402 CORRELATION OF PHYSICAL AND VITAL FORCES. 



of the nutriment to the production of the living organized 

 tissues of which the several parts of the body are composed, 

 is to be regarded as a chemical action as if any combination 

 of albumen and gelatine, fat and starch, salt and bone-earth, 

 could make a living Man without the constructive agency in- 

 herent in the germ from which his bodily fabric is evolved. 



Another class of reasoners have cut the knot which they 

 could not untie, by attributing all the actions of living bodies 

 for which Physics and Chemistry cannot account, to a hypo- 

 thetical " Vital principle ;" a shadowy agency that does every 

 thing in its own way, but refuses to be made the subject of 

 scientific examination ; like the " od-force" or the ik spiritual 

 power" to which the lovers of the marvellous are so fond of 

 attributing the mysterious movements of turning and tilting 

 tables. 



A more scientific spirit, however, prevails among the best 

 Physiologists of the present day ; who, whilst fully recogniz- 

 ing the fact that many of the phenomena of living bodies can 

 be accounted for by the agencies whose operation they trace 

 in the world around, separate into a distinct category that 

 of vital actions such as appear to differ altogether in kind 

 from the phenomena of Physics and Chemistry, and seek to 

 determine, from the study of the conditions under which these 

 present themselves, the laws of their occurrence. 



In the prosecution of this inquiry, the Physiologist will 

 find it greatly to his advantage to adopt the method of philos- 

 ophizing which distinguishes the Physical science of the pres- 

 ent from that of the past generation ; that, namely, which, 

 whilst fully accepting the logical definition of the cause of any 

 phenomenon, as " the antecedent, or the concurrence of ante- 

 cedents on which it is invariably and unconditionally conse- 

 quent" (Mill), draws a distinction between the dynamical 

 and the material conditions ; the former supplying the power 

 which does the work, whilst the latter affords the instrumental 

 means through which that power operates. 



