In Das Kapital Marx defined Constant Capital as that part of capital advanced in the means of production; he defined Variable Capital as the part of capital advanced in wages (Marx, 1867, Vol. I, ch. 6). These definitions come from his concept of Value: he defined the value of commodities as the amount of labour directly and indirectly necessary to produce commodities (Vol. I, ch. 1). In other words, the value of commodities is the sum of class="EmphasisTypeItalic ">C and N, where C is the value of the means of production necessary to produce them and N is the amount of labour used that is directly necessary to produce them. The value of the capital advanced in the means of production is equal to C.