800 PATHOGENIC MICROORGANISMS 



Meyer and Shaw 12 have recently examined skin reactions in connec- 

 tion with B. abortus bovis and B. melitensis, and claim that this 

 method establishes a very close association between the two. 



Of great importance to the sanitarian is the fact that the B. 

 abortus may appear in the milk of cattle that have aborted and 

 may also be present in the milk of cattle that are carriers and have 

 suffered no abortion themselves. Cotton 13 has shown that the Bacil- 

 lus may persist in the genital organs for forty-six days after aborti9n 

 has taken place. From the studies of Schroeder and Cotton, 14 

 Stafseth 15 and others, it appears that the B. abortus does not es- 

 tablish itself permanently in the uterine cavity, and Stafseth 's 

 recent investigations seem to show that it does not penetrate into 

 the deeper layers of the mucous membrane and remain there as a 

 latent infection. 



Theobald Smith 16 in 1912 called attention to the tuberculosis- 

 like lesions in guinea pigs caused by B. abortus, a subject which 

 later was studied in more detail by Smith and Fabyan. 17 Fabyan, 

 as well as Schroeder demonstrated the presence of the B. abortus 

 in milk by guinea pig injection.. Characteristic lesions not unlike 

 tubercles developed in such animals in about eight to ten weeks, and 

 Evans found the Bacillus in the milk of six out of twenty-four 

 cows that had not aborted. Huddleson 18 has recently studied 

 methods of isolating B. abortus from milk, other than by guinea- 

 pig injection. He uses a liver or spleen infusion agar, developed 

 by Stafseth, a medium in the preparation of which overheating and 

 filtration through paper is avoided. The optimum hydrogen ion 

 concentration is P H 6.6. He adds to this medium gentian violet 

 to a final concentration of 1 :10,000. Ten c.c. of milk is centrifuged 

 at 2,000 revolutions for about two hours. 0.1 c.c. of the sediment 

 is taken out with a capillary pipette and distributed over the surface 

 of a gentian violet agar plate. These plates are incubated in jars 

 in which about 10 per cent of the air has been displaced "by C0 2 . 



12 Flcischner, Meyer and Shaw, Rep. Hooper Foundation, Univ. of Calif., 4, 1918. 



13 Cotton, Amer. Veter. Rev., 44, 1913, 307. 



14 Schroeder and Cotton, Jour. Amer. Vet. Assoc., 3, 1916, Quoted from Stafseth (3). 



15 Stafseth, Stud, of Infectious Abortion, Mich. Agric. College, 49, 1920. 



16 Smith, Theobald, Footnote in article by Cotton, quot. from Fabyn, Jour. Med. 

 Res., 28, 85, 1913. 



17 Smith and Fabyan, Cent. f. Bakt. Orig., 61, 1912, 549. 



18 Huddleson, Mich. Agric, College Exper. Station, 49, Nov. 1920, 25. 



