out as Asiatic cholera on the wings of the wind, sweeping the wide
world with havoc. Settled on the tropical shores of the Eastern
Atlantic, they lie in wait for their victims in the sluggish and
terrible coast fever. On the western coast of the same ocean, perhaps
from some cause connected with oceanic or atmospheric currents, they
make devastating irruptions inland, as yellow fever, in every
direction where the walls of their enclosure are low enough to be
freely passed. These, let us remember, are all essentially the same
organic poison that is engendered _wherever_ life and death are plying
their perpetual game; and this, like Cleopatra's "worm, will do its
kind" in the veins of man, wherever obstructions, natural or
artificial, temporary or permanent, interfere with its prompt
diffusion in the vastness of the general atmosphere. Our "house of
life" stands generously open, for every "inmate bad" to come and go
through the absorbent, unquestioned, except in the stomach, where the
tangible poisons have to go by the act of swallowing and where they
are often challenged and ejected. It seems at first thought very
strange that we are not so well protected by natural instinct or
sensibility from the subtle poisons of the atmosphere as from those
that can affect us only by the voluntary act of swallowing. The
obvious explanation, however, of this apparent neglect is that Nature
protects us in general from gaseous poisons by her own system of
ventilation; and if, when we devise houses, necessarily excluding that
system, we fail to devise also a sufficient substitute for it, the
consequences of such negligence are as fairly due as when we swallow
tangible poison.

I have hitherto referred only to the _dispersion_ of poisonous
exhalations, as if the best and most necessary thing the atmosphere
can do for us were to dilute the dose to a comparatively harmless