Correlation of Uric Acid Production with Growth of Kidney Tubules in Chick Embryos.

Abstract

In previous microchemical studies it was shown 1 that uric acid is the chief end-product of nitrogen metabolism in chick embryos, that it begins to accumulate in the allantoic cavity sometime during the fifth day of incubation and that the rate of its excretion rises, in general, proportionally with the body weight. By the end of the first 13 days of incubation the allantoic fluid contains, on the average, 15 mg. of uric acid dissolved more or less completely in about 6 cc. of water. These facts have sufficed to prove that the mesonephros is an active excretory organ and that protein is burned by the developing embryo to a significant degree.

The present article represents a continuation of this cooperative study with Dr. Fiske, in which attention has been focused on the morphological development of the mesonephric tubules. As a basis of study 7 serially sectioned chick embryos from the Harvard Embrological Collection, ranging from 5 to 14 days of incubation, were selected for reconstruction. These were graded embryos that had been collected and serially sectioned, some years before, under the supervision of the writer. Every third section throughout the length of the mesonephros of each embryo was drawn to scale under an Edinger projection apparatus. On these drawings each glomerulus was systematically recorded and the total number counted. Then, by the Born method, wax models of the Wolffian bodies were reconstructed. Finally, at a much higher magnification, 7 mesonephric tubules—one from each embryo, and selected from comparable portions of the left Wolffian body—were reconstructed in wax. The modelling of these tubules proved to be a difficult undertaking, especially in the 55 mm. embryo where the convolutions were exceedingly tortuous.