STUDIES ON ERYTHRO‐KINETICS IN INFANCY:XIII. <i>The mean Life Span and the Life Span Frequency Function of Red Blood Cells Formed during Foetal Life</i>

Abstract

Summary Equations were developed for the relation between the production rate, the life span frequency function and the number of circulating erythrocytes and for the relation between the production rate, the life span frequency function and the relative number of circulating cells after random labelling. With the help of explicit expressions for the production rate and the life span frequency function of erythrocytes formed during the latter part of foetal life, the increase in number of circulating cells during this period and the relative decrease in circulating labelled cells in a simulated cord red blood cell survival experiment were calculated on a digital computer and compared with experimental data. Through the simulation procedure, the parameters in the life span frequency function and the production rate function were estimated. The life span frequency function of the red blood cells did not change appreciably during the last 60 days of foetal life. The mean cell life span was found to be between 45 and 70 days. The life span frequency function was skew with the majority of cells dying before the mean life span. The relative rate of production of erythrocytes during the last two months of gestation was found to be 3–5 times that of normal adults.