This so-called three-field system of agriculture was distinctly disadvantageous in many ways. Much time was wasted in going back and forth between the scattered plots of land. The individual peasant, moreover, was bound by custom to cultivate his land precisely as his ancestors had done, without attempting to introduce improvements. He grew the same crops as his neighbors--usually wheat or rye in one field; beans or barley in the second; and nothing in the third. Little was known about preserving the fertility of the soil by artificial manuring or by rotation of crops; and, although every year one-third of the land was left "fallow" (uncultivated) in order to restore its fertility, the yield per acre was hardly a fourth as large as now. Farm implements were of the crudest kind; scythes and sickles did the work of mowing machines; plows were made of wood, occasionally shod with iron; and threshing was done with flails. After the grain had been harvested, cattle were turned out indiscriminately on the stubble, on the supposition that the fields were common property. It was useless to attempt to breed fine cattle when all were herded together. The breed deteriorated, and both cattle and sheep were undersized and poor. A full-grown ox was hardly larger than a good-sized calf of the present time. Moreover, there were no potatoes or turnips, and few farmers grew clover or other grasses for winter fodder. It was impossible, therefore, to keep many cattle through the winter; most of the animals were killed off in the autumn and salted down for the long winter months when it was impossible to secure fresh meat. [Sidenote: Peasant Life on the Manor] Crude farm-methods and the heavy dues exacted by the lord [Footnote: In addition to the dues paid to the lay lord, the peasants were under obligation to make a regular contribution to the church, which was called the "tithe" and amounted to a share, less than a tenth, of the annual crops.] of the manor must have left the poor man little for himself. Compared with the comfort of the farmer today, the poverty of sixteenth-century peasants must have been inexpressibly distressful. How keenly the cold pierced the dark huts of the poorest, is hard for us to imagine. The winter diet of salt meat, the lack of vegetables, the chronic filth and squalor, and the sorry ignorance of all laws of health opened the way to disease and contagion. And if the crops failed, famine was added to plague. On the other hand we must not forget that the tenement-houses of our great cities have been crowded in the nineteenth century with people more miserable than ever was serf of the middle ages. The serf, at any rate, had the open air instead of a factory in which to work. When times were good, he had grain and meat in plenty, and possibly wine or cider, and he hardly envied the tapestried chambers, the bejeweled clothes, and the spiced foods of the nobility, for he looked upon them as belonging to a different world.