It is scarcely necessary to point out once more that the primary fact is the transformation of a natural tendency, in consequence of changes in the organism, and that satisfaction and appeasement only come _afterwards_. II. Nutrition—_i.e._, the essential act of physiological life—is safeguarded by two distinct kinds of tendencies. (I am still speaking of those only which come within the bounds of consciousness, and therefore have a psychological character.) On the one hand, we have the positive tendencies, consisting in an attraction towards and attack on the external world (in this case, food and drink)—viz., hunger and thirst. On the other hand, the negative tendencies consisting in aversion, refusal, flight, and summed up in the state known as disgust. Disgust is due to excitement of the pneumogastric nerve, producing vomiting, nausea, or mere _malaise_. This repulsive instinct is connected (1) directly and immediately with taste and smell, two senses which can scarcely be isolated, and whose function is to watch over all substances entering the organism; (2) indirectly and through association of ideas with visual and tactile sensations (sticky, slimy bodies, etc.), by analogy and metaphorically with certain objects which have nothing in common with the nutritive functions—the ugly, the immoral, etc. In virtue of that law of transference or association of analogous sensations, of which we have spoken, the tendency departs more and more from its primary form; but in all cases there is a common groundwork of repulsion, refusal, desire to escape, etc. Disgust under its primary form (the only one now occupying us) has not been much studied. Writers have contented themselves with classing it among organic sensations, while neglecting its emotional side, _i.e._, its function in the conservation of the individual. The only work I know on this subject is the excellent monograph of Ch. Richet,[131] of which I here give a summary. ----- Footnote 131: “On the Causes of Disgust,” in _L’Homme et l’Intelligence_, pp. 41-84. -----