regulating the Vital and Physical Phenomena. S87 



possessed of vitality, speedily resolve themselves into new com- 

 binations, a fact so obvious that it has given rise to the well 

 known definition of life, that is, the power by which decompo- 

 sition is resisted. Hence it is inferred, that the affinities which 

 hold together the elements during life are of a different nature 

 from those which operate in producing their subsequent sepa- 

 ration. Now, it may be replied to this argument, that no solid 

 or fluid compounds which have a disposition to spontaneous 

 decay after death, can continue to exist without change during 

 life ; that the activity of the processes of interstitial absorp- 

 tion and reposition seems to bear a pretty constant ratio in every 

 case with the natural tendency to decomposition ; and that the 

 maintenance of the original combination is not so much owing 

 to any thing peculiar in its vital affinities, as to the constant pro- 

 vision for the removal of particles in a state of incipient decay, 

 and their replacement by others freshly imited, — processes 

 •which are obviously dependent on vital actions for their con- 

 tinuance. Thus we find that all the most permanent parts of 

 the animal frame, such as the massive skeletons of the poiypi- 

 fera, the calcareous tegument of the mollusca, the bony scales 

 of fishes, all of which are believed by geologists to have re- 

 mained almost unchanged for thousands of centuries, are com- 

 pletely extravascular in the living animal, undergoing no in- 

 terstitial change when once formed ; next to these in order of 

 durability are the osseous structures of animals and the woody 

 fibre of vegetables, whose connection with the circulating sys- 

 tem seems rather adapted to meet the exigencies of growth, in- 

 jury, or disease, than to maintain a constant change required 

 by the tendency to decomposition. When we examine the 

 softer tissues, on the other hand, we find that the rapidity of 

 interstitial change fully compensates for the increased tendency 

 to decay ; and that if, from any cause, this change be prevent- 

 ed, decomposition and consequent loss of vital properties ensue, 

 as in the case of spontaneous gangrene from obstructed circu- 

 lation. It is interesting to remark also, that the liberation of 

 carbonic acid, which, when it begins to take place after death, 

 is one of the first signs of putrefaction, is the most constant and 

 necessary excretion of the body during hfe. It might also be 

 argued, that, independently of the changes already adverted 



