Page:An introduction to physiological and systematical botany (1st edition).djvu/37

 Rh indeed, or increasing by the mechanical addition of extraneous substances, or by the laws of chemical attraction, but not fed by nourishment taken into an organized structure. Their curious crystallization bears some resemblance to organization, but performs none of its functions, nor is any thing like a vital principle to be found in this department of Nature.

If it be asked what is this vital principle, so essential to animals and vegetables, but of which fossils are destitute, we must own our complete ignorance. We know it, as we know its Omnipotent Author, by its effects.

Perhaps in the fossil kingdom heat may be equivalent to a vital principle; but heat is not the vital principle of organized bodies, though probably a consequence of that principle.

Living bodies of animals and plants produce heat; and this phænomenon 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