CHAPTER II 



HISTORICAL REVIEW CONCERNING THE ORIGIN AND DE- 

 VELOPMENT OF IDEAS AND THEORIES REGARDING 

 MOVEMENTS IN PLANTS AND ANIMALS WITH 

 SPECIAL REFERENCE TO THE QUESTION 

 OF TROPISMSi 



I. Early Investigations and Ideas concerning Movement in 



Organisms 



To primitive man motion was the criterion of life. 

 Everything that moved was aHve, not only plants and 

 animals but also various elements in nature, — water, wind, 

 fire, and the heavenly bodies. Motion was thought to 

 be under the control of higher beings, or the result of the 

 action of mind with which all living things were endowed. 

 The philosophers of early civilized races abandoned the 

 idea that all things which move are alive, but they still 

 considered that all physiological processes are due to vital 

 spirits. Aristotle (384-322 B.C.), thought that plants as 

 well as animals had souls. The pith was supposed to be 

 the seat of the soul in plants and all movements and other 

 phenomena characteristic of living things were regarded 

 as due to Its activity. During this period, all but a few 

 thinkers seemed to rest content that nothing more could 

 be learned about the cause or sequence of physiological 

 processes, and these few made only feeble attempts from a 



^ The following works are the main sources of information regarding 

 the earlier views on plant and animal activity: History of Botany, by Julius 

 von Sachs (1875), translation revised by I. B. Balfour, Oxford (1890); 

 General Physiology, by Max Verworn (1894), translation second edition 

 by F. S. Lee, New York (1899); Contemporary Psychology, by Guido Villa, 

 translated by H. Manacorda, London, 1903. 



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