Meanwhile, beginning a few hundred years ago, when greater privilege of inquiry became possible in a jealous society, naturalists had tried to attack the problem from a new angle. They asked themselves whether they might not, by intensive study of living things, find the quality of life itself, hoping that if that could be done the source of it might be disclosed. In their earnest work they constantly improved their methods and their instruments, and so penetrated deeper and deeper into the constitution of plants and animals, until at last they found the ultimate particle in the cell and discovered living things so simple that they consisted of one cell alone; but why that microscopic particle was _alive_, while the grain of crystal beside it, or the drop of water in which it swam, was _not_ alive, remained unexplained. Thereupon some of the naturalists fell back into the ranks of the speculative and religious persons who were content to believe the endowment of the world with life an act of a Divine Creator--something above and outside of nature as otherwise manifested; others asserted an equivalent but more materialistic doctrine that they styled "spontaneous generation," which presently was shown to be untrue, at least in the way they formulated it; and a third group confessed that they did not know whence life came, nor were they much concerned to know. LIFE CONSTANTLY ORIGINATED BY NATURE'S PRODUCTIVE ENERGY This quest having failed--although it had taught much by the way--the chemists, who had been making marvelous discoveries in the inorganic lifeless half of nature, undertook a far more serious exploration of the organic living half. You have interpreted very fully, they told the naturalists, the forms, and structure, and functions of organisms, but can get no further; now let us chemists try whether we cannot find the principle of life by analyzing the _substance_ of living things. Profiting by their experience, they turned to the colloids in hope of a clue. A colloid is a substance that shows no power of crystallization, and is composed of molecules united by their own affinity, and not by atomic affinity. They have a gelatinlike nature or composition, although varying greatly in chemical composition and general character. They differ widely in stability, for instance, some being easily upset by a change in conditions; and this peculiarity is of great importance in relation to the phenomena of life, for colloids enter largely into the composition of all living bodies, but always in a delicately balanced union with crystalloids. "The colloid is in fact," declared Thomas Graham, who first investigated its properties, "a dynamical state of matter; the crystalloid being the statical condition. The colloid possesses Energia. It may be looked upon as the probable primary source of the force appearing in the phenomena of vitality."