Developing pancreases from rat embryos of the sixteenth day of pregnancy and adrenals from embryos of the nineteenth day were grown in organ culture for six days. The cultures were transferred to fresh media twice, after 48 hours and after 96 hours of incubation. Control cultures consisted of pancreas alone and of adrenal alone.
The pancreatic islets which were too young to have granulated beta cells on the sixteenth day of pregnancy differentiated into islets with many granulated beta cells during the culture period of six days. The pattern of granulated beta cells and the estimated number of these cells in cultures with adrenals were variable (not consistently different from those in the control cultures without adrenals).
The adrenals from embryos of the nineteenth day had two zones of the fetal cortex outer and inner. Cultures of adrenals survived. The adrenals, whether minced or unminced at the time of the explantation and whether cultured alone or with pancreases, underwent little if any additional differentiation during the culture period.