428 PRODUCTS OF BACTERIAL DECOMPOSITION OF TYROSINE. [BOOK II. 



of hydrochloric acid be added, and then two or three drops of a very 

 dilute solution of ferric chloride and the mixture be then heated, it 

 becomes, even before the boiling-point is reached, of an intense violet 

 colour. If the solution be more dilute (1 : 100,000) the reaction is 

 still very distinct ; if more concentrated, a larger quantity of acid and 

 iron solution must be added, and the colour is, in that case, an 

 intense cherry-red. 



Occurrence Salkowski has found that when skatol- carbonic acid 



of skatoi-car- j g introduced into the body, it is excreted unchanged in 

 bonic acid in ,, . j-i i j A j r TT 



the urine. e unne > where it may readily be detected. He 



believes that he detected the presence of this body in 

 normal human urine 1 . Baumann does not however hold the evidence 

 on this point to be decisive 2 . 



DERIVATIVES OF TYROSINE FOUND IN THE PRODUCTS OF THE 

 BACTERIAL DECOMPOSITION OF PROTEIDS. 



Besides indol, skatol, and skatol-carbonic acid, certain aromatic 

 bodies which have been shewn to be derived from tyrosine are 

 found amongst the products of the bacterial decomposition of the 

 albuminous and albuminoidal bodies, and therefore in pancreatic 

 digestions complicated with putrefaction. Our knowledge of these 

 aromatic products of putrefaction of tyrosine is based on the researches 

 of Baumann, Brieger, E. and H. Salkowski, Th. Weyl and others. It 

 is to Baumann that we are indebted for the conception of the way 

 in which the principal products of the decomposition of proteids are, 

 probably, related to one another (refer to page 248). 



1. According to Baumann, tyrosine, when subjected to putre- 

 faction, yields by a process of reduction, as the first product, hydro- 

 paracumaric acid, thus : 



rH (OHp 



4 ( CH 2 . CH(NH 2 ). COOH. + 



Paroxyphenyl-a-amidopropionic acid (Tyrosine) 



PTT (OH 

 U6tL4 lCH 2 .CH 2 .COOH. + 



Para-oxyphenyl-propionic or hydroparacumaric acid. 



2. By a process of decomposition and subsequent oxidation 

 (compare equations 2 and 3, p. 248) hydroparacumaric acid yields 

 paroxyphenylacetic acid (E. and H. Salkowski). 



Para-oxyphenyl-acetic acid. 



1 E. Salkowski, 'Ueber das Verhalten der Skatolcarbonsaure im Organismus,' 

 Zeitsch. f. phys. Chem. Vol. ix. (1885), p. 32. 



2 Baumann, Ber. d. deutsch. chem. Gesellsch. Vol. xin. p. 284. 



