The whole anatomical structure, the feet, the hands, the limbs, the size and form of the head, the features, the hair, the color, the tout ensemble of the negro being, as it is revealed to the sense, embodies the negro inferiority when compared with other races; and as regards the white man or Caucasian, it presents a contrast so striking and an interval so broad and unmistakable that it seems impossible any one's senses could be so blunted, or his perceptions so perverted as to be rendered incapable of perceiving it. The flexible grace of the limbs, the straightlines of the figure, the expressive features, the broad forehead and transparent color, and flowing beard, all combine to give a grace and majesty to the Caucasian that stamps him undisputed master of all living beings, and even the creatures of the animal world perceive and acknowledge this supremacy. It is not an uncommon thing in India for a tiger, rendered desperate by hunger, to suddenly leap into a crowd and to carry off a man, but instead of a European he invariably selects a native, and while such a thing as the seizure of a white man is unknown, the negroes in Sierra Leone are frequently carried off and eaten by lions. The instinct of the animal leads it to attack the inferior, and therefore feebler being, as even our domestic animals are far more likely to attack children than adults.
--John H. Van Evrie, White Supremacy and Negro Subordination, pp. 96-97, 1861.
Interestingly enough, this is the same reason why black characters always die first in horror movies.