The following investigation was undertaken in the hope that actual photographic records might be submitted of the renal vessels in the later stages of their distribution and that the evidence produced might definitely eliminate the doubt that exists regarding certain features of their finer circulation. A review of the literature reveals an inconsistency of findings, together with a certain looseness of terminology. Slight differences in terminology are to be expected, but one does not expect to find such diversity of opinion regarding the finer circulation of an organ of such importance as the kidney. The two outstanding points of controversy seem to be ( a ) the origin of the arteriae rectae of the medulla and ( b ) the existence or nonexistence of any blood supply to the cortex from the renal artery, which has not previously traversed a glomerulus. In 1842, Bowman 1 wrote his classic account of the renal circulation. He