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 

 peculiar 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. 



32. Definition. — Life might be defined as the possession 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 

 life but would demonstrate this only under certain favorable conditions. 



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

 ous vital force acts through living 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 nonliving matter and, as far as is known, throughout the 

 universe. 



34. Vitalism and Mechanism. — Those who have believed in this vital 

 force have been termed vitalists, and their view vitalism. Over against 

 this is the conception that the body is like a machine, played upon by 

 forces in its environment, and that life phenomena are mechanical 

 responses to these forces. Those who have contended for this view have 

 been termed mechanists, and their view mechanism. 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 living 

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



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