1(J2 THE STORY OF LIFE'S MECHANISM. 



the sum of the activities of its separate cells ; 

 just as the activities of a city are the sum of the 

 activities of its individual inhabitants. The bit 

 of protoplasm was the unit, and this was a 

 chemical compound or a simple mixture of com- 

 pounds to whose combined physical properties we 

 have given the name vitality. 



THE DECLINE OF THE REIGN OF PROTOPLASM. 



Hardly had this extreme chemical theory of life 

 been clearly conceived before accumulating facts 

 began to show that it is untenable and that it must 

 at least be vastly modified before it can be received. 

 The foundation of the chemical theory of life 

 was the conception that protoplasm is a definite 

 though complex chemical compound. But after a 

 few years' study it appeared that such a concep- 

 tion of protoplasm was incorrect. It had long 

 been suspected that protoplasm was more complex 

 than was at first thought. It was not even at 

 the outset found to be perfectly homogeneous, 

 but was seen to contain minute granules, together 

 with bodies of larger size. Although these bodies 

 were seen they were regarded as accidental or 

 secondary, and were not thought of as forming 

 any serious objection to the conception of proto- 

 plasm as a definite chemical compound. But 

 modern opticians improved their microscopes, 

 and microscopists greatly improved their methods. 

 With the new microscopes and new methods 

 there began to appear, about twenty years ago, 

 new revelations in regard to -this protoplasm. 

 Its lack of homogeneity became more evident, 

 until there has finally been disclosed to us the 



