Thus we have clearly before us the idea of the organic state as one of tension, dependent upon an opposition to chemical affinities. And we see, too, how this tension is produced, at least in some cases: namely, by the previous operation of those very affinities themselves. But some interesting questions suggest themselves here, to which it is in our power to give at least probable answers. We may ask whether this dependence of the living state on chemical action is universal; or whether other forces, such as light and heat, may not also directly produce it? There appears reason to believe that the latter is not the case; but that a process of chemical change is always connected with the vitalizing of matter, and that any other forces which contribute to this end do so by first exciting chemical activity. Where the latter is not present, no amount of other force suffices to induce the vitalizing process. And so far from these other forces being always absorbed when growth is in progress, we see a notable instance of the contrary in the germination of the seed, which is attended with a decided rise of temperature. It appears that here the amount of chemical change is in excess of the vital action consequent upon it, and that, therefore, while a part of the force it generates goes to reproduce the vital state, and bring about the growth of the young plant, part of it passes off as heat.