LIVING SUBSTANCE 3 



difference between something alive and something 

 that is not, he would hardly be taken seriously. 

 Yet, if such a layman should be pressed to define 

 just what he meant by "being alive," he might be 

 hard put. It might be assumed that some charac- 

 teristic chemical compounds are to be found in liv- 

 ing matter which are absent in non-living matter. 

 But thousands of exact chemical analyses have 

 been made of every sort of living thing and no ele- 

 ment or compound has ever been found which is 

 essentially different from what may exist in the 

 non-living world. Long ago a distinction used to 

 be made between "organic" and "inorganic" 

 substances, the former being the product of 

 living "organisms." But such a distinction has 

 broken down. It is possible to synthesize substances 

 in the test tube, identical in chemical composition 

 with those formed in Nature's laboratory, the 

 tissue of plant and animal. Indeed, the ability to 

 artificially reproduce natural products in this way 

 has proved of great value commercially, and arti- 

 ficially synthesized indigo, camphor, etc., now 

 supplement in large measure Nature's meager store 

 of such things. 



Nor is it easier to discover any unique physical 

 phenomena in living things. So far as we can 

 observe, and the more our observations are 

 extended, the more is the conclusion confirmed, 

 living matter obeys the same physical laws that 

 obtain in the rest of the universe. Again, living 

 things grow : but so do crystals and clouds. They 



