CHEMICAL CHANGES IN LIVING MATTER. FERMENTS 173 



the agency of bacteria lose a molecule of carbon dioxide and are 

 converted into a corresponding amihe. 



For instance, lysine, which is diamino-caproic acid, is converted into 

 pentamethylene diamine or cadaverine. Thus : 



CH 2 .NH 2 CH 2 .NH 2 



CH 2 CH 2 



I I 



CH 2 becomes CH 2 



CH 2 CH 2 



CH.NH 2 CH 2 .NH 2 



COOH 



In the same way ornithine derived from the breakdown of arginine is 

 converted by putrefactive bacteria into tetra-methylene diamine or 

 putrescine. Other examples of this process of decarboxylation are : 



Isoamylamine from leucine, (CH 3 ) 2 .CH.CH 2 .CH 2 .NH 2 . 



/3 phenylethvlamine from phenylalanine, C 6 H 5 .CH 2 .CH 2 .NH 2 . 



Para, oxyphenylethylamine from tyrosine, OH.C 6 H 4 .CH 2 .CH 2 .NH 2 . 



A similar process has been supposed to take place as a step in the 

 successive oxidation of the carbon atoms in the long chain fatty acids 

 or carbohydrates, but a thorough study of this process as it occurs 

 in the higher animals is still wanting, and its very existence is indeed 

 still hypothetical. In the case of the fats the oxidation takes place 

 chiefly or entirely in the /3 position. On the other hand, decarboxyla- 

 tion certainly takes place in substances such as the a amino-acids, 

 where the first oxidation change occurs in the a group, and probably 

 closely follows this oxidation change. The reverse reaction, namely, 

 the insertion of the group CO . at the end of the long carbon chain, 

 is not known to take place, but would furnish a means by which the 

 organism with apparent simplicity could build up long carbon chains 

 and so imitate the process which in the laboratory is generally effected 

 by attaching a CN group to the end of the molecule. In the case of the 

 fats the building up, like the oxidative breakdown, appears to occur 

 by two carbon atoms at a time ; hence all the fatty acids met with in 

 the body have an even number of carbon atoms in their chain. 



It is worthy of note that all the changes which we have been 

 considering changes which not only account for the greater part of 

 the chemical reactions of the living body, but may lead to the produc- 

 tion of the most complex substances known are performed with little 



