. Chemical embryology. Embryology. II50 THE METABOLISM OF NUCLEIN AND [pt. iii used White Leghorn embryos. As Fig. 347 shows^ the ratio, far from being, as Targonski thought, a constant, changes very markedly. Attention may first be concentrated on the curve obtained from LeBreton & Schaeffer's data, the curve for embryo alone, the membranes not being included. It begins at a very high value but immediately descends to reach a minimum on the 11 th day, or, in other words, a condition when the excreted purine—the uric acid— somewhat exceeds the architecturally utilised purine. This min
. Chemical embryology. Embryology. II50 THE METABOLISM OF NUCLEIN AND [pt. iii used White Leghorn embryos. As Fig. 347 shows^ the ratio, far from being, as Targonski thought, a constant, changes very markedly. Attention may first be concentrated on the curve obtained from LeBreton & Schaeffer's data, the curve for embryo alone, the membranes not being included. It begins at a very high value but immediately descends to reach a minimum on the 11 th day, or, in other words, a condition when the excreted purine—the uric acid— somewhat exceeds the architecturally utilised purine. This minimum precisely corresponds, as is shown by the vertical line on the graph, with the point of maximum intensity of uric acid production, which has been already described, and which is pictured in Fig. 323. Later, Targonski's ratio rises again, and then falls slightly, although the uric acid excre- tion always exceeds the laying- up of purines in the cells. If now the Fridericia curve is considered, it will be seen that the ratio does not dip below the unity line till the i8th day, which shows that, if the purines in the membranes are taken into consideration, then the anabolic purines rather exceed the cataboHc purine during most of development. The first trough is present, although shifted some 2 or 3 days forward, but the time of the subsequent peak is little changed. In short, Tar- gonski's ratio varies during development with the intensity of protein metabolism, as we should expect from the fact that the main end- product of protein metabolism in the bird is a purine ring. 10-2. The Nucleoplasmatic Ratio This expression was originally introduced by R. Hertwig, who in 1903 suggested that there was a definite relation between the mass of the nucleus and the mass of the cytoplasm. "The diminution of the nuclear mass seems, as Boveri has shown, to bring with it a diminution in cell size; the augmentation of the nuclear mass, according to Gerassimov, leads to augmentatio
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