The influence of race and sex on the incidence of prematurity has been considered in several previous investigations. Riggs1 and Pride2 found that the average birth weight of Negro infants is less than that of white infants. Employing birth weight as the criterion for prematurity, Woodbury,3 Ford4 and Bivings5 noted a higher incidence of prematurity in the Negro race. It has long been known that the average birth weight of girls is less than that of boys. The influence of both race and sex on birth weight has been reported by Bakwin and Bakwin6 and by Dunham, Jenss and Christie.7 In a roentgenographic study of the osseous development of newborn infants, Christie, Dunham, Jenss and Dippel8 have shown that for the same weight groups the center of ossification for the cuboid bone is more frequently present in infants of the Negro race