l86 FROM FISH TO PHILOSOPHER 



is why and how protoplasm, or some biotic precursor of 

 protoplasm as we know it, came into existence, survived, 

 and multipHed in the Archeozoic seas to produce the 

 first hving cells— once called the Protozoa {protos = first; 

 zoion = animal) but better called Protista (from pro- 

 tistoSy meaning simply 'first'), because at this level it is 

 meaningless to distinguish between animals and plants. 



When, at a higher stage of evolution and in conse- 

 quence of natural selection, the products of cell division 

 formed a hfelong association to give rise to the multi- 

 cellular animals or Metazoa {meta — between; zown — 

 animal), certain cells became specialized in such a way 

 that physiological labor might be divided between 

 them: muscle cells to contract, gland ceUs to secrete, 

 bone cells to give physical support, nerve cells to con- 

 duct, while the reproductive cells remained protected 

 in the germinal tract to reproduce generations without 

 end. It is estimated that the body of a man weighing 155 

 pounds contains 26,500,000,000,000 cells (not coimting 

 the red blood cells, of which there are 10,240,000,000,- 

 000 in each of his 12 pints of blood). Except for the 

 subtle dynamics of cell reacting on ceU, nothing in- 

 trinsically new was added in the Metazoa: though not so 

 elaborately or quickly, the protistic cell can contract, 

 conduct, secrete, resist, divide; it possesses every intrin- 

 sic physiological property discoverable at the metazoan 

 level. 



The metazoan is thus a congeries of many cells in 

 imsteady balance with each other, incessantly disturbed 

 by the internal stresses of metabohsm, growth, and de- 

 formation, as well as by a multitude of external stimuli; 

 and by a wide variety of devices seeking to reduce these 

 stresses to a minimum, just as did the protistic cell. In 

 the evolution of the kidney, the organism acquired an 

 organ that operates automatically to supply the multi- 

 tudinous cells of the body with an immutable environ- 

 ment in which to live with minimal disquietude. The 

 evolution of the nervous system represents the evolution 



