. Chemical embryology. Embryology. SECT. 2] AND WEIGHT 433 â whole embryo (Murray and Needham) Bcalorlfic value (Murray) Ddry solid (Murray) Ocarbohydrate (Needham) ®protein (Murray and Needham) e fat (Murray) cent, per day. The lowest rate of growth ever reached by the rat after birth is 3 per cent, per day. Given percentage rates of growth, therefore, do not signify equivalent stages of development irrespective of the species of animal. Calculation of the rates of growth for various processes and indivi- dual components in the development of the embryo has also been done by other investigat
. Chemical embryology. Embryology. SECT. 2] AND WEIGHT 433 â whole embryo (Murray and Needham) Bcalorlfic value (Murray) Ddry solid (Murray) Ocarbohydrate (Needham) ®protein (Murray and Needham) e fat (Murray) cent, per day. The lowest rate of growth ever reached by the rat after birth is 3 per cent, per day. Given percentage rates of growth, therefore, do not signify equivalent stages of development irrespective of the species of animal. Calculation of the rates of growth for various processes and indivi- dual components in the development of the embryo has also been done by other investigators using the Minot method. In 1927 I calculated the percentage growth-rate for the total carbohydrate content of the chick embryo; it fell from 56 to 22 per cent. In Fig. 54 is shown the fall in the Minot curves for the wet weight of the whole embryo, the calorific value, the dry weight of the whole embryo, the sugar, protein, and fat content of the embryo. All of ^° them fall, but we have here an instance of the limited but real value of the Minot curves, which, although no absolute conclusion can be drawn from them, do show that the tissue constituents and the dry weight have a different behaviour from the wet weight. It can easily be seen that they form a plateau between the loth and the 15th day, during which they grow at a constant rate while the wet weight is falling all the time. This plateau also appears on the curves for carbon dioxide output calculated in the same manner as percentage growth- rates from the figures of Bohr & Hasselbalch; Atwood & Weakley; and Murray in 1927 by Brody. The plateau must be due to the fact that the growth of dry substance is specially rapid during the middle phase of development; it is then that the embryo makes the most rapid strides from wetness to dryness. It is interesting to see that the growth-rate of carbohydrate is never as high as some of the others, and never drops so low. It is significant, moreover, that on the
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Keywords: ., bookcentury1900, bookpublishernewyorkthem, booksubjectembryology
