Necessity of differentiating demand with respect to the time element, 131. — Meaning of long and short run, 132. — Spending without free current choice, 132. — Saving, 133. — Habitually consumed goods, 134. — "Petty" goods, 134. — Social demand curve for such goods, 135. — Stocking up, 135. — Significance of the demand schedule in such cases, 136. — Experimental spending, 137. — Residual saving, 138. — Demand in the long run, 138. — The markets for the great staples, 141. — Conclusion, 142.