I.— PHYSIOLOGY. 163 



the advantage of speed and simultaneity of response in parts of the body 

 remote from one another. The two factors are not antagonistic ; the one 

 is not gradually supplanting the other, but each plays its part in its own 

 peculiar sphere. 



When we recognize the exactness of the co-ordination of the different 

 functions in normal life we cannot fail to appreciate the relative crudity 

 of some of the experimental methods we are forced to use in physiology. 

 Methods that interfere with the mutual interdependence of the different 

 organs can only give us a partial insight into the problem of life, and if 

 we use these methods we must correct the impression that we gain by 

 comparison with the true normal. 



In attempting to put before you what appear to me the outstanding 

 contributions which we owe to human physiology — the quantitative 

 changes of organ activity associated with normal life, the close functional 

 linkage of the different organs, and the power of adaptation to altered 

 circumstances — I have, as is only natural, dwelt upon those branches of 

 physiology with which I personally have been mainly brought in contact. 

 But the study of human physiology is by no means limited to these fields, 

 and we must not forget that we owe much to work undertaken primarily 

 in the cause of clinical medicine, a debt which we can repay in part as we 

 develop new methods by which we may investigate the physiology of man. 

 Instances of spontaneous derangement of function in man have helped 

 very considerably to elucidate the influence of the ductless glands, and 

 modern methods of clinical examination have amplified our knowledge 

 of the processes of digestion and the movements of the alimentary canal ; 

 while the neurologist is widening the field in which we can find scope for 

 the application of the fundamental principles of reflex action which, 

 based originally on the experimental investigation and analysis of the 

 properties of the lower nervous system, have already been extended by 

 the physiologist to embrace some at least of the functions of the cerebral 

 hemispheres in the intact animal. 



When we review the development of physiological thought in the last 

 quarter of a century we cannot close our eyes to the fact that investiga- 

 tions on man are becoming of increasing importance, and that the contri- 

 bution made by human physiology does not involve mere matters of 

 detail. There is something of far more importance than that, for the 

 evidence of balanced interaction of the functions of the different organs 

 with the preservation of the functional integrity of the whole, which is 

 so convincingly brought home to us in experiments on the human subject, 

 has made us appreciate that in physiology the organism as such, be it 

 man or one of the lower animals, is our unit, and that, whatever methods 

 we may employ in our investigations, we must keep that essential fact 

 before us. In the problem of what is meant by life we have set ourselves 

 the most complicated puzzle in existence. I firmly believe that human 

 physiology, limited though our knowledge may as yet be, has already 

 given us a vague glimpse of the final picture which we hope to complete, 

 and has put us in a better position to fit together the individual fragments, 

 the tiny components of the puzzle, which we have been accumulating in 

 such profusion in years past. 



The truth is that we cannot confine ourselves exclusively to any one 



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