ERUPTIONS OF THE ACUTE SPECIFIC DISEASES 141 



" There is a disease to which the horse from his state of domesticatiou 

 is frequently subject. Farriers have named it the grease; it is an inflam- 

 mation and swelling in the heel, accompanied at its commencement with 

 small cracks and fissures, from which issues matter possessing properties oi 

 a very peculiar kind. 



" If the men who dressed the horses' heels were called upon to milk 

 cows, they communicated to them the malady known as the cow-pox." 



Several cases are recorded in proof of this statement, and from one 

 particular case Jenner was led to believe that the virus which produced 

 cow-pox might be obtained from other parts of the body of the 

 horse. 



It is now perfectly well known that the facts as stated are correct, but 

 that the explanation is wrong. The fact is that the horse suffers from 

 a form of variola, and also suffers from cracked and greasy heels, and when 

 horse-pox, equine variola, attacks a horse which happens at the time to be 

 suffering from grease, the characteristic eruption of horse-pox is quite likely 

 to appear in the already irritated skin of the heel, and in such case the 

 matter of greasy heels, together with the variolous contagion, might every 

 now and then be carried to the udder of the cow and produce cow-pox. 

 It would, however, probably be more correct to look upon the recorded 

 outbreaks of cow-pox which followed the act of milking by the hand of 

 a man who had dressed the greasy heels of a horse as mere coincidences. 

 It is quite certain that the matter of ordinary grease will not produce 

 cow-pox; it is equally true that the horse is subject to a genuine variola, 

 which, when transmitted to the cow, induces the other form of variola, i.e., 

 vaccine disease. 



Horse-pox, or variola, although it undoubtedly occurs in this country 

 in isolated cases, has never assumed the virulence which it exhibits on the 

 Continent. In Professor Crookshank's work on vaccination several exten- 

 sive outbreaks are described. The first one which has been recorded 

 occurred in 1860, and it is stated that in less than three weeks there were 

 more than a hundred cases. The horses suffered from slight fever, rapidly 

 followed by the local symptoms, swelling of some of the joints, and an 

 eruption of small pustules on different parts of the body, especially on the 

 lips, nostrils, buttocks, and generative organs. In about a fortnight the 

 pustules dried up, the crusts with patches of hair fell off, leaving marked 

 scars. 



In some instances the pustules apj^eared inside the nostrils, giving rise 

 to a suspicion that the animal was affected with glanders. Cases have 

 occurred in this country of eruption of small pustules on the legs, outside 

 of the nostrils, and on different parts of the body, simulating the form of 



