M — C represents the conversion of a sum of money into a sum of commodities; the purchaser transforms his money into commodities, the sellers transform their commodities into money. What renders this act of the general circulation of commodities simultaneously a functionally definite section in independent circuit of some individual capital is primarily not the form of the act but its material content, the specific use-character of the commodities which change places with the money. These commodities are on the one hand means of production, on the other labour-power, material and personal factors in the production of commodities whose specific nature must of course correspond to the special kind of articles to be manufactured. If we call labour-power L, and the means of production MP, then the sum of commodities to be bought, C, is equal to L + MP, or more briefly C M — C, considered as to its substance is therefore represented by M — C that is to say M — C is composed of M — L and M — MP. The sum of money M is separated into two parts, one of which buys labour-power, the other means of production. These two series of purchases belong to entirely different markets, the one to the commodity-market proper, the other to the labour-market.
