CHAPTER VI 

 LIFE 



As indicated in the preceding topic, life is always associated with a 

 certain type of organization of matter. It can be defined neither in 

 terms of the chemical elements which enter into it, none of which is 

 pecuHar to it, nor in terms of the forces which act through it, since those 

 forces are the same as those which also act through nonliving matter, the 

 results being different only because of the organization. 



33. Definition.— Life might be defined as the functioning of a certain 

 type of organization or as embracing certain phenomena. It might be 

 conceived of as energy manifested in a manner made possible by its organi- 

 zation. A precise definition is difficult to give in a form with which all 

 would agree, but the following is suggested: Life is a continual series of 

 reactions in a complexly organized substance known as protoplasm, by 

 means of which the organization tends to adjust itself to a constantly 

 varying environment. According to this definition a dormant mass of 

 protoplasm, such as that in a seed, might possess the capacity to exhibit 

 fife but would demonstrate this only under certain favorable conditions. 



34. Vital Force. — The theory has been held in the past that a mysteri- 

 ous vital force acts through hving matter and is responsible for the 

 characteristic phenomena of life, but every attempt to demonstrate the 

 existence of such a force has ended in failure. As knowledge of life phe- 

 nomena has increased, it has constantly become more evident that all 

 such phenomena can be explained by reference to the same forces which 

 also operate in nonUving matter and, as far as is known, throughout the 

 universe. 



35. Vitalism and Mechanism. — Those who have beheved in this vital 

 force have been termed vitalists, and their view vitalism. Mechanism, 

 on the other hand, is the view that all forces operating within the organism 

 are wholly physical or chemical in nature. Those who have contended 

 for this view have been termed mechanists. While vitalism is not a 

 tenable conception today, the most extreme form of mechanism also does 

 not appeal to the greater number of biologists, who observe phenomena 

 which are distinguished as vital. The view of the majority might be 

 stated as a modified form of mechanism. It is true that there is nothing 

 peculiar in the chemical elements or the physical forces in hving matter 

 as distinguished from nonliving matter, but that does not mean that the 

 chemical changes in protoplasm are precisely the same as those occurring 



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