278 alsberg: biochemical analysis of nutrition 



oxyphenylethylamine, is formed in the self-digestion of the 

 pancreas from tyrosine, as shown by Emerson. It is tyrosine 

 from which carbonic acid has been removed. This is of great 

 interest, since it was at one time believed that carbonic acid 

 was formed in living organisms solely by oxidation. This ob- 

 servation shows that it can also be formed by enzymatic cleav- 

 age. This is of profound biological interest, since in all prob- 

 ability the energy which is required by organisms living in an 

 environment free from oxygen is obtained by reactions of this 

 type. Ordinarily we think of such organisms as being limited 

 to the fungi, but there are quite highly organized animals which 

 live in this way; for example, parasitic intestinal worms. The 

 gases of the intestines are practically free from oxygen. In all 

 probability these worms obtain the energy necessary for the 

 maintenance of life by cleavages, rather than by direct oxidation. 

 Finally, it is interesting to note that most of these physiologically 

 active substances are amines, probably derived from amino- 

 acids by removal of carbonic acid, that is, by the elimination 

 of the carboxyl, COOH. This method of the formation of 

 amines is probably quite common in plants and leads to the 

 formation of various poisonous plant bases. It has been sug- 

 gested that the active principle of ergot is formed in this way. 



In making this digression to explain that physiologically 

 active substances may be formed from amino-acids, it was my 

 purpose to suggest that the defective or incomplete proteins, 

 when the main or sole nitrogenous element of the diet, may 

 not merely produce a form of starvation, but that they may 

 also have an indirect action through failure to supply the raw 

 materials which are needed by certain glands to elaborate their 

 specific products. 



It should not be inferred from what has been said that these 

 incomplete or defective proteins are without food value. On 

 the contrary they may be of great food value. They are merely 

 not of themselves sufficient, but they can be made sufficient 

 if supplemented in relatively small amounts by other proteins 

 that contain the lacking elements. This is a matter of the 

 greatest practical importance in the feeding of farm animals. 



