202 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1916. 



formation of coal tar. According to this theory, coal in course of 

 distillation is decomposed into very simple gaseous products with 

 open-chain molecules, and these products by impact with the sides 

 of the heated retort undergo cyclisation. We shall see hereafter what 

 estimate should be given to this explanation. 



But the cyclic compounds are found not in coal tar alone; they 

 are met with in substances which have never been subjected to the 

 action of great heat, such as petroleum. They are found above all 

 in abundance in living organisms and, in particular, in plants. Here 

 the agent causing the cyclisation is no longer heat energy, and a 

 further search will be necessary to determine what it is. 



First, however, permit me to make an observation. From what I 

 said awhile ago it might appear that the properties of an organic 

 compound must differ completely according to whether that com- 

 pound belongs to the class of bodies with open chains or to those of 

 cyclic form. But investigations so far recorded show this is not 

 always the case. In both groups are found alcohols, acids and bases, 

 substances having taste or odor and others not, substances that are 

 poisons, and others that are harmless. Chemical industry draws in- 

 differently from either gi'oup its perfumes and its explosives, and 

 also its therapeutic medicines. Color alone seems to be found in 

 connection with cyclic structure, and yet only to a limited extent. 



It might be concluded that these properties are but slightly or not 

 at all influenced by the architectural structure of the molecule ; that 

 they depend essentially on the nature of the external groupings 

 which encircle this structure and which appear to be the same in both 

 cases. This would be a strange fact. It is hard to understand how 

 so essential a thing, from the theoretic viewpoint, as the structure of 

 the molecule is not reflected in the fundamental properties of the 

 material. But according to my personal observations this anomaly, 

 which would be inexplicable, does not really exist. I believe I may, 

 in a measure, affirm, on the contrary, that there is always a harmonj'' 

 in the fundamental properties of the material which are regulated 

 by the nature, either cyclic or linear, of the molecular structure. 

 These properties are the ones whicli come into play in all manifesta- 

 tions of life. It is this which I shall try to prove. 



In order to study vital phenomena in their greatest simplicity, 

 they must be observed not only in animals but also in plants. Con- 

 sider then the green plant, the organism upon which devolves the 

 task of transforming the mineral substances it contains into organic 

 materials, and finally into living matter, which the animal needs only 

 to decompose and oxidize in order to utilize the energy that they 

 contain in a potential state. 



What is the mechanism of this marvelous synthesis ? Our present 

 knowledge is very imperfect ; but we do Imow the intermediary prod- 



