474 HISTORY OF PHYSIOLOGY. 



survey has yet gone, no genuine physiological prin- 

 ciple. All the trains of physiological research which 

 we have followed have begun in exact examination 

 of organization and function, and have ended in 

 wide conjectures and arbitrary hypotheses. The 

 stream of knowledge* in all such cases is clear and 

 lively at its outset; but, instead of reaching the 

 great ocean of the general truths of science, it is 

 gradually spread abroad among sands and deserts 

 till its course can be traced no longer. 



Hitherto, therefore, we must consider that we 

 have had to tell the story of the failures of physio- 

 logical speculation. But of late there have come 

 into view and use among physiologists certain prin- 

 ciples which may be considered as peculiar to organ- 

 ized subjects ; and of which the introduction forms 

 a real advance in organical science. Though these 

 have hitherto been very imperfectly developed, we 

 must endeavour to exhibit, in some measure, their 

 history and bearing. 



