In origin all Muslim art had a Byzantine beginning, but the traditions of Byzantine art received a peculiar direction by passing through a Persian medium, and this medium colours all work done after the close of the `Umayyad period. Only in the west, in Spain, and to a less degree in North Africa, do we find traces of direct Byzantine influence in later times. But Persian art, as developed under the later Sasanids, was itself derived from Byzantine models, and mainly from models and by craftsmen introduced by Khusraw I. (circ. A.D. 528); but even at that early stage there were also some Indian influences apparent in Persian and East-Byzantine work, as, for example, in the use of the horse shoe arch which first appears in Western Asia in the church of Dana on the Euphrates, circ. A.D. 540. But the horse shoe arch in pre-Muslim times, as in India, is purely decorative and is not employed in construction. Thus it appears that the real work of Islam in art and architecture lay in connecting the various portions of the Muslim world in one common life, so that Syria, Persia, `Iraq, North Africa, and Spain shared the same influences, which were ultimately Greek or Graeco-Persian, the Indian element, of quite secondary importance, entering directly through Persia. Already before the outspread of Islam, Byzantine art had entirely replaced native models in Egypt, and this was largely the case in Persia as well. At most we can say that Islam evolved a quasi-Byzantine style which owed its distinctive features to the limitations of the Persian artists, but which occasionally attained a better level by the importation of Byzantine craftsmen. Exactly the same general conclusions hold good in the history of the ceramic arts and in the illumination of manuscripts, though here the observance of the Qur´anic prohibition of the portrayal of animal figures, strictly observed only in some quarters and least regarded in Persia and Spain, caused a greater emphasis to be laid on vegetable forms in decoration, and on geometrical patterns.