This thesis has been principally maintained in America by H. Nichols (_Philosophical Review_, July 1892), and in France by Bourdon (_Revue Philosophique_, September 1893). The former applies it to pleasure and pain, considering them fundamental sensations as distinct from one another as they are from other sensations. This article contains some ingenious considerations on the part played by the association of ideas. Bourdon applies it only to pleasure, and considers pain irreducible. He regards pleasure as a special sensation, not a common one or an attribute of all sensations; it is “of the same nature as the special sensation of tickling.” By adducing the pleasure of tickling (in which he follows Descartes and others), Bourdon partially escapes the criticism already advanced. It must be remarked, however, that tickling is itself a sensation of which the organic conditions are very vaguely determined. Besides the cutaneous impression, there are certainly also diffused reflex actions which connect it quite as much with internal sensibility as with the sense of touch. ----- The manifestations taking place within the organism are better known when we are in a condition of pleasure. Let us take as typical the constant pleasures, putting aside those which, by their exuberance, as we shall see later on, border on pathological forms. Whether the point of departure is a physical excitation, a representation, or a concept, two distinct events take place, as in the case of grief: on the one hand an internal state of consciousness, which we describe as agreeable; on the other a bodily external condition, of which the following are the principal characteristics. Taken as a whole, they may be opposed, almost point for point, to the description already given of the physical manifestations of grief, and betray a heightening of the vital functions. This contrast is not without importance in favour of the common thesis which regards pleasure and pain as a pair of opposites. 1. The circulation increases, especially in the brain, as shown by various symptoms, in particular the increased lustre of the eyes. The experiments of Lehmann, already quoted (Chapter I.), prove that physical, as well as æsthetic pleasure, is accompanied by dilatation of the vessels and an increase of the heart’s contractions.[34] ----- Footnote 34: Dr. G. Dumas has made experiments on the condition of the circulation in states of joy and of sadness. He has attempted an experimental verification of Lange’s theory by showing that a definite condition of the circulation always accompanies various agreeable and painful emotions, and that “joy and sadness may thus be regarded as the mental reverberation of these circulatory conditions and their organic consequences.” See “Recherches expérimentales sur la Joie et la Tristesse,” _Revue Philosophique_, June-August 1896.—ED. -----