internal congestion; has he a weak point in the vascular system of his
brain, it renders that point liable to pressure and rupture, with
apoplexy as the sequence; is he suffering from bronchial disease, and
obstruction, already, in his air passages, here is a means by which
the evils are doubled; has he a feeble, worn-out heart, it is unable
to bear the pressure that is put upon it; has he partial obstruction
of the kidney circulation, he is threatened with complete obstruction;
is he indifferently fed, he is weakened generally. It is from this
extent of action that the mortality of all diseases runs up so fast
when the low wave of heat rolls over the population, affecting, as we
have seen, the feeblest first.

Another danger sometimes follows which is remote, but may be fatal,
even to persons who are in health. It is one of the best known facts
in science that when a part of the surface of the body has been
exposed long to cold, the greatest risk is run in trying suddenly to
warm it. The vessels become rapidly dilated, their coats relax, and
extreme congestion follows. But what is true of the skin is true
equally, and with more practical force, of the lungs. A man, a little
below par, goes out when the wave of temperature is low, and feels
oppressed, cold, weak, and miserable; the circulation through his
lungs has been suppressed, and he is not duly oxidizing; he returns to
a warm place, he rushes to the fire, breathes eagerly and long the
heated air, and adds to the warmth by taking perchance a cup of
stimulant; then he goes to bed and wakes in a few hours with what is
called pneumonia, or with bronchitis, or with both diseases. What has
happened? The simple physical fact of reaction under too sudden an
exposure to heat after exposure to cold. The capillaries of the lungs
have become engorged, and the circulation static, so that there must
be reaction of heat, inflammation, before recovery can occur. Nearly