|Two Xolos, one hairless and one coated.|
|The three sizes|
In Mexico, these dogs were used to treat numerous ailments, acting as living hot water bottles because of their warm skin. In certain areas, the dogs still serve this exact purpose. They were also used as guardians, and sometimes sacrificed on the death of their owner in the belief that they would guide the soul to the afterlife. They were also eaten, considered a delicacy before the arrival of the Spanish.
The Xoloitzcuintle was featured in a rather amusing spot on Animal Plant's Dog's 101.
Sources are the AKC and FCI breed standards and Vet Street. Images are from Wikimedia Commons under creative common licenses: one, two