My purpose in dwelling so much upon these mixed relations and disappointments, has been more especially to fully expose the predisposing causes of neuroses and more essentially of the sexual variety. As I shall labor to show that neurosis is the condition throughout our list of sexual diseases, and that all the foregoing changes, excesses and defects, depending upon the sexual, are more or less influential in predisposing human beings to brain and spinal cord disease. No person, so well as the physician, will comprehend, after once meditating upon this theme, the necessity for thorough study and a more rational understanding of the sexual. Medical writers, with one or two exceptions, have only ventured now and then an isolated paragraph, and left the physician to draw his own conclusion. Among the aboriginal tribes, the sexual appetite is and has always been indulged _ad libitum_; not only in the natural manner, but in every conceivable way, without noticeable harm to the organs themselves, or to the nervous system. In a lesser degree this is true of slaves, sailors and peasantry, and the lower orders of civilization. Sexual endurance diminishes in proportion to the advancement in civilization and intellectual culture. A long-cultured family can not sustain, in sexual indulgence, what to the uncivilized would be a matter of indifference. Sexual intercourse, when not contra-indicated, may relieve nervous tension and produce sleep in a moderately feeble individual; but on the other hand, if carried to excess, it may produce nervous tension, wakefulness, headache and exhaustion. There are no definite rules to regulate the sexual appetite, more than the stomach for food. The evils of sexual intemperance are temporary, and if recent, quickly recoverable by rest only. Says Dr. Briggs, of New York, “The sexual system is notoriously the seat of excitement and depression from psychical and mental influences. It is under the control of the sympathetic nerves, and influenced by the solar flexus. Much of the peculiar sensibility experienced in this part of the body is directly referable to the mind and imagination: the manifestations are controlled by the sympathetic nerves, from the impulse given in this manner. But the mind and will, however intense, have little power over the sexual functions, except through this medium. The emotions are superior.”