About this time of year, for 500 years or more, in Atzacoaloya, Mexico, a ritual dance is offered to the gods in return for fertile fields. Young boys are transformed into pigs, goats and donkeys, the victims of ravaging tigers who the day before were fellow villagers. In their turn, a farmer and a herdsman with long wooden shotguns slay the tigers and miraculously resurrect the dead.

Such is the strength of this dance that after their conquest of Mexico, the Spanish -- though they taught their own history in dance battles by masked Spaniards and Moors -- forbade the wearing of certain traditional masks, such as that of the tiger.

The tigers, the Moors, the Spanish grandees, barnyard animals and farmers, as well as many stranger humans and beasts, hang on the Beaux Arts walls and bloom on poles set in the greenery of Meridian House in "Dancing Faces: Mexican Masks in a Cultural Context," an exhibition up through April 15. The collection of 160 masks, three costumes and many photographs of masks in movement includes examples from as early as the pre-Hispanic classic period, before A.D. 900, and as late as the handsome decorative masks now a prime source of income and artistic expression for Mexican craftsmen.

A muscovite stone mask, green shading into brown, shows the sophistication and strength of the Indian artist of the late Classic Maya period (A.D. 600 to 900). A stone mask from Guerrero, circa 1970, half skull, half flesh, a copy of a pre-Columbian mask, shows that Mexican artists still keep their power.

Most of the masks are owned by Jose Moya Rubio, whose important and international collection is the core of the Museum of the Mask in San Luis Potosi, Mexico. Others are from the Smithsonian and Dumbarton Oaks. The informative catalogue by North Carolina anthropologist Marion Oettinger Jr., as well as the show, was financed in large part by the Ford Motor Co.

The dance masks were made for a marvelous mixture of fertility rites, invoking Catholic saints and the ancient Aztec god Tlaloco to bless the seeds and bring the rain during the February-May dry season. The fetes are held all over the country, but primarily in the more isolated and agricultural Indian communities of central Mexico, the northern states of Sinaloa and Sonora, and the southern area of Chiapas.

The masks are sometimes made by a hereditary masquero (mask-maker), who is often also the village santero (saint-maker). Talent, training and tools are handed down from father to son. Oettinger points out a grisly death's head with a working jaw, made by a village postmaster, his grandfather's successor in Atliaca, Guerrero.

A few of the papier-ma che' masks, Oettinger says, were made by a husband and wife partnership, Juan and Macedonia Francisco of Acatla'n, Guerrero. In their seventies, they still make the masks, layering wet paper on clay molds handed down in Francisco's family. Both learned the art from his father. They make masks when it's too dry to farm. But the masks are unfinished, powerless until initiated in a ritual dance.

The decorative masks in the show include, among standouts, a huge, almost totem, carved wooden mask and a beaten copper mask with a long beard, both from Guerrero, and a complicated ceramic mask from Metepec, famous for its tree of life sculptures. Many Mexican masks, made anonymously for the collectors' trade, are not, as on some other continents, simply airport artifacts. If considered as art, not artifact, they can stand up against much so-called serious contemporary sculpture.

But the dance masks are not made to be admired, but to be respected. To put on a mask is to become a sharp-toothed tiger, ruthless, brave, vicious. Or a crowned marquis, aristocratic, autocratic. Or a white-bearded old man, vulnerable, venerable. Or perhaps a bleached bone skeleton, fearful, dreadful. Or any one of the many fierce or fanciful creatures shown whose strange lives and deaths permit the mask-wearer to change his own, no matter how briefly.