THE ATMOSPHERE 209 



(5) Aromatic nuclei. The phenyl-aiuido-propionyl nucleus constantly 

 appears, as in Phenyl-alaniii, Tyrosin. 



OH . . . .(1) 



CH 2 .CH.NH 2 .COOH(4) 



(6) Nuclei of the pyrrol group ; pyrrolidin carbonic acid. 



(7) Nuclei of the indol group; indol, skatol, tryptophan (skatol amido 

 acetic acid) 



C .CH 2 .CH.NH 2 .COOH 



C C H 4 GH 



Sn/ 



(8) Nuclei of the pyridin group ; after long lasting peptic digestion of 

 albumin, and heating the product with NaOH, a smell of pyridine results. 



