The effect of the interior is extremely grand and imposing.  It is of great height, whilst the side chapels and outer aisles give it an appearance of more breadth than it deserves.  The apse is polygonal.  The principal nave, with its large arches, its curved triforium, and its flamboyant windows, bears the mark of the fifteenth century.  The choir is thirteenth century, and possesses a triforium with a double gallery, surrounded by gothic arches supported by small columns, of which the capitals are extremely elegant.

The church has a peculiarity which is not often found, at any rate in so pronounced a manner.  The chancel is not in a line with the nave, but inclines to the left, or north.  Thus, in standing at the west end, only a portion of the apse can be seen.  The effect is singular, and, at the first moment, seems to offend.  But after a time the peculiarity becomes decidedly effective.  The stiffness of the straight line, of the sides running exactly parallel one with the other, is lost.  One grows almost to like the break in the uniformity of design.  It appeals to the imagination.  Certain other cathedrals incline in the same way, but in a more modified form.  The architects’ reasons for thus inclining the choir are lost in obscurity.  By some it has been supposed that their motive was purely effect; by others that it was in imitation or commemoration of our Lord, Who, when hanging upon the cross, inclined His Head to the left.

Many of the windows are old, and add greatly to the fine effect of the interior.  Those in the nave date from the end of the fifteenth century.  Some of those in the choir—­unfortunately the most conspicuous—­are modern; but a few are ancient.  The whole interior has suffered in tone by restoration and scraping.

The high-altar is richly decorated with enamels and precious stones.  The tabernacle—­in the centre of which is a figure of the Saviour in the act of blessing—­is flanked by twelve arcades, containing the figures of the Apostles in relief, holding the instrument of their martyrdom.  It is crowned by a cross with double rows, or branches, at the foot of which are the evangelists with their symbolical animals.  The lower arms of the cross bear the figures of the Virgin and St. John weeping at the feet of the crucified Redeemer.

Amongst the treasures of the cathedral are preserved three drops of blood, of which the following is the legend:—­

A pilgrim of Quimper, on starting for the Holy Land, had confided a sum of money to a friend.  On returning, he claimed the money, but the friend denied having received it, offering to take an oath to that effect before the crucifix in the church of St. Corentin.  At the moment of raising his hand to take the oath, he gave a stick that he carried to his friend to hold.  The stick was hollow and contained the gold.  As soon as he had taken the oath, the stick miraculously broke in two, and the money rolled on to the pavement.  At the same moment the feet of the crucifix, held together by a single nail, separated, and three drops of blood fell on to the altar.  These drops were carefully absorbed by some linen, which is preserved amongst the treasures of the church.  The miracle is reproduced in a painted window of one of the chapels.