IV. 



VITALITY. 



THE origin, growth, and energies of living things 

 are subjects which have always engaged the 

 attention of thinking men. To account for them it 

 was usual to assume a special agent, free to a great ex- 

 tent from the limitations observed among the powers 

 of inorganic nature. This agent was called vital force; 

 and, under its influence, plants and animals were sup- 

 posed to collect their materials and to assume deter- 

 minate forms. Within the last few years, however, our 

 ideas of vital processes have undergone profound modi- 

 fications; and the interest, and even disquietude, which 

 the change has excited are amply evidenced by the 

 discussions and protests which are now common, re- 

 garding the phenomena of vitality. In tracing these 

 phenomena through all their modifications, the most 

 advanced philosophers of the present day declare that 

 they ultimately arrive at a single source of power, from 

 which all vital energy is derived; and the disquieting 

 circumstance is that this source is not the direct fiat of 

 a supernatural agent, but a reservoir of what, if we do 

 not accept the creed of Zoroaster, must be regarded as 

 inorganic force. In short, it is considered as proved 

 that all the energy which we derive from plants and 

 animals is drawn from the sun. 



A few years ago, when the sun was affirmed to be 

 the source of life, nine out of ten of those who are 

 alarmed by the form which this assertion has latterly 

 46 



