Abstract
Using antibodies against human growth hormone and ovine prolactine, it is possible to identify somatotropic and prolactin cells in the anterior lobe of the hypophysis (pars distalis) of the monkey, Macacus irus. These cells are present in both adult and infant male and female monkeys. The density of the somatotropic cells is greater at the periphery of the anterior lobe. Prolactin cells are of two types: one type is dispersed throughout the pars distalis and consists of small and large cells, the other type forms clusters of large cells.