SECTION I.— PHYSIOLOGY. 



THE RELATION OF PHYSIOLOGY TO 

 OTHER SCIENCES. 



ADDBESS BY 



PROF. C. LOVATT EVANS, D.Sc, M.R.C.S., F.R.S., 



PRESIDENT OF THE SECTION. 



Our subject of physiology has developed so rapidly during the last few- 

 decades, has taken so definite a place among the sciences, and has such 

 intimate relations with other subjects, that its position as a branch of 

 natural knowledge is one of some general interest. 



Physiology has a threefold appeal — as the master-key of medicine its 

 practical value is self-evident, as a science it has now a distinctive position, 

 while its relations to philosophy command the attention of all thoughtful 

 men. We will consider it, for convenience sake, from these three stand- 

 points. 



From the earliest times, physiological knowledge, whether known by 

 that name or not, has had the closest association with medicine. It would 

 indeed be difficult to imagine any great advance in the one that was not 

 immediately reflected in the other. Their methods, though necessarily 

 different, are convergent, their meeting-point being the disclosure of 

 normal functions. It is the business of the physician to attend to the 

 urgent call of pain and disease, and to use for their relief such information 

 as he has at his disposal. As he does so he observes, compares, and draws 

 conclusions on the basis of which a theory of the causation of the disorder 

 may be built. The clinical observations and deductions drawn from them 

 give a basis of rational physiological theory from which we have learnt 

 that a state of disease is never a thing in itself, but is always a result of 

 a quantitative change in some physiological process, an increase or 

 diminution of something that was there to begin with. Reflection upon 

 the observed bodily states in, say, a fever, jaundice, diabetes, nephritis, 

 or even mental disorders, reveals only overaction or underaction of some 

 physiological function as the feature which distinguishes the affected from 

 the normal individual. It is perhaps easier to speak of the normal than 

 to define it. In the long run, the normal is the description given by a 

 majority of individuals of their own build or behaviour. It is abnormal 

 to have unequal legs, to be eight feet high, or to believe the earth is flat ; 

 but as no two individuals are exactly alike the definition of normality is 

 more a matter of a statistical average than of precise definition. 



Disease is a departure from the normal which threatens life or which 

 in some way reduces its value. The physician's duty with regard to it is 

 a threefold one ; he must diagnose, prognose and treat. In diagnosis and 



