One of Heaven's great hygienic teachers is now abroad in the world, giving lessons on health to the children of men. The cholera is like the angel whom God threatened to send as leader to the rebellious Israelites. "Beware of him, obey his voice, and provoke him not; for he will not pardon your transgressions." The advent of this fearful messenger seems really to be made necessary by the contempt with which men threat the physical laws of their being. What else could have purified the dark places of New York? What a wiping-up and reforming and cleansing is going before him through the country! At last we find that Nature is in earnest, and that her laws cannot be always ignored with impunity. Poisoned air is recognized at last as an evil,--even although the poison cannot be weighed, measured, or tasted; and if all the precautions that men are now willing to take could be made perpetual, the alarm would be a blessing to the world. Like the principles of spiritual religion, the principles of physical religion are few and easy to be understood. An old medical apothegm personifies the hygienic forces as the Doctors Air, Diet, Exercise, and Quiet; and these four will be found, on reflection, to cover the whole ground of what is required to preserve human health. A human being whose lungs have always been nourished by pure air, whose stomach has been fed only by appropriate food, whose muscles have been systematically trained by appropriate exercises, and whose mind is kept tranquil by faith in God and a good conscience, has _perfect physical religion_. There is a line where physical religion must necessarily overlap spiritual religion and rest upon it. No human being can be assured of perfect health, through all the strain and wear and tear of such cares and such perplexities as life brings, without the rest of _faith in God_. An unsubmissive, unconfiding, unresigned soul will make vain the best hygienic treatment; and, on the contrary, the most saintly religious resolution and purpose may be defeated and vitiated by an habitual ignorance and disregard of the laws of the physical system.