Studies on the Mechanical Fragility of Erythrocytes : I. Normal Values for Infants and Children

1. The mechanical fragilities of incubated and nonincubated erythrocytes of normal newborn infants, children and adults have been determined through the use of a simplified rotator.

2. The mean mechanical fragility of nonincubated erythrocytes was 7.1 per cent for newborns, 4.0 per cent for children and adults; the mean mechanical fragility of incubated erythrocytes was 13.4 per cent for newborns, 10.5 per cent for children and 10.8 per cent for adults.

3. The possible relationship of increased mechanical fragility of erythrocytes in the newborn to increased hemolysis in the neonatal period is suggested.

4. Possible causes of variation in the determination of mechanical fragility of incubated erythrocytes are discussed.