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A reconsideration of nitrogen excretion by the chick embryo

✍ Scribed by Clark, Hugh ;Fischer, Daniel

Publisher
John Wiley and Sons
Year
1957
Tongue
English
Weight
660 KB
Volume
136
Category
Article
ISSN
0022-104X

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✦ Synopsis

T W O FIGURES

Previous observations on the nitrogenous excreta of the chick, summarized by Needham ('31) showed a peak of ammonia production at 4 days, of urea at 9 days and of uric acid at 11 days. Total nitrogen excreted was reported as 11.124 mg. of which uric acid constituted 91.35%, urea 7.58%, and ammonia 1.07%. The sequence of excretory products was cited as an outstanding example of recapitulation; the quantities of excreted nitrogen, with certain other data, served as a basis for estimation of energy sources, and the significance of uric acid in water conservation was stressed as essential for the cleidoic vertebrate egg. The findings with regard to the chick were extrapolated to the reptiles, so that the pattern described above is cited as the sauropsid pattern.

The observations were made in the black snake embryo (Clark, '53) that (1) only 20% of the nitrogenous excreta appeared as uric acid, (2) total N excreted (12.5 mg) by the snake embryo attaining a wet weight of 7 grams exceeded that reported for the chick, (3) there was a subterminal decline in accumuIated urea, coincident with a sharp rise in uric acid production and (4) urease was identified in the fetal liver and kidney, coincident with the urea-uric acid reciprocal relationship. It seemed expedient, therefore, to re-examine the excretory pattern of the chick. Specifically the data sought

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