PRODUCTS OF METABOLISM. 1 15 



The ptomains (p. 417) are alkaloid-like bodies of basic character and 

 of more or less well-known structure. Some of them are notorious for 

 being very strong poisons, while others are quite harmless. These bodies 

 are usually called ptomains because they were first discovered in putrefy- 

 ing corpses. The best-known compounds of this character are the 

 putrescin or tetra-methylen diamin [NH 2 (CH 2 ) 4 NH 2 ] and the cadaverin 

 or penta-methylen diamin [NH 2 (CH 2 ) 5 NH 2 ], which can scarcely be 

 considered poisonous. The methyl-guanidin 



/ 

 HN=C< 



X NHCH 3 



may be mentioned as an example of a very poisonous ptomain. Another 

 poisonous ptomain is the neurin CH 2 =CH N(CH 3 ) 3 OH which has 

 been found frequently as a product of putrefaction. 



All the products of protein degradation mentioned so far may be 

 formed in the absence of oxygen. The decomposition of protein to 

 amino-acids is partly hydrolytic, and probably it consists also of intra- 

 molecular changes comparable to the alcoholic and lactic fermentations. 

 None of the processes mentioned so far requires oxygen. Even the 

 amino-acids can be hydrolyzed further under anaerobic conditions, form- 

 ing ammonia and hydroxy-acids. 



HOH+NH 2 CH 2 COOH=NH 3 +HOCH 2 COOH 



Amino-acetic acid Hydroxy-acetic acid 



In this way, ammonia is formed quite commonly from amino-acids. 

 In the products of protein degradation mentioned above only those 

 compounds have been considered which contain nitrogen. It is quite 

 evident, however, that in the cleavage of the large and complex protein 

 molecules, certain pieces of the broken molecule will contain no nitrogen. 

 An example of how such nitrogen-free compounds might be formed is 

 given in the hydrolysis of amino-acetic acid to hydroxy- acetic acid. Many 

 organic acids, like acetic, butyric, capronic, benzoic and phenylacetic 

 acids are quite generally found among the products of putrefaction. 

 Alcohols too, especially benzene derivatives like phenol and cresol, are 

 not unusual at all. Gas is often formed in putrefaction, especially 

 carbon dioxide and hydrogen; occasionally these gases are mixed with 

 traces of nitrogen and methane. Carbon dioxide is formed to some 

 extent by the hydrolysis of organic acids, as the following example shows: 



