No. 498] 



PHYSIOLOGY 



informed, does not in either its theory or its practise 

 imply cruelty or inhumanity. 



Physiology has long since passed the stage where un- 

 aided observation alone is of value, and has become pre- 

 eminently an experimental science. It is the task of the 

 experimenter to alter one or more of the conditions under 

 which the phenomenon occurs, to observe its change, if 

 such appears, and thus to throw light upon the nature of 

 the phenomenon itself, its relation to both its original and 

 its changed conditions, and its causes. Herein lies the 

 enormous difficulty of physiological work. The vital 

 process is of a complexity unapproached, much less 

 equaled, in the inorganic world. Living substance is 

 never exactly the same at two successive periods. It is 

 ever in unstable equilibrium, the seat of constant change, 

 of augmentations and depressions, of physical and chem- 

 ical mutations, and of what we in our ignorance call spon- 

 taneous activities ; and the conditions of its activities are 

 manifold and often obscure and unsuspected. To main- 

 tain the majority of these conditions intact, while alter- 

 ing one or more, is a superhuman task, one that is ap- 

 proached, but probably never realized in its entirety. 

 The physiologist is thus constantly baffled in his pursuit 

 of the desired object, and must needs exercise unwonted 

 patience in the face of not infrequent failure. His 

 progress is slow and his results can only approximate the 

 lnntlieniatieal exactness of the experimenter who deals 

 with stable non-living matter. 



Since the time when physiology a>>nnicd its physico- 

 chemical aspect and entered upon its modern phase, what 

 has been the trend of its research? Its energies were 

 first directed chiefly to the study of the mechanical and 

 other physical problems of the organs of vertebrate ani- 



