252 Science Religion and Reality 



themselves, one thing is certain. No other element but carbon, 

 and in a much lesser degree silicon, possesses the power of combining 

 with itself to form long chains of atoms. If it were not for this 

 power, which ensures the formation of the enormously complex 

 molecules of organic chemistry, life as we know it would be quite 

 impossible. The second conditioning factor for the appearance 

 of living matter is the colloidal state. People who have no intimate 

 acquaintance with biochemistry have no idea of the importance 

 of the colloidal state of matter in life. Thomas Graham in 1 862 

 first recognised the fact that solutions of substances in each other 

 may be of two kinds, crystalloidal or homogeneous, and colloidal or 

 heterogeneous. An ordinary solution of salt in water is homo- 

 geneous because the dissolved molecules are so small as to have no 

 surface in the real sense of the word, but a solution of a fat in water 

 is heterogeneous because the molecules are collected into mole- 

 cular aggregates, too small indeed to be seen except with the 

 ultra-microscope, but large enough to affect profoundly all the 

 properties of the solution. So different, as a matter of fact, are 

 colloidal and crystalloidal solutions, owing to the enormous increase 

 of surface in the former by thousands of times, that they form, as 

 Graham said, " two quite different worlds of matter." Now 

 colloidal solutions do occur in nature among inorganic systems to 

 a certain extent and may have played a great part in geological 

 processes, but their association with carbon compounds is what 

 is pre-eminently characteristic of living matter. Thus physical 

 and chemical processes, though obeying fundamentally the same 

 laws both outside and inside the organism, appear different to us 

 simply because they are taking place on surfaces in a colloidal 

 system nothing very nearly analogous to which exists in inorganic 

 nature. Johann Christian Reil, a German physiologist, had the 

 remarkable intuition to grasp this fact long before anything very 

 exact was known of colloidal solutions. In an extremely interest- 

 ing and rather rare article published in 1796, called " IJeher 

 der Lebenskraft" he discusses the various theories, vitalistic and 

 mechanistic, of living beings, and finally comes to the conclusion 

 that the physical and chemical processes of the animal organism 

 are identical with those of inanimate matter, save that they are 

 conditioned by the nature of living stuff. 



" We have for the Existence of Vital Spirits, no knowledge 

 through Experiment," he says. ' In the Composition and Form of 



