306 PHYSIOLOGY OF ALIMENTATION. 



After starvation for a week, in order to free the alimentary 

 tract from food, analysis of another six litres of blood yielded 

 practically the same results : 



Tyrosin 2 . 60 percent 



Glutamic acid 8.20 " 



The horse was now fed a protein (gliadin) which is much 

 richer in glutamic acid than blood serum and contains about 

 the same percent of tyrosin. Even when 1500 to 2500 grams 

 of the protein were fed analysis of the blood showed prac- 

 tically no variation in its composition. The following table 

 gives the results of three experiments: 



1500 gms. 1500 gms. 2500 gms. 

 Percent. Percent. Percent. 



Tyrosin 2.24 2.52 2.48 



Glutamic acid 7.88 8.25 8.00 



It seems, therefore, as though an actual synthesis of pro- 

 tein occurs in the wall of the intestine itsslf. From the 

 most varied kinds of protein consumed by an animal are con- 

 structed first of all the serum albumin and serum globulin found 

 in the. blood-serum of that animal, and from this serum, so 

 constant in its composition, the different cells of the body each 

 take the substances necessary for their purposes. Indirectly 

 we find in these considerations support for the idea that the 

 proteins are absorbed from the alimentary tract only in the 

 form of the simple digestion products, for these can most 

 readily be joined chemically to produce the protein bodies 

 characteristic of the animal under consideration. 



As ABDERHALDEN 1 has well pointed out, these conceptions 

 place the functions of the alimentary tract and its enzymes in 

 an entirely new light. They together guarantee a proper met- 

 abolism of the body as a whole. The ferments through their 

 action on the various foodstuffs break these up into their 

 elements, which are the same even when derived from the 



1 ABDERHALDEN: Lehrbuch d. physiol. Chem., Berlin, 1906, p. 232: 



