386 VITALITY. 



It is, however, abundantly evident- that the great Originator of nature has 

 chosen to accomplish His purpose by a wondrous succession of fixed laws, open 

 to our investigation, and revealing depth beyond depth to a most remote and 

 obscure profundity. 



With this fact before us, on the hypothesis that the force of life, like its 

 Author, possesses an unknown, perhaps an unknowable nature, we should not 

 expect its interposition to be conspicuous ; we should, I think, expect its agency 

 to be executed only behind a succession of fixed laws, forming a vista, having 

 its termination almost lost in the distance. The natural evidence in the two 

 cases must of necessity, as we have seen, be of the same character, not direct 

 nor demonstrative, but implied and inferential. 



Whatever weight may be due to the considerations here urged in favor of the 

 specialty of the vital principle, at all events they answer these expectations and 

 conditions. Those arguments on which most stress has been laid arise at points 

 where, if evidence be possible, any one who thinks at all on the subject 

 would expect to find it. Something altogether unusual in nature marks the 

 boundary of the province in which life-force prevails ; and the phenomena of life 

 do not submit to be accounted for under the rigid laws which govern the appli- 

 cation of all forces that are known. 



APPENDIX. 



BY THE SECRETARY. 



In the early study of mechanical and physiological phenomena, the energy 

 which was exhibited by animals, or, in other words, their power to perform what 

 is technically called work, that is to overcome the inertia and change the form 

 of matter, was referred to the vital force. A more critical study of these phe- 

 nomena has, however, shown that this energy results from the mechanical power 

 stored away in the food and materials which the body consumes ; that the body 

 is a machine for applying and modifying power, precisely similar to those ma- 

 chines invented by man for a similar purpose. Indeed, it has been shown by 

 accurate experiments that the amount of energy developed in animal exertion 

 is just in proportion to the material consumed. To give a more definite idea of 

 this, we may state the general fact that matter may be considered under two 

 aspects, namely, matter in a condition of power, and matter in a state of entire 

 inertness. For example, the weight of a clock or the spring of a watch when 

 wound up is in a state of power, and in its running down gives out, tick by tick, 

 an amount of power precisely equal to the muscular energy expended in winding 

 it up. When the weight or the spring has run down, it is then in a condition of 

 inertness, and will continue in this state, incapable of producing motion, unless it 

 be again put in a condition of power by the application of an extraneous force. 

 Again, coal and other combustible bodies consist of matter in a condition of power, 

 and in their running down into carbonic acid and water, during their combustion, 

 evolve the energy exhibited in the operations of the steam engine. The coni- 

 bustible material may be considered the food of the steam engine, and experi- 

 ments have been made to ascertain the relative economy in the expenditure of 

 a definite amount of food in the natural machine and the artificial engine. The 

 former has been found to waste less of the motive power than the latter. 



In pursuing this trainof investigation the question is asked, "Whence does 

 the coal or food derive its power?" The answer is, that these substances are 



