608 
Journal of Agricultural Research 
Vol. XXVIII, No. 7 
McFadyean and Stockman 4 in their early investigations of the disease also 
gave the matter of artificial immunization attention and described in detail ex¬ 
perimental work dealing with two virgin heifers that received subcutaneously 
single massive doses of Bacterium abortus cultures. These animals were later 
bred and during their gestation periods received enormous amounts of material 
containing abortion bacteria. When destroyed in an advanced stage of preg¬ 
nancy failure was experienced in detecting pathological changes in their uteri or 
in isolating therefrom the abortion organism. Such findings led these workers 
to conclude that the treatment practiced preceding conception conferred an active 
immunity. 
Stockman 5 in discussing infection abortion at a later date gave further con¬ 
sideration to artificial immunization as a means of preventing abortion losses. 
He described results that were obtained in infected herds where single massive 
doses of living cultures or suspensions of Bacterium abortus were administered to 
nonpregnant animals and where heavy suspensions of killed abortion bacteria 
were administered to the pregnant animals at monthly intervals up to the sixth 
month of pregnancy. Instead of making use of chemical agents for killing the 
organisms, as was practiced by Bang in his preparation of bacterins, the suspen¬ 
sions were subjected to a temperature of 65° C. for one-half hour. Those ani¬ 
mals receiving the viable organisms were not bred for a period of at least two 
months following the injections. Badly infected herds are mentioned as having 
been selected for experimentation. An estimate of the value of the immunizing 
procedure was arrived at by comparing the number of abortions that subse¬ 
quently occurred in the treated groups with those that occurred in control ani¬ 
mals in the same herds. With this method of evaluation the results derived from 
the employment of living abortion bacteria appeared to be highly encouraging, 
for whereas 23.4 per cent of the 432 controls aborted, the abortion rate in the 
493 treated subjects was but 6.5 per cent. Inasmuch as 21 per cent of 110 
animals that received repeated injections of killed organisms aborted, it was con¬ 
cluded that the benefits derived from the use of the killed organisms was not 
sufficiently marked to compensate for the labor involved in the making of the 
numerous injections. 
Investigators in this and foreign countries, other than those previously men¬ 
tioned, who have contributed data bearing on the subject of artificial immuniza¬ 
tion include the following: Giltner, Hallman, Williams, Hadley, Huddleson, 
Barnes, Hagan, Klimmer, Zwick and his coworkers, and others. 
The results of immunizing experiments that have been reported from time to 
time have for the most part been disappointing where either killed abortion bac¬ 
teria or serum with a high agglutinating titer for abortion bacteria have been 
utilized as immunizing agents. On the other hand, when viable abortion bac¬ 
teria have been employed in connection with nonpregnant subjects, the resistance 
of the animals to the pathogenic action of Bacterium abortus has subsequently 
appeared to be materially increased. 
THE PRESENT EXPERIMENTS 
The experimental work recorded in this paper, which was inaugurated during 
the latter part of 1917, was prompted largely by the encouraging results pre¬ 
viously mentioned as having been reported by Stockman in connection with the 
extensive immunizing work carried out in England. While the principal object 
< McFadyean, J., and Stockman, S.—Report of the departmental committee appointed by the 
BOARD OF AGRICULTURE AND FISHERIES TO INQUIRE INTO EPIZOOTIC ABORTION. Appendix to Part I. 43 p. 
London. 1909. 
* Stockman, S— Epizootic abortion. Internat. Vet. Cong. Rpt. 10 (2). 343-354. 1915. 
