72 ON THE STUDY OF PHYSIOLOGY. 



bodies, and the strong contrast of tliclr respeetlve properties, 

 naturally excited curiosity respecting the causes of this 

 diversity, and endeavours to shew the mode in which it 

 was effected. Here we quit the path of observation, and 

 wander into the regions of imagination and conjecture. It 

 is the poetic ground of physiology ; but the union is unna- 

 tural, and, like other unnatural unions, unproductive. The 

 iiction spoils the science, and the admixture of science is 

 fatal to inspiration. The fictitious beings of poetry are ge- 

 nerally interesting in themselves, and are brought forwards 

 to answer some useful purpose ; but the genii and spirits of 

 physiology are awkward and clumsy, and do nothing at last, 

 which could not be accomplished just as well without 

 them : they literally incumber us with their help. 



For those, who think it impossible that the living organic 

 structures should have vital properties without some extrin- 

 sic aid ; — although they require no such assistance for the 

 equally wonderful affinities of chemistry, for gravity, elas- 

 ticity, or the other properties of matter, a great variety of 

 explanations, suited to all tastes and comprehensions, has 

 been provided. 



Some are contented with stating that the properties of 

 life arise from a vital principle. This explanation has the 

 merit of simplicity, whatever we may think of its profound- 

 ness : and it has the advantage of being transferable and 

 equally applicable to any other subject. Some hold that 

 an immaterial principle, and others, that a material, but in- 

 visible and very subtle agent, is superadded to the obvious 

 structure of the body, and enables it to exhibit vital pheno- 

 mena. The former explanation will be of use to those who 

 are conversant with immaterial beings, and who understand 

 how they are connected with and act on matter, but I 

 know no description of persons likely to benefit by the 

 latter. For subtle matter is still matter ; and if this fine 

 stuff can possess vital properties, surely they may reside in 

 a fabric which differs only in being a little coarser. 



Mr. Hunter has a good substantial sort of living princi- 

 ple j he seems to have had no taste for immaterial agents. 



