The Hypophysial Portal System of Vessels in Man

The portal system of vessels in the pituitary body of man has been studied by means of injection methods and red cell staining techniques. 2. The capillaries within the neural tissue of the hypophysial stalk and the lower infundibular stem constitute a first capillary bed. In both these areas the capillaries are arranged in characteristic formations, the more complex groups being confined to the hypophysial stalk. From this first capillary bed the blood is conveyed by long and short hypophysial portal vessels to a second capillary bed, the sinusoids of the pars distalis. The short hypophysial portal vessels drain the capillaries in the lower infundibular stem; the longer portal vessels drain the capillaries in the neural tissue of the hypophysial stalk. 3. The hypophysial portal vessels are the only afferent channels to the sinusoids of the pars distalis. 4. The significance of the findings is discussed in relation to the results of transection or experimental occlusion of the hypophysial stalk, and to the pathogenesis of post‐partum necrosis of the anterior pituitary.