CHAPTER XX. 



CONTAGIOUS BISWASES— continued. 

 VAPJOLA VACCi:^iE (COW-POX). 



Sjjnonyms. — Vaccine (F.) ; Kiihijoclcen (G.) 



Definition. — A contagious, febrile, and eruptive disease, known 

 in most parts of the globe, resulting from the presence of a 

 specific fixed virus, which is reproduced and multiplied in the 

 animal body during the course of the malady. After a period of 

 latency of from six to nine days, the contagium causes the 

 development of an eruption on the surface of the mammary 

 gland, which eruption passes through the stages of pimple, 

 vesicle, pustule, and scab. The disease runs a definite and mild 

 course, and destroys the susceptibility of the affected animal to 

 another attack; but in hot countries it sometimes assumes a 

 diffuse and severe character. 



PATHOLOGY AND SYMPTOMS. 



Cow-pox has been described by high medical authorities as 

 a malignant disease which destroyed cattle almost as extensively 

 as small-pox did the human race. This view of the malignancy 

 of cow-pox is evidently the result of a pathological error, which 

 led observers to confuse the cow-pox with cattle plague. 



Jenner believed in the identity of cow-pox and small-pox, and 

 that both had a common origin in the " grease " of the horse. 

 Jenner did not, however, perform any inoculations of cattle with 

 the lymph of human small-]30x. The first successful experiment 

 of inoculating the cow with human small-pox was performed at 

 the Berlin Veterinary College in 1801 ; the efforts previous to 

 tliat period having been unsatisfactory. In 1807 Gassner of 



