284 DISEASES OF CATTLE, SHEEP, GOATS, ETC. 



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 

 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 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 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 due to a certain 

 attenuation derived during its passage through the system of the cow 

 or horse. The result of numerous experiments, which have been car- 

 ried out for the purpose of determining the relationship existing be- 

 tween variola of the human and bovine families, seems to show, how- 

 ever, that although possessing many similar characteristics, they are 

 nevertheless distinct, and that in spite of repeated inoculations from 

 cattle to man, and vice versa, no transformation in the real character 

 of the disease ever takes place. 



Symptoms. The disease appears in four to seven days after nat- 

 ural infection, or may evince itself in two or three days as the result 

 of artificial inoculation. Young milch cows are most susceptible to 

 an attack, but older cows, bulls, or young cattle are by no means im- 

 mune. The attack causes a slight rise in temperature, which is soon 

 followed by the appearance of reddened, inflamed areas, principally 

 upon the teats and udder, and at times on the abdominal skin or the 

 skin of the inner surface of the thighs. In a few cases the skin of 

 the throat and jaws has been found similarly involved. If the af- 

 fected parts are examined on the second day after the establishment 

 of the inflammation numerous pale red nodules will be found, which 

 gradually expand until they reach a diameter of one-half inch or 

 even larger within a few days. At this period the tops of the nodules 

 become transformed into vesicles which are depressed in the center 

 and contain a pale serous fluid. They usually reach their maturity 

 by the tenth day of the course of the disease and are then the size of 

 a bean. From this time the contents of the vesicles become purulent, 

 which requires about three days, when the typical pox pustule is pres- 

 ent, consisting of a swelling with broad, reddened base, within which 

 is an elevated, conical abscess varying from the size of a pea to that 

 of a hazelnut. 



