Manuscripts written in burnished gold, on vellum stained with the brilliant purple from the _murex_ shell, were largely produced, especially for the private use of the Byzantine Emperors. This _murex_ purple, produced with immense expenditure of labour, came to be considered the special mark of Imperial rank[31]. A golden inkstand containing purple ink was kept by a special official in waiting, and no one but the Emperor himself might, under heavy penalties, use for any purpose the purple ink; and the sumptuous gold and purple manuscripts were for a long time written only for Imperial use. _Gold and purple gospels._ The principal class of manuscripts which were written either in part or wholly in this costly fashion were _Books of the Gospels_; and of these a good many magnificent examples still exist, dating not only from the early Byzantine period, but down to the ninth or tenth century. In these manuscripts the burnished gold and the brilliantly coloured pigments which are used for the illuminations are still as bright and fresh in appearance as ever, but the _murex_ purple with which the vellum leaves were, not painted, but dyed, has usually lost much of its original splendour of colour. _Monotony of style._ Before describing the characteristics of Byzantine illuminated manuscripts it may be well to note that the Byzantine style is unique in the artistic history of the world from the manner in which it rapidly was crystallized into rigidly fixed forms, and then continued for century after century with marvellously little modification or development either in colour, drawing or composition. This absence of any real living development was due to the fact that paintings of all kinds in the Eastern Church, from a colossal mural picture down to a manuscript miniature, were produced by ecclesiastics and for the Church, under a strictly applied series of hieratic rules. _Hieratic rules._ The drawing, the pose, the colours of the drapery of every Saint, and the scheme of composition of all sacred figure subjects came gradually to be defined by ecclesiastic rules, which each painter was bound to obey. Thus it happens that during the many centuries which are covered by the Byzantine style of art, though there are periods of decay and revival of artistic skill, yet in style there is the most remarkable monotony. This makes it specially difficult to judge from internal evidence of the date of a Byzantine painting. In manuscripts the palaeographic, not the artistic evidence, is the best guide, aided of course by various small technical peculiarities, and also by the amount of skill and power of drawing which is displayed in the paintings. _Absence of change._