The sages saw that the female of the white-rumped antelope has two white, ball like formations in the area of her womb. At first the sages thought that these were the female’s own testicles and so they forbade the balls for consumption, for animal testicles may not be eaten unless properly slaughtered. One of the sages, Rav Safra, corrected them, and argued that these white formations are not the female’s own testicles, but are the semen of gazelles which have accumulated and formed two white testicle-like balls. How did the gazelle’s semen get into the white-rumped antelope’s womb? Answer: The gazelle has a purpose in seeking out the antelope. When the gazelle wishes to mate, he first seeks out a female gazelle. But the female gazelles, whose vaginas are narrow, find mating painful, and so refuse the males. Filled with desire which is unfulfilled, the gazelles seek out the female antelopes and mate with them. Because of their unfulfilled desire the gazelles have accumulated a great quantity of semen, which is poured into the white-rumped antelope’s womb. These masses of semen, argues the sage, are the white balls found in the white-rumped antelope’s womb. Therefore these formations are permissible for consumption, for the semen of pure animals is permitted for consumption even before slaughtering.
(Babylonian Talmud, Tractate Bechorot 7b)