28 CHEMISTRY OF THE PROTEIDS CHAP. 



B. RING-COMPOUNDS. (See Histidin under No. 14.) 



(i) pyrrolidin compounds. 



22. a-pyrrolidin-carboxylic acid C 5 H 9 N0 2 . 



23. hydroxy-pyrrolidin-carboxylic acid C 5 H 9 N0 3 . 

 (k) aromatic amino-acids. 



24. phenyl-amino-propionic C 9 H n N0 2 . 



25. phenyl-hydroxy-amino-propionic C 9 H n N0 3 . 



26. indol-amino-propionic C n H 12 N 2 O 2 . 



C. AMMONIA. 



(/) ammonia. 



27. ammonia NH 3 . 



D. THIO-AMINO-ACIDS. 



(m) diamino-di-thio di-carboxylic acid. 



28. cystin C 6 H 12 N 2 O 4 S 2 . 



The following substances have been definitely shown to be primary 

 products : 



1. Glycocoll, or Amino-acetic Acid, C 2 H 5 N0 2 



NH 2 .0 



H C CQ 

 H X OH, 



is normal a-amino-acetic acid or 'glycin.' Glycocoll is the simplest of 

 all amino-acids, and its peculiar property of acting both as a base and 

 as an acid, is typical of all amino-acids, and therefore also of the 

 albumins (see Chapter V.). It was discovered by Braconnot 1 in gelatine, 

 and by Stadeler 2 in the fibroin of silk, while the first quantitive deter- 

 minations for gelatine 3 and silk 4 were made by E. Fischer. Later 

 Spiro 5 and E. Fischer 6 and Abderhalden 7 have found it also in serum- 

 globulin, fibrin, edestin, and in horn. Spiro converted glycocoll into 

 hippuric acid, while E. Fischer, in preparing it, made use of the insolu- 

 bility of the glycocoll-ethyl-ester hydrochloride. Glycocoll can be deter- 

 mined quantitatively more accurately than any other mono-amino acid. 

 In most proteids it is absent altogether, a fact of special interest as 



1 H. Braconuot, Ann. de Ghim. et de Physique (Gay-Lussac and Arago), 13- 113 

 (1820). 



2 G. Stadeler, Liebigs Ann. 111. 12 (1859). 



^ 3 E. Fischer, Zeitschr. f. physiol. Chem. 35. 229 (1902) ; E. Fischer, P. A. Levene, 

 and R. H. Aders, ibid. 35. 70 (1902). 



4 E. Fischer and A. Skita, ibid. 33. 177 (1901). 



5 K. Spiro, ibid. 28. 174 (1899). 



6 E. Fischer and T. Dorpinghaus, ibid. 36. 462 (1902). 



7 E. Abderhalden, ibid. 37.^499 (1903) ; E. Abderhalden and W. Falta, ibid. 

 39. V 143 (1903). 



