522 Diseases of the Genital Organs 



infections, such as tuberculosis and syphilis, the patient 

 may survive indefinitely and the infection continue in viable 

 form. The system of the patient acquires a power of re- 

 sistance to the ravages of the infection, but not the power 

 commonly to destroy it or to prevent reinfection. 



Those who regard the B. abortus as the specific cause of 

 abortion in cattle hold confused views as to whether it is 

 acute or chronic. Those who claim to have induced abortion 

 experimentally, constructively hold that it is an acute in- 

 fection. Some believe that they have induced abortion in 

 five to ten days. At first that was the general belief. Bang 

 in his first experiments believed he was dealing with an 

 acute infection having a short incubation period. Experi- 

 menters believing in the specific character of cattle abor- 

 tion generally hold that it is an acute infection for guinea 

 pigs : that is, if the B. abortus is injected into a pregnant 

 guinea pig, she will abort in five to ten days. Numerous in- 

 vestigators now hold that the B. abortus infection is virtu- 

 ally an acute infection in the uterus and a chronic infection 

 in the mammary glands. That is, the infection can not in- 

 vade the uterus until pregnancy is definitely established, 

 and can not continue in the uterus for more than a few 

 days after the termination of pregnancy. They further hold 

 that, after one. fetal cadaver has been expelled, the uterus 

 acquires an immunity and the B. abortus can not again 

 readily invade it and cause a second abortion, but the mam- 

 mary gland, once invaded, is permanently infected. Schroe- 

 der thinks that the mammary gland is the permanent hab- 

 itat of the B. abortus and periodically, during pregnancy, 

 the infection may in part pass from the mammae to the 

 uterus, cause abortion, and then promptly disappear from 

 the uterus. It is reasonably well established that the B. 

 abortus may be a permanent resident of the milk glands. 

 So far as I have seen recorded, it has not been searched for 

 elsewhere than in the genital canal and milk glands. One 

 cow in my experimental herd, now ten years old, was inocu- 

 lated in the jugular in her first pregnancy at about seven- 

 teen months of age. She was probably already infected 



