Besides, it is enough to recall the researches inaugurated by Fechner in his _Vorschule der Æsthetik_, and since continued, especially in Germany, under the name of elementary æsthetics,[72] which so greatly emphasise the part played by the sensory element in the genesis of æsthetic pleasure and pain. We may thus briefly summarise them: There are two constituent factors in the æsthetic sentiment—one direct, connected with sensations and perceptions; the other indirect, connected with representations (images and associations of ideas). One or the other predominates, according to the particular art: the direct factor in music and the plastic arts, the indirect in poetry. The direct factor, by its very definition, depends on the organism. The colours are not simple sensations, they have an affective tone proper to themselves. According to Wundt, white suggests gaiety; green, a quiet joy; while red corresponds to energy, strength, etc. We may or may not admit these correspondences; Scripture gives others, and they probably vary from one individual to another; but the principle is unassailable. Féré’s previously quoted experiments, on exciting and depressing colours, tend in the same direction. It is the same with sounds:—according as they are high, deep, or medium, they induce a special mood. If from simple sensation we pass to perceptions, direct physical action is not doubtful; we find it in the arrangement of colours, in the phenomena of contrasts, in the outlines and forms of certain lines, in the innate pleasure of symmetry and regularity, in rhythm, measure, cadence, in the perception of harmony and dissonance, etc. In truth, the authors cited, have insisted rather on the sensory action than on the organic and motor modifications accompanying it. But it always remains indisputable that the æsthetic sentiment is necessarily connected with physiological conditions. ----- Footnote 72: Wundt, _Physiologische Psychologie_, 4th (German) ed., chap. xx.; Külpe, _Grundriss der Psychologie_, p. 250 (English edition), § 38; Sully, _Sensation and Intuition_, Part II.; Grant Allen, _Mind_, July 1879 (“The Origin of the Sense of Symmetry”). ----- Since we are maintaining the proposition that the intensity of even the superior emotions is in direct ratio to the quantity of the physiological occurrences accompanying them, I propose in the following paragraphs to examine a single one separately, and in some detail. Which is the most emotional of all arts? Music. There is no possible doubt as to the answer—eliminating, of course, those persons on whom it has no effect, and who must be rejected for the purposes of this argument. No art has a deeper power of penetration, no other can render shades of feeling so delicate as to escape every other medium of expression. So much is unanimously admitted.