It is considered by many people to be little more than adecorative means of giving pleasure. This is not always the case; however, at times,art may be seen to have purely functional side as well. Such could be said of thesand paintings of the Navaho Indians of the American Southwest; they have amedicinal as well as an artistic purpose.  According to the Navaho traditions, one who suffers from eithera mental or physical illness has in some way disturbed or come in contactwith the supernatural-perhaps a certain animal, a ghost, or the dead. Tocounteract this evil contact, the ill person or one of his relatives will employa medicine man called"singer"to perform ahealing ceremony which will attract a powerful supernatural being. During theceremony, which may last from 2 to 9 days, the "singer" will producea  sand painting onthe floor of the Navaho Hogan. On the last day of the ceremony, the patient willsit on this sand painting and the "singer"will rub the ailing partsof the patient'sbody with sand from a specific figure in the sand painting. In this way the patientabsorbs the power of that particular supernatural being and becomes strong like it.After the ceremony, the sand painting is then destroyed and disposed of, so its powerwill not harm anyone.  The art of sand painting is handed down from old"singers"to their students The materials used are easily found in theareas the Navaho inhabit: brown, red, yellow, and white sandstone, which ispulverized by being crushed between two stones much ascorn is ground into flour. The"singer" holds a small amount of this sand in his handand lets it flow between his thumb and forefinger onto a clean, flat surface on thefloor. With a steady hand and great patience, he is thus able to create designs of stylizedpeople, snakes and other creatures that have power in the Navaho beliefsystem. The traditional Navaho does not allow reproduction of sand paintings, sincehe believes the supernatural powers that taught him the craft have forbidden this.However, such reproductions can in fact be purchased today in tourist shops inArizona and New Mexico These are done by either the Navaho Indians or byother people who wish to preserve the craft. 
Why does the'singer'rub sand on the patient?