PHYSIOLOGY OF AGING - PROCESSES OF AGING OPERATE DURING ALL OF ADULT LIFE - DECLINE IN FUNCTION THAT ACCOMPANIES THESE PROCESSES IS APPARENTLY DUE TO PROGRESSIVE LOSS OF BODY CELLS

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Abstract
Gerontology, a young discipline dealing with the process of aging, underlies the increased susceptibility to disease that is the concern of geriatrics. This new science has found that in general the body after 30 years declines in capacity and function each day, associated with loss of overall weight and functional cells in specific tissues. The common demominator of capacity to do work was measured as the maximum amount of work an individual could do and have his heart return to normal within 2 minutes after stoping the hand crank ergometer. Using large groups of different ages, and measuring strength with a squeeze-grip device, it was found that the strength of the dominant hand drops from 44 kg at age 35 to 23 kg at age 90. Endurance (the average grip pressure for 1 min.) drops from 28 kg at age 20 to 20 kg at age 75. Speed of impulse transmission through nerves declines only 10-15% in elderly people, but the greatest losses are in the central nervous system, where memory loss is substantial. Blood flow from the heart during work falls from 3.75 l/min./m2 of body surface at age 20 to 2 1 at age 90. Twenty-year-old men take up 40 1 of O2/min., as compared to 1.5 1 at age 75, with 75% more ventilation of the lungs. Kidney functions decrease with age. Among the endocrine glands, the adrenals decrease in activity, but the thyroid retains most of its functional capacity. With age the blood takes longer to return to normal acidity and normal glucose level after experimental displacements.

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