It would be simply hypocrisy and unworthy of a scientific work which should always aspire to reveal the truth, were we to deny the fact that many old bachelors and spinsters present a series of nervous symptoms, especially dyspepsia and hyperchlorhydria and pains in the stomach, far more than other persons, which we must explain by the action of impulses coming from the sexual organs to the sympathetic and pneumogastric, the principal nerves of the stomach and intestines, and thus producing a hyperæsthesia of the nerves of the stomach. In such persons some kinds of food, well digested by a normal stomach, will act as an injurious foreign body, and be felt as such by the over-sensitive stomach nerves, and the gastric glands will respond with a large flow of secretion and much acid upon agencies that produce no such stimulation in a normal stomach. That the sexual glands also influence the intellect is best proved by the observation that in cases of testicular or ovarian insufficiency intelligence is often diminished. Thus we were consulted by the parents of a young man of eighteen years who was mentally backward; he could not remember anything; his arms and legs were abnormally long, but his body short, thus resembling a eunuch’s—and indeed I found his testicles were not yet descended. His voice was that of a child, and he also exhibited the other symptoms of testicular insufficiency described in the second chapter of this book. On the other hand we may see a precocious highly developed intellect in children with a premature sexual development. We know of a boy of six years who tried to have sexual intercourse with a little girl of the same age, and who at the age of four and one-half years knew all the capitals of the world by heart. Hence the education of precociously bright children should be especially guarded, for they can become great men but also not rarely, if neglected, great criminals. As, however, in these days of scepticism we do not believe in anything until demonstrated by experiments (often forgetting the fact that what does for dogs or rabbits does not always do for man) which should only assist our judgment, but not exclusively govern it, we shall have to prove the correctness of our clinical observations on the influence of the sexual glands—i.e., on the nervous system and mentality—by experiment, and we believe we have sufficient facts at hand to do so.