BLOOD VESSELS OF THE MAMMALIAN RENAL MEDULLA.

Sections and macerated specimens of kidneys from several species of wild and domestic mammals injected with India ink or vinyl acetate, or both, show that the specialized blood vessels of the renal medulla (vasa recta) consist of parallel, relatively unbranched vessels which break up into plexuses at different levels of the medulla. This concept differs from that expressed in many current textbooks. In some species there is a distinct zonation of the medullary blood supply, and in certain other species no zonation was observed. Functional differences exist between these two groups, and it is suggested that these differences may be due to the vasa recta.