n 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 injuries 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
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[2] 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, which was on the
8th day after she received the infection, I found her affected with
general lassitude, shiverings, alternating with heat, coldness of the
extremities, and a quick and irregular pulse. These symptoms were
preceded by a pain in the axilla. On her hand was one large pustulous
sore, which resembled that delinated in Plate No. 1.

It is curious also to observe, that the virus, which with respect to
its effects is undetermined and uncertain previously to its passing
from the horse through the medium of the cow, should then not only
become more active, but should invariably and completely possess
those specific properties which induce in the human constitution
symptoms similar to those of the variolous fever, and effect in it
that peculiar change which for ever renders it unsusceptible of the
variolous contagion.

May it not, then, be reasonably conjectured, that the source of the
Small-pox is morbid matter of a peculiar kind, generated by a disease
in the horse, and that accidental circumstances may have again and
again arisen, still working new