BIOLOGY IN RELATION TO OTHER NATURAL SCIENCES. 443 



difficulty 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 tliat however complicated 

 may be the conditions under which vital energies manifest themselves, 

 they can l)e split into processes which are identical in nature with those 

 of the non-living world, and, as a corollary to this, that the analyzing 

 of a vital process into its i^hysical and chemical constitnents, so as to 

 bring these constituents into measurable relation with physical or chem- 

 ical 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 i^hysiologists (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 aftbrd solutions of many physiological in'oblems. One 

 of these was the progress which liad been made in the science of chem- 

 istry, 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 tliemore complete knowledge which 

 had been thereby acquired of their chemical constitutions and rela- 

 tions. In like manner the new school protited by the advances which 

 had been made in physics, partly by borrowing from the physical lab- 

 oratory various improved methods of observing the phenomena of liv- 

 ing 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 maybe noted 

 that two of those who (along Avith 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. 1 will not attempt even to enumerate the achievements of 

 that epoch of progress. I may however 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 research finds himself pro- 

 vided with the most elaborate means of investigation, the chief obsta- 

 cle to his success being that the problems which have been left over by 

 his predecessors are of extreme difticulty, all of the easier questions 

 having been worked out. There were then also ditflculties, but of an 

 entirely different kind. The work to be done was in itself easier, but 

 the means for doing it were wanting, and every investigator had to 

 depend on his own resources. Consequently the successful men Avere 

 those who, in addition to scientific training, jiossessed the ingenuity to 

 devise and the skill to carry out methods for themselves. The work by 

 which du Bois-Reymond laid the foundation of animal electricity would 



