6 ON THE VITAL PRINCIPLE. 



Living bodies of animals and plants produce heat ; 

 and this phaenomenon has not, I think, been entirely 

 explained on any chemical principles, though in fossils 

 the production of heat is in most cases tolerably well 

 accounted for. In animals it seems to have the closest 

 possible connexion with the vital energy. But the 

 effects of this vital energy are still more stupendous in 

 the operations constantly going on in every organized 

 body, from our own elaborate frame to the humblest 

 moss or fungus. Those different fluids, so fine and 

 transparent, separated from each other by membranes 

 ^s fine, which compose the eye, all retain their proper 

 situations (though each fluid individually is perpetually 

 removed and renewed) for sixty, eighty, or a hundred 

 years, or more, while life remains. So do the infinitely 

 small vessels of an almost invisible insect, the fine and 

 pellucid tubes of a plant, all hold their destined fluids, 

 conveying or changing them according to fixed laws, 

 but never permitting them to run into confusion, so 

 long as the vital principle animates their various forms. 

 But no sooner does death happen, than, without any 

 alteration of structure, any apparent change in their 

 material configuration, all is reversed. The eye loses 

 its form and brightness ; its membranes let go their 

 contents, which mix in confusion, and thenceforth 

 yield to the laws of chemistry alone. Just so it hap- 

 pens, sooner or later, to the other parts of the animal 

 as well as vegetable frame. Chemical changes, putre- 

 faction and destruction, immediately follow the total 



