Another sort of deception is the alteration of pictures by artists less-known or of inferior reputations to suit more fashionable and profitable names.  In this way many works of much local interest, and often indeed of equal merit to those they are made to represent, are exterminated, to the serious detriment of the history of art, Lombardy, Umbria, and the Legations especially have suffered in this way.

Though no deception be intended, if pedigrees are lost, criticism is often sorely perplexed to decide upon authorship.  Out of the multitudes of pictures in the European galleries, which are so decidedly baptized in catalogues, the public would be surprised to learn how few comparatively can be historically traced to their authors.  The majority are named upon the authority of local judges, whose acquaintance with art may be limited to one speciality, or who rely upon such opinions as can be gathered from the best available sources.  Hence the frequent changes in the nomenclatures.  We cannot, therefore, accept such documents as infallible, except in those cases where internal evidence and historic record are alike unimpeachable.

The difficulty of deciding often arises from repetitions, and the excellence of pupils painting from the designs of their masters, and not unfrequently assisted by them.  As we go back in art, this difficulty increases, from the oblivion which has overtaken once well-known names, and from the greater uniformity of processes and the more limited range of motives of the earliest artists.

The great religious masters of the thirteenth and fourteenth centuries gathered around them crowds of scholars, who travelled with them from city to city, partaking in their commissions and executing their designs, especially of ex-voto pictures, multiplied in that age by the piety of noble families, to commemorate some special interposition of divine power in their behalf and to honor their patron saints.  Their usual compositions were the Madonna enthroned with the infant Jesus in her arms, surrounded by holy personages or angels, with the portraits of those who ordered the paintings, in general of diminutive size to express humility, and kneeling in adoration with clasped hands and upraised eyes.  Unless the characteristics of the master-hand are unmistakable in this class of works, they are to be ranked as of the schools of the great men whose general features they bear.  And it must not be forgotten that frequently pupils developed into distinguished masters themselves.  Taddeo Gaddi and Puccio Capanna worked under Giotto while he lived, and afterwards acquired distinction in an independent career.