money, but in cotton, which they credit on the books in terms of money to the customer--a point which Fisher mentions in an appendix. (_Ibid._, p. 371.) The difference on this point is a difference in degree merely.[152] Further, Fisher makes the same point with reference to deposits subject to check that he makes with reference to book-credits, namely, that their use increases the velocity of money. To say that one has a _direct_ effect on prices, and the other only an indirect effect is absolutely arbitrary. If buying and selling are what count, if prices are forced up by the offer of money or credit for goods, and forced down as the amount of money and credit offered for goods is reduced, then one exchange must count for as much as any other of like magnitude in fixing prices. The same is true of transactions in which bills of exchange or other credit devices serve as media of exchange. Of course these considerations do not render the equation of exchange, as presented by Fisher, untrue. The equation simply states that the money and bank-deposits used in paying for goods in a given period are equal to the amount paid for those goods in a given period. It makes no assertion concerning payments for other goods, and makes no assertion as to the amount of other transactions which are paid for in other ways. General Walker, presented with the problem of credit phenomena, simplifies the thing even more.[153] He rules out all exchanges which are effected by credit devices, counting only those performed by coin, bank-notes and government paper money, and insists that the general price-level is determined in those exchanges in which money alone (as thus defined) is employed. His equation--if he had considered it worth while to use one--would then have been simply MV = PT where T would be merely the number of goods exchanged by means of money. One could make a similar equation, equally true, by defining money as gold coin, and reducing T correspondingly. Is there any reason for limiting the equation at all?[154] Is there any reason for supposing that any one set of exchanges is more significant for the determination of the price-level than any other set of exchanges? Does not the logic of the quantity theory require us to include all exchanges which run in terms of money?--If one wishes a complete picture of the exchanges, some such equation as this would be necessary: MV + M'V' + BV'' + EV''' + OV'''' = PT, where B represents book-credit, V'' the number of times a given average amount of book-credit is used in the period, E bills of exchange, and V''' their velocity of circulation, and O all other substitutes for money, with V'''' as their velocity of circulation. Even then we have not a complete picture, if direct barter or the equivalents of barter can be shown to be important.