. Chemical embryology. Embryology. SECT. 7] OF EMBRYONIC DEVELOPMENT 993 O wet weight ©dry ,. B mgmsyocoagulable protein dissappear- ing perday: wet weight: calc. from Sakurao'. The work of Bialascewicz and Mincovna will be considered in more detail in Sections 9-9 and 11-3. The conception of an ontogenetic succcession of energy sources has to reckon, however, with a few facts which do not easily fit it. Perhaps the most difficult phenomenon to explain from this point of view is the apparent combustion of carbohydrate exclusively by mammalian embryos (Bohr). It must be admitted that the eviden
. Chemical embryology. Embryology. SECT. 7] OF EMBRYONIC DEVELOPMENT 993 O wet weight ©dry ,. B mgmsyocoagulable protein dissappear- ing perday: wet weight: calc. from Sakurao'. The work of Bialascewicz and Mincovna will be considered in more detail in Sections 9-9 and 11-3. The conception of an ontogenetic succcession of energy sources has to reckon, however, with a few facts which do not easily fit it. Perhaps the most difficult phenomenon to explain from this point of view is the apparent combustion of carbohydrate exclusively by mammalian embryos (Bohr). It must be admitted that the evidence for this is slender, but even if it were true, it would not be surprising, as most Living cells combust carbohydrate if they can get it, and the continuous perfusion system of viviparity may provide such a supply. Perhaps mammalian embryos might be regarded as having prolonged their carbohydrate period to cover the whole of their pre-natal life, and, if this were so, the peaks in basal metabolic rate found by Wood; DuBois, and others on mammals shortly after birth might be associated with maximum intensities of protein combustion. Probably other substances besides protein, fat and carbohydrates may be utilised to supply energy in some forms of life. For example, the recent discovery by Heilbron of great amounts of spinacene, a cholesterol-like substance, in selachian eggs, may lead to the solution of the problem of the energy-source of these eggs. What they combust has so far been quite unknown. Grafe in 1910 thought that there might be some connection be- tween the period of carbohydrate utilisation in the chick's develop- ment and the fact that at that time the most profound morphogenetic changes were going on. And it has been suggested that the fat period at the end might be associated with preponderance of change of size over change of shape. But perhaps the time has not yet arrived for correlations of this kind. Again, some connection may appear between the succession
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Keywords: ., bookcentury1900, bookpublishernewyorkthem, booksubjectembryology
