Far from merely animating the organs, it is closely associated with the forces of which we have already spoken. Living beings are heavy, and therefore subject to gravitation; they are the seat of numerous and various physico-chemical phenomena which are indispensable to their existence and which must be referred to the action of etherodynamy. But these phenomena are here manifested under the influence of _another force_. It is for this reason that the results of these phenomena are often quite different to those in inanimate bodies, and that living beings have their special products. Life is not antagonistic to the inanimate forces, but it governs and rules their action by its laws. Therefore it makes them produce tissues, organs and individuals instead of crystals; it organizes germs, and maintains through space and time, in spite of the most complex metamorphoses, that _unity of definite living forms_ which we call _Species_. If the anti-vitalists would only seriously reflect upon the matter, they would acknowledge that, considered from this point of view, there is nothing more mysterious in living beings than in some of the commonest phenomena presented by inanimate bodies. The intervention of Life as a modifying agent of actions purely etherodynamic may be as easily admitted as that of etherodynamy itself modifying and overcoming the action of weight. It is just as strange to see a piece of iron attracted and supported by a magnet, as to see carbon, oxygen, hydrogen and nitrogen combine and dispose themselves so as to form an animal or vegetable cell instead of any imaginable inorganic composition. I have repeatedly, and for many years, maintained the doctrine which I have summed up here. It seems to me confirmed in the highest degree by the researches undertaken for the elucidation of the problem of which we are treating. The experiences of M. Bernard in particular, relative to the action exercised by anæsthetics upon plants as well as upon animals, makes it impossible for us to doubt for a moment the intervention of an agent distinct from physico-chemical forces in organic beings. In employing the word _Life_ to designate this agent, I only make use of an established expression, without pretending to go beyond the information gained from experiment and scientific observation.