6 GENERAL PHYSIOLOGY 



atoms, and the various motions of the atoms, which fill universal 

 space, are jegarded as producing all phenomena in nature. 



If it be the task of physiology to explain the occurrence of vital 

 phenomena, i.e., to investigate their causes, it then becomes a 

 question whether, in living nature likewise, all phenomena can be 

 reduced to the motions of atoms, or whether it is necessary to take 

 refuge in another principle. Next to determining the boundaries 

 of the field of investigation, the chief task of physiology lies in 

 answering this question. 



Since early times mankind has been conscious of the great gap 

 that exists between two groups of vital phenomena, the physical 

 and the mental. Hence the above question is a double one. If it 

 be possible actually to reduce the physical phenomena of life to 

 the same elementary causes as the phenomena of the lifeless world, 

 the result will not necessarily hold good for psychical phenomena, 

 and the relations between the physical and the psychical must be 

 analysed. If it be impossible to trace psychical phenomena to the 

 same ultimate cause as the events of the physical world, another 

 explanation must be sought, and the important question will then 

 arise whether psychical phenomena can be explained at all. But if 

 it be allowed that they can be brought into causal relations with 

 the phenomena of the physical world, the question will still remain. 

 What are atoms ? The question of the possibility of answering 

 this will then arise. If it can be answered, will our craving for 

 causality then be satisfied ? 



The investigation of life is thus confronted with a multitude of 

 questions, which tax to the uttermost the capabilities of the human 

 mind. 



II. The History of Physiological Research i 



An examination of the history of physiological research is not 

 only interesting, but important for a correct judgment of the 

 present condition of physiology and the future course which it has 

 to take in order to accomplish its established purpose. 



A. THE EARLIEST TIMES 



The earliest traces of naive phj^siological ideas are lost in the 

 impenetrable obscurity of prehistoric times. A picture of them 

 has been handed down in the mythology of the early civilised 

 races. This represents a condition in which all knowledge and 

 all formation of ideas are grouped about the veneration of higher 



' The account of the earlier epochs in the development of physiology is based 

 upon the following works : K. Sprengel, Versuch tiiKr pnigmatischen Geschichte 

 rler Arzin.ikmide ; H. Haeser, Lehrbtich der Oeschichte der iledidn. In his 

 Elemente der allgemeinen Physiologie, Preyer gives a short sketch of the history 

 of physiology based upon the latter book. 



