82 THE PROTEIN SUBSTANCES. 



from which then volatile fatty acids such as acetic acid, valeric acid and also 

 butyric acid are formed, also tyrosine from which latter phenol is formed and 

 indol and skatol. 



Most proteins are split by proteolytic enzymes in the same manner 

 as on hydrolysis with acids or alkalies, but more or less completely depend- 

 ent upon the kind of enzymes. In the first place proteoses and peptones 

 (see below) are formed, then also polypeptids and amino-acids of 

 various kinds, in certain cases also oxyphenylethylamine, diamines, and 

 a little ammonia and other bodies. 



A great many substances are produced in the putrefaction of pro- 

 teins. First the same bodies as are formed in the decomposition by 

 means of proteolytic enzymes are produced, and then a further decom- 

 position occurs with the formation besides ammonia, carbon dioxide 

 and hydrogen, of a large number of bodies belonging in part to the aliphatic 

 and in part to the aromatic and heterocyclic series. 



To the aliphatic series belong volatile fatty acids and as shown 

 by NEUBERG 1 and collaborators not only fatty acids of the normal chain 

 but also with branched chains, also optically active acids, also succinic 

 acid, methane, methyl mercaptan and others. To this series belongs 

 also the two putrefaction bases cadaverine and putrescine, produced from 

 the diamino acids, and also the so-called ptomaines or cadaver alkaloids 

 which may originate, at least in part, from other tissue constituents 

 and not from proteins. 



The putrefactive products of the aromatic and heterocyclic series 

 originate from the corresponding amino-acids. From tyrosine the 

 aromatic oxy-acids such as p-oxyphenyl-propionic acid, the p-cresol, 

 phenol and oxyphenylethylamine are formed. The phenylalanine is the 

 mother substance of the phenylpropionic acid, the phenylacetic acid and 

 the phenylethylamine. Indolpropionic acid, indolacetic acid, skatol 

 and indol originate from the tryptophane (indolaminopropionic acid) ; the 

 imidazolpropionic acid and imidazolethylamine originate from the histi- 

 dine. 2 



By the moderate action of chlorine, bromine, or iodine upon proteins, 

 these halogens enter into more or less firm combination with the proteins 

 and according to the method of procedure we can prepare derivatives 

 having different but constant amounts of halogens. The proteins are 

 so changed that they do not split off sulphur on treatment with alkali, 

 nor do they respond to MILLON'S or ADAMKIEWICZ-HOPKINS reaction. 

 Side processes, oxidations and cleavages may also take place here. The 

 most striking fact seems to be a substitution of hydrogen by iodine in the 



1 Bioch. Zeitschr., 37, where the earlier works of Neuberg are cited. 



2 Ackermann, Zeitschr. f. physiol. Chem., 65. 



