DYNAMIC ACTION OF PROTEINS 123 



be entirely negligible in the extensive energy trans- 

 formations for body maintenance." 



These results are in accord with conclusions reached 

 earlier by Rubner who denied that the work of diges- 

 tion and assimilation could be held responsible for the 

 effects observed after food ingestion. 



Benedict is of the opinion that from the food sub- 

 stances are absorbed which, carried by the blood, stimu- 

 late cells to greater activity, and he further indicates 

 that these unknown bodies are of an acid character. 

 From his extensive investigation on the influence of 

 amino acids upon metabolism, that is, their specific 

 dynamic action, Lusk believes that the explanation of 

 Rubner as to the cause of specific dynamic action must 

 be revised. "Amino acids act as stimuli upon the 

 cells, raising their power to metabolism. They may 

 act instead of nerve stimuli when increased heat pro- 

 duction is required in the presence of external cold 

 the chemical regulation of temperature of Rubner. 

 The energy liberated in response to these stimuli may 

 be supplied by carbohydrate or fat. When fat and 

 carbohydrate are given separately or together there 

 may be an increased heat production on account of 

 the increase in the quantity of materials available for 

 the nutrition of the cells. With the cessation of 

 absorption and the return of the blood to the compo- 

 sition it possessed before food was taken the metabo- 

 lism falls to its basal value." When glucose and an 

 amino acid, as alanine, are given together the metab- 

 olism is increased to a point where the resultant effect 



