CHAPTER XLI 



THE GENERAL LIFE PROCESSES 



It is important to keep in mind that the fundamental 

 life processes of plants and animals are the same and that 

 whether life manifests itself in a plant or in an animal it 

 works in the same way. 



The reason for this becomes plain when it is known that 

 there is only one. living substance, which is known as 

 protoplasm. Protoplasm is not life itself, but it is the 

 material through which life manifests itself. Huxley 

 called it "the physical basis of life." Of course proto- 

 plasm is a substance of supreme interest, and constant 

 effort is being inade to discover its composition, but thus 

 far little more has been found out than that it is enormously 

 complex. It breaks up into numerous compounds, but 

 how these are put together in the living substance is not 

 known. It is this protoplasm that makes all the other sub- 

 stances and structures of plant and animal bodies. 



In general protoplasm occurs in very small masses 

 known as protoplasts, and the ordinary plant or animal 

 body is made up of thousands or millions of these proto- 

 plasts. Each protoplast usually builds some kind of wall 

 about itself, and this wall-encased protoplast is called a cell. 

 In case the protoplast has no wall it is usually called a 

 naked cell, and these are very common especially in animal 

 bodies. These cells are often spoken of as the units of 



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