PHYSIOLOGICAL VALUE OF DIFFERENT PROTEINS 493 



protein ingestion is not an unmixed good to the adult body ; 

 aside from the fact that it forces upon the kidneys an in- 

 creased functional demand, it also makes increased demands 

 upon the provisions for temperature regulation. Later on, 

 in connection with the subject of heat production in the body, 

 this particular point in protein metabolism, for which Eub- 

 ner has introduced the term ' i specific-dynamic action, ' ' will 

 be again taken up. 



Physiological Value of Different Proteins. Heterospe- 

 cific and Homospecific Proteins. The question may here be 

 taken up, whether the different proteins are to be considered, 

 as far as their nutritive value is concerned, as physiologically 

 equivalent. It is obvious that the organism, in order to con- 

 struct the proteins peculiar to its tissues, makes use of 

 "building stones," particularly aminoacids, in the same pro- 

 portion in which they exist in the tissues. That the con- 

 struction of the body is largely independent of the char- 

 acter of the food has been shown by Abderhalden and 

 Samuely : 24 the serum proteins contain eight to nine per 

 cent, of glutaminic acid, while a vegetable protein, gliadin, is 

 made up of about half (according to T. B. Osborne, 43 per 

 cent.) of this latter. It has been shown that the constitution 

 of the serum proteins of the horse is in no wise disturbed by 

 gliadin feeding. 



There is a question here which forces itself upon every 

 one who reflects upon protein metabolism how it happens 

 that the same amount of protein which is broken down in the 

 course of fasting is not sufficient to maintain the body in 

 nitrogen equilibrium when ingested. C. Voit long since rec- 

 ognized that if we seek to maintain this, a multiple of the 

 nitrogen which appears in the urine in protracted fasting 

 must be given in the form of protein. Michaud 25 (in Liithje's 

 Clinic) has raised the question whether it may not perhaps be 



24 E. Abderhalden and F. Samuely, Zeitschr. f . physiol. Chem., 46, 193, 1905. 



25 L. Michaud (Liithje's Clinic, Frankfurt a. M.), Zeitschr. f. physiol. 

 Chem., 59, 405, 1909. 



