[34] He expounded the theory that ideas on the sexual function had been falsified through fear of venereal diseases at a time when people did not know either how to avoid or cure those diseases. He showed that the condemnation of a natural function by divers religions was based on that fear. He analysed the deplorable consequences of that, and set forth the necessity of returning to more wholesome ideas, more in conformity with nature and allowing the study and avoidance of many evils. He thought that, in this connection, a new direction should be given to the education of children and to marriage. He then examined the part played by the sexual function in the lives of men of genius and, with that object, read many biographies and literary works. During his illness he read books concerning Victor Hugo and Napoleon, J. J. Rousseau's _Confessions_ and even parts of the _Nouvelle Héloïse_. Another question occupied him at that time, that of first-born children. Certain data led him to think that men of genius were but rarely the first-born of their parents, and he sought for every possible information on the subject. In his constant desire to improve life-conditions, he even thought that a demonstration of this fact might have a desirable influence on the increase of population in France after the war; if it were proved that the most successful children are not the first-born, perhaps the system of having two children only would be given up in order to have a chance of giving the country a more capable population. His reflections on the sexual questions led him to seek for experimental means of studying gonorrhoea. He thought of inoculating the gonococcus into the eye of new-born mice and entrusted M. Rubinstein, the only worker left in the laboratory, with these experiments. The latter began them and obtained encouraging results, but he left Paris in the spring and the work remained unfinished. Metchnikoff's mind never ceased to work unless interrupted by acute pain; until the very end, his brain never failed him. He often used to say how far he was from any mystic aspirations, and how sure he was of remaining a rationalist until the end. And such was the case. Faithful to himself, not even in the most painful moments did he feel a desire to look for support outside the ideas and principles of his whole life. Yet his soul was sad and full of care; the war grieved him utterly, every newspaper he read renewed his sorrow. When a severe engagement, Verdun for instance, was going on, he lost the little sleep he had, and his agitation became painful. He was deeply disillusioned by the Germans. Having always felt great esteem for their scientific work, he had believed in their high culture, and now he was absolutely disconcerted by the mentality which they manifested during the war.