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the work which they began at that remarkable time (1845-55), and which 

 is now being carried on by their pupils or their pupils' pupils in England, 

 America, France, Germany, Denmark, Sweden, Italy, and even in that 

 youngest contributor to the advancement of science, Japan, that physio- 

 logy has been gradually built up to whatever completeness it has at 

 present attained. 



What were the conditions which brought about this great advance 

 which coincided with the middle of the century ? There is but little 

 diflficulty in answering the question. I have already said that the change 

 was not one of doctrine, but of method. There was, however, a leading 

 idea in the minds of those who were chiefly concerned in bringing it 

 about. That leading notion was, that, however complicated may be the 

 conditions under which vital energies manifest themselves, they can be 

 split into processes which are identical in nature with those of the non- 

 living world, and, as a corollary to this, that the analysing of a vital 

 process into its physical and chemical constituents, so as to bring these 

 constituents into measurable relation with physical or chemical standards, 

 is the only mode of investigating them which can lead to satisfactory 

 results. 



There were several circumstances which at that time tended to make 

 the younger physiologists (and all of the men to whom I have just 

 referred were then young) sanguine, perhaps too sanguine, in the hope 

 that the application of experimental methods derived from the exact 

 sciences would aiford solutions of many physiological problems. One of 

 these was the progress which had been made in the science of chemistry, 

 and particularly the discovery that many of the compounds which before 

 had been regarded as special products of vital processes could be 

 produced in the laboratory, and the more complete knowledge which had 

 been thereby acquired of their chemical constitutions and relations. In 

 like manner, the new school profited by the advances which had been 

 made in physics, partly by borrowing from the physical laboratory various 

 improved methods of observing the phenomena of living beings, but 

 chiefly in consequence of the direct bearing of the crowning discovery of 

 that epoch (that of the conservation of energy) on the discussions which 

 then took place as to the relations between vital and physical forces; 

 in connection with which it may be noted that two of those who (along 

 with Mr. Joule and your President at the last Nottingham meeting) took 

 a prominent part in that discovery — Helmholtz and J. R. Mayer — were 

 physiologists as much as they were physicists. I will not attempt even 

 to enumerate the achievements of that epoch of progress. I may, how- 

 ever, without risk of wearying you, indicate the lines along which research 

 at first proceeded, and draw your attention to the contrast between then 

 and now. At present a young observer who is zealous to engage in re- 

 search finds himself provided with the most elaborate means of investiga- 

 tion, the chief obstacle to his success being that the problems which have 



