608 MICROBIOLOGY OF THE DISEASES OF MAN AND ANIMALS. 



have recognized an epizootic form or a contagious abortion, a definite 

 transmissible disease of which the loss of the foetus is the most prominent 

 characteristic. This disease appears to be generally distributed in all 

 agricultural communities. Cows, especially, are affected, but a some- 

 what similar if not identical disease also occurs in other domestic animals. 



In 1897 Bernhard Bang discovered in the uterine exudate of a cow, 

 slaughtered during an attack of this disease before the abortion had 

 occurred, a small bacterium which he was able to grow in pure culture, 

 and, by inoculating pure cultures of this organism, he produced the 

 disease in cows, sheep, goats and rabbits. 



The microbe is a short non-motile rod, staining with moderate ease, 

 and decolorized by Gram's method. It does not form spores but the 

 vegetative forms are fairly resistant to drying and may, perhaps, live for 

 some weeks under ordinary conditions in pastures and stables. Its artificial 

 culture requires special technic because of its peculiar oxygen require- 

 ment. The bacterium usually fails to grow in the presence of the atmos- 

 pheric air or under anaerobic conditions. It requires for its develop- 

 ment a partial pressure of oxygen somewhat less than that of the atmos- 

 phere. When inoculated into deep serum-gelatin-agar tubes and in- 

 cubated in the air, the colonies develop only in a particular zone about 

 five millimeters beneath the surface of the medium. When cultures are 

 placed in the proper atmosphere, development on the surface may be 

 obtained. 



In the diseased animal, the specific bacteria are found in the placenta 

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

 in the tissues of the f octal organs, and in the wall of the maternal uterus. 

 The placenta appears to be the particular organ favorable to the develop- 

 ment of the germ, and when this has been discharged from the body 

 the abortion bacilli no longer flourish, although 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 possibly 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 permanently 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 discharge 

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



