That is harking back to simple reproduction all over again. It is quite true, of course, that the capitalists A and the capitalists B are constantly accumulating a hoard of money bit by bit so as to be able to renew their constant (fixed) capital from time to time, and in this way they really are assisting one another in realising their products. Yet this accumulating hoard does not drop from the clouds--it is simply a natural precipitation of the fixed capital that is (in terms of value) continually being transferred in instalments to the products which are then one by one realised in the process of sale. Owing to its very nature, the accumulated hoard can only cover the renewal of the old capital; there cannot possibly be enough to serve further for purchasing additional constant capital. That means that we are still within the limits of simple reproduction. Perhaps, though, that part of the medium of circulation which hitherto served the capitalists for their personal consumption, and is now to be capitalised, becomes a new source of additional money? For that to be true, however, we should have to be back at the unique and fleeting moment that has no more than theoretical existence--the period of transition from simple to enlarged reproduction. Beyond this gap accumulation cannot proceed--we are in truth going round in circles. So the capitalist hoarding will not do as a way out of our difficulties. This conclusion should not come as a surprise, since the very exposition of the difficulty was misleading. It is not the source of money that constitutes the problem of accumulation, but the source of the demand for the additional goods produced by the capitalised surplus value; not a technical hitch in the circulation of money but an economic problem pertaining to the reproduction of the total social capital. Quite apart from the question which had claimed Marx's entire attention so far, namely where B, B´, etc., (I), get the money to buy additional means of production from A, A´, etc., (I), successful accumulation will inevitably have to face a far more serious problem: to whom can B, B´, etc., now sell their increased surplus-product? Marx finally makes them sell their products to one another: 'It may be that the different B, B´, B´´, etc., (I), whose virtual new capital enters upon its active function, are compelled to buy from one another their product (portions of their surplus-product) or to sell it to one another. In that case, the money advanced by them for the circulation of their surplus-product flows back under normal conditions to the different B's in the same proportion in which they advanced it for the circulation of their respective commodities.'[122]