A search of the sixteenth-century literature, however, leaves no doubt as to the prevalence of cannibalism among the central Mexicans. The Spanish conquistadores wrote amply about it, as did several Spanish priests who engaged in ethnological research on Aztec culture shortly after the conquest. Among the latter, Bernardino de Sahagun is of particular interest because his informants were former Aztec nobles, who supplied dictated or written information in the Aztec language, Nahuatl.
According to these early accounts, some sacrificial victims were not eaten, such as children offered by drowning to the rain god, Tlaloc, or persons suffering skin diseases. But the overwhelming majority of the sacrificed captives apparently were consumed. A principal -- and sometimes only -- objective of Aztec war expeditions was to capture prisoners for sacrifice. While some might be sacrificed and eaten on the field of battle, most were taken to home communities or to the capital, where they were kept in wooden cages to be fattened until sacrificed by the priests at the temple-pyramids Most of the sacrifices involved tearing out the heart, offering it to the sun and, with some blood, also to the idols. The corpse was then tumbled down the steps of the pyramid and carried off to be butchered. The head went on the local skull rack, displayed in central plazas alongside the temple-pyramids. At least three of the limbs were the property of the captor if he had seized the prisoner without assistance in battle. Later, at a feast given at the captor's quarters, the central dish was a stew of tomatoes, peppers, and the limbs of the victim. The remaining torso, in Tenochtitlan at least, went to the royal zoo where it was used to feed carnivorous mammals, birds, and snakes.
Recent archaeological research lends support to conquistadores' and informants' vivid and detailed accounts of Aztec cannibalism. Mexican archaeologists excavating at an Aztec sacrificial site in the Tlatelolco section of Mexico City between 1960 and 1969 uncovered headless human rib cages completely lacking the limb bones. Associated with these remains were some razorlike obsidian blades, which the archaeologists believe were used in the butchering. Nearby they also discovered piles of human skulls, which apparently had been broken open to obtain the brains, possibly a choice delicacy reserved for the priesthood, and to mount the skulls on a ceremonial rack.
Harner, "The Enigma of Aztec Sacrifice"