On changes in the glomeruli and tubules of the kidney accompanying activity

The experiments described in this paper were designed to test the correctness of the view put forward by one of us, namely, that the glomerulus is a propulsor. If this view be correct, the marked dilatation of the tubules, which is so prominent a feature in a kidney after active diuresis, is simply the expression of the forcible distension of the tubule from within, effected by the discharge of fluid from the glomerulus down the tubule, the active propelling and dilating force being the intraglomerular blood-pressure transmitted through the glomerular capillary cells and epithelium. As, however, the condition of the glomerulus after active secretion has not been made the subject of extensive observation, it seemed probable that a thorough study of the alterations in size and appearance of both tubule and glomerulus might give many points of importance in criticising the propulsion theory. Thus, if the capsule be free to expand, we may find it enlarged after active diuresis; and again, if the propulsive action of the glomerulus is complete and instantaneous, we should find the glomerulus filling Bowman’s capsule completely under all conditions. But it was also possible that, after a very free secretion of water, there might be a considerable accumulation of fluid between the glomerulus and the capsule wall. We therefore measured the sizes of the capsules, the glomeruli and the tubules in kidneys, before and after diuresis had been set up under varying conditions. The more important of these states were:— 1. The kidney at rest. 2. The kidney secreting freely. This we term an “active free” kidney. 3. Decapsulated and secreting freely. This we term an “active decapsulated” kidney. The aim of the procedure was to test the explanation offered by the theory as to the meaning of the Capsule.