To live happily, we must in the first place live. Transparent truism, but how often forgotten! How many of our pleasures tend to weaken life, rather than to strengthen and to lengthen it!

Some philosophers have found the sense of existence a sufficient synonym for happiness. Sir William Hamilton expressed this opinion with perhaps an ambiguous under-meaning when he said,—“To lead a happy life is to live all the days of one’s life;” but Dr. Johnson, moralizing on the learned pig, expanded the idea more clearly when he maintained that the mere prolongation of existence is a sufficient compensation for a very considerable amount of suffering. We see the correctness of his observation in the multitude of examples of those who cherish their years when poverty, old age, and disease would seem to have

robbed them of all value. When nothing else is left but life, life alone becomes worth all else.

Self-preservation, therefore, which means the care of life and health, is the first and a necessary condition of personal happiness. But what a task is this!

When the child wakes to consciousness and surveys the scene around him, he finds himself on a battle-field divided between two mighty combatants in unremitting conflict—Necessity and Chance, the laws of Nature and the caprices of Accident. Not even the gods, said the ancient Greeks, can struggle with Fate and Fortune, those elemental powers, Anangke and Tyke. What is man that he dare venture the fray?

Each individual is scarcely more than a volume of quotations from the works of his ancestors, selected with little appropriateness to the Essay on Life which he has himself to compose. Mysterious and unrecorded influences extending over untold generations have combined to make him what he is, and to endow him with a personality which he can never escape from, nor transcend. The boy, the man, can no more run away from his parents than he can from himself. He may renounce and cast out the traits which he has inherited, but he cannot get rid of them. Unbidden and unnoticed, they will slink back and abide with him forever. They are not his servants, but belong to his family, his clan, his race. He can change or dismiss them no easier than he can the color of his skin or the shape of his skull.

These are the laws of Heredity. They bind the individual as with a tether to an immovable stake. But the tether is not a fetter. It allows him a certain freedom, so that within the limits of those laws he can wonderfully modify himself and better his fortunes. More than that, he can “cozen the gods,” and outwit both Fate and Fortune, if he sets about it right. And how is that? By learning the laws of his own nature and of the physical surroundings which environ him. Knowing them, he can turn them to his own advantage.

Let us see what these are; and first, those which concern the bodily and mental constitution of the individual, so far as they bear upon his happiness in life.

Those who have studied this subject, physicians and physiologists, draw a twofold distinction in the traits of the individual, discriminating between those which he has by birth, and those which can be traced to incidents in his own history after birth. Of the former, some are “hereditary,” that is, traceable with reasonable surety to his ancestors; and others “congenital,” meaning those which appear to be due to incidents in his own history before birth. To this latter curious class belongs the development of what anatomists call “monsters;” and there are thousands such in the moral world from allied causes, of whom the anatomist takes no heed, the whole complexion of whose lives has been changed by some light impression at this infinitely susceptible period.

Of hereditary traits, the most salient are those which