1 Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York
ANSWERS to pressing questions of life and health in the neonatal period are being widely sought in both therapeutic trials and nontherapeutic investigations. As the search for knowledge about "babies" continues, it may be helpful to relate the accumulating evidence of the heterogeneity of this population to problems of experimental design.
Obvious differences among babies may be noted first (Table I). Variation among newborn infants in age, size, and resting metabolism may approximate the changes in these dimensions to be observed over the greater part of the remaining life span. It would seem as inappropriate for the small and large neonate to be included together in experimental studies under the label "baby," as for the baby, child, and adolescent to be grouped with the adult under the heading "people."