56 THE LIVING WORLD. 



Whether in its ultimate analysis it is still to be so 

 regarded is an open question. The marvellous pow- 

 ers of living things, and the great mystery surround- 

 ing the processes of growth and reproduction, have 

 caused thinkers to believe that the property of life 

 was something more than a simple abstraction, and 

 to regard it as. a distinct and mysterious force resid- 

 ing in organisms, capable of indefinite expansion, and 

 having its origin in some direct creative power. 

 This conception has been retained while the belief 

 in the general mechanism of nature has been gaining 

 universal acceptance. 



This conclusion, that of the vitalistic school, has 

 for some time been subject to criticism. The mys- 

 te'rious activities and powers of living things have 

 been in a measure explained as the results of known 

 forces of nature. The discovery of the law of con- 

 servation of energy, the discovery of the close rela- 

 tion of chemistry to vital processes, the manufacture 

 of organic products in the chemist's laboratory, and 

 the study of the various properties of the complex 

 compounds of carbon have all united in proclaiming 

 a close relation between the laws governing the liv- 

 ing and the non-living world. It was inevitable that 

 the conclusion would be reached that what we call 

 life is nothing more than a manifestation of ordinary 

 forces of nature under special conditions furnished 

 by the substance protoplasm. Such a position is 

 assumed by the mechanical theory of life. 



Even when this position is taken, the fact remains 

 that at the present time protoplasm does not arise 

 except through the agency of other protoplasm. 



