X-rays usually reveal that the bones have points of radiolucency (darkness),
indicating less bone density than is normally found, a phenomena that many vets refer to as «thumb print» lesions.
Furthermore, when a measurement did not match a precise number of «land rods» — their standard unit of linear measurement, which corresponded to about 2.5 meters — the Aztecs added symbols, such as an arrow, a heart, a hand, or a
bone, to
indicate remaining length that was
less than one rod.