When the blemish is in an accessory figure, it is of lesser importance as there it becomes an incidental circumstance on the mind of the observer. Thus, in Reynolds's Infant Hercules, where Alcmena, on seeing the child holding the snakes, opens her mouth with surprise and alarm, the action of the central figure is so strong that the importance of the others present is comparatively insignificant.[a] Nevertheless in a Pompeian fresco of the same subject, care has been taken to close the mouth of Alcmena. Where the design represents several persons singing, it is well possible to indicate the action without showing the mouths open, as in Raphael's St. Cecilia.[b] In a picture of a like subject, with the Saint in the centre of a group of five singers, Domenichino shows only the two outside figures with open mouths, and one of these is in profile. There are several works where David is seen singing to the accompaniment of a harp, but though his mouth is open, the figure is in profile, and the lips are hidden by moustache and beard.[c] [a] Hermitage, Petrograd. [b] Bologna Museum. [c] For example, Rubens's David's Last Song, Frankfort Museum. It may be observed, however, that in certain cases artificial conditions may render an open mouth in a picture of comparatively little significance. A painted laugh for instance may only become objectionable to the observer when the work is constantly before him; but when it is in a picture gallery and he sees it but rarely, the lasting character of the feature is not presented to his mind. The Laughing Cavalier of Franz Hals, though violating the principle, does not appear in bad taste to the average visitor to the Wallace Collection. In the case of Rembrandt's portrait of himself with Saskia on his knee, where the artist has his lips parted in the act of laughing, there is an additional reason why the transient expression should not tire. Because of the number of self-portraits he painted, the countenance of Rembrandt is quite familiar to most picture gallery visitors, and to these the laugh in the Dresden picture could not possibly pass as an habitual expression. [Illustration: PLATE 15 (See page 176) Winslow Homer's All's Well (_Boston Museum_)] CONTRASTS