Buffon names organic molecules. According to Buffon, the oak owes all the peculiarities of its organization to the special oak-molecules of which it consists; and so all the differences in the vegetable or animal kingdom, from the lowest to the highest species, depend on fundamental peculiarities with which their respective molecules were primarily endowed. There must, of course, be as many kinds of molecules as there are different species of living beings; but, while the molecules of the same species were supposed to be exactly alike and to have a strong affinity or attraction for each other, those of different species were assumed to be inherently distinct and to have no such affinities. Buffon further assumed that these molecules of organic Nature were diffused more or less widely through the atmosphere and through the soil, arid that the acorn grew to the oak simply because, consisting itself of oak-molecules, it could draw only oak-molecules from the surrounding media.
With our present knowledge of the chemical constitution of organic beings, we can find a great deal that is both fantastic and absurd in this theory of Buffon, but it must be remembered that the science of chemistry is almost wholly a growth of the present century, while Buffon died in 1788; and, if we look at the theory solely from the standpoint of his knowledge, we shall find in it much that was worthy of this great man. Indeed, in our time the essential features of the theory of Buffon have been transferred from natural history to chemistry almost unchanged.
According to our modern chemistry, the qualities of every substance reside or inhere in its molecules. Take this lump of sugar. It has certain qualities with which every one is familiar. Are those qualities attributes of the lump or of its parts? Certainly of its parts. For, if we break up the lump, the smallest particles will still taste sweet and show all the characteristics of sugar. Could we then carry on this subdivision indefinitely provided only we had senses or tests delicate enough to recognize the qualities of sugar in the resulting particles? To this question, modern chemistry answers decidedly: No! You would before long reach the smallest mass that can have the qualities of sugar. You would have no difficulty in breaking up these masses, but you would then obtain not smaller particles of sugar, but particles of those utterly different substances which we call carbon, oxygen, and hydrogen, in a word particles of the elementary substances of which sugar consists. These ultimate particles of sugar Ave call the molecules of sugar, and thus we come to the present chemical definition of a molecule, "The smallest particles of a substance in which its qualities inhere," which, as you see, is a reproduction of Buffon's idea, although applied to matter and not to organism.
A lump of sugar, then, has its peculiar qualities because it is an aggregate of molecules which have those qualities, and a lump of salt differs from a lump of sugar simply because the molecules of salt differ
