During this period, nephrology organized itself around quantifying renal function and understanding renal hemodynamics. Researchers developed tracer-based and excretory metrics to estimate tubular excretion, renal blood flow, and filtration rate, while isolated-kidney and in vivo models illuminated how vascular shifts modulate glomerular pressure. These efforts tied anatomy to disease, linking structural change with nephritic and hypertensive phenotypes and establishing experimental approaches to dissect kidney function. Influential Works: Intercapillary Lesions in the Glomeruli of the Kidney described glomerular capillary lesions as central to nephritic disease, linking microvascular pathology to kidney function and shaping later classifications. The measurement of the tubular excretory mass, effective blood flow and filtration rate in the normal human kidney established a quantitative framework for renal physiology, enabling standardized research and future estimation of glomerular filtration rate. Studies showing that renal inflammation can provoke persistent arterial hypertension, and identification of a circulating renal vasoconstrictor, laid groundwork for vascular–nephron mechanisms underlying hypertension and foreshadowed concepts central to renin-angiotensin system discussions.