618 METABOLISM, NUTRITION AND DIETETICS 



her tissue waste completely, but she had produced from it every- 

 thing necessary for the development of the embryo rats up to full 

 term, and after that everything necessary (in the form of milk) 

 for their normal growth during the period of suckling. On the 

 whole, a very large amount of body tissue in proportion to the 

 original weight of the mother must have been formed or renewed 

 in the 200 days or more during which the experiment continued, 

 and during which gliadin was being steadily transmuted into tissue 

 protein, and latterly into the proteins of milk as well, by what 

 might almost be called a feat of chemical legerdemain. There must 

 have occurred a synthesis ' not only of the Bausteine (the " building- 

 stones ") deficient in the protein intake, but likewise of tissue and 

 milk components like the nucleic acids (with their content of purins, 

 pyrimidins, and organically combined phosphorus) and phospho- 

 proteins like casein, etc., which were completely missing ' in the food. 



It has been suggested that the bacteria of the alimentary canal, 

 which, of course, are plant cells, may have and may exercise on a large 

 scale the power of building up new amino-acids from a variety of 

 materials in the intestinal contents, and that they may thus be synthe- 

 sizing agents, thanks to which inadequate proteins may be reshaped to 

 proteins adequate to the needs of the body. It is precisely, however, 

 in the case of incomplete proteins like gelatin deficient in cyclical 

 compounds, that the body fails to effect the necessary transformation 

 in spite of the fact that plant cells are supposed to be specially capable 

 of forming these compounds. In any case bacterial action would not 

 explain why proteins like gliadin and hordein are only adequate for the 

 renewal of tissue, and not for its growth. This points rather to the 

 possibility that the processes by which the nitrogenous compounds 

 degraded in cellular metabolism are replaced are not of the same char- 

 acter as the processes by which new nitrogenous complexes are built 

 up into growing protoplasm. If, for instance, the protein molecule is 

 not completely disrupted in ordinary metabolism, it will not need to be 

 completely reconstructed, while in the formation of new tissue complete 

 protein molecules will have to be synthesized. Incomplete proteins 

 like gliadin may furnish building-stones adequate for repairing the 

 house, but inadequate for building it from the foundations. 



Income and Expenditure of Carbon The Carbon Balance-Sheet. 

 This division of the subject has been .necessarily referred to in 

 treating of the nitrogen balance-sheet, and may now be formally 

 completed. 



Carbon Equilibrium. A body in nitrogenous equilibrium may or 

 may not be in carbon equilibrium. It has been repeatedly pointed 

 out that the continued loss or gain of carbon by an organism in 

 nitrogenous equilibrium means the loss or gain of fat ; and, since 

 the quantity of fat in the body may vary within wide limits without 

 harm, carbon equilibrium is less important than nitrogen equili- 

 brium. It is also less easily attained when the carbon of the food 

 is increased, for the consumption of fat is not necessarily increased 





