Introduction 7 



regarded as merely a form of dissociation because 

 the progeny of living organisms are structurally 

 similar to the parent, whereas the particles which 

 result from chemical dissociation are always dis- 

 similar from the undissociated molecules. 



The ultimate cause of life, whether it be a cer- 

 tain substance or a specific detail of physical 

 structure, must be the same for all living organ- 

 isms because the specific differences which distin- 

 guish one living organism from another disappear 

 as we go down the scale of plant or animal life. 

 Since there are innumerable species of bacteria 

 which exhibit no internal heterogeneity what- 

 ever, even under the most powerful magnifica- 

 tion, it appears that the ultimate units of liv- 

 ing matter must exist on a scale smaller than 

 the limit of microscopic vision, which is about 

 1/50,000 cm = 2,000 Angstrom units. Since the 

 largest organic molecules which have been pre- 

 pared synthetically measure about ten Angstrom 

 units (10X10 -8 cm) across, it is evident that the 

 ultimate units of living matter must exist in a 

 region where we come dangerously close to the 

 details of chemical structure, and that the ulti- 

 mate cause of life must be looked for in the realm 

 of chemistry rather than in the realm of physics. 



That the fundamental life processes must be 

 due, either wholly or partly, to specific chemical 



