Page:Popular Science Monthly Volume 2.djvu/686

666 other: the one being delighted in finding out and making his way into the unknown, while the pleasure of the other consists in seizing results, and putting them into shape, so that they may be servants to our will. The history of electricity strikingly displays these distinct aptitudes and pursuits. Volta, Franklin, Arago, and Faraday, were leading discoverers of the properties and laws of electricity. They cared far less about the every-day use which might be made of the newly-discovered force, than of gaining a complete insight into its nature, and of making it the means of unlocking other secrets of the natural world. On the other hand, Morse and Wheatstone thought only of electricity as a means to an end, or of reaching, through some ingenious contrivance, the means of rendering human communication, at distant points, practically instantaneous.

A knowledge of the leading facts upon which sanitary science is founded is, at least, as old as history itself. It antedates the time of Moses; many of the rules of hygiene having been taught by the Egyptian priests. But more especially within the past two centuries has the knowledge of the ways in which disease is produced, and may be avoided, been corrected and extended. It is within this period that the first attempt was made in Europe to establish quarantines. The sum of the precautions taken in London during the middle ages to guard against the ravages of the plague, was the isolation of infected houses, and putting a red cross on house-doors, on which were inscribed the words, "Lord, have mercy on us."

The physician of to-day, who has devoted half as much thought to the prevention of disease as to its cure, firmly believes in human ability to avoid nearly all the ills to which flesh is now subject. Given a good constitution, and the conditions of health or sickness are almost wholly in our own power. He believes this, and on precisely the same grounds that the geologist believes that fossils are not what was once universally believed, the primary result of the action of a plastic or creative force in Nature. A like belief exists in the popular mind in reference to health and longevity, though in a less positive form. Families known to be of good constitution, and of ancestry noted for their length of days, are not expected to be sickly and short-lived. When any member of such a family does become a permanent invalid, and likely soon to die, it is a familiar expression, and notoriously true, that he or she has abused the endowment inherited.

Passing over the evidence which has convinced those the most competent to judge in reference to the prevalence of disease—the physicians—to their conclusion, that if all possessed good constitutions, and lived as they ought to live, in accordance with hygienic law, there would be no disease, or next to none, and death would not come upon the human family through a morbid process, but by the only truly natural mode of dying—old age; the question arises, How do men come by good constitutions? Through a course of life by progenitors for