the body,
and is then easily transferred to the cow, if the same man grooms and
dresses the horse and milks the cow. It may also appear in the cow by
infection, more or less direct, from a person who has been successfully
vaccinated. Many believe that it is only a form of the smallpox of man
modified by passing through the system of cow or horse. It is, however,
unreasonable to suppose that this alleged modified smallpox could have been
transmitted from child to child (the most susceptible of the human race)
for 90 years, under all possible conditions, without once reverting to its
original type of smallpox. Chauveau's experiments on both cattle and horses
with the virus of smallpox and its inoculation back on the human subject go
far to show that in the climate of western Europe, at least, no such
transformation takes place. Smallpox remains smallpox and cowpox, cowpox.
Again, smallpox is communicable to a person who visits the patient in his
room but avoids touching him, while cowpox is never thus transferred
through the air unless deliberately diffused in the form of spray.

The disease in the cow is ushered in by a slight fever, which, however, is
usually overlooked, and the first sign is tenderness of the teats.
Examined, these may be redder and hotter than normal, and at the end of two
days there appear little nodules, like small peas, of a pale-red color, and
increasing so that by the seventh day they may measure three-fourths of an
inch to 1 inch in diameter. The yield of milk diminishes, and when heated
it coagulates slightly. From the seventh to the tenth day the eruption
forms into a blister, with raised margins and a depression in the center,
and from which the whole of the liquid can not be drawn by a single
puncture. The blister, in other words, is chambered, and each chamber must
be opened to evacuate the whole of the contents. If the pock forms on a
surface where there is thick hair it does not rise as a blister, but oozes
out a straw-colored fluid which concretes on the hairs in an amber-colored
mass. In one or two days after the pock is full it becomes yellow from
contained pus and then dries into a brownish-yellow scab, which finally
falls, leaving one or more distinct pits in the skin. Upon the teats,
however, this regular course is rarely seen; the vesicles are burst by the
hands of the milker as soon as liquid is formed, and as they continue to
suffer at each milking they form raw, angry sores, scab