INTRODUCTION. 25 



which the forces of chemistry and physics cannot 

 account for ? Are there limits to the application 

 of natural law to explain life ? Can there be 

 found something connected with living beings 

 which is force but not correlated with the ordinary 

 forms of energy ? Is there such a thing as vital 

 energy, or is the so-called vital force simply a 

 name which we have given to the peculiar mani- 

 festations of ordinary energy as shown in the 

 substance protoplasm ? These are some of the 

 questions that modern biology is trying to 

 answer, and it is the existence of such questions 

 which has made modern biology a new science. 

 Such questions not only did not, but could not, 

 have arisen before the doctrines of the conser- 

 vation of energy and evolution had made their 

 impression upon the thought of the world. 



SIGNIFICANCE OF THE NEW BIOLOGICAL PROBLEMS. 



It is further evident that the answers to these 

 questions will have a significance reaching beyond 

 the domain of biology proper and affecting the 

 fundamental philosophy of nature. The answer 

 will determine whether or not we can accept in 

 entirety the doctrines of the conservation of 

 energy and evolution. Plainly if it should be 

 found that the energy of animate nature was not 

 correlated with other forms of energy, this would 

 demand either a rejection or a complete modifi- 

 cation of our doctrine of the conservation of 

 energy. If an animal can create any energy 

 within itself, or can destroy any energy, we can 

 no longer regard the amount of energy of the 



