So far as regards the immediate effects of the great mortality. Its after-effects, felt within a year or two, upon the economics and morals of the country, upon the power of the old governing class, upon the dispersion of industries and the new life of towns, upon the system of farming, upon the development of the legal profession in London, and upon various other things, are a much more intricate and disputable subject, some part of which will be dealt with in the next chapter in connexion with the subsequent history of plague or its domestication upon the soil of England. Many things in England were noted as having happened “sithen the Pestilence,” to quote the stock phrase of the ‘Vision of Piers the Ploughman,’ and not the least of them was the frequent recurrence of plague, or a prevalence of sickness so steady that the poet compares it to the rain coming in through a leaky roof. Some historians have doubted whether after all the Black Death made so very much difference to the course of affairs[280]. It is perhaps inevitable that scholars, accustomed to deal only with obvious human causation, should look with some distrust upon the large claims made, in the way of moral and social consequences, for a phenomenon which has been apt to be classed with comets and earthquakes. The sudden thinning of the population may indeed become a subject for economists without any regard to the causation, and irrespectively of the means by which the numbers were reduced; and that has been the only historic interest of the great mortality hitherto. But the operation of pestilence is peculiar; the thinning of the population is not effected as if in the due course of nature; the analogy is closer with a decimating or exterminating war. The invasion of the Black Death was part of the great human drama, just as if a swarming people or a barbarous conqueror had been visibly present in it. If things were moving in the fourteenth century towards a particular issue, as historians find in their retrospect that they were, then the coming of a great plague was part of that movement, organically bound up with the other forces of it, and no more arbitrary than they. Thus it becomes of interest to trace the antecedents of the Black Death before we attempt to follow out its consequences; and it is not the less of interest to do so, that the train of events leads us as far eastwards as the soil of China, and to the incidents that attended the collapse of the greatest government of the Middle Ages, the empire of the Great Khan. The Antecedents of the Black Death.