570 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



ordinary hippuric acid is formed. After eating apple-parings and other vege- 

 table substances, hippuric acid is found in human urine. It is further stated 

 thai phenyl-aeetic acid and phenyl-propionic acids are normal products of 

 proteid putrefaction, though in very small quantities ; hippuric acid and phen- 

 aceturic acid must therefore be constantly present in traces in human urine. 

 Hippuric acid is split into its constituents by hydrolysis through the action of 

 the Micrococcus ureoe. 



p-Oxyphenyl-acetic Acid, 0, H,.OH.CH 2 COOH. — This is a product of 

 the intestinal putrefaction of proteid and of tyrosin (which see). It occurs 

 in the urine either paired with sulphuric acid or as an alkaline salt of oxyphenyl- 

 acetic acid. 1 



p-Hydrocumaric Acid, C t .H 4 .OH.C 2 H 4 COOH. — This second oxy- acid is 

 likewise derived from proteid and tyrosin (which see) putrefaction. Its occur- 

 rence in the urine is similar to the above oxy- acid. 



Tyrosin, Amido-hydrocumaric Acid, ^-Oxyphenyl-amido-propionic 

 Acid, C 6 H 4 .OH.C 2 H 3 NH 2 COOH. — Tyrosin is a constant product of the putre- 

 faction of all proteid bodies (except gelatin), and is therefore found in cheese. 

 It may be formed in large quantities by boiling horn-shavings with sul- 

 phuric acid. Leucin is always formed whenever tyrosin is. Tyrosin forms 

 characteristic sheaf-shaped bundles of crystals. All the aromatic bodies thus 

 far described have been eliminated in the urine with their benzol nucleus 

 intact. Tyrosin, however, may be completely burned in the body. This 

 seems to be because of the presence of the amido- group on the side chain, for 

 phenyl-amido-propionic acid is likewise destroyed. Tyrosin is found in the 

 urine in yellow atrophy of the liver, in phosphorus-poisoning, etc. (see Leucin, 

 p. o40). Through cleavage, oxidation, or reduction, the following reactions 

 take place, phenol being the final product. 2 The substances not found in intes- 

 tinal putrefaction are named in italics: 



C 6 H 4 .OH.C 2 H 3 NH 2 COOH - H 2 C 6 H 4 .OH.C 2 H 4 COOH + NH 3 



p-TIydrocumaric acid. 



C 6 H 4 .OH.C 2 H 4 COOH C 6 H 4 .OH.C 2 H 5 + C0 2 



p-Ethylphenol. 



C 6 H 4 .0H.C 2 H 5 + 30 C 6 H 4 .0H.CH 2 C00H - H 2 



p-Oxyphenyl-acetic acid. 



C 6 H 4 .0H.CH 2 C00H C 6 H 4 .0H.CH, + CO, 



/<-« resol. 



C 6 H 4 .OH.CH 3 + 30 CJLOHCOOH + H 2 



p-Oxybenzoic acid. 



CeH 4 .0H.C!00H C 6 H 5 OH + C0 2 



Phenol. 



It has never been shown that tyrosin i- a normal product of proteid metabolism 

 within the tissues. With leucin it is a normal product of pancreatic diges- 

 tion (see p. 540). 



Homogentisic Acid, Dioxyphenyl-acetic Acid, Hydroquinone-acetic Acid — 

 Tlii^ i.- found in the urine in alcaptonuria. Feeding tyrosin in this disease increases the 



1 Baumann: Zeitsehriftfur physiologische Chemie, 1886, Bd. 10, S. 125. 



J Baumann : Berichte der deidschen ehemisehen Gesellschaft, 1879, Bd. 12, S. 1450. 



