THE DECOMPOSITION PRODUCTS OF PROTEIDS, 29 



prepared synthetically. 1 Tyrosine (C (J H 11 N0 3 ) is oxyphenyl amidopropionic 

 acid, HO.C H 4 .C 2 H 3 (NH 2 ).COOH. This substance has also been made 

 synthetically. 2 The crystalline forms of these two substances are seen in 

 the accompanying figures (Figs. 7 and 8). Aspartic or asparaginic acid 3 

 (C 4 H 7 N0 4 ) is amido-succinic acid, C 2 H 3 (NH 2 )(COOH) 2 . That ammonia 

 is produced in prolonged pancreatic digestion, under conditions preclud- 

 ing the possibility of putrefaction, was shown by Stadelmann. 4 



To this list must be added lysine, lysatinine, arginine 5 (see p. 

 33), glutaminic acid, and proteinchromogen, 6 a substance of un- 

 certain nature which gives a reddish -violet product with chlorine or 

 bromine water. 



Within the intestine many changes occur which are due to bacterial 

 action. The products which have just been enumerated arise first, 

 and then by different changes other substances are formed; of these 

 the following may be mentioned : indol, skatol, skatol-carbonic acid, 

 oxyphenylpropionic acid, phenylpropionic, and phenylacetic acids, 

 parakresol, and phenol, and simpler bodies like carbonic anhydride, 

 water, ammonia, hydrogen, and sulphuretted hydrogen, arnido-fatty acids, 

 and fatty acids themselves. 7 The most interesting point to note here 

 is the large number of derivatives containing the benzene nucleus. The 

 indol group has never been obtained from the proteid molecule by any 

 other method than that of bacterial decomposition. 8 



We can now pass to the second category of investigations, namely, 

 those carried out in vitro. 



The first action produced by most reagents, especially if they bring 

 about hydrolysis, is the formation of proteoses and peptones ; these are 

 then broken up into more simple substances. The subject may be most 

 conveniently treated of under the heads of the different methods employed. 



1. Treatment with alkalis. Mulder 9 treated albumin with caustic 

 potash, and obtained the substance which we now call alkali-albumin ; 

 this material is free from most of the sulphur present in the original 

 proteid, namely, that which is present in loose combination ; the firmly 

 combined sulphur, however, remains undisturbed. 10 



Mulder thought that by this method he had obtained the base of 

 all albuminous material, and called it "protein"; he described many 



1 For recent literature on lencine, see Sclmlze and Likiernik, Ztschr. f. physiol. Chem. 

 Strassbtirg, Bd. xviii. ; Gmelin, ibid., Bd. xviii. ; Hiifner, "Synthesis of Leucine," Journ. f. 

 praJct. Chem., Leipzig, N. F., Bd. i. ; E. Schulze, Barbieri and Bosshard, Ztschr. f. physiol. 

 Chem., Strassburg, Bde. ix. and x. ; Cohn, ibid., Bd. xx. 



2 Erlenmeyer and Lipp, Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. xv. S. 1544. 



3 For chemistry and preparation, see Hlasiwetz and Habermann, Ann. d. Chem., 

 Leipzig, Bd. clxix. S. 160 ; E. Schulze, Ztschr. f. physiol. Chem., Strassburg, Bd. ix. 



4 Ztschr. f. Biol., Mimchen, 1888, Bd. xxiv. S. 261. See also Hirschler, Ztschr. f. 

 physiol. Chem., Strassburg, Bd. x. S. 302. 



5 Hedin, Arch. f. Physiol., Leipzig, 1891, S. 273. 



6 Stadelmann, Ztschr. f. Biol., Mimchen, Bd. xxvi. S. 491. Neumeister suggests the 

 name tryptophan for this substance, ibid., S. 324 ; Nencki, Ber. d. deutsch. chem. Gesellsch., 

 Berlin, Bd. xxviii. S. 560. 



7 Salkowski, ibid., Bd. xii. S. 648; Tappeiner, Ztschr. f. Biol., Mimchen, Bd. xxii. 

 S. 236. 



8 For recent- work on the mycological processes in the intestines, see V. D. Harris, 

 Journ. Path, and Bacteriol., Edin. and London, 1895, vol. iii. p. 310. On the putrefaction 

 of pure proteids see 0. Emmerling (Ber. d. deutsch. chem. Gesellsch., Berlin, 1896, Bd. xxix. 

 S. 2721) ; in addition to the substances enumerated above he tinds betaine. 



9 Journ. f. prakt. Chem., Leipzig, Bd. xvi. S. 129; Bd. xvii. S. 312; Ann. d. Chem., 

 Leipzig, Bd. xxxi. S. 129. 



10 Kriiger, Arch. f. d. ges. Physiol., Bonn, Bd. xliii. S. 244. 



