It will be seen that the conclusions we have reached indirectly involve the assumption that the spinal nervous centers, through which the sexual mechanism operates, are not sufficient to account for the whole of the phenomena of the sexual impulse. The nervous circuit tends to involve a cerebral element, which may sometimes be of dominant importance. Various investigators, from the time of Gall onward, have attempted to localize the sexual instinct centrally. Such attempts, however, cannot be said to have succeeded, although they tend to show that there is a real connection between the brain and the generative organs. Thus Ceni, of Modena, by experiments on chickens, claims to have proved the influence of the cortical centers of procreation on the faculty of generation, for he found that lesions of the cortex led to sterility corresponding in degree to the lesion; but as these results followed even independently of any disturbance of the sexual instinct, their significance is not altogether clear (Carlo Ceni, "L'Influenza dei Centri Corticali sui Fenomeni della Generazione," _Revista Sperimentale di Freniatria_, 1907, fasc. 2-3). At present, as Obici and Marchesini have well remarked, all that we can do is to assume the existence of cerebral as well as spinal sexual centers; a cerebral sexual center, in the strictest sense, remains purely hypothetical. Although Gall's attempt to locate the sexual instinct in the cerebellum--well supported as it was by observations--is no longer considered to be tenable, his discussion of the sexual instinct was of great value, far in advance of his time, and accompanied by a mass of facts gathered from many fields. He maintained that the sexual instinct is a function of the brain, not of the sexual organs. He combated the view ruling in his day that the seat of erotic mania must be sought in the sexual organs. He fully dealt with the development of the sexual instinct in many children before maturity of the sexual glands, the prolongation of the instinct into old age, its existence in the castrated and in the congenital absence of the sexual glands; he pointed out that even with an apparently sound and normal sexual apparatus all sorts of psychic pathological deviations may yet occur. In fact, all the lines of argument I have briefly indicated in the foregoing pages--although when they were first written this fact was unknown to me--had been fully discussed by this remarkable man nearly a century ago. (The greater part of the third volume of Gall's _Sur les Fonctions du Cerveau_, in the edition of 1825, is devoted to this subject. For a good summary, sympathetic, though critical, of Gall's views on this matter, see Möbius, "Ueber Gall's Specielle Organologie," _Schmidt's Jahrbücher der Medicin_, 1900, vol.