MICROBIAL DISEASES OF MAN AND ANIMALS. 609 



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

 grass or other feed soiled with it. Doubtless the male is an important 

 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 thor- 

 ough 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, especially 

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

 that the Bad. abortus of Bang can infect some of these animals. Its 

 importance as a factor in the epizootics of abortion occurring naturally 

 among them is still uncertain. In horses at any rate another organism 

 appears to be more frequently involved. 



DIPHTHERIA.* 



Bacterium diphtheria. 



The disease is epidemic in all large communities especially in Europe 

 and America. It is, however, almost absent from tropical regions. 

 Epidemics and pandemics occur in cycles. Essentially diphtheria is a 

 disease peculiar to man. Avian diphtheria, however, is known, although 

 seemingly due to another cause, and on rare occasions natural infection 

 has been found in the horse. 



The period of incubation is said to be two to five days. 



In man the disease usually begins with lassitude and fever followed 

 in a few hours by "sore throat." The inflamed area on the pharyngeal 

 wall, tonsils, larynx or wherever it may be becomes in typical cases the 

 seat of degenerative changes in the epithelium and underlying tissues with 

 abundant fibrinous exudation resulting in the formation of a comparatively 

 tough membrane or pesudo-membrane, which is a striking and character- 

 istic feature of the disease. This local lesion is almost always found on 

 mucous membranes though occasional instances of infection of wounds 

 have been noted. 



* Prepared by Edward Fidlar. 

 39 



