[31] Traité de Chimie Organique. Par M. J. Liebig. pp. 88. “It results from the foregoing[32] that the carbonic acid, the ammonia, and the water, include in their elements the conditions necessary for the production of all the principles of living beings. These three bodies are the ultimate products of the putrefaction and of the _eremacausis_ (slow combustion) of all animal and vegetable races. All the products of the vital force, so numerous and so varied--all after death return to the primitive forms in which they first appeared or from which they originally sprung. Death, the complete dissolution of a generation, is always the source of a new generation.” [32] Liebig, _loc. cit._ Equally curious, but foreign to my present purpose, is the inquiry into the sources of the inorganic principles in plants and animals. These sources were inappreciable until a more refined chemistry appeared. Sea-water contains only the 1/12,400th of its weight of carbonate of lime, and yet this quantity suffices for the production of the essential components of the shells of myriads of crustaceans and corals. Whilst the atmosphere contains but 4/10,000ths to 6/10,000ths of its volume of carbonic acid, the amount in sea water is more by a hundred times, and yet in this medium we find another world of animal and vegetable life, which finds re-united in the ammonia and carbonic acid the same conditions which enable human beings on the surface of the solid earth (_terra firma_) to live and to maintain their species. It would even seem that the essential constituents of some organs have altered in the course of ages, without affecting, or being materially affected by, the principles of life. Thus it would seem that fossil bones contain the fluate (fluorure de calcium) of calcium in much larger quantities than the bones of recent animals; and the same remark has been made in respect of the composition of the crania of men found at Pompeii. They resemble in this respect the antediluvian fossil remains.