THE FIRST SIGN of something different going on at the Museum of Fine Arts hits you when you walk in the door. At the top of the grand staircase, blocking out the gold leaf, the Sargent murals and the classical columns, looms a 15-foot, glaring, carved wooden Thunderbird.

The bird is a Tlingit Indian totem pole--a striking introduction to the museum's current exhibition of American Indian and Eskimo art. This exhibit, which the museum calls "the most important exhibition of Native Alaskan art ever assembled" finally brings ethnic art into the main exhibition halls of a great art museum, a place which, by its quality, it has long deserved.

The show is made up of everyday objects--of baskets and rugs, robes and belts given a special place by the Northern society. The main strength of the Eskimo and North-Coast Indian cultures is their special relationship with the natural world around them. Reflected in the forms is a spirit of a union with nature--of men and women belonging with the land, watched by animal gods who offer protection during the winter in return for worship.

So, the Eskimos, the Aleuts, the Tlingits and the Athabaskans incorporate rams' heads into their basket designs and polar bears into their pipes. When these people grace a carved ivory harpoon rest with two otters, it's not for the sake of design, but for their religion, that the two belong together.

This interdependence of man and animal lends the people themselves to dress as animals as they call on the spirits. Their ceremonial masks are the focal point of this show, and their beauty blends both religious utilitarianism and aesthic form. A forehead mask, of a loon, an elegant swoop of painted wood, decorated with seagull feathers, eagle down and willow branches, becomes the frightened figure of a dying animal.

The mask in the photograph is of an Eskimo tribe--an important distinction, for there is a real difference in the qualities of the work of the arctic Eskimo and Aleut and the two other, more southern tribes. The signs at the show credit this difference to environment: icebergs giving inspiration to the open, bold images of the Eskimo, northern rain forests spawning the more colorful, stylized forms of the Indian tribes. This is true, as far as it goes, but there is another, a more foreign element that seperates further the styles of these two groups.

THAT ELEMENT is the presence of the white man. Nineteenth century pioneers weren't attracted to the Aleutian islands, but the Alaskan gold rush made the land of the Indian tribes into a white-man's thoroughfare. The Tlingit and Athabaskan art comes to have European influences that disturb the fusion of beauty and purpose that makes the art of the Eskimos so moving.

The ceremonial masks of the Indian tribes are less wild than the Eskimos'--they have less fear behind them. The simplified form of an Athabaskan fox-mask, a single piece of wood, doesn't convey a belief in the power behind it. The lush countryside of the Canadian coastal forest might explain this art's concentration on repeating patterns, and these forms are more refined than the colorless, stark Eskimo style. But they are also less striking. The white man's influence shows most clearly in an "Octopus bag" made of felt, cotton, calico and brightly colored polychrome beads--all brought by white men. The resulting design is uncomfortably garish and foreign to the rest of the style.

Not all Tlingit art was infiltrated by white gold-seekers. That glaring Thunderbird and his ilk must have scared a good number of interloping foreigners back to safety and Seattle. But that glorious beast has been toned down enough by the 19th century classicism of the MFA rotunda to loose this power. On the whole, it's a good thing. People should not be scared away from this show.