170 LECTURE VIII. 



The decomposition, however, does not end here. The bacteria break 

 these down in two directions. On one hand they split off the amino 

 acids. Simple acids remain: acetic acid is produced from glycocoll; pro- 

 pionic acid from alanine; valeric acid from amino- valeric acid; etc. The 

 <5-amino-valeric acid, found in putrefying mixtures, may be produced 

 from ornithine, or by splitting off the pyrrole ring from a-pyrrolidine- 

 carboxylic acid. Tartaric acid, phenyl-propionic acid, p-hydroxyphenyl- 

 propionic acid, and skatole-acetic acid are also found. On the other hand, 

 carbon dioxide is split off from the amino acids by bacterial action. This 

 process gives us pentamethylenediamine (cadaverine) from lysine; while 

 tetramethylenediamine (putrescine) results from arginine and ornithine. 



From phenylalanine we obtain phenylethylamine CeB^ . CH 2 - CH 2 NH 2 , 

 with evolution of carbon dioxide; and from tyrosine, oxyphenylethyl- 

 amine. As a rule the decomposition does not stop at these products. 

 They are oxidized. We can indicate the further destruction of tyrosine 

 (p-hydroxyphenyl-amino-propionic acid) as follows: 



p-hydroxyphenyl-amino-propionic acid CeH 4 . OH . CH 2 . CH.NH 2 .COOH 

 p-hydroxyphenyl-propionic acid CeH 4 . OH . CH 2 . CH 2 .COOH 



p-hydroxyphenyl-acetic acid C 6 H 4 . OH . CH 2 . COOH 



p-hydroxymandelic acid C 6 H 4 . OH . CH(OH) . COOH 



p-cresol C 6 H 4 . OH . CH 3 



phenol C 6 H 5 . OH 



In an analogous manner phenylalanine (phenyl-amino-propionic acid) 

 breaks down through phenyl-propionic acid and phenyl-acetic acid. 

 Tryptophane (skatole-amino-acetic acid) gives skatole-acetic acid, skatole- 

 carbonic acid, skatole and indole. We shall meet with phenol, skatole, 

 and indole in the animal organism. They are produced in intestinal 

 putrefaction, and appear in the urine combined with sulphuric acid. 

 Sulphureted hydrogen is liberated from cystine. 



