RECENT PHYSIOLOGICAL PROGRESS 47 



central nervous system must be abandoned. 

 In the nervous system physiologists are also 

 faced with the problem presented by the re 

 coveries of functional activity after destruc 

 tion of centres or nerve paths on which this 

 activity normally depends. In the case of 

 other parts of the body this recovery of 

 function is also evident enough ; but in the 

 central nervous system differentiation of 

 function is so complex and definite that 

 recovery of functions stands out as a fact 

 of extraordinary interest and significance. 

 For this phenomenon it is difficult to imagine 

 any physico-chemical explanation. 



To sum up, the application to physiology 

 of new physical and chemical methods and 

 discoveries, and the work of generations of 

 highly-trained investigators, have resulted in 

 a vast increase of physiological knowledge, 

 but have also shown with ever-increasing 

 clearness that physico-chemical explanations 

 of elementary physiological processes are as 

 remote as at any time in the past, and that 

 they seem to physiologists of the present time 

 far more remote than they appeared at the 

 middle of last century. 



