492 NUTRITIONAL REQUIREMENTS 



For decades the propriety of this differentiation has been a 

 matter of contention. Pfliiger in particular has most vio- 

 lently assailed it. The author frankly confesses that he has 

 never fully appreciated the importance of this contention. 

 Is there anything so remarkable in the point that con- 

 stituents of the body, so distinct from an anatomical stand- 

 point as blood-proteins and tissue-proteins, should from 

 many aspects also present distinctive physiological features ? 

 Is it to be assumed as a fact that every protein which a few 

 hours after a meal occasions an increased nitrogen elimina- 

 tion had previously become ' ' organized" ? Investigations in 

 recent years have clearly shown that a differentiation 

 between endogenous and exogenous tissue-metabolism is 

 thoroughly justified; while the urea elimination seems pri- 

 marily dependent upon the protein which is introduced we 

 realize that the excretion of other urinary constituents, as the 

 oxyproteic acids, urochrome, creatinin and uric acid, is de- 

 termined essentially by the break-down of tissue. 22 It may 

 be that the author is not enough of an expert to be able to 

 thoroughly comprehend fine points of distinction; but he 

 cannot rid himself of the feeling that in the endless disputa- 

 tions over these and many related ideas there is a trace of the 

 scholasticism of the Middle Ages. 



Specific-dynamic Action of Protein. While the introduc- 

 tion of fat and of carbohydrates in the food leads to an in- 

 crease in the body stores, increase of the proteins of the food 

 gives rise merely to an increased protein exchange. Accord- 

 ing to Rubner's theoretical views the protein undergoes a 

 cleavage into a nitrogenous and a non-nitrogenous fraction. 

 To the latter, along with the carbohydrates and fats, falls the 

 role of providing for the energy requirements of the 

 economy ; continuous combustion of the nitrogenous moiety, 

 in as far as it cannot be made of use for purposes of tem- 

 perature regulation, leads to a loss of energy. 23 Increase of 



23 Cf. O. Hammersten's Lehrb., 7th ed., 851, et seq., 1910. 

 23 Cf . O. Hammersten, 1. c., p. 859. 



