The surplus-product, the bearer of surplus-value, does not cost its appropriators, capitalists I, anything. They are by no manner of means obliged to advance any money or commodities in order to obtain it. Even among the physiocrats an advance was the general form of value embodied in elements of productive capital. Hence what capitalists I advance is nothing but their constant and variable capital. The labourer not only preserves by his labour their constant capital; he not only replaces the value of their variable capital by a corresponding newly created portion of value in the form of commodities; by his surplus-labour he supplies them with a surplus-value existing in the form of surplus-product. By the successive sale of this surplus-product they form a hoard, additional potential money-capital. In the case under consideration, this surplus-product consists from the outset of means of production of means of production. It is only when it reaches the hands of B, B', B'', etc. (I) that this surplus-product functions as additional constant capital. But it is this virtualiter even before it is sold, even in the hands of the accumulators of hoards, A, A', A'' (I). If we consider merely the amount of value of the reproduction on the part of I, we are still moving within the bounds of simple reproduction, for no additional capital has been set in motion to create this virtualiter additional constant capital (the surplus-product), nor has any greater amount of surplus-labour been expended than that on the basis of simple reproduction. The difference is here only in the form of the surplus-labour performed, in the concrete nature of its particular useful character. It has been expended in means of production for I c instead of II c, in means of production of means of production instead of means of production of articles of consumption. In the case of simple reproduction it was assumed that the entire surplus-value I is spent as revenue, hence in commodities II. Hence the surplus-value consisted only of such means of production as have to replace constant capital II in its bodily form. In order that the transition from simple to extended reproduction may take place, production in department I must be in a position to fabricate fewer elements of constant capital for II and so many the more for I. This transition, which does not always take place without difficulties, is facilitated by the fact that some of the products of I may serve as means of production in either department.