80 THE PROTEIN SUBSTANCES. 



protein characteristics, and these then suffer further decomposition 

 until finally we obtain simpler, generally crystalline, or at least well- 

 characterized, end products. 



On heating protein with barium hydroxide and water in sealed tubes to 150- 

 250 C., SCHUTZENBERGER l obtained a mixture of products among which were 

 ammonia, carbon dioxide, oxalic acid, acetic acid, and, as chief product, a mix- 

 ture of amino-acids. The conclusion he drew from this experiment, that the 

 protein is a complex ureide or oxamide, cannot be considered for several reasons. 2 



On fusing proteins with caustic alkali we obtain ammonia, methyl mercaptan, 

 and other volatile products; also leucine, from which then volatile fatty acids, 

 such as acetic acid, valeric acid, and also butyric acid are obtained, and also 

 tyrosine, from which latter phenol, indol, and skatol are produced. 



As to the products obtained by hydrolytic cleavage with mineral 

 acids, we have a number of investigations by various experimenters, 

 especially HLASIWETZ and HABERMANN, RITTHAUSEN and KREUSLER, 

 E. SCHTJLZE and his collaborators, DRECHSEL, SIEGFRIED, R. COHN, 

 KOSSEL and his pupils, K. MORNER, ABDERHALDEN and co-workers, 

 OSBORNE and CLAPP, SKRAUP, and recently E. FISCHER and his collab- 

 orators. 3 The chief products thus obtained are monamino acids, such 

 as glycQcoll, alanine, aminovaleric acid, leucine, phenylaminopropionic 

 acid, aspartic and glutamic acids, cysteine and its sulphide cystine; the 

 so-called hexone bases, lysine, arginine, and histidine, of which the first 

 two are diamino acids; tyrosine, oxymonarnino acids, such as serine, 

 oxyaminosuccinic acid, and oxyaminosuberic acid; oxydiamino acids, 

 such as oxydiaminosuberic acid, oxydiaminosebacic acid, diaminotri- 

 oxydodecanoic acid, caseanic and caseinic acids; a-pyrrolidine and oxy- 

 pyrrolidine carboxylic acids; tryptophane (indolaminopropionic acid); 

 sulphuretted hydrogen, ethyl sulphide, leucinimide, ammonia, and 

 melanoidins, 4 which latter seem to be secondary condensation products. 



The proteins can be split into a large number of bodies by the proteo- 

 lytic enzymes, and these will be presented later. In the first place 

 proteoses and peptones are produced, also an abundance of monamino- 

 acids of different kinds, hexone bases, tryptophane, and finally oxy- 

 phenylethylamine, diamines, and a little ammonia and other substances. 



A great many substances are produced in the putrefaction of pro- 

 teins. First the same bodies as are formed in the decomposition by 



1 Annal. de chim. et phys. (5), 16, and Bull. Soc. chim., 23 and 24. 



2 See Habermann and Ehrenfeld, Zeitschr. f. physiol. Chem., 30. 



3 In regard to the literature see O. Cohnheim, Chemie der Eiweisskorper, Braun- 

 schweig, 1904, and F. Hofmeister, Ergebnisse der Physiologic, Jahrg. I, Abt. 1, 759, 

 1902; E. Fischer, Untersuchungen iiber Animosauren, Polypeptide uiid Proteine (1899- 

 1906), Berlin, 1906; also Mann, Chemistry of the Proteids, London, 1906. See also 

 special references. 



4 See Samuely, Hofmeister's Beitrage, 2. 



