110 



MAINTENANCE RATIONS OF FARM ANIMALS. 



snmably from the amino-acids containing a larger number of carbon 

 atoms. Whether a change in the opposite direction, that is, a syn- 

 thetic change, can take place can be at present only a matter of specu- 

 lation, but such a change would be entirely analogous to the building 

 up of the fatty-acid chains from carbohydrates, which is a common 

 occurrence in the body. Moreover, Knoop, 1 and Embden and 

 Schmitz 2 have found that certain amino acids may be formed syn- 

 thetically from the corresponding fatty acids and ammonia, thus 

 indicating a possible chemical mechanism by which a deficient sup- 

 ply of some one amino-acid might be to some extent overcome. While, 

 therefore, we can hardly suppose that the proportions of the different 

 cleavage products is a matter of entire indifference, we can easily 

 imagine that there may be more or less transformation of one into 

 another in case of need. 



Finally, there is the possibility that in the absence of some one 

 amino-acid from the feed, the corresponding acid resulting from the 

 katabolism of protein tissue may to a greater or less extent escape the 

 action of the deamidizing enzyms and be regenerated to protein. 

 This would obviously be quite in accord with the conception of the 

 protein metabolism as a complex of reversible enzym reactions which 

 was outlined on page 87. 



1 Zeitschrif t fur Physiologische Chemie, vol. 67, p. 489. 



2 Biochemische Zeitschrift, vol. 29, p. 423. 



O 



