CHANGE IN THIOCYANATE AND SODIUM24 SPACES DURING GROWTH

Abstract

The spaces occupied by one or more of the four substances, thiocyanate, sodium24, mannitol and inulin, were determined in 36 subjects ranging from premature infants to adults. No conclusions could be drawn concerning the spaces occupied by mannitol and inulin, since, under the conditions of the observations in our human subjects, neither of these spaces reached a constant value. There is a definite decrease in the spaces occupied by thiocyanate and sodium24 as growth proceeds. If the changes in the spaces occupied by these two substances reflect corresponding changes in extracellular fluid volume, they indicate that young infants have an extracellular volume which is 57 (sodium24) to 78 (thiocyanate)% greater than that of the adult. The decrease in the spaces occupied by thiocyanate and sodium24 occurs at two distinct periods of growth: primarily during early infancy and also during adolescence.