ACTION OF INTESTINAL BACTERIA ON PROTEIDS. 467 



(&) Substances formed directly and not from tyrosine indol, skatol, and 

 skatolcarbonic acid. 



Of these substances, Zuinft 1 found indol, skatol, phenol, and para- 

 kresol in the large intestine of man, but skatolcarbonic acid was absent ; 

 this latter acid has not yet been detected in the intestine. According 

 to E. Salkowski, it is excreted unchanged in the urine, and he states that 

 he has detected it in normal urine. 2 



These several substances may now be considered seriatim. 



Derivatives of tyrosine formed in putrefaction? Hydroparacumaric acid, 

 or paraoxyphenylpropionic acid (HO.C H 4 .C 2 H 4 .COOH) crystallises from 

 water in anhydrous monoclinic crystals, melting at 125-128 C., soluble 

 in water, alcohol, and ether. It gives a transient blue coloration with ferric 

 chloride, and a red coloration or red precipitate when boiled with Millon's 

 reagent. It is the oxy-acid of phenylpropionic acid, which lias also been 

 found among the putrefaction-products of proteids. Phenylpropionic acid 

 crystallises in slender needles, melting at 47-48 C. (B-Pt. 280 C.). As 

 follows from its constitution, its solutions do not give Millon's reaction. 



Paraoxyphenylacetic, acid (HO.C 6 H 4 .CH 2 .COOH) crystallises from water 

 in prismatic crystals, melting at 148 C., and soluble in water, alcohol, and 

 ether. With ferric chloride it gives a faint violet coloration, changing to 

 a dirty grey -green. It also gives Millon's reaction. Phenylacetic acid 

 crystallises in scales, which melt at 76 '5 C. 



Phenol and parakresol 4 are also formed in the bacterial decomposition of 

 tyrosine ; they are absorbed from the alimentary canal, and after conversion 

 into ethereal sulphates are excreted in the urine. The amount of these 

 ethereal sulphates in the urine gives a measure of the amount of bacterial 

 decomposition going on in the intestine. 5 



Tyrosine and its derivatives are very closely related to one another. In 

 the derivation of these compounds, according to Baumann, 6 tyrosine (paraoxy- 

 phenyl-a-amidopropionic acid) undergoes reduction, ammonia being split off, 

 and hydroparacumaric acid (paraoxyphenylpropionic acid) formed. This 

 compound, by a series of oxidations, accompanied by a splitting off of carbon- 

 dioxide, yields paraoxyphenylacetic acid and parakresol. Parakresol is said 

 to similarly yield phenol. 



These changes are illustrated by the following equations : 



/OH (p) /OH (p) 



C G H/ + H 2 = C C H/ 



X CIl,CH(^ r H,).COOH X CH 2 .CH 2 .COOH 



(paraoxyphenyl-a-amidopropionic (paraoxyphenylpropionic acid 



acid or tyrosine) or hydroparacumaric acid) 



/OH (p) /OH (p) 



2G 6 H 4 < + 30o = 2C 6 H 4 < 



X CH 2 .CH. 2 .COOH X CH 2 .COOH 



(paraoxyphenylpropionic acid) (paraoxyphenylacetic acid) 



1 Arch. d. sc. biol., St. Petersbourg, 1892, vol. i. p. 497. 



2 Ztsckr. f. physiol. Ohem., Strassburg, 1885, Bd. ix. S. 32. 



3 See Baumann. Ztschr.f. physiol. Ckem., Strassburg, 1877-1880, Bd. i. S. 60 ; iv. S. 304 ; 

 Ber. d. deutsch. diem. Gesellsch., Berlin, 1879, Bd. xii. S. 1450; 1880, Bd. xiii. S. 279; 

 Baumann and Brieger, Ztschr.f. physiol. Ckem., Strassburg, 1879, Bd. iii. S. 149; E. 

 and H. Salkowski, Ber. d. deutsch. chem. Gesellsch., Berlin, 1879, Bd. xii. S. 648; E. 

 Salkowski, Ztschr. f. physiol. Chem., Strassburg, 1878-9, Bd. ii. S. 420 ; Weyl, ibid., 

 1877-9, Bd. i. S. 339 ; iii. S. 312. 



4 For a description of the physical and chemical properties of these bodies, see 

 Gamgee, " Physiological Chemistry of the Animal Body," 1893, vol. ii. p. 434. 



5 Baumann, Ztschr. f. physiol. Chem., Strassburg, 1886, Bd. x. S. 123. 



6 Ber. d. deutsch. chem. Gesellsch., Berlin, 1879, Bd. xii. S. 1450. 



