Where individual life is not menaced by poverty or destitution, disease is the bane of existence, the barrier to physical comfort and to both mental and moral advance. Alas! how few of us have any permanent possession of sound health. In spite of medical science, sanitary protection, progress made during the last hundred years in knowledge of pathological conditions, and vast resources now at our command for subduing and mitigating every form of physical evil, disease dogs our footsteps from infancy to maturity and onwards to the grave. We have the young attacked by consumption, the middle-aged suffering from failing health, the aged struck by paralysis or bowed down by rheumatism; and everywhere we meet husbands and wives permanently saddened by the loss of the chosen companion of their life, and mothers whose light-hearted buoyancy died out for ever when the babe, prized beyond all treasure, was snatched from their arms to be laid in our appallingly numerous children’s graves. In order to form an approximately correct conception of disease, we must glance for a moment at the conditions of health. Life in all its forms, physical or mental, morbid or healthy, is in close relation to the individual organism and external forces. Health, as the consequence and evidence of a successful adaptation to the conditions of existence, implies the preservation, well-being and development of the organism; while disease marks a failure in organic adaptation to external conditions, and leads to disorder, decay and death. If we could perceive all the conditions, outward and inward, and take them into account, a distinct line of causation would become apparent. We should find disease no more an accident than the storm that breaks upon the seaboard or the volcanic flames that burst from the mountain top. The extreme complexity and delicacy of biological phenomena precludes a wide grasp of conditions in individual cases, but scientific investigation has established the point that of the antecedents to disease the largest proportion is some heritage of weakness transmitted from parents—some disabilities for healthy life resulting from a bad descent. When, for instance, mental anxiety produced by adverse circumstances is said to have made a man mad, there is implied some inherent infirmity of nervous element which has co-operated. “Were the nervous system in a state of perfect soundness and in possession of that reserve power which it then has of adapting itself, within certain limits, to the varying external conditions, it is probable,” says Maudsley, “that the most unfavourable circumstances would not disturb permanently the relation and initiate mental disease. But when unfavourable action from without conspires with an infirmity of nature within, then the conditions of disorder are established and a discord or madness is produced.” (_The Physiology and Pathology of the Mind_, p. 199.)