216 SECRETS OF ANIMAL LIFE 



remains an unread riddle; but, in spite of admittedly 

 great difficulties, many evolutionists incline to the 

 theory that very simple living creatures may have 

 arisen from so-called inanimate materials as the 

 outcome of natural synthetic processes. If this be 

 so, a new significance appears in the abundance of 

 carbon, hydrogen, and oxygen on the surface of the 

 juvenile earth, and in what the chemists tell us of 

 the unique ensemble of properties possessed by 

 these three wonderful elements. They have great 

 reactivity; they make great diversity possible; 

 they make for concentrations and complexifica- 

 tions, and these again favor the formation of 

 colloidal systems. Now, all living creatures are 

 essentially built up of proteins and other carbon 

 compounds in a colloidal state. Only in that state 

 could materials have the pliancy and the per- 

 meability which are characteristic of organisms, 

 and that " energia " of which Thomas Graham 

 wrote in 1861 that it " may be looked upon as the 

 probably primary source of the force appearing in 

 the phenomena of vitality/' Now, while almost 

 all substances can be made to assume the hetero- 

 geneous colloidal state, with ultra-microscopic 

 particles or droplets in suspension or dispersion in 

 some medium, there is a notable readiness on the 

 part of complex chemical substances to pass into 

 that "dynamical state," as Graham called it. But, 

 as Professor Henderson reminds us, " of all the 

 chemical elements, hydrogen, carbon, and oxygen 

 possess the greatest number of compounds and 



