Were there one fixed standard of health to which all could attain, the practice of hygiene would be attended by a charming simplicity. Unfortunately, modern science forces us to conclude that each individual can only reach his own particular standard of well-being. The grades of health are consequently infinite in number, and the task which devolves on parents and guardians to secure that the standard possible to each child under their care be attained is no light one. So general is the blindness to these truths, that the degree of health enjoyed is in most cases far below the possible standard; the results of ancestral vice, of parental ignorance, or of defective environment having sapped prematurely the springs of progressive potentiality.[116] The mental and physical balance is thus rendered relatively less stable and the powers of resistance to adverse conditions are diminished. Happily, by virtue of its inherent power, but strictly in proportion to the vigour of this power, an organism is usually able to strike a new balance; for the capacity to regain its equilibrium is exquisitely delicate in human nature, _if_ the change be neither too sudden nor too severe. Throughout life this process of self-adaptation to the presence of morbid influences is constantly exercising its protective power. If, however, the effort to overcome disadvantageous conditions be very great or much prolonged, the life of the individual is never quite so vigorous and symmetrical as it might and should have been. In a luminous address, delivered at the University of Leeds some few months ago,[117] Lord Justice Fletcher Moulton instituted a comparison between the human organism, which invariably tends to swing back to the normal whenever the balance of health is disturbed, and a ship which has safely weathered a stormy voyage. The ship, he writes, "is not stable, if stability means that she can defy the forces that bear on her to move her from her normal upright position, for ... the slightest roll of the sea ... will make her heel over. But she is stable, because when made to lean over, there is thereby generated a system of forces tending to return her to her place, which grows greater the greater is the displacement, and thus ultimately becomes sufficient to overpower the disturbing forces.... As the ship arrives safely, her construction must be such that disturbances tend to right themselves when stability is seriously endangered. Some corresponding righting force also tends to bring back an organism to its normal state." The caution may not be amiss that the amplitude of the swing of a human pendulum, as well as the accuracy of its final balance, depends not only upon inherited nature and the amount of reserve force possessed, but will be stable or feeble, durable or transient, according to the influence of environment.