130 ANNUAL KEPORT SMITHSONIAN INSTITUTION, 19 34 



Though speculations concerning the origin of life have given in- 

 tellectual j)leasure to many, all that we yet know about it is that 

 we know nothing. Sir James Jeans once suggested, though not 

 with conviction, that it might be a disease of matter — a disease of 

 its old age 1 Most biologists, I think, having agreed that life's 

 advent was at once the most improbable and the most significant 

 event in the history of the universe, are content for the present to 

 leave the matter there. 



We must recognize, however, that life has one attribute that is 

 fundamental. Whenever and wherever it appears the steady in- 

 crease of entropy displayed by all the rest of the universe is then 

 and there arrested. There is no good evidence that in any of its 

 manifestations life evades the second law of thermodynamics, but 

 in the downward course of the energy-flow it interposes a barrier 

 and dams up a reservoir which provides potential for its own re- 

 markable activities. The arrest of energy degradation in living 

 nature is indeed a primarj^ biological concept. Related to it, and 

 of equal importance is the concept of organization. 



It is almost impossible to avoid thinking and talking of life in this 

 abstract way, but we perceive it, of course, only as manifested in 

 organized material systems, and it is in them we must seek the 

 mechanisms which arrest the fall of energy. Evolution has estab- 

 lished division of labor here. From far back the wonderfully effi- 

 cient functioning of structures containing chlorophyll has, as every- 

 one knows, provided the trap which arrests and transforms radiant 

 energy — fated otherwise to degrade — and so provides power for 

 nearly the whole living world. It is impossible to believe, however, 

 that such a complex mechanism was associated with life's earliest 

 stages. Existing organisms illustrate what was perhaps an earlier 

 method. The so-called " autotrophic " bacteria obtain energy for 

 growth by the catalyzed oxidation of materials belonging wholly to 

 the inorganic world, such as sulphur, iron, or ammonia, and even free 

 hydrogen. These organisms dispense with solar energy, but they 

 have lost in the evolutionary race because their method lacks 

 economy. Other existing organisms, certain purple bacteria, seem 

 to have taken a step toward greater economy, without reaching that 

 of the green cell. They dispense with free oxygen and yet obtain 

 energy from the inorganic world. They control a process in which 

 carbon dioxide is reduced and hydrogen sulphide simultaneously 

 oxidized. The molecules of the former are activated by solar energy 

 which their pigmentary equipment enables these organisms to arrest. 

 Are we to believe that life still exists in association with systems 

 that are much more simply organized than any bacterial cell? The 

 very minute filter-passing viruses which, owing to their causal rela- 



