212 



LECTURE X. 



undoubtedly carries mainly albumin, which occupies the same relation 

 to the albumin metabolism that grape-sugar does to the transport of the 

 carbohydrates. As the sugar content of the blood is very constant, so, 

 also, the sum total of the albumins in the blood-serum is subject to but 

 little variation. The serum-albuminous bodies are mainly composed of 

 albumin and globulin. Their relative amounts vary. During starvation 

 the former gradually diminishes, while the latter increases. We could 

 imagine that the composition of the serum-albuminous bodies were depend- 

 ent on that of the albumin in the food. This ought to be subject to proof 

 by direct experiment. 1 Six liters of blood were taken by venesection 

 from a horse, which had been fed mainly on hay and oats, and the amounts 

 of tyrosine and glutamic acid present in the serum were estimated. The 

 animal was then made to fast a whole week in order to guarantee that the 

 intestines were entirely emptied of their contents. Another sample of 

 blood (six liters) was taken, and the amounts of tyrosine and glutamic 

 acid present in the serum again determined. The animal was now fed an 

 albuminous substance which possessed 36.5 per cent glutamic acid 

 and 2.37 per cent tyrosine. The serum-globulin of the horse contains, 

 under normal conditions, about the same amount of tyrosine, but only 

 8 . 5 per cent glutamic acid. Serum-albumin contains 7 . 7 per cent glu- 

 tamic acid. The animal under investigation, therefore, was fed an albu- 

 min, gliadin, which possessed five times as much glutamic acid. The 

 following table gives a summary of the results : 



EXPERIMENT I. 



EXPERIMENT II. 



E. Abderhalden and F. Samuely: Z. physiol. Chem. 46, 193 (1905). 



