2298. Afterwards it was said by those who were with me at the time that if there were no microscopes by which people can look at things too small for the eye to see as it sees larger parts of matter, then because they could not see the interiors of those parts, they would also think of them as a unit, not consisting of countless components. Microscopes have discovered that things formerly thought to have been units contain innumerable parts, as that a little worm scarcely visible to the closest focus of the eye has sense organs, internal organs, just as many as a large animal, that it has a brain, spinal marrows, pulmonary pipes, generative organs, and thus is not a single unit. And what about each of these members? No microscope has yet detected whether or not they consist of follicles, little tubes, vessels, tissues, and in these whether there is not a vital fluid, and so on. This shows how much lies concealed only in bodily and earthly things; but what about in purer things? for any vital element coming from them, comes by means of organic substances. 1748, 11 June.