436 DISEASES OF CATTLE. 



was justified by any experiments or observations which he reported, 

 and he did a great deal of harm, which will be manifested for years 

 to come, to those who endeavor to guard the human race from the 

 dangers, of animal tuberculosis. The researches which have been 

 alluded to make these dangers more definite and certain than they 

 have appeared before, and sanitarians should therefore most ear- 

 nestly endeavor to counteract the erroneous and harmful impression 

 which was made by Koch's address at London and his subsequent 

 address at the International Conference on Tuberculosis at Berlin. 



VARIOLA. 



Variola of cattle, commonly known as " cowpox," is a contagious 

 disease of cattle which manifests its presence through an elevation of 

 temperature, a shrinkage in milk production, and by the appearance 

 of characteristic, pustular eruptions, especially upon the teats and 

 udders of dairy cows. Although this is a contagious disease, strictly 

 speaking, it is so universally harmless and benign in its course that 

 it is robbed of the terrors which usually accompany all spreading 

 diseases, and is allowed to enter a herd of cattle, run its course, and 

 disappear without exciting any particular notice. 



The contagion of cowpox does not travel through the air from 

 animal to animal, but is transfused only by actual contact of the 

 contagious principle with the skin of some susceptible animal. It 

 may be carried in this manner, not alone from cattle to cattle, but 

 horses, sheep, goats, and man may readily contract the disease when- 

 ever suitable conditions attend their inoculation. 



An identical disease frequently appears upon horses, attacking 

 their heels, and thence extending upward along the leg, producing, as 

 it progresses, inflammation and swelling of the skin, followed later 

 by pustules, which soon rupture, discharging a sticky, disagreeable 

 secretion. Other parts of the body are frequently affected in like 

 manner, especially in the region of the head, where the eruptions may 

 appear upon lips and nostrils, or upon the mucous surfaces of the 

 nasal cavities, mouth, or eyes. 



Variola of the horse is readily transmitted to cattle, if both are 

 cared for by the same attendant, and, conversely, variola of cattle 

 may be carried from the cow to the hoi"se on the hands of a person 

 who has been milking a cow affected with the disease. 



The method of vaccination with material derived from the erup- 

 tions of cowpox as a safeguard against the ravages of smallpox in 

 members of the human family is well known. The immunity which 

 such vaccination confers upon the human subject has led many 

 writers to assert that cowpox is simply a modified form of smallpox, 

 whose harmless attack upon the human system is owing to a certain 

 attenuation derived during its passages through the system of the 



