vi PREFACE 



Thus there are atoms and molecules which exist and move 

 and form configurations — that is, constitute physico-chemical 

 systems in space and time. When we speak about a " mechan- 

 ism," we mean the motions and configurations of material 

 particles. Already we have gone a long way, via inferences, 

 from our " real and actual " observations of the passage of 

 nature, which observations are space- time coincidences; but 

 never mind that : let us stick to our notion of mechanism — systems 

 of material particles and their motions and configurations. The 

 descriptions of such systems by making use of space measure- 

 ments, and the devising of mathematical relationships between 

 them (the differential equations), are the method of science. 

 What we call " space " may be measured in terms of x and y 

 and z, the old space dimensions, and t the time one ; and so the 

 equations that we make involve the four " variables," x, y, z, 

 and t. 



That is what physiology does ; whatever its particular methods 

 may be, they involve the observations of space-time coincidences 

 — the readings of the pointers, scales, etc., of instruments. It 

 observes systems of material particles (the atoms and molecules 

 making up tissues) in certain configurations, and then, after 

 intervals of time, in other configurations. Sometimes the differ- 

 ences between the configurations can be thrown into mathe- 

 matical forms, but more often they cannot. 



This, therefore, is what is called mechanism, and it is the 

 method of physiology. It is the study of the successive phases 

 of a material energetic configuration or system. Note that it is 

 not necessarily the study of an organism. Usually what is 

 investigated is a part of an organism, or even the dead material 

 of the latter. And in all cases it is the study of the physico- 

 chemical activities of the organism that is the object of physiology. 

 In the very act of investigation these activities are necessarily 

 dissociated from each other, and the result is a number of partial 

 views of the whole organic activity. Of course, all this is in- 

 dispensable, and so the greater part of this book is really a sum- 

 mary of the main results of physiological science, and is intended 

 to give the reader an attitude (for he must supplement what is 

 said here) in his attempt to understand life. 



It would be inconvenient, and even pedantic, to state these 

 results in terms of the fundamental space-time concepts, and so 

 our analyses of the activities of the living organism must continue 



