It may seem that such impulses and such devices to gratify them are altogether unnatural. This is not so. They have a zoölogical basis and in many animals are embodied in the anatomical structure. Many rodents, ruminants, and some of the carnivora show natural developments of the penis closely resembling some of those artificially adopted by man. Thus the guinea-pigs possess two horny styles attached to the penis, while the glans of the penis is covered with sharp spines. Some of the Caviidæ also have two sharp, horny saws at the side of the penis. The cat, the rhinoceros, the tapir, and other animals possess projecting structures on the penis, and some species of ruminants, such as the sheep, the giraffe, and many antelopes, have, attached to the penis, long filiform processes through which the urethra passes. (F.H.A. Marshall, _The Physiology of Reproduction_, pp. 246-248.) We find, even in creatures so delicate and ethereal as the butterflies, a whole armory of keen weapons for use in coitus. These were described in detail in an elaborate and fully illustrated memoir by P.H. Gosse ("On the Clasping Organs Ancillary to Generation in Certain Groups of the Lepidoptera," _Transactions of the Linnæan Society_, second series, vol. ii, Zoölogy, 1882). These organs, which Gosse terms _harpes_ (or grappling irons), are found in the Papilionidæ and are very beautiful and varied, taking the forms of projecting claws, hooks, pikes, swords, knobs, and strange combinations of these, commonly brought to a keen edge and then cut into sharp teeth. It is probable that all these structures serve to excite the sexual apparatus of the female and to promote tumescence. To the careless observer there may seem to be something vicious or perverted in such manifestations in man. That opinion becomes very doubtful when we consider how these tendencies occur in people living under natural conditions in widely separated parts of the world. It becomes still further untenable if we are justified in believing that the ancestors of men possessed projecting epithelial appendages attached to the penis, and if we accept the discovery by Friedenthal of the rudiment of these appendages on the penis of the human fetus at an early stage (Friedenthal, "Sonderformen der menschlichen Leibesbildung," _Sexual-Probleme_, Feb., 1912, p. 129). In this case human ingenuity would merely be seeking to supply an organ which nature has ceased to furnish, although it is still in some cases needed, especially among peoples whose aptitude for erethism has remained at, or fallen to, a subhuman level.