BASES DERIVED FROM THE PROTEINS 241 



They are generally regarded as the toxic constituents of 

 poisonous food, although most cases of so-called ptomaine 

 poisoning are presumably due to infection with a living micro- 

 organism. Some cases, however, are certainly caused by 

 thermostable and very poisonous substances about which little 

 is known. Brieger, who retained the term ptomaine "for the 

 sake of tradition," also applied it to poisonous bases formed 

 in cultures of pathogenic bacteria. On the whole, it is probably 

 best not to speak of ptomaines when putrefaction bases are meant. 



Of the principal groups of substances entering into the 

 composition of living organisms, only the proteins can in 

 general form basic substances. In certain cases it is indeed 

 conceivable that the nitrogen may be derived from ammonia 

 but apart from a few doubtful cases, it is certain, or at least 

 probable, that the natural bases are formed from decomposition 

 products of proteins. 



Methylation Bases from Amino-Acids in the Higher Plants 



Plants rarely contain primary bases ; this applies not 

 only to the true plant alkaloids but also to simpler products 

 derived from proteins, which frequently differ from the corre- 

 sponding substances of animal origin by having one or more 

 methyl groups. Thus xanthine occurs in animals but theo- 

 phylline and theobromine (both dimethylxanthine) and caffeine 

 (trimethylxanthine) are found in plants. Adrenaline and 

 sarkosine are among the few substances of animal origin 

 containing a methylamino-group. 



It is noteworthy that bacteria and probably also fungi in 

 this respect resemble animals rather than the higher plants. 

 All the putrefaction bases formed by bacteria from amino-acids 

 are primary bases and many are also present in ergot and 

 in other fungi. In vascular plants, methyl derivatives of these 

 bases are found occasionally. The base tetramethylputrescine 

 (CH 3 ) 2 N.CH 2 .CH 2 .CH 2 .CH 2 .N(CH 3 ) a , has been isolated by 

 Willstatter from Hyoscyamns mitticus ; the alkaloid hordenine, 

 isolated by Leger from malt germs {Compt. rend. 1906, 142, 

 108), in like manner is the N-dimethyl derivative of />-hydroxy- 

 phenylethylamine, OH . C 6 H 4 . CH 2 . CH 2 . N(CH 3 ) 2 . Pictet 

 obtained from tobacco the " protoalkaloid " methylpyrrolidine, 

 CH 3 .N=C 4 H 8 ; pyrrolidine itself has not yet been found as 

 a product of putrefaction but it is probably formed. 



16 



