I'h'ODl t-TS or rUTREFACTION AND FERMENTATWX 571 



Considering- tlu'iu lirst according to their origin and chemical nature, 

 we take up iirst the products of: 



A. PROTEIN PUTREFACTION 



(1) SUBSTANCES DERIVED FROM THE AROMATIC RADICALS OF 

 THE PROTEIN MOLECULE 



In the protein molecule are contained the following amino-acids 

 with an aromatic nucleus : 



Tyrosine, Ho/ y-CH^— CH — COOH 



riu'iiylalaniiu', <^ \ cH.- — CH — COOH 



NH2 

 Ti yptopliane, / N_ C — CH2 — CH — COOH 



\ CH 



V 



H 



In the intestinal contents have been found a number of substances 

 that are undoubtedly derived from these aromatic radicals. They 

 are (1) phenol, . — . 



which is formed in small quantities, presumabl}^ from tyrosine, as 

 also is the closely related (2) paracresol, 



and also (3) para-oxyphenyl acetic acid, 



HO / \ CH, — COOH 

 and (4) para-oxyphenyl-propionic acid, 



HO / N CH, — CH.. — COOH 



From the tryptophane are formed numerous important substances, 



as follows: 



NH2 



_ C — CH2 — CH — COOH 



\/ '" 



XH 

 (tryptophane) 



readily yields, through splitting off the NIT, group and addition of 

 H, iiidole propionic acid (formerly incorrectly called sl-atole acetic 

 acid), which is 



