“…For instance, the altered responsiveness of lymphoid tissue and the macrophage system results in reduced antibody production and reduced general resistance to infection. Similarly, the lessening of adrenal function and the rigidity of the vascular system alter the process of inflammation, producing, in Lehr's (1) words, “an amazing poverty of constitutional and local reactions to injury and infection.” In the past, researchers in the field of gerontology have aimed at prolonging life with hormones, vessel‐protecting agents, serums, drugs and grafts. More recently the emphasis has been shifted to investigations into the basic cellular causes of aging.…”