88 THE CHEMICAL COMPOSITION OF THE BODY 



plexity are obtained. But, running through the cleavage compounds are 

 certain nuclei or constitution complexes, which in all probability are found 

 in the proteid itself, in fact form the basic structure of the molecule. The 

 following account is taken from the excellent discussion by Witthaus (" The 

 Medical Student's Manual of Chemistry"): 



"Active oxidizing agents attack the proteid molecule profoundly, yield- 

 ing products which are for the most part far removed from the original sub- 

 stance, and which are themselves products of decomposition of the 'atomic 

 complexes' above referred to; acids and aldehydes of the fatty, oxalic, and 

 benzoic series and their nitrils, including hydrocyanic acid, ketones, amido- 

 acids, carbon dioxid, and ammonia. With HNO 3 various nitro derivatives 

 are obtained, and with Cl, Br, and I halid derivatives. By oxidation with 

 K 2 Mn 2 O 8 an acid, oxyprotosulfonic, containing the sulfonic group, is 

 formed, and by continued oxidation peroxyprotonic acid. In oxidation with 

 BaMn 2 O 8 guanidin is one of the products. 



" Fusion with caustic alk'alies also causes deep decomposition, the prod- 

 ucts being ammonia, mercaptan, fatty acids, amido fatty acids, tyrosin, 

 indol, and skatol. 



" By boiling with dilute mineral acids, or with HC1 -j- SnQ 2 , the pro- 

 teids are hydrolyzed with formation of hydrogen sulfid, ethyl sulfid and 

 ammonia as simple products, and amido-acids, hexon bases, pyrrolidin and 

 oxypyrrolidin carboxylic acids, and melanoidins, the last-named being also 

 products of decomposition of the melanins, substances to which the hair 

 and other dark portions of the body owe their color. The amido-acids, 

 including serin, tyrosin, and cystin, produced in this and other hydrolytic 

 decompositions probably exist in the proteids as polypeptids, formed by 

 the union of several amido-acid complexes. 



" Considering the nitrogen which is split off, in more or less complex 

 combination, on hydrolysis of proteids by boiling with dilute acids, it appears 

 to have existed in the parent proteid in five forms of combination, corre- 

 sponding to five classes of decomposition products: i, Easily separable, 

 so-called amino-nitrogen, given off as NH 3 ; 2, Urea-forming nitrogen, in the 

 guanidin remainder of argenin; 3, Basic nitrogen, or diamido-nitrogen, 

 contained in basic nitrogen compounds, precipitable by phosphotungstic 

 acid; 4, Monamido-nitrogen, in monamido-acids; 5, Humus nitrogen, in 

 humus-like melanoidins, dark-colored, amorphous, nitrogenous remainders. 



" The quantitative distribution of nitrogen in these five groups differs in 

 different proteids : i. Is entirely absent in protamins; i to 2 per cent in gela- 

 tin; 5 to 10 per cent in other animal proteids; 13 to 20 per cent in vegetable 

 proteids. 2, In protamins 22 to 44 per cent; in histons 12 to 13 per cent; 

 in gelatin 8 per cent; in other proteids 2 to 5 per cent. 3, In protamins 

 63 to 88 per cent; in histons 35 to 42 per cent; in other animal proteids 

 15 to 25 per cent; in vegetable proteids 5 to 37 per cent. 4, The greater 



