Again, money functions as a means of circulation, only because in it the values of commodities have independent reality. Hence its movement, as the medium of circulation, is, in fact, merely the movement of commodities while changing their forms. This fact must therefore make itself plainly visible in the currency of money. The twofold change of form in a commodity is reflected in the twice repeated change of place of the same piece of money during the complete metamorphosis of a commodity, and in its constantly repeated change of place, as metamorphosis follows metamorphosis, and each becomes interlaced with the others.
The linen, for instance, first of all exchanges its commodity-form for its money-form. The last term of its first metamorphosis (C—M), or the money-form, is the first term of its final metamorphosis (M—C), of its re-conversion into a useful, commodity, the Bible. But each of these changes of form is accomplished by an exchange between commodity and money, by their reciprocal displacement. The same pieces of coin, in the first act, changed places with the linen, in the second, with the Bible. They are displaced twice. The first metamorphosis puts them into the weaver's pocket, the second draws them out of it. The two inverse changes undergone by the same commodity are reflected in the displacement, twice repeated, but in opposite directions, of the same pieces of coin.
If, on the contrary, only one phase of the metamorphosis is gone through, if there are only sales or only purchases, then a given piece of money changes its place only once. Its second change corresponds to and expresses the second metamorphosis of the commodity, its re-conversion from money into another commodity intended for use. It is a matter of course, that all this is applicable to the simple circulation of commodities alone, the only form that we are now considering.
Every commodity, when it first steps into circulation, and undergoes its first change of form, does so only to fall out of circulation again and to be replaced by other commodities. Money, on the contrary, as the medium of circulation, keeps continually within the sphere of circulation, and moves about
