VITALITY. 385 



The uniformity of the period through which life extends in any given species 

 is a result that no one would anticipate if the vital principle be of the nature of 

 the known forces. The physical elements of animals are said to undergo an 

 entire renewal in the course of a few years. Surely, then, with renewed mate- 

 rials to work upon, and with something akin to the imponderables to do the work, 

 animals should never grow old. Why should they — any more than oxygen 

 should lose its vigor Jind grow tired of uniting with hydrogen? 



We have now noticed some of the considerations which appear to favor the 

 supposition that the vital principle is a thing sui generis: 



1st. The unparalleled hiatus which exists between things animate and things 

 inanimate. 



2d. The great dissimilarity between the properties of the imponderables and 

 those of vitality. 



3d. The diflSculty arising from the hypothesis that the embryo of a living thing 

 is developed only by agencies analogous with known forces. 



4th. The permanence of form and structure observable during many genera- 

 tions of the same species. 



5th. The absence of any indications as to what becomes of the vital principle 

 at death. 



6th. The periodicity of life. 



It is not contended that these considerations amount to a demonstrative proof 

 Ihat the vital principle is a thing sui generis, but the question naturally arises, 

 how far, supposing our conclusion to be a right one, a demonstrative proof is 

 possible. 



An instance somewhat parallel may be found in the field of natural theology, 

 in which is assumed, as a starting point, the existence of a first Supreme Cause, 

 whose nature is beyond all comprehension ; certain facts are adduced which 

 agree with this assumption ; also, its rejection is shown to involve many great 

 difficulties; but all this is not proof; and in fact proof here seems to be out of 

 the question, for the simple reason that whatever that might be of which the 

 existence could be proved, it would not be the Infinite One. In logic, as in me- 

 chanics, action and reaction are equal, and the very locus standi required by a 

 proof, in the thing to be proved, puts demonstration in this case out of the 

 question. Similarly, if the existence of vitality as a distinct thing were capable 

 of being demonstrated by direct proof, the vital principle must be of the nature 

 of other agencies, which is contrary to the original hypothesis. 



It Avould be very interesting to trace the course of those discoveries in physi- 

 ology which have led some eminent observers to class vitality with other known 

 forces. It cannot be denied that a very large number of facts connected with 

 the phenomena of life, formerly supposed to be attributable only to the unde- 

 fined agency of the vital principle, are now accounted for on principles which 

 are pu.rely scientific. For example: the constituents of some of the proximate 

 elements of organic substances, such as starch, albumen, &c., were known long 

 ago ; but the power to combine these constituents so as to produce the proximate 

 elements was regarded as being possessed by the vital principle alone, the work- 

 ing of which in the formation of the proximate elements could, it was thought, 

 by no means be imitated in the laboratory. This is now known to be an error; 

 the chemist by his science does that which before was cqnsidered to be th<, 

 peculiar function of the vital principle. In these and many other instances it 

 has been proved that the aid of the vital principle has been unnecessarily invoked 

 to account for results explicable on scientific grounds. 



In all this we have a parallel to that which has taken place in the more ex- 

 tensive field of the cosmos. Yet there are some who are conscious that if it 

 were possible to trace the existing state of things by a regular series of scientific 

 deductions to a nebular condition of the universe, no approach would be made 

 thereby to the oossibility of dispensing with a first Supreme Cause. 

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