2 92 PHENOMENA OF PUTEEF ACTION. 



invariably produced during the putrefaction of albumin ; its smell 

 is even more repulsive than that of indole. A closely allied 

 derivative of skatole, viz., /3-methyl indole acetic acid, was dis- 

 covered by M. VON NENCKI (IV.) among the putrefaction products 

 occasioned by Bacillus liquefaciens magnus in the absence of air. 

 Phenol was first recognised as a product of albumin putrefac- 

 tion by E. BAUMANN (I.) in 1877, and orthocresol and paracresol 

 by E. BAUMANN and L. BRIEGER (I.) in 1879. The capacity 

 of a large number of (mostly pathogenic) species of bacteria for 

 producing the above-named substances was investigated by A. 

 LEWANDOWSKI (I.). 



M. von Nencki and his pupils made a series of investigations 

 on the products of albuminoid putrefaction. Of their discoveries 

 we will now briefly mention those referring to leucine and tyro- 

 sine. These amido substances are secreted by the pancreatic 

 glands, and are almost always present in fresh faeces. They 

 are also produced, under certain conditions, in the putrefac- 

 tion of various albuminoids. Now, according to NENCKI'S (V.) 

 researches, leucine is further decomposed by the activity of bac- 

 teria, the chief product being valeric acid, along with carbon 

 dioxide, hydrogen, and ammonia. The reaction is approximately 

 expressed by the equation 



CH 3 CH 2 CH 2 CHo CH . NH 2 COOH + 2H 2 = 

 Leucine. 



(CH 3 ) 2 = CH CH 2 



Valeric acid. 



The decomposition of tyrosine may be effected in two different 

 ways : in presence of air as was shown by E. BAUMANN (II.) 

 the NH 2 group is separated, and hydroparacumaric acid, of which 

 tyrosine may be regarded as the amine (alanine), is formed 



.OH /OH 



C 6 H 4 < yields C 6 H/ 



CH 2 CH.NH 2 COOH CHa CH 2 COOH. 



Tyrosine. Hydroparacumaric acid. 



When air is excluded, the results are, however, very different, 

 indole, together with carbon dioxide and hydrogen, being pro- 

 duced. This reaction is approximately represented by the equa- 

 tion 



.OH /HN. 



C 6 H 4 < - C 6 H 4 < >CH + C0 2 + H 2 + H 2 . 



CH 2 CH . NH 2 -COOH CH f 



Tyrosine. Indole. 



The evolution of sulphuretted hydrogen is a frequent accom- 

 paniment of putrefaction. A large number of bacteria are endowed 

 with the power of liberating this gas, the production of which 



