BACILLUS ABORTUS 417 
ajj^lutinins with B. abortus. If the two are shown to be serologically 
identical, the entire question of milk-borne infection with these organ- 
isms must be studied anew.^ B. tularense also possesses common 
agglutinins with B. melitensis and B. abortus.- 
Immunity.— Cows which have aborted once or twice appear toacquire 
an immunity which is supposed to be due to the formation of anti- 
bodies in the blood. Although no extracellular toxins have been 
demonstrated as yet, it is probable that the infected animal is sensitized 
by endotoxins of the abortion bacillus, for such animals injected with 
"Abortin" (an extract of the abortus bacillus) usually give a definite 
reaction. 
Of extreme importance is the frequent occurrence of the organism 
in milk. Melvin^ has found B. abortus in 8 out of 77 samples of 
market milk and in the milk of 6 dairies out of a total of 31 examined. 
As early as 1894 Theobald Smith"* called attention to peculiar tuber- 
cle-like lesions induced in guinea-pigs following the injection of cow's 
milk. He recognized that the disease was not tuberculosis; later 
Schroeder^ made similar observations. In the same year Smith and 
Fabyan*^ showed that the tubercle-like lesions were caused by B. 
abortus, and in 1913 Fabyan^ demonstrated conclusively the extremely 
important fact that B. abortus is very frequently found in the milk 
of cows that have aborted. He also showed that pasteurization of 
milk, if carried out in the proper manner, will certainly destroy the 
bacillus. Whether certain cases of abortion observed in man are due 
to the organism is not yet proved.'^ Several observers, however, have 
demonstrated agglutinins which suggest that infection may have 
taken place. ^ 
Bacteriological Diagnosis.— The bacteriological diagnosis is best 
made by injecting guinea-pigs with suspected milk or material from 
a diseased animal and observing the development of the characteristic 
tubercle-like lesions. If the animal does not die within a reasonable 
time it should be killed and autopsied. 
Serological Diagnosis.— The blood serum of infected cattle usually 
agglutinates B. abortus in dilutions greater than 1 to 50. The value 
of the agglutination reaction as a method of diagnosis is as yet debat- 
able. The extensive statistics of MacFadyen and Stockman ^'^ upon 
' See Zeller: Berl. tierarztl. Wchnschr., 1920, 36, 285. Beziehungen zwischen dem 
Erreger der Infektiosen Abortus der Kinder und des Maltafiebers. 
2 See Bacillus tularense. 
» Vet. Jour., 1912, 68, 526. 
< Bureau of Animal Industry, 1894, Bull. No. 7, p. 80. 
^ Bureau of Animal Industry, Circ. No. 198, November 2, 1912. 
6 Centralbl. f. Bakteriol., orig., 1912, 61, 549. 
' Jour. Med. Res., 191.3, 28, 85. 
' Larsen and Sedgwick (Am. .Jour. Dis. Child., 1913, 6, 326) examined blood serum 
from 425 children by the method of complement-fixation; 73 were positive, 325 were 
negative. See also Evans: Public Health Reports, 1924, 39, 501. 
9 Arnold and Miller: Proc. Soc. Exp. Biol, and Med., 1927, 24, 836. Fitch: Jour. 
Infec. Dis., 1922, 31, 2?:^. Meyer. Shaw and Fleischner: Ibid., 1922, 31, 159. 
'» Jour. Comp. Path, and Therap., 1912, 25, 22. 
27 
