(b) That many young people who for various reasons, such as housing or financial difficulties or inherited disease, feel themselves unable to have a family, would if such knowledge were available marry much earlier, and their natural desires would be satisfied, while apart from marriage they might resort to promiscuous intercourse. (c) That homes where the growing difficulties and strain of a continually increasing family are leading to estrangement between husband and wife, are restored to happiness when saved from the difficult choice between continence, which they have never trained themselves to practice, or many children with which they cannot cope. There are, however, serious fallacies in these contentions. The propagandists of conception control appear to take it for granted that after preventive measures in early youth, children may be conceived at will whenever they are desired; and, moreover, it is assumed that apart from such precautions every woman will conceive annually and will continue to do so until 10-12 children have been born. Neither of these suppositions is supported by facts. On the contrary, there are large numbers of married couples who would give anything to have children, but have postponed it until circumstances should seem quite desirable, and then, to their grief, no children are given to them. It is very unfair to teach people that they may safely postpone the natural tendency to bear children in youth and rely upon having them later in life. Probably gynæcologists are consulted more often by women who desire children but do not have them, than by those who wish to avoid having them--the truth being that the tendency among people in comfortable surroundings is towards relative sterility rather than towards excessive fertility. Those who are interested in this aspect of the question will find the facts admirably set forth in Mr. Pell's book on _The Law of Births and Deaths_, being a study of the variation in the degree of animal fertility under the influence of environment. He finds that the all-important factor which determines fertility is the amount of nervous energy of the organism, and that nervous energy is produced or modified by three specially influential factors, viz., Food, both quantity and quality; Climate, hot or cold--moist or dry; and, lastly, all those varied conditions which make for greater or lesser mental and physical activity. Fertility, broadly speaking, varies in inverse proportion to the degree of nervous energy or what we may call vitality.