Capital Is Differentiated by Marx into Constant and Variable Capital (Machinery and Wages); Machinery Yields No Surplus Value; Labour Has the Whole Burden of Providing Surplus Value

It will be observed that the whole of the surplus value is derived from labour. Indeed, on the theory, as initially stated, it would appear to be derived from the individual worker; each individual worker would appear to be robbed by his own particular employer. This view is, however, modified by later elaborations of the analysis. That the surplus value comes from labour, and from labour alone, is reinforced by a distinction which is fundamental to the Marxian analysis. Capital is differentiated by Marx into constant and variable capital, corresponding broadly to the distinction between machinery and wages. But machinery yields no surplus value. It is of the essence of a machine that, in being used up, it transfers its value, neither more nor less, to the product. Whatever be thought of the validity of the argument, it has at least the advantage that it thrusts on labour the whole burden of providing surplus value. It should be noted for its significance later that industries will vary from each other according to their 'organic composition'; the ratio of constant to variable capital, low in some industries, will be high elsewhere.

--Alexander Gray, The Socialist Tradition: Moses to Lenin (London: Longmans, Green, 1946), 311.