CHANGES IN THE GROSS CHEMICAL COMPOSITION OF THE MOUSE DURING GROWTH IN RELATION TO THE ASSESSMENT OF PHYSIOLOGICAL AGE

Abstract

The body composition of 111 male white mice in terms of protein, water, fat and ash was determined. On the average, the protein, water and ash fractions appeared to exhibit differential growth with respect to the body weight and to the fat-free weight. The concentration of fat in the body was extremely variable and presumably reflected nutritive condition. The regularity of the average changes in the composition of the fat-free body appeared to be a fundamental property of the growth of mice, the percentage of water decreasing and of protein and ash increasing as growth proceeds. A new index of physiological age, the protein to water ratio, is suggested and evidence for its usefulness is presented.