The Renal Heart

FOR several centuries physiologists have concentrated their researches on the production of urine by the kidney. Many theories have been formulated, and it now seems to be established that this is a process of filtration and selective reabsorption. The problem cannot yet be said to have been completely elucidated. Perhaps partly because of the exhausting nature of their researches, and the lack of finality aChieved, they have devoted little attention to the next stage-the conveyance of the urine to the bladder. This dynamic function begins when the urine leaves the apices of the pyramids by the openings of the collecting tubules, to enter the pelvis of the ureter. The ureter achieves its union with the kidney by expanding into a triangular chamber, from which bud forth two limbs, which we call the major-calyces, and from these again spring other limbs, three to four from each calyx. These end in little cups, each embracing one or more pyramids of the renal medulla. The collecting tubules open irnto these cups, and so they receive the finished product of the kidney. By a little tedious dissection, the pelvis of the ureter can be coaxed from its embrace of the inner surface of the kidney proper; leaving .behind the hollow space properly called the renal sinus. I emphasise this distinction between the renal sinus and pelvis because the latter is essentially part of the ureter, and should be called pelvis of ureter, not of kidney, as so often happens. This collecting chamber of bizarre shape is, of course, the dynamic mechanism by which the urine is propelled down ureter to bladder. 'Its walls, and those of the ureter, have their smooth muscle of muscularis mucosa type, and there is a peristaltic rhythm, probably in normal circumstances at a rate of' about four contractions per minute. It was not until I began to study the effects of hydro-nephrosis, that it became impressed upon me that some sort of ordered peristalsis must be operative. The physiologists have-been handicapped by lack of abnormal material, which in this case gives the first clue to normal function. It is, of course, well known that any hindrance to the flow of urine into the bladder, acting over any length of time, will cause dilatation of the ureter and its pelvis. In most of the cases I encountered, this dilatation was confined to the pelvis of the ureter, and the site …