When I began to study kidney function at the beginning of the century, the so-called secretion theory was widely accepted, which denied filtration in the glomerulus. At that time, I provided evidence of filtration there; it has remained unacknowledged. Gradually, under the influence of Cushny, who advocated for urine formation solely through filtration and reabsorption, and Rehberg, who conducted the mathematical treatment of this type of urine formation, this theory has become generally dominant. Furthermore, the demonstration of secretion processes, such as those of urea, uric acid, or sulfate, and more recently of phenol red, perabrodil, and p-aminohippuric acid, has not been able to shake this theory. Thus, the assumption of strong filtration and selective reabsorption is propagated through the literature almost like a dogma, as a fundamental principle.