VACCINATION AGAINST SMALLPOX 171 



cow, as it rarely happens that the horse affects his dresser 

 with sores, and as rarely that a milkmaid escapes the infec- 

 tion 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, 18 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 

 gives 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 affected 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 extremely 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 in- 

 juries which occasion abrasions of the cuticle, to punctures 

 from thorns, and such like accidents ; so that they are always 

 in a state to feel the consequence of exposure to infectious 

 matter. 



It is singular to observe that the cow-pox virus, although 



" It is very easy to procure pus from old sores on the heels of horses. 

 This I have often inserted into scratches made with a lancet, on the 

 sound nipples of cows, and have seen no other effects from it than simple 



