MICROBIAL DISEASES OF MAN AND DOMESTIC ANIMALS 8ll 



about five millimeters beneath the surface of the medium. When cul- 

 tures are placed in the proper atmosphere, development on the surface 

 may be obtained. Prolonged cultivation on artificial media obscures 

 this peculiar property of the microbe so that old culture strains grow 

 well under ordinary aerobic conditions. 



In the diseased animal, the specific bacteria are found in the pla- 

 centa and amniotic fluid, frequently also inside the foetal intestine, 

 sometimes in the tissues of the fcetal organs, and in the wall of the 

 maternal uterus. The placenta appears to be the particular organ 

 favorable to the development of the germ, and when this has been 

 discharged from the body the abortion bacilli no longer flourish, al- 

 though the infection may continue as a chronic uterine inflammation 

 for a long time. The general health is only slightly disturbed. At the 

 next pregnancy the disease is practically certain to reappear, and pos- 

 sibly again also at the succeeding one. After two or three abortions the 

 animals appear to have acquired an immunity to the infection, and may 

 sometimes breed normally thereafter, although some animals are per- 

 manently sterile after a few attacks of the disease. 



The organisms escape from the diseased animal in the products of 

 conception at the time of the abortion, and in the chronic uterine dis- 

 charge which may continue for a long time afterward. The disease may 

 be conveyed to other animals by contact with this material and by 

 eating grass or other feed soiled with it. Doubtless the male is an im- 

 portant factor, possibly the most important factor, in transmitting the 

 disease, although no serious inflammation is produced in him. 



The control of the disease depends upon the isolation of the infected 

 animals, cremation of infected foetus, placenta and discharges, and 

 thorough disinfection of the premises. Heifers and healthy cows 

 should not be allowed to mingle with cows which have aborted, nor 

 should they be served by a bull which has covered infected animals at 

 any time. Local antiseptic treatment of the cow which has aborted 

 diminishes the danger of the persisting discharge. 



Contagious abortion also occurs in other domestic animals, espe- 

 cially in horses, sheep, goats and swine. Inoculation experiments have 

 shown that the Bact. abortus of Bang can infect some of these animals. 

 Its importance as a factor in the epizootics of abortion occurring natu- 

 rally among them is still uncertain. In horses at any rate another organ- 

 ism appears to be more frequently involved. 



