PROTEIN METABOLISM 83 



of increase at all was obtained in the comparatively small amount 

 of blood which could be examined. Abderhalden (I.e.) attempted 

 to prove the presence of amino acids in the blood after a full 

 proteid meal, but without success. The method which he 

 employed was the very excellent one devised by Fischer, in 

 which the amino acids, even when present in small amount, 

 form crystalline compounds with /3-naphthalinsulphochloride. 

 Howell (I.e.), by using this same method in conjunction with 

 a process of dialysis, has reported that he has been able to 

 detect small amounts of amino acids in the blood taken from 

 dogs at the height of digestion ; more, further, in the portal 

 blood than in blood taken from the general systemic circula- 

 tion. Even in the blood of dogs which had fasted for a 

 considerable number of hours, a positive reaction could still 

 be obtained. 



A point in favour of the full breakdown of the protein 

 molecule was given in a piece of work by Abderhalden and 

 Samuely, 1 in which an attempt was made to affect the con- 

 stitution of serum protein. A horse was bled to an extreme 

 degree, and then was fed with a protein obtained from wheat — 

 gliadin. This protein differed very markedly from the con- 

 stitution of the serum protein, especially in its content of 

 glutaminic acid (gliadin has 36*5 per cent, glutaminic acid, whereas 

 serum albumen has only 77, and serum globulin 8*5). When the 

 horse on the gliadin diet had regenerated its blood to a large 

 extent, it was again bled, and the constitution of the newly 

 formed serum proteid investigated. Results, as regards the 

 alteration of the internal constitution of the body protein by 

 the nature of the food protein, were quite negative. The serum 

 protein obtained resembled that formerly present in every 

 respect. The fact, too, that Howell (I.e.) was able to detect 

 amino acids, but no trace of albumoses or peptones in the blood, 

 seems to lend support to the view that the hydrolytic changes 

 in the intestine are pretty thorough. 



In what form, then, does the absorbed protein reach the 

 tissues proper? Is it absorbed as simple amino acids in solution 

 absolutely unchanged ? In all probability not to any great 

 extent, as is shown by the slight increase of the nitrogen in 

 the blood. Of course, it might be absorbed by means of the 

 leucocytes, as suggested by Hofmeister, and that owing to 



1 Abderhalden and Samuely, Zcit. f. physio I. Client. 46, 1905, 193. 



