Semi-CentPAinial Volume. 195 



calcium and .126 per cent of magnesium. Compared with milk, corn has 

 more than sufficient majinesium, but should have 55 times as much cal- 

 cium as it has. 



It has been found that in biological processes there is a certain 

 antagonism between calcium and magnesium; that normal functioning 

 requires a proper balance between them, and that presentation of excess 

 of magnesium causes loss of calcium. With these facts in view it may be 

 reasonably suspected that at least a part of the unfavorable results with 

 corn are due to deficient and unbalanced ash. 



Another possible explanation of the defective nutritional power of 

 corn may be found in the constitution of its principal protein zein. An 

 understanding of this requires some knowledge of the inner constitution 

 of the proteins. These indispensable and highly complex compounds for 

 many years baffled investigation of their chemical nature, and little real 

 progress was made until about the beginning of this century. It is now 

 known that to a large extent they consist of combinations of molecular 

 nuclei derived from amino acids. These, vdth nuclei representing other 

 classes of compounds, are linked together to form structures of only 

 partially known and almost inconceivable intricacy. The proteins 

 peculiar to different plant and animal tissues differ in their inner make-up, 

 and to build up any one, in an animal tissue, for example, it is necessary 

 that most of the specific nuclei of the body protein be present in the food 

 protein. To only a limited extent, and in certain lines, is it possible for 

 the tissue to synthesize its own nuclei. 



There are about twenty amino acids which are represented in the pro- 

 teins, and may be produced from proteins by suitable procedure, and in 

 a somewhat loose way may be spoken of as present in the proteins. In 

 digestion the amino acids are produced from the proteins, and are ab- 

 sorbed by the blood and by that channel distributed to all of the tissues 

 of the body. The body organs synthesize their characteristic proteins 

 from the amino acids and other substances, but the extent to which 

 they are able to do this is limited by the amino acids that are present 

 in the relatively minimal quantities. If a certain amino acid is required 

 that is not present no protein can be produced; if it is present in but 

 small amounts, relatively, others present in abundance can be used only 

 to the extent that they are demanded to go with the one present in 

 small amount, and so but little protein can be formed. 



Mendel and Fine* have made digestion determinations upon the pro- 

 teins of corn and have found that they are digested and metabolized 

 somewhat less completely than those from meat. This does not show, 

 however, that corn proteins are utilizable for the same purpose or with 

 the same physiological economy as are meat proteins. The corn kernelf 

 contains several different proteins, the principal ones being zein, which 

 is present to the extent of about six per cent of the corn, and maize 

 glutelin four and one-half per cent. Other proteins aggregate about 

 four per cent. Together these proteins seem to contain nuclei of all of 

 the animo acids, but zein, the most abundant one, is incomplete, glycin, 



* Jour. Biol. Chem. X (1911'12) 345. 



t Osborne, Jour. Chpm. Soc. XIX; .'jSS. .\n. Rept. Conn. Agr. Expt. Sta., 1896, p. 391. 



