This was not the only official act of Sixtus IV. in favour of the feast. In 1479 he built a chapel in old St Peter’s, which he dedicated and endowed in honour of our Lady’s conception and in honour of the Franciscan saints, Francis of Assisi and Anthony of Padua. In 1483, however, he was compelled to forbid, by a special constitution, the supporters and opponents of the doctrine of Mary’s exemption from original sin to call each other heretics. This proves that the strife between the two parties had then waxed warm. Even in Germany there were bitter contentions concerning the point in question in Frankfurt, Marburg, Heidelberg, and at Bern in Switzerland. By the decree of Sixtus IV., in 1477, the office for the feast was finally prescribed for the diocese of Rome as a _duplex_, but not for other dioceses; these were free as before to adopt it or not. Clement VIII. raised it to a _duplex majus_. Clement IX., added an octave, and Clement XI., by a decree of 6th December 1708, prescribed it for the whole Church.[565] It had already been observed in Spain as a regular holy day of obligation, for Philip IV. petitioned Innocent X. for it and the pope had granted his request in a constitution of 10th November 1644.[566] It was only in 1854 that it became, through the zeal of Pius IX., a holy day of obligation for the whole Catholic world. The steps in regard to this feast taken by Rome were, as we have seen, separated from one another by considerable periods of time. With regard to the significance of the feast, however, in spite of the declaration of the Council of Trent, a policy of delay and _laissez-faire_ was maintained. The feast remained a simple _festum conceptionis_, and the idea of the _immaculata conceptio_ did not receive outward expression, except that Paul V. permitted the recitation on all free Saturdays of an _officium conceptionis B.M.V._, in which the _invitatorium_ is, “Immaculatam conceptionem Mariæ virginis celebremus.” Pius IX. had a new office drawn up which he prescribed for use on the 25th September 1863, in which the idea contained in the _invitatorium_ is expressed beyond all doubt. Hymns expressing the same idea were inserted, and the bull “Ineffabilis” was drawn upon for some of the lections, while for others the preference was given to the homilies of the later Greek writers. The pope’s letter elevating the feast to the rank of a holy day of obligation for all Christendom received an enthusiastic reception everywhere. The rank of the feast was not increased. It was only by Leo XIII. that it was placed on an equality with the three chief festivals of the year.