With birds, as we have seen, the law of battle plays an important part in sexual selection; but it is often counter-balanced by other less brutal influences. This is rarely the case in regard to mammals, with whom especially the right of the strongest regulates the unions. The law of battle prevails among aquatic as well as land mammals. The combats of the male stags, in the rutting season, are celebrated. The combatants have been known to succumb without being able to disentangle their interlocked antlers; but seals and male sperm-whales fight with equal fury, and so also do the males of the Greenland whale.[20] In mammals, as in birds, and as in man, sexual desire raises and intensifies all the faculties, and seems to elevate the individual above the level of normal life. Animals in a state of rut become bolder, more ferocious, and more dangerous. The elephant, pacific enough by nature, assumes a terrible fury in the rutting season. The Sanskrit poems constantly recur to the simile of the elephant in rut to express the highest degree of strength, nobility, grandeur, and even beauty. But obviously I must not linger very long over the loves of the animals. My chief object is to study sexual union and marriage amongst human beings. The rut of animals and their sexual passions merely interest us here as preliminary studies, which throw light on the origin of analogous sentiments in mankind. Before leaving this subject, however, it will be useful to note a few more facts which, from the point of view of sexual psychology, bring animals and men near to each other. The old Cartesian paradox, which makes the animal an unconscious machine, has still many partisans. A widely-prevailing prejudice insists that animals always obey blind instincts, while man alone, _homo sapiens_, made after the image of God, weighs motives, deliberates and chooses. Now, as procreation constitutes one of the great necessities of organised beings, and is an imperious law which no species can elude without disappearing, surely we ought to find amongst animals the most exact regularity in the acts connected with it. Man alone ought to have the privilege of introducing caprice and free choice into love. It is not so, however. On this side of his nature, as on all the others, man and animal approach, resemble, and copy each other. In his celebrated invocation to Venus, Lucretius has truly said, proclaiming the universal empire of the instinct of reproduction-- “Per te quoniam genus omne animantum Concipitur, visitque exortum lumine solis.” The animal, as well as the morally developed man, is capable of preference and individual passion; he does not yield blindly and passively to sexual love.