A scholar like Quesnay, the author of the work on animal economy[39] and a diligent student of Harvey’s new discovery, was precisely the man to carry the biological idea over into the realm of sociology. He made use of the idea in his _Tableau économique_, which is simply a graphic representation of the way in which the circulation of wealth takes place. The appearance of this table caused an enthusiasm among his contemporaries that is almost incredible,[40] although Professor Hector Denis declares that he is almost ready to share in Mirabeau’s admiration.[41] We know by this time that this circulation is much more complicated than the Physiocrats believed, but it is still worth while to give an outline of their conception.[42] Quesnay distinguishes three social classes: 1. A productive class consisting entirely of agriculturists—perhaps also of fishermen and miners. 2. A proprietary class, including not only landed proprietors, but also any who have the slightest title to sovereignty of any kind—a survival of feudalism, where the two ideas of sovereignty and property are always linked together. 3. A sterile class, consisting of merchants and manufacturers, together with domestic servants and members of the liberal professions. The first class, being the only productive class, must supply all that flow of wealth whose course we are now to follow. Let us suppose, then—the figures are Quesnay’s and seem sufficiently near the facts—that the value of the total wealth produced equals 5 milliard francs. Of this 5 milliards 2 milliards are necessary for the upkeep of the members of this class and its oxen during harvest and sowing. This portion does not circulate. It simply remains where it was produced. The produce representing the remaining 3 milliards is sold. But agricultural products alone do not suffice for the upkeep of Class 1. Manufactured goods, clothes, and boots also are required, and these are got from the industrial classes, for which a milliard francs is given. There remain just 2 milliards, which go to the landowners and the Government in rents and taxes. By and by we shall see how they attempted to justify this apparent parasitism. Let us pass on to consider the propertied class. It manages to live upon the 2 milliards which it receives by way of rents, and it lives well. Its food it must obtain from the agricultural class (unless, of course, the rents are paid in kind), and for this it possibly pays a milliard francs. It also requires manufactured goods, which it must get from the sterile class, and for which it pays another milliard francs. This completes their account.