PREFACE 



It is the purpose of this book to serve as a short 

 introduction to the comparative physiology of the 

 brain and of the central nervous system. 



Physiology has thus far been essentially the physi- 

 ology of Vertebrates. I am convinced, however, that 

 for the establishment of the laws of life-phenomena 

 a broader basis is necessary. Such a basis can be 

 furnished only by a comparative physiology which 

 includes all classes of the animal kingdom. My ex- 

 perience in the course on comparative physiology 

 at Wood's Holl seems to indicate that the transition 

 from the old to the comparative physiology can be 

 most readily accomplished through the physiology of 

 the central nervous system. 



The physiology of the brain has been rendered 

 unnecessarily difficult through the fact that meta- 

 physicians have at all times concerned themselves 

 with the interpretation of brain functions and have 

 introduced such metaphysical conceptions as soul, 

 consciousness, will, etc. One part of the work of 

 the physiologist must consist in the substitution of 

 real physiological processes for these inadequate con- 

 ceptions. Professor Ernst Mach, of Vienna, to whom 



