So much for nerve-poison; but blood-poisoning is a still more terrible characteristic of house-protected existence. It is now the almost universal opinion of the medical profession that the whole class of malarial and zymotic diseases that make such frightful progress and havoc in the most civilized communities, are due to living germs with which the exhalations of organic waste and decay are everywhere loaded in inconceivable numbers. They are known to multiply themselves many times over, every two or three hours. They swarm into the blood by millions, through all the absorbents, especially those of the lungs, that drink the atmosphere in which they are suffered to linger and propagate. Mr. Dancer, the eminent microscopist, counted in a sample from such an atmosphere a number of organized germs equivalent to 3,700,000 in the volume of air hourly inhaled by one person. That is over 60,000 germs per minute, and about 2,000 in every breath. In the blood, they still propagate, and feed, and grow, consuming its oxygen, thus defeating its purification, and turning that stream of otherwise healthful and invigorating nutrition into a stream of effete and corrupt matter--a sewer rather than a river of life--or at best an impoverished and impure supply for the support of existence.
The same pestilential but invisible hosts of bacteria, mustered and bred in the close filthiness of Oriental cities, and jungles, swarm 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.