This line was indicated by discoveries of the Sidralmo or bio-chemical families, and the Ooaromo or psycho-physiological families. The Sidralmo had long been investigating the ultimate constituents of living matter; and again and again, when seeming to be on their track, they were baffled by the escape of some element, and left with only the _caput mortuum_ to analyse. Under their clirolans too, powerful though they were, the principle of life showed itself in many ways to their senses, and yet evaded all attempt to isolate it. The lavolan, which showed the inner structure of living bodies as they lived and moved, brought them nearest of all to the veil that hung over the secret of vitality. Plants and stationary animal organisms allowed them full scope for their investigations. In them they could see the life ebb and flow, as death approached or receded; in them they could find every material element entering into their composition, and test with their varied and minute meteorological apparatus all the forms of energy which moved them; they checked the current of life, and watched in the plant or animal the elements and energies that remained comparatively stable and those that deteriorated; they let it die out, and watched the throb and struggle of the various constituents and forces as they collapsed; then, when it seemed to have surrendered all life or hope of life, they brought it back, by their knowledge of its existence, to the upward struggle again and no feature of the return escaped their notice; most watchful of all were they on that dim borderland between life and death, where dawn is sunset and sunset dawn. In every stage were they able to isolate each strand of the thread of life; yet the essential secret of all escaped them. Once the organism had shrivelled into a bundle of dead fibres or fallen to dust, no effort of theirs could give it the throb of life again. They could reproduce every element and tissue and fibre, and under their clirolans place them together in the forms of life with marvellous art. One thing was still wanting to make it all it had been. They could even mimic the flow of life through it by means of their command over the sources of energy; but the result was only mechanical; they had not supplied it with the never-failing spring of vitality.