THE CHLOROPLAST PIGMENTS 



483 



things. For years we have known and 

 studied every phase of the nitrogen cycle in 

 nature, until we are all quite familiar with 

 this cycle. Is it not worth our time to 

 study pyrrole and seek to know just what 

 part it plays in living cells? Since pyrrole 

 contains nitrogen and is found in blood 

 and in chlorophyll, why should we not 

 •study every phase of this problem? At 

 last we have come to the place where we 

 are not contented with the chemist's or the 

 geologist's viewpoint regarding the origin 

 of soil. Soil is something more than 

 mineral matter; it is a very complex body 

 which contains organic as well as in- 

 organic materials, both of which are of 

 ! great value to the plant, which spreads its 

 roots through the soil in search of food for 

 its metabolic processes. 



Another possible relation of chlorophyll 

 shows that in the higher plants the 

 vitamines are localized in the seeds and in 

 green leaves. Maybe we can agree with 

 Mockeridge when she says that there is a 

 vitamine cycle though we may not agree 

 with her explanation of the way things 

 work. At least it is probably true that we 

 will all agree that the entire world obtains 

 its vitamines from plants, even though we 

 may not agree how they are formed in 

 plants. However, the general conclusion 

 seems to be that vitamines are necessary 

 for nearly all plant and animal life. 



The exact nature of the vitamines has 

 never been revealed but the evidence seems 

 to show that they may be nitrogen com- 

 pounds which are cyclic . Many workers 

 are of the opinion that they contain 

 carbon, hydrogen and nitrogen and some 

 even venture to guess that some of the 

 vitamines may be pyrrole compounds. It 

 is my understanding that at the present 

 time the tests for pyrrole compounds are 

 • not very definite because many other 

 chemical compounds will also give the 

 pyrrole tests. From what little we 



already know of pyrrole compounds and 

 their probable relation to vitamines an 

 investigation of the field could probably 

 give us far more knowledge than the 

 present scheme of pyramiding what we 

 already know about the properties of 

 vitamines. The field is one that has 

 taxed the chemist to the utmost, but 

 should be considered by all who are 

 seriously interested in vitamines. The 

 investigation will necessarily have to be a 

 cooperative affair. Maybe now we will 

 agree with Funk that it is best to stop 

 marking time, cease our quibbling and 

 get busy on the real problem and maybe 

 we too can hope with him that the 

 chemical isolation of the vitamines will 

 not be far distant. To discover the role 

 of pyrrole in nature, looking forward to 

 the possible finding of a pyrrole cycle, is a 

 problem worthy of the efforts of all who 

 are interested in the biochemistry of 

 living processes. 



Maybe by gathering this mass of ideas 

 together we can frame a real story of life 

 that will satisfy each group of us; agri- 

 culturists, biochemists, chemists, soil 

 scientists, plant physiologists, etc. Is 

 not nitrogen — organic and inorganic — 

 taken up by the plant and then found as 

 organic nitrogen in the various parts of 

 the plant? Maybe the inorganic nitrogen 

 goes to form chlorophyll and the organic 

 nitrogen to form other complex nitrogen 

 compounds. Is the chlorophyll — a tetra 

 pyrrole — broken down by light to form 

 various pyrrole bodies which may later 

 function as what we know as vitamines? 

 If such are the facts we might expect 

 vitamines to be found in almost any part 

 of the plant, and so when plant parts are 

 eaten the vitamines pass into the bodies of 

 animals. When these living organisms — 

 plants and animals — decompose, shall not 

 we then find in the humus pyrrole com- 

 pounds which have been set free from 



