ANTERIOR AND POSTERIOR GROUPS OF PORTAL VESSELS IN AVIAN PITUITARY

Distinct anterior and posterior groups of portal vessels originating from the primary capillary plexus of the median eminence and supplying, respectively, the cephalic and caudal lobes of the pars distalis of the avian pituitary have been demonstrated in fifteen species of birds. It is suggested that the existence of two distinct groups of portal vessels is correlated with the cytological differentiation of the pars distalis and may be widespread among birds. © 1969.