THE CHEMISTRY OF THE BODY. 



Phenylalanine ..... 



Tyrosine (oxyphenylalanine) . 

 Proline (pyrrolidine carboxylic acid) 

 Oxyproline (oxypyrrolidine carboxylic 

 acid) ...... 



Tryptophane (indolamino-propionic acid) 



> Benzene derivatives. 



[Heterocyclic com- 

 f pounds. 



The "hexone bases.' 



Diamino-acids and their Compounds. 



Lysine (diamino-caproic acid) 



Arginine (guanidinamino-valeriariic acid) 



Histidine (iminazolalanine) . 



Diamino-tryoxydodecoic acid (derived from a 12-carbon acid). 



Cystine (derived from amino-thiopropionic acid). 



Arginine is not a simple amino-acid, but is a compound of amino- 

 valerianic acid with guanidine. A similar compound of guanidine occurs 

 in muscle as creatine, or methylguanidine acetic acid. When creatine 

 is boiled with baryta water it is split into urea and sarcosine (methyl- 

 glycine), thus giving rise to an amino-acid. 



The second of these tables shows that the special characteristics 

 of the separate proteins are associated with differences in the relative 

 proportions of their constituent amino-acids, and it has also been shown 

 that there are differences in the way in which the amino-acids are 



