Horse-radish peroxidase was injected intraperitonealy to fasted and fed newborns. The protein was rapidly absorbed by the fasting animals and more slowly by the fed newborns. The tracer was progressively segregated into the supranuclear cluster of dense tubules and dense bodies. The cellular sap of several cells was deeply stained after the intraperitoneal injection. Control experiments showed that peroxidase has a high affinity for the matrix of the dense bodies in the first days of neonatal life.