This experience taught the government that the spread of Christianity was attended by the gravest dangers to public tranquillity. Strict laws were therefore enacted for its suppression. Foreigners who came to Japan for the purpose of propagating the faith were refused admission, and those who declined to depart despite the edicts were put to death. Thenceforth Buddhism was adopted as the national religion, receiving the allegiance of all classes, high and low. It is interesting to note that the revival of Buddhist influence was not only simultaneous with the downfall of Catholicism, but also due largely to an institution which was now for the first time placed on a religious basis. The system of taking a census at regular intervals, which was introduced by the Taikwa reformers, had never been successfully practiced for a long period of time, until the Tokugawa government made the extermination of Catholicism an occasion for the restoration of the system. It was ordered in 1716 that the census should be taken in each fief and the results duly reported every six years. Births, deaths, and marriages were registered in books kept by Buddhist priests, so that no Christian should remain in society under the protection of law. The operation was called, from its religious character, _shūmon-aratame_, or examination of faith. This of course contributed materially to the influence of the Buddhist church, for which the Tokugawa period was an era of marked prosperity, the number of temples throughout the empire aggregating four hundred thousand. Nevertheless, the government was careful to avoid a return to the excesses of former days. The building of new temples was forbidden, the lands assigned for the support of those already in existence were rigidly defined, and the people were encouraged to study Chinese literature, so that the corruption which disfigured the Buddhist priesthood in earlier ages was, in great part, corrected.