The result is no doubt too simple. The reader must sample for himself the rich confusion in which the central core of analysis is imbedded, and must judge for himself whether the core has been mishandled in the process of digging it out.[1] Our author takes her departure from the numerical examples for simple reproduction (production with a constant stock of capital) and expanded reproduction (production with capital accumulating) set out in volume ii of Marx's _Capital_. As she points out,[2] Marx completed the model for simple reproduction, but the models for accumulation were left at his death in a chaos of notes, and they are not really fit to bear all the weight she puts on them (Heaven help us if posterity is to pore over all the backs of old envelopes on which economists have jotted down numerical examples in working out a piece of analysis). To follow her line of thought, however, it is necessary to examine her version of Marx's models closely, to see on what assumptions they are based (explicitly or unconsciously) and to search the assumptions for clues to the succeeding analysis. To begin at the beginning--gross national income (for a closed economy) for, say, a year, is written _c + v + s_; that is, constant capital, variable capital and surplus. Variable capital, _v_, is the annual wages bill. Surplus, _s_, is annual rent, interest, and net profit, so that _v + s_ represents net national income. (In this introduction surplus is used interchangeably with rent, interest and net profit.) Constant capital, _c_, represents at the same time the contribution which materials and capital equipment make to annual output, and the cost of maintaining the stock of physical capital in existence at the beginning of the year. When all commodities are selling at normal prices, these two quantities are equal (normal prices are tacitly assumed always to rule,[3] an assumption which is useful for long-period problems, though treacherous when we have to deal with slumps and crises). Gross receipts equal to _c + v + s_ pass through the hands of the capitalists during the year, of which they use an amount, _c_, to replace physical capital used up during the year, so that _c_ represents costs of raw materials and wear and tear and amortisation of plant. An amount, _v_, is paid to workers and is consumed by them (saving by workers is regarded as negligible[4]). The surplus, _s_, remains to the capitalists for their own consumption and for net saving. The professional classes (civil servants, priests, prostitutes, etc.) are treated as hangers-on of the capitalists, and their incomes do not appear, as they are not regarded as producing _value_.[5] Expenditure upon them tends to lessen the saving of capitalists, and their own expenditure and saving are treated as expenditure and saving out of surplus.