May 17, 1924 
Immunology of Bovine Infectious Abortion 
621 
CONCLUSIONS 
The data derived from the experimental procedure described seem to justify the 
following conclusions: 
1. That it is possible to demonstrate in cattle an immunity to Bacterium 
abortus infection. 
2. That such immunity may be demonstrated both in cows that have sustained 
an attack of the malady, but give evidence of having overcome the infection in 
their bodies, and in susceptible animals that have been subjected, previously to 
conception, to the subcutaneous administration of viable abortion bacteria. 
3. That whatever immunity may be engendered by the treatment of animals 
with abortion bacterin, even when administered in large and frequent dosages 
both preceding and following conception, is limited and transitory in character. 
4. That the vaccination of abortion-infected animals, as well as of those which 
have overcome the infection, is in all probability an illogical and valueless pro¬ 
cedure. 
5. That the vaccination of nonpregnant heifers near breeding age with suspen¬ 
sions made from strains of Bacterium abortus that have been under artificial 
cultivation for a year or longer appears seldom to result in the permanent infec¬ 
tion of such animals. 
6. That the possibility of causing permanent infection is greater when the 
vaccinated animals have functioning udders. 
7. That susceptible heifers may occasionally remain negative to the serological 
tests for this disease for a period of at least four months after Bacterium abortus 
exposure of such severity as to result subsequently in abortions. 
8. That through the ingestion of fetal-stomach material containing Bacterium 
abortus susceptible pregnant animals may readily become infected with the 
disease. 
Table V.— Detailed records of individual experimental animals ° 
VACCINATED HEIFER NO. 402 
Serological results 
Date 
Feb. 28,1917 
Mar. 7,1917 
Mar. 21,1917 
Apr. 5,1917 
Apr. 21,1917 
May 5,1917 
May 17,1917 
June 1,1917 
June 16,1917 
June 29,1917 
July 13,1917 
July 27,1917 
Aug. 11,1917 
Aug. 26,1917 
Sept. 7,1917 
Sept. 21,1917 
Oct. 4,1917 
Oct. 18,1917 
Nov. 1,1917 
Nov. 14,1917 
Nov. 28,1917 
Dec. 13,1917 
Jan. 4,1918 
Agglutination 
Complement fixation 
Remarks 
0.04 
I 
0.02 0.01 
0.005 
0.002 
0.001 
0. 04 
0.02 
0.01 
0.005 
0.002 
Mar. 2,1917, subcutaneous injection 
of 20 cc. abortion vaccine. 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
P 
P 
S 
P 
s 
p 
s 
+ 
+ 
4 - 
s 
p 
s 
+ 
+ 
+ 
s 
s 
Apr. 27, 1917, bred. 
Nov. 2, 1917, received 5 cc. fetal- 
stomach contents (case 42). 
S 
P 
s 
p 
<* Explanation of symbols: The plus sign indicates complete clumping of bacteria; P, partial clumping; 
S, slight trace of agglutination; minus sign, no evidence of clumping. 
Note.—F igures at head of columns indicate cubic centimeters. 
