CHAPTER II 



PROTOPLASM 



In spite of the enormous amount of work which has been done upon 

 protoplasm during a period of many years, our knowledge of its constitu- 

 tion and behavior must still be regarded as very superficial. Some have 

 inclined to the view that a given kind of protoplasm is a single complex 

 chemical compound, but at present it seems more probable that it 

 represents a somewhat looser combination of substances, many of which 

 are themselves very elaborate in composition. It furthermore seems 

 probable that these substances differ from those which may exist apart 

 from protoplasm, not so much in their fundamental chemical nature 

 as in the degree of their complexity, their energy content or reactivity 

 (Mathews, 1924), and especially in their mutual organization. Proto- 

 plasm is made up of proteins, fats, salts, water, carbohydrates, and other 

 compounds, but it is not a mere mixture of these materials: it is an intri- 

 cately organized system of substances of many types, and only by virtue of 

 this specific physico-chemical organization does it serve as the material 

 substratum for those peculiar orderly activities characterizing the 

 organism, namely, synthetic metabolism, irritability, reproduction, 

 and adaptive response. Living protoplasm should always be thought of 

 as a system in dynamic equilibrium; it is continuously maintaining itself 

 through a balance of constructive and destructive processes. The "abil- 

 ity to transform environmental material into its own specifically organized 

 and active substance is the distinctive criterion of living as distinguished 

 from non-living matter" (R. S. Lillie, 1923). 



The Chemical Nature of Protoplasm.^ — The operation of any system, 

 living or lifeless, depends upon the materials of which it is made up (its 

 chemical composition), the arrangement of these materials (its physical 

 organization), and the set of surrounding conditions under which it acts 

 (its environment). 



The chemical composition of protoplasm has been determined 

 approximately in a number of instances. For this purpose the plasmodia 



1 See on this subject A. Zimmermann (1896), Hammarsten (1909), Zacharias 

 (1910), Czapek (1913, 1920), Wells (1914), Bayliss (1915), Mathews (1916, 1924), 

 Palladin (1923), Meyer (1920), T. B. Robertson (1920), B. Moore (1921), R. W. 

 Thatcher (1921), Walter (1921), Pratje (1920), Tischler (1921-1922, Chap. II), 

 Lundeg&rdh (1922, Pt. I, Chap. XI, B), Grafe (1922, Chap. IV), Onslow (1923), 

 Trier (1924), Heilbrunn (1928), Gortner (1929), and Kiesel (1930). 



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