. Chemical embryology. Embryology. 1040 CARBOHYDRATE METABOLISM [PT. Ill Fig. 288). The blood sugar, however, is not a large enough factor to affect to any great extent the free glucose of the embryo as a whole, as a rough calculation demonstrates. Assuming 230 mgm. per cent, for the 20th day, the amount of blood in the embryo would be 1-54 gm. (from the formula of Dreyer & Ray, 5 = -^, takmg the mouse value (6-7) for K as the mammal nearest in weight to the hatching chick). This would give 3-53 mgm. of blood sugar, which, although a high estimate, is only 15 to 20 per cent, of all th
. Chemical embryology. Embryology. 1040 CARBOHYDRATE METABOLISM [PT. Ill Fig. 288). The blood sugar, however, is not a large enough factor to affect to any great extent the free glucose of the embryo as a whole, as a rough calculation demonstrates. Assuming 230 mgm. per cent, for the 20th day, the amount of blood in the embryo would be 1-54 gm. (from the formula of Dreyer & Ray, 5 = -^, takmg the mouse value (6-7) for K as the mammal nearest in weight to the hatching chick). This would give 3-53 mgm. of blood sugar, which, although a high estimate, is only 15 to 20 per cent, of all the free sugar in the embryo. The results which have been obtained on mammalian embryos are sHghtly more coherent. Aron investigated the blood 99nU ^Schr sugar of embryos of the guinea-pig, rabbit, dog, cow and pig, using the Fontes- Thivolle method and accu- mulating the results shown graphically in Fig. 289. Al- though the points arrange themselves roughly along de- finite curves, Aron did not treat them as if this was so, but simply averaged out the data, and concluded that for each species of embryo there was a characteristic blood sugar level which did not change appreciably throughout intra-uterine Hfe. The values thus calculated were as follows: 220 210 200 190 '180 Hanans lowest O Normal adult level (ScheunertS^,Pelchrzim). Fig. 288. Blood sugar in mgm. % Species Foetal Maternal Guinea-pig 60 107 Rabbit It 125 Dog no Cow no 100 Pig 139 100 Thus in some cases the glucose concentration in the foetal blood was higher, in other cases it was lower, than in the maternal blood. For comparison, the following values of other observers may be advan- tageously placed Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Needham, Joseph, 1900-. New York: The MacMillan Co.
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