INFECTIOUS DISEASES OF CATTLE. 445 



it advisable to take any measures against it, he \Yent far beyond what 

 was justified by any experiments or observations which he reported, 

 and he did an immense amount 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 hannless 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 disease is quite common in this country, especially in the 

 Eastern States. 



The contagion of cowpox does not travel through the air from ani- 

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

 tagious 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 whenever 

 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 secre- 

 tion. 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 horse 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 eruptions 

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

 of the human family is well known. The immunity which such vac- 

 cination confers upon the human subject has led many writers to 

 assert that cowpox is simply a modified form of smallpox, whose 



