. Chemical embryology. Embryology. SECT, ii] FAT METABOLISM 1171 acids of the chick embryo and the rest of the egg throughout develop- ment. Her resuks are plotted in Fig. 365, from which it appears that there is little change during the first 10 days of development, but that after that time the iodine value of the fatty acids in the chick rises, while that of the fatty acids in the remainder of the egg falls. This decrease in the iodine value of the yolk-fat during development is highly suggestive of a primary absorption of the less saturated fats with a subsequent equal absorption of saturat
. Chemical embryology. Embryology. SECT, ii] FAT METABOLISM 1171 acids of the chick embryo and the rest of the egg throughout develop- ment. Her resuks are plotted in Fig. 365, from which it appears that there is little change during the first 10 days of development, but that after that time the iodine value of the fatty acids in the chick rises, while that of the fatty acids in the remainder of the egg falls. This decrease in the iodine value of the yolk-fat during development is highly suggestive of a primary absorption of the less saturated fats with a subsequent equal absorption of saturated and unsaturated fat. The increase in the iodine value of the embryonic fatty acids points to an absorption of the more desatu- rated fatty acids, and suggests that in the early stages the chick embryo does not possess the power of per- forming the desaturation. If the embryonic liver was incapable of desaturating fatty acids until, say, (O Chick Eaves <• Remainder (3 Whole egg. Days-*-5 To is 20" the loth day of development, it P^ g might be supposed that the unsatu- rated fatty acids would be preferentially absorbed, as the saturated ones would be of no use to the embryo. However, no a priori argu- ments are here of importance, and I accordingly arranged a series of experiments to test the hypothesis. An aqueous emulsion of embryonic tissues was mixed with the corresponding yolk and vigorously shaken, after which it was allowed to stand anaerobically under toluene for 5 days at 37°. The results were as follows (fatty acids being separated by the Mottram-Lemeland technique): Iodine value 6-day yolk alone 6-day embryo and 6-day yolk ... 2-day embryo and 12-day yolk ... 9-day embryo and 19-day yolk ... Before After experiment experiment 76-0 66-8 69-8 66-4 72-8 qi-6 6i-2 8o-o Thus where the 12th and 19th day embryonic cells were present there was a very marked desaturation occurring, but not in the case of the 6th day embryo, nor the 6th day yolk alone. If this set
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Keywords: ., bookcentury1900, bookpublishernewyorkthem, booksubjectembryology
