1012 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



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. 983). Through cleavage, oxidation, or reduction, the following reactions 

 take place, phenol being the final product. 1 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, = C 6 H 4 .OH.C 2 H 4 COOH + NH S 



p-IIydrocumaric 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 .OH.C 2 H 5 + 30 = C 6 H 4 .OH.CH 2 COOH + H 2 



p-Oxyphenyl-acetic acid. 



C 6 H 4 .OH.CH 2 COOH = C 6 H 4 .OH.CH 3 + CO, 



j)-Cresol. 



C 6 H 4 .OH.CH 3 + 30 = C 6 H 4 OHCOOH + H 2 



p-Oxybenzoic acid. 



C 6 H 4 .OH.COOH = C 6 H 5 OH + CO, 



Phenol. 



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

 within the tissues. With leucin it is said to .be a normal product of pancreatic di- 

 gestion (see p. 983), being derived only from hemipeptone (Kiihne, Chittendeu). 



Pyridin. This body has the accompanying formula, one of the CH groups in benzol 

 H 

 



HC CH 



being substituted by N : || When pyridin is fed, methyl-pyridin ammonium 



HC CH 



y 



hydroxide, OH.CH 3 .NC 5 H 5 , is excreted in the urine. 2 This is another case, besides those 

 of selenium and tellurium, of methylation in the body. 



H H 



C C 



HC C CH 



| || 

 HC C 



Chinolin. The accompanying formula | || | illustrates the composition 



CH 



N C 

 H 

 of this body. Several of the methyl-chinolins burn readily in the body. 8 



1 Bauraann : Serichte der deutschen chemischen Gesellschaft, 1879, Bd. 12, p. 1450. 



2 His: Archiv fiir exper. Pathologie und Phai-makologie, 1887, Bd. 22, p. 253. 



3 Cohn : Zeitschrift fiir physiologische Chemie, 1894, Bd. 20, p. 210. 



