312 INFECTIVE DISEASES. 



Bacteria in Horse-pox Outbreaks of horse-pox have not 



been investigated from the bacteriological point of view, and the 

 nature of the contagium is unknown. 



Cow-pox. 



Cow-pox is a vesicular disease of the teats of cows. It is never 

 infectious, and only attacks cows in milk, the virus being transferred 

 from cow to cow by the hand of the milker. The disease is com- 

 municable to milkers, and the virus artificially inoculated produces 

 what is commonly known as vaccinia. In its chnical history and 

 epidemiology cow-pox is totally distinct from human small-pox, and 

 the hypothetical and entirely erroneous suggestion that the disease 

 arises from milkers suffering from human small-pox is responsible 

 for the belief which prevailed until recently, that cow-pox was an 

 extinct disease in this country ; but, by the author's researches, this 

 has been shown to be a mistake. 



Cow-pox is not a rare dise£|,se, and it has never been found to 

 arise from a milker suffering from small-pox. As this is a matter 

 of great importance in discussing the etiology of the disease, the 

 history of outbreaks and the clinical characters of cow-pox will be 

 given in considerable detail. 



According to Jenner, cow-pox had been known among farmers 

 from time immemorial. He refers to cases occurring in 1770, 1780, 

 1782, 1791, 1794, 1796, and 1798. In 1799 cow-pox was raging in 

 the dairies in London, and outbreaks were investigated by Woodville, 

 Pearson, and Bradley. In the same year cow-pox broke out at 

 Norton Nibley, in Gloucestershire. Pearson and Aikin referred to 

 the prevalence of cow-pox in Wilts, Somerset, Devon, Bucks, Dorset, 

 Norfolk, Suffolk, Leicestershire, and Staffordshire ; and Barry men- 

 tioned its prevalence in Ireland. 



From this time onwards, for a long period, natural cow-pox 

 received little or no attention in this country. Fresh stocks of lymph 

 were raised for the purposes of vaccination, but no further attention 

 was given to studying the disease in the cow. In 1836 Leese 

 described an outbreak of cow-pox, and m 1838 Estlin discovered an 

 outbreak in Gloucestershire. In 1838-39 cow-pox was met with 

 by Mr. Fox, of Cerne Abbas, and again in 1839, in Dorsetshire, by 

 Mr. Sweeting. Ceely frequently met with cow-pox in the Vale of 

 Aylesbury, and particularly refers to outbreaks in 1838, 1840, 1841, 

 and 1845. But after this, outbreaks of this disease in the cow were 

 not recorded, though several medical practitioners met with the 

 disease and raised fresh stocks of vaccine lymph. Thus, when 



