The axiom that disuse leads to atrophy applies perhaps even more to mental activity, for resting and rusting of the brain slow the pace of the whole body, whereas an alert mind can exist in an infirm body. There is no doubt that occupation with a strong desire to live for the accomplishment of a definite purpose exerts a most beneficial influence, and there have not been wanting some, such as Karl Marx, who have preached that old age is in great part a matter of will. Speaking of the circle in which Madame du Deffand moved Lytton Strachey[66] says “They refused to grow old; they almost refused to die. Time himself seems to have joined their circle, to have been infected with their politeness, and to have absolved them, to the furthest possible point from the operation of his laws. Voltaire, d’Argental, Moncrif, Hénault, Madame d’Egmont, Madame du Deffand herself all lived to be well over eighty, with the full zest of their activities unimpaired.” Want of this joy in life necessarily engenders carelessness and neglect of personal hygiene, and loss of the power to react to the environment. As the years advance and the younger generation come up, the suggestion that “his day is done,” that he has had his innings, and that it is time for him to step aside, is made to the senior not only by his family and his juniors--hetero-suggestion--but by himself, and he may then, after the modern fashion, get into the habit of repeating mentally “I am getting older and older every day.” A slight illness or incapacity may be magnified into a conviction that the end is near, and as a result of the loss of self-reliance a state of increasing invalidism is established and becomes progressive without any other cause. Just as a fall, an exacerbation of rheumatic pain, a slight operation or indisposition, necessitating rest in bed for a short time, may be followed by a functional loss of power in the lower extremities, so a more general suggestion of failing powers may lead to mental deterioration. Thus too often a man’s last occupation is to shorten his existence and make it miserable. Finot,[67] who rather optimistically believes that man should be able to live 150 years, regards this poisonous auto-suggestion as one of the factors that prevent such an achievement. Observation of contemporaries suffering from premature senile changes, due to pathological factors, may no doubt stimulate this destructive form of auto-suggestion. There is therefore a basis for the idea[68] attributed to the late Lord Rhondda that old age was a transferable disease, and for his avoidance, as far as possible, of the society of the aged on account of the risk of contagion. Association with the young keeps one more or less of the same age, very probably by suggestion to the unconscious, or in Oliver Wendell Holmes’s words “While we’ve youth in our hearts we can never grow old.” From experience at the Royal Hospital, Chelsea, where there