PRESlDENTiAL, ADDRESS. 295 



To find oneself President of a, Section of the British Association is an intima- 

 tion that one has joined the ranks of the veterans and a warning that one's days 

 of active work are drawing to a close. 



But, while one accepts the situation with some twinges of regret, one is 

 consoled by the thought that a long association with physiology has enabled one 

 to take a wider general survey than one did in one's younger days, to see more 

 clearly the bearing of one part upon another and to recognise some of the 

 dangers to which we, as investigators and teachers, are exposed. 



It has often been urged that physiology, the study of Life, cannot possibly 

 be an exact science in the same way as are physics and chemistry. My old 

 friend. Prof. P. G. Tait, used to twit me with the possession of a mind 

 ' debauched by the so-called science of biology.' 



I am not quite sure vrhat the charge that biology is not an exact science 

 really means. But if it means that in it direct methods of measurement are 

 not possible, then I am inclined to reply that in many of the phenomena of 

 molecular physics, including chemistry, such direct methods are still wanting, 

 or have only recently been devised, while in physiology the whole trend of 

 the science has been to devise graphic or self-registering methods, and to 

 exclude more and more the fallacies of observation through the senses. 

 It is only when our study of life involves, as it must often involve, the 

 consideration of consciousness, that we are thrown back upon observational 

 methods, that the personal element is introduced as a disturbing factor, 

 and that our results are open to many different interpretations. Of course 

 the same fallacy may invade the investigation of many of the vital mani- 

 festations not involving consciousness, but the fault then is in the observer. 

 It is so difficult to avoid forcing the interpretation which appeals to us. But 

 it should be recognised that the evidence, when set down quite .simply and 

 without comment, should lead others to the same conclusion as that to which 

 we have arrived. We are not justified in dressing it up in order to secure 

 it more ready acceptance. In doing so, we cease to be scientific men and become 

 special pleaders. 



Yet this dressing up of one's view eo as to make it convincing is one of 

 the most tempting of crimes — a crime -which all of us, usually unconsciously, 

 have doubtless committed in our time and will go on committing. And the 

 worst of it is that the abler the exponent, the greater is the harm done. Every 

 part of physiology affords startling examples of this. That which first occurs 

 to me is the theory of secretion of urine, upon which a recent writer frankly 

 takes up one hypothesis and with great ability defends it through many pages, 

 as a conclusion to be unreservedly accepted. It is so difficult to say, ' the 

 evidence is inconclusive, to give the verdict of " Not proven." ' The same 

 thing is seen in the old fight between the exponents of the two main theories of 

 colour vision, neither of which is necessarily right. An attractive interpre- 

 tation, boldly stated by an able advocate, is apt to seize the imagination even 

 of a critical physiologist and to lead to an abrogation of judgment and a blind 

 acceptance. Especially is this the case when the work is not in our own special 

 line and when it is announced by a due flourish of trumpets and is supported 

 bv the invention of more or less incomprehensible Greek words devised by some 

 classical colleague. Dangerous and unscientific as is this championing of one 

 interpretation of a series of observations or experiments, it has not infre- 

 quently helped forward the advance of knowledge. It has often stimulated 

 other workers and led to the true solution of the problem — witness the 

 fascinating work and the able deductions drawn from it by Heidenhain on 

 lymph formation which stimulated Starling to subsequent investigations thus 

 lending to a better understanding of the facts which Heidenhain had observed. 

 Witness too the admirable study of cutaneous sensibility by Head, Sherwen and 

 Rivers and their interpretation of the results, uncritically accepted by some, but 

 which stimulated others to restudy the subject and to indicate simpler interpreta- 

 tions of the observations, and these have reacted again to induce further work 

 upon the problems. 



A consideration of these dangers in the physiological inquiry helps us to 

 understand how seldom any line of investisation goes straight to the goal : 

 a zigzag forward progression is almost universal — at one time many points 

 off the straight line in one direction — at another just as man^r off in another. 



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