110 THE AMINO ACIDS 



sugar production. If we take a typical protein as egg 

 albumin, and then on the assumption that all the nitro- 

 gen present is eliminated from the body as urea, we 

 find left over a large carbon residue, the so-called 

 "carbon moiety," of the protein which may be regarded 

 as material capable of being transformed into carbo- 

 hydrate. This potential of carbohydrate forming 

 material must gain access to the blood stream, hence 

 to the tissues, in the form of amino acids, in accord- 

 ance with the present-day view of the processes of 

 metabolism. The problem under consideration, there- 

 fore, resolves itself in the question, "Are amino acids 

 capable of being transformed into carbohydrates?" 

 The most convincing work in this direction is that of 

 Lusk and his pupils. They have administered to dogs 

 rendered diabetic with phlorhizin various amino acids 

 and have observed that some yield sugar whereas 

 others fail to do so. In their experiments the relation- 

 ship between the dextrose and nitrogen of the urine, 

 the D : N ratio, was determined. Under suitable con- 

 ditions this becomes a constant. The ingestion of 

 sugar forming substances changes this constant and 

 any change serves as an index to the quantity of sugar 

 formed from a given amount of substance introduced. 

 It was found that the N-f ree parts of glycocoll, alanine, 

 aspartic acid, and glutamic acid, containing respectively 

 two, three, four, and five carbon atoms may be either 

 completely or partially transformed to dextrose. All 

 of the glycocoll and all of the alanine were converted 



