s as recorded by Murchison. We do not yet know how the
poison obtains entrance to the body. Hence, the need for thorough
disinfection.

Age, Occurrence, Susceptibility.--All children exposed to the disease do
not contract the disease. It is less contagious than measles. A person who
is exposed once, and does not take it, may take it at a future exposure.
It occurs at any age and in all countries. It occurs oftener in autumn
(September) and winter (February). Isolated cases occur, and then it is
called sporadic. This disease attacks nursing children less frequently
than older children. It is not often seen during the first year of life.

How Often?--As a rule, it attacks a person only once; yet there are
recorded cases of well observed second and third attacks, but fortunately
these are very rare. I once attended a family where they had it and
claimed to have had it before, but very lightly.

Incubation.--The vast majority of cases develop within three to five days
after exposure. If eleven days elapse without the appearance of symptoms
we may reasonably expect that the danger is past, at least in the great
majority of cases exposed.

Contagiousness.--There is danger of catching the disease during the stages
of incubation, eruption and scaling. It is most contagious in the last two
stages.

Onset.--Sometimes the onset is sudden; there may be a convulsion, preceded
by a sharp rise in the temperature. An examination in such cases may
reveal a marked sore throat or a membranous deposit on the tonsils
preceding the eruption, and nothing more. A chill followed by fever and
vomiting ushers in a large number of cases. These may be mild or severe.
The severity of these symptoms usually indicates the gravity of the
attack.

Rash.--The rash or eruption appears from twelve to thirty-six hours after
the onset, usually on the second day, and looks like a very severe heat
rash, but is finer and thicker. It consists of a very finely pointed
rose-colored rash. In mild cases it is hardly noticeable. Usually it first
appears on the upper part of the chest around the collar bones, spreads
over the chest and around upon the back. Also it is now seen on the neck,
beneath the jaw, behind the ears and on the temples, thence spreads over
the body. There is a paleness about the mouth and wings of the nose, while
the cheeks are flushed with a flame-like redness. There is much itching if
the rash is severe. It attains the full development at