46 THE PHYSIOLOGY OF PROTEIN METABOLISM 



recovered from the blood which flowed from the upper cut end of the 

 jugular vein during the period that the amino acid was being injected 

 into the lower end. More alanine was recovered from the blood of the 

 normal animal than of the one with the Eck fistula (i.e. with the liver 

 cut out of the circulation) and more alanine from the urine of the 

 operated animal than from that of the normal. Even when the alanine 

 was fed to one of the operated dogs the alanine could be isolated from 

 both the blood and the urine. As regards the fate of the diketopipera- 

 zines (glycineanhydride and alanineanhydride), neither in dog nor 

 man was there definite evidence of either being attacked, whereas in 

 rabbits the breakdown took place with the subsequent excretion of 

 part of the amino acid in the urine. Abderhalden (i) thought that the 

 anhydride compound was probably first converted into the dipeptide, 

 then to the simple amino acids. Abderhalden and Walker (30) 

 showed later that part of the anhydride appears as such in the urine. 

 Among other workers in this field are Stolte (387), Plant and Reese 

 (326), Friedmann (146). Their results confirm the data previously 

 given. 



The Administration of Amino Acids as a Test of Functional 



Activity. 



The fact that the administration of certain amino acids leads to a 

 rise in the output of urea in the urine has been known for many years 

 (Nencki and Schultzen (299), Salkowski (350)), but not until the /8- 

 naphthalene sulphochloride method was introduced was there any 

 practical means of ascertaining whether part of the administered amino 

 acid was excreted unchanged. With the introduction of this method 

 which is roughly quantitative, many new observations have been made. 

 Glaessner (i 55), for example, has made practical use of this utilization of 

 amino acids in the body for testing the functional activity (particularly 

 of the liver in his opinion) of the tissues and organs. He determined 

 first the amounts of amino acids which could be dealt with by the 

 normal tissues (liver?), and found that 25 grm. alanine, 25 grm. 

 aspartic acid, 25 grm. glycine and about 20 grm. leucine could be 

 dealt with, the nitrogen of the amino acids given appearing as urea. 

 He then tested the tissues under different pathological conditions, and 

 obtained the results given in the following table : 



