"At a Parsi funeral a dog (with certain spots above the eyes) is brought in to gaze at the body and so exorcise the Nasu"
Temple of Silence
The dog in question should be a 'four-eyed' dog, one with a spot above each eye.The word 'Nasu' means 'unclean', and in this context refers to the corpse demon, which is also associated with decay and infection. The dog, gazing upon the body, gets rid of this spirit of corruption.
The soul is guided by the dog across the Bridge of Separation into the next life.
After the funeral rites, the dead are left exposed on the top of a tower (or temple) of silence for carrion birds to devour, the bones being disposed of later.