MARCEL NENCKI, 1847— 1901 519 



the chemical differences in the proteins were due to the fact 

 that they are built up of different groups, for the amount of 

 hydrolysis products, such as glycocoll, leucine, and tyrosine, 

 vary greatly in proteins of different origin. These hydrolysis 

 products, then, in the presence of bacteria undergo further 

 degradation ; scission of ammonia takes place, and various 

 volatile fatty acids are formed, such as acetic, butyric, and 

 valerianic acids. By the direct action of putrefactive bacteria 

 on the hydrolysis products, some of the lower degradation 

 products can be obtained. Thus, by treating leucine with 

 putrefying ox-pancreas, products were isolated the formation 

 of which could be accounted for by the following equations : — 



C,H I4 NOj + O. = C 5 H 9 0,NH 4 + CO,, 



ammonium valerianate being thus formed, the acid of which 

 on further oxidation, 



C 5 H l0 O, + O a = C 6 H b (X + CO, -f H 2 0, 



yields butyric acid. 



The discovery of the difference in the chemical action of the 

 secreted enzymes and that of bacteria (at that time known as 

 unorganised and organised ferments) induced Nencki to suspect 

 that the real seat of formation of indol was in the large intestine, 

 and that its formation was due, not to the ordinary secreted 

 ferments such as pancreatin, acting on the proteins, but rather 

 to the action of the micro-organisms which are always found in 

 this organ. It seemed therefore probable that the products of 

 putrefaction would be found in the faeces, and a chemical 

 examination of these excreta was therefore undertaken. This 

 work was entrusted to Brieger, who succeeded in isolating for 

 the first time the important putrefaction product skatol. The 

 empirical chemical relationship of this body to indol was soon 

 recognised. 



In the course of time various other products of putrefaction 

 were isolated, amongst which may be mentioned phenylethyl- 

 amine, skatolacetic acid, and mercaptan. 



The question then arose — To what aromatic hydrolysis 

 products of proteins are these various putrefaction products 

 due? — for indol, skatol, etc., cannot be obtained by direct 

 hydrolysis — they are the products of the action of bacteria 

 on such bodies. 



Salkowski, who with his pupils had also been working 



