The Christian physiologist, pondering the inexorable law of purity as shown by history, is compelled to re-examine the physical and moral facts of the human constitution, on which the rise and fall of races depend. The question distinctly arises, Is Christianity a superstition, dying out in the nineteenth century of science and material development; or does it contain within itself a principle whose transforming power has been hitherto unrecognised, but which will now come into play, and lead the nations into renewed and more permanent vigour of life? One of the first subjects to be investigated by the Christian physiologist is the truth or error of the assertion so widely made, that sexual passion is a much stronger force in men than in women. Very remarkable results have flowed from the attempts to mould society upon this assertion. A simple Christian might reply, ‘Our religion makes no such distinction; male and female are as one under guidance and judgment of the Divine law.’ But the physiologist must go farther, and use the light of principles underlying physical truth in order to understand the meaning of facts which arraign and would destroy Christianity. It is necessary, therefore, to determine what is meant by strength and what is meant by passion. In one sense a bull is stronger than a man, and many of the inferior animals are superior in muscular force or keenness of special sense to human beings, yet man is more powerful than the animal world which he dominates to his will. Any assertion that the animal is stronger than the human being fails to recognise the very essence of humanity--viz., mental or moral strength. Again, in one sense, the whirlwind or the earthquake is stronger than the creative action of Nature; their rapid devastation strikes the terrified imagination, yet at the very moment of their ravage reparative and creative force is being exerted all over the world with immeasurably more power than any sudden outbreak of destruction. In determining the strength of races and the strength of individuals, the various elements which constitute vital power must be considered. Endurance, longevity, special aptitudes with the proportionate amount of vital force given to their fulfilment--these are all elements of relative strength. In any attempt to settle the comparative strength of man and woman, therefore, all these elements must be weighed. Thus the powers of endurance which are demanded by each kind of life must be accurately measured; the care of a sick child must be balanced against the anxiety of business, the ceaseless cares of indoor life against the changes of outdoor life, etc. The impossibility of so weighing the burden which each sex bears in the various trials and difficulties of practical life shows the futility of attempting to measure the amount of vital power possessed by men or by women separately.