Reproductive isolation from a cross between a horse and a donkey or between a mare and a donkey, respectively. These animals are nearly always sterile due to the difference in the number of chromosomes between the two parent species. Both horses and donkeys belong to the genus "Equus", but "Equus caballus" has 64 chromosomes, while "Equus asinus" only has 62. A cross will produce offspring (mule or hinny) with 63 chromosomes, that will not form pairs, which means that they do not divide in a balanced manner during meiosis. In the wild, the horses and donkeys ignore each other and do not
Equus (play) the owner of the stables, Harry Dalton, and Alan agrees. Dysart meets with Dalton, who tells him that he first held Alan to be a model worker, since he kept the stables immaculately clean and grooms the horses, including one named Nugget. Through Dysart's questioning, it becomes clear that Alan is erotically fixated on Nugget (or 'Equus') and secretly takes him for midnight rides, bareback and naked. Alan also envisions himself as a king, on the godhead Equus, both destroying their enemies. Dysart gives Alan a placebo "truth pill". Revealing a tryst with Jill, he begins to re-enact the event.