You can scarcely form an estimate of the immense consequences that followed this discovery. It was found not alone to affect chemistry, properly speaking, it threw a flood of light on every allied science. The chemistry of that day was overthrown. Without any exaggeration, I characterize it as the capital discovery of the last age, rivaling in its importance and in its results the great discovery of the preceding century, universal gravitation, by Newton. Extended by the chemists of England, France, and Germany, it has utterly exploded metaphysical physiology, which, taking its origin in the dark ages, has been the great barrier to the progress of rational medicine. Whoever will take pains to study with attention the works devoted to the exposition of that ancient system, must be struck with the impenetrable obscurity in which it is enveloped. You turn over page after page, and the more you read the more you become confused. It is a constant putting of words for things, of phrases for facts. Even in the hands of the most powerful writers, metaphysical physiology is essentially unintelligible; but not so with that other physiology which has arisen in our times, all its statements are clear, precise, distinct; it relies on the exact sciences, such as chemistry and natural philosophy, because it is itself exact. The progress of all the departments of human knowledge is often the same. Two thousand years ago the pagans peopled Olympus with many gods; and so in the infancy of medicine the corporeal frame was peopled with many intangible forms—a soul, a mind, a vital power, an instinct, a nervous agent, an aura, and animal spirits without end. But a better knowledge of these things is fast teaching us the eternal truth that, as there is but one God in the heavens, so there is but one spirit in man; a presiding agent that supervises and directs all; that all the acts of life are brought about by the inhalation of atmospheric air; and that every living animal owes its so-called vital properties to the action of air within its system; that there thus arise oxidations and other alterations in the economy, so that not a movement takes place, nor a thought occurs, without contemporaneous structural changes. The introduction of air by breathing is, I say, the fundamental fact in physiology; nay, more, it is the fundamental event in the action of the brain. I rest my opinions not on scientific facts, though they are numerous and irresistible, but I go at once to an authority far beyond all chemists and metaphysicians. In vain the physiologist asks me to deny the combustive influence of air in the body, and affects a fictitious fear of the tendencies of such a doctrine. Shall I not believe the positive declaration of him who is the artificer of these beautiful contrivances?—shall we accuse the Almighty of materialism when he tells us that "he breathed into his nostrils the breath of life, and man became a living soul?"
The circumstances that first direct the mind of a philosopher to discoveries destined to exert an influence over the whole human race cannot fail to be full of interest. So it is in the present case. It hap-
