ITS SCOPE AND METHOD 79 



A point, and this must be our final one, is however 

 raised by the sensations connected with the body's tem- 

 perature. Phenomena inseparable from changes in the 

 temperature of the skin, we have met them as it were 

 naturally and perforce in the course of our physiological 

 inquiry. But what of our comparison between the physio- 

 logist and the engineer as both students of machines? 

 Are sensations part of the output of the living corporeal 

 machinery ? Does, then, sensation come in under the 

 conservation and equivalence of energy ? That is a 

 form assumed to-day by the perennial question of the 

 relation of mind to matter. It is debatable whether 

 such a question belongs to Physiology. I mention it 

 merely to note that the very obviousness with which 

 it intrudes itself in the pursuit of our physiological 

 argument illustrates how boundaries of natural sciences 

 exist, like those of natural species and descriptive pro- 

 vinces of all kinds, largely as human conventional dis- 

 tinctions, no more than and just so much worthy of 

 observance as they may serve utility. ' Sensation ' is a 

 subject matter of Psychology, but it seems useful at this 

 present that physiology and psychology should overlap 

 to some extent in their investigations. 



What then from our brief sketch may we conclude 

 regarding Physiology, its scope and method ? I think 

 it has become clear to us that Physiology is an experi- 

 mental science, for by means of experiment she puts 

 her conceptions to the touchstone of fact ; and that 

 Physiology is a branch of energetics, though morphology 

 in many cases shapes her field. She traces the current 

 of energy constantly flowing through that part of Nature 

 which we term alive. She finds the individual life a sort 

 of eddy or node in a great stream of energy, an eddy 

 checking an infinitesimal fragment of that stream, for 



