The mechanism of appetites is thus a lower mechanism and has its seat in the primitive nervous centers. As _Yersin_ has proved, a cricket deprived of its brain may copulate so long as the sensory irritations can reach the sexual nervous centers. We can thus say that the mechanism of appetites belongs to automatic actions deeply inherited by phylogeny. Although complicated and composed of coördinated reflex movements which follow one another in regular succession, it has no actual power of modifying the so-called voluntary acts, which depend entirely on the cerebral hemispheres, and of which we men only have a conscious feeling. The appetites are not capable of adapting themselves to new circumstances and cease to be produced when the chain is interrupted. We are obliged to admit that the instincts or appetites are accompanied by a sub-conscious introspection which, as such, can hardly enter into direct relation with our higher consciousness, that is, with our ordinary consciousness in the waking state. In spite of this, when their intensity increases, the appetites overcoming the central nervous resistances, reach the cerebral hemispheres, and consequently our introspection or higher consciousness, under a _synthetic or unified appearance_, and influence in a high degree the cerebral activities, which are reflected in association with all the elements of what we call our mind in the proper sense of the term, that is to say, our intellect, sentiments and will. It is from this point of view that sexual appetite must be considered in order to make it comprehensible. Love, with all that appertains to it, belongs as such to our mind, that is, to the activity of our cerebral hemispheres, but it is produced there by a secondary irradiation from the sexual appetite, which alone concerns us at present. We may also remark that sexual ideas when once awakened in the cerebral hemispheres by sexual appetite, are worked up there by the attention, that is to say by concentrated cerebral activity, then associated with other ideas, which on their side react strongly on the sexual appetite, developing or paralyzing it, attracting or repelling it, or finally transforming its attributes and objects. By sexual desire (libido sexualis) we mean the manner in which the sexual appetite manifests itself in man. Each term may be employed for the other. =The Sexual Appetite in Man.=--Man represents the active element in sexual union, and in him the sexual appetite, or desire for coitus, is at first the stronger. This desire develops spontaneously, and the role of fecundator represents the principal male activity. This appetite powerfully affects the male mind, although sexual life plays a less important part in him than in the female.