Some uncertainty must necessarily attach to conclusions based on the statistics drawn from medieval sources; and there can be little doubt that the estimates of the mortality due to the Black Death, made by contemporary writers, were grossly exaggerated. Many records, however, exist of the deaths in particular places, or among a special class such as the parochial clergy; and these statements appear to be well worthy of credit. It seems to be generally agreed that at least half of the population was swept away by the successive visitations of this pestilence. While we cannot easily conceive what must have been the full effects of such wholesale destruction, we may at least conclude that considerable tracts of country were depopulated, so that the area devoted to tillage was necessarily reduced; we have also abundant evidence of labour agitation in many branches of industry. The whole system of regulated rates and prices was seriously undermined; under the new conditions the old payments had become unsatisfactory; changes of some kind, both as to the terms on which land was rented and as to those on which labour was employed, were inevitable.
The constant wars of the latter half of the fourteenth and the fifteenth centuries were another disruptive force and proved fatal to the maintenance of the highly organised system of medieval times. In the countries which were the scene of frequent warlike operations, immense mischief was done to agriculture; it is difficult to understand how a rural population should have survived in France at all, when we read of the ravages of the English armies, and the devastations caused by the factions. The chronic disorder not only affected tillage and the food-supply, but rendered internal trade so insecure that it was practically suspended altogether. What had been a prosperous kingdom, with many well-organised cities, and with fairs that were frequented by merchants from all parts of Europe, was reduced to utter desolation and ruin. Similar results attended the Hussite Wars in Bohemia, and, to a lesser degree, the Wars of the Roses in England; the Italian cities must also have found their intercivic hostilities a serious drain on their resources. Venice and Genoa had carried on a long-protracted struggle about Chioggia; Pisa was at length forced to succumb to Florence, and Milan gradually established her superiority over her neighbours. Doubtless, to many districts the wars brought profit as well as loss; Swiss and Italian mercenaries often engaged in fighting as a regular trade, in which much booty was to be obtained; and successful cities might recoup themselves for their outlay by securing new avenues of commerce at the expense of their rivals. Still the fact remains that war was a disturbing element; the instability introduced by it into all the relations of' life was irreconcilable with the maintenance of the old industrial system or old trading connexions. The countries which for any considerable period enjoyed a relative immunity from external war, such as Flanders, the duchy of Burgundy, the Rhineland, and Bavaria, made