglutinate suspensions of abortion bacilli. 



6. That colostrum from cows with infected udders has enormously 

 high agglutinating potency for abortion bacilli. 



7. That the agglutinating potency of the blood serum of a preg- 

 nant cow is not a reliable measure of the probability of an abortion or 

 a normal parturition. 



8. That careful tests made with blood, the hearts, livers, kidneys, 

 lungs, spleens, lymph glands from all portions of the body, nerve and 

 brain tissues, muscles, uteruses, ovaries, etc., from cows infected with 

 abortion bacilli have failed to reveal the presence of the bacilli else- 

 where than in the udder, supramammary lymph glands, rarely in 

 some of the lymph glands of the pelvis, and in the uterus only near 

 the time of an abortion or at parturition. 



9. That the abortion bacillus is an organism which is amazingly 

 resistant to natural germ-destroying agencies. 



The best known means of guarding against the ravages of this 

 serious disease is the proper use of the agglutination test, which is 

 very reliable and not expensive. The test should be applied to every 

 new animal purchased before it is permitted to come into contact 

 with the uninfected herd. The chronic carriers of abortion bacilli, 

 which we have proved to be numerous, must be regarded for the time 

 being as the greatest menace against which the herd should be pro- 

 tected so far as this disease is concerned, and the agglutination test 

 has a high potency in detecting such chronic disseminators. 



TUBERCULOSIS. 



Most of the work on tuberculosis has been a continuation of the 

 investigations and studies which have been in progress for a number 

 of years. The small cost in money and labor with which several 

 tuberculous and several nontuberculous groups of animals have been 

 kept at the station year after year without the transmission of the 

 disease in a single instance from the former to the latter, throws 

 an encouraging light on the practicability of eradicating this disease 



The persistence of tubercle bacilli in the bodies of rats and mice, 

 in a seemingly dormant state so far as the production of disease is 

 concerned, has received further attention. Rats as well as mice, 

 after being permitted to eat tuberculous animal tissues one day only, 

 may continue to carry in their bodies tubercle bacilli, which cause no 

 disease referable to them, for more than a year. Tests are being 



