90 THE AMINO ACIDS 



parts, one nitrogen- free, the other containing nitrogen. 

 Inasmuch as the nitrogen-containing part plays little 

 role in energy exchange, its fate is left somewhat in- 

 definite. The part free from nitrogen forms the 

 dynamic quota of the protein ingested. When protein 

 is disintegrated into its two parts mentioned above, 

 there occurs a certain liberation of heat which is of no 

 value to the body cells and is therefore lost. This lib- 

 eration of energy has been called by Rubner the "spe- 

 cific dynamic action" of protein. 



"A highly speculative hypothesis explained how the 

 various changes took place. All protoplasm was not 

 regarded as being of the same type, one kind might 

 be thermolabile, another thermostable, but all varieties 

 had in common a certain molecular grouping which 

 acted as a kind of nucleus to which other protein 

 groups (for example those which were thermostable 

 or thermolabile) could attach themselves. The mech- 

 anism of the energy exchange, which is characteris- 

 tic of activity, was effected by a distinct vibratory 

 movement of the whole or a definite part of the proto- 

 plasm. Owing to the specific oscillation, the proto- 

 plasm had the power of bringing about the breakdown 

 of contiguous foodstuffs. The 'affinities' (specific 

 oscillations) must be of a specific nature for each 

 tissue and were probably somewhat akin to ferment 

 action. Thus, in diabetes, the 'affinities' which 

 brought about the breakdown of carbohydrates, were 

 for some reason or other in a state of suspension, 

 inoperative or actually destroyed, whereas those which 



