428 A SHORT HISTORY OF SCIENCE 



increased after it has acted on the nipples of the cow, as it rarely 

 happens that the horse affects his dresser with sores, and as rarely that 

 a milkmaid escapes the infection when she milks infected cows. It 

 is most active at the commencement of the disease, even before it 

 has acquired a pus-like appearance; indeed I am not confident 

 whether this property in the matter does not entirely cease as soon 

 as it is secreted in the form of pus. I am induced to think it does 

 cease, and that it is the thin darkish-looking fluid only, oozing from 

 the newly-formed cracks in the heels, similar to what sometimes 

 appears from erysipelatous blisters, which give the disease. Nor 

 am I certain that the nipples of the cows are at all times in a state to 

 receive the infection. The appearance of the disease in the spring: 

 and the early part of the summer, when they are disposed to be af- 

 fected with spontaneous eruptions so much more frequently than at 

 other seasons, induces me to think, that the virus from the horse must 

 be received upon them when they are in this state, in order to produce 

 effects : experiments, however, must determine these points. But 

 it is clear that when the Cow Pox virus is once generated, that the 

 cows cannot resist the contagion, in whatever state their nipples may 

 chance to be, if they are milked with an infected hand. 



Whether the matter, either from the cow or the horse will affect 

 the sound skin of the human body, I cannot positively determine ; 

 probably it will not, unless on those parts where the cuticle is ex- 

 tremely thin, as on the lips for example. I have known an instance 

 of a poor girl who produced an ulceration on her lip by frequently 

 holding her finger to her mouth to cool the raging of a Cow-Pox sore 

 by blowing upon it. The hands of the farmers' servants here, from 

 the nature of their employments, are constantly exposed to those 

 injuries which occasion abrasions of the cuticle, to punctures from 

 thornes and such like accidents ; so that they are always in a state to 

 feel the consequences of exposure to infectious matter. 



It is singular to observe that the Cow Pox virus, although it renders 

 the constitution unsusceptible of the variolous, should, nevertheless, 

 leave it unchanged with respect to its own action. I have already 

 produced an instance to point out this, and shall now corroborate it 

 with another. 



Elizabeth Wynne, who had the Cow Pox in the year 1759, was 

 inoculated with variolous matter, without effect, in the year 1797, 

 and again caught the Cow Pox in the year 1798. When I saw her, 



