ANTONIA SAW THE ORYX FIRST <i> by Maria Thomas (Soho: $17.95; 296 pp.) </i>

Maria Thomas has written a beautiful, sometimes difficult first novel about the deepening affinity between a white woman doctor and a black woman “healer” in East Africa.

It is a poetic exploration of half a dozen different themes: “civilized” versus “primitive,” male versus female, an effort to suggest a profound and particular woman’s way of knowing, sisterhood across barriers of age and culture, and the decay of colonial structures in a Third- World society.

Antonia, of the title, is the doctor. She was born and reared in Africa, the daughter of an American coffee planter. Her childhood was a magic kingdom. She lived as a lordling of creation: taken on hunting expeditions by her father, who cherished her, and surrounded by affectionate servants who made her bed with crisp, clean sheets two and three times a day. They were there when wanted; invisible when not.

Now, in her 30s, her life is utterly changed. Having studied medicine in the United States, she is one of a shriveled community of whites in a society that doesn’t want them, and barely needs them. She hangs on--though she won’t for much longer--thanks to her services at the local hospital, but mostly thanks to the dwindling protection of Luenga, the hospital director. A black fellow student at Harvard, he was her lover and shared a dream of returning to Africa to work together. Now, distanced and powerful, he sees her abstractly as a colonialist.

Luenga, the new Marxist, is one variant of a simplified male outlook. Antonia’s benevolent planter father was another. A third, in a different way, is the increasingly irrelevant medical science she practices in a hospital whose discipline and services are failing for lack of means, and in the face of an endless flood of patients. None of the three has more than a superficial and partial relationship to the vast and undefined reality of Africa.

Antonia--attenuated but open-minded--doubts her role but clings to it, having no other. Then one night, a young black prostitute walks in, badly cut up by a demented Greek sailor.

Esther is a mystery to Antonia and to us. More important, she is a mystery to herself. Her slow, instinctive discovery of who she is provides the triumph of a book that is often uneven, and whose passionate insight both flaws it and makes it remarkable.

Esther is not the passive, elusive patient that Antonia is used to. She pulls the transfusion needle from her arm; she proves to have patchily precise notions of such things as infection and the circulatory system. The needle to her is an image of the mosquito’s probe, transmitting not health but disease.

Esther has been on a long, transfiguring voyage of her own, it turns out, and when Antonia meets her, she is in mid-passage. Her father, native assistant to a doctor, had picked up smatterings of Western medicine. Taking Esther with him, he would go among the interior villages as a kind of anti-shamanistic prophet, countering their spiritist medicine with talk of germs and asepsis.

As attached to her father as Antonia was to hers, Esther is sold, after his death, to a village notable. She faces a woman’s tribal lot: circumcision and a life of servitude. With her father’s example as her personal talisman, she escapes to the capital, works for a French and then a Hindu family, and ends up as a bar girl.

Upon Antonia, she asserts a series of peremptory claims. She insists on learning rudiments of medicine, but this insistence is in conflict with something she has discovered in herself. She has a healer’s gift; she can put her hands on the ill and cure them. Her father’s inklings of Western science are at war, inside her, with an older truth.

Esther goes to the interior with her lover, Nkosi, a sick and aging revolutionary, and performs her healing feats along the way. Antonia, struck by the perpetual questing spirit of this young woman, goes after her. She has become convinced that the mechanical treatment of symptoms in a sea of African suffering is as much an act of superstition as a witch doctor’s rituals. Nkosi dies--Esther, helpless in her own way, can’t cure him. Antonia will leave and Esther will stay on, but a link has been forged; the solidarity of two women whose strengths are unable to prevail over the peremptory demands of the male world, will outlast them.

There is an extraordinary richness to Thomas’ writing. The nostalgic magic of Antonia’s childhood is contrasted in telling detail with the decrepit remains of the colonial life. Antonia lives in a bleak housing project, unsoundly built in some short-lived Eastern Europe aid scheme. The Westerners still go to what used to be their country club. The manager’s relatives occupy it; the kitchen has become a series of outdoor cooking pots. When the clients move out to the terrace, a waiter follows with the sole functioning light bulb.

Esther--fragile, determined, instinctive--is unforgettable. Her wanderings through the backlands and slums of the new Africa are a picaresque masterpiece. Thomas manages with apparent effortlessness and total conviction the feel of a deserted village market, the intricate, chatty life of a city tenement, the dense and anxious ritual of a Hindu family facing eventual displacement. In 10 words, she gives us an unearthly picture of a rabid dog on a village street: “Its head was low and its mouth boiling like soup.”

Antonia is less vivid than Esther, but that is the author’s intention. The bond between them, unlikely as it seems, is entirely convincing. Thomas takes no sides. Neither the instinctive healing lore of a traditional society nor the problem-solving science of the West is sufficient; both can find themselves powerless. What counts is the distance Esther and Antonia move to discover each other and themselves.

With one exception, the men are schematic; one or two are little more than female fantasy objects. The portrait of Esther’s dying lover, Nkosi, on the other hand, is subtle and touching. An expatriate, who lived comfortably in Europe with his Swedish wife, Nkosi abandons her and their children to return to the idealized Africa he’s assembled in his head, and whose liberation he will pursue with a forlorn band of fellow guerrillas.

Esther and her healing powers go with him. She sets up photographs of his wife and children beside him. “Who was it that lived in London all those years and Sweden all those years? Who was it that wore those clothes hanging there?” he asks himself, his fantasies punctured. Esther’s earth-magic has shattered him into authenticity.

Not all the writing in “Antonia” works so well. Thomas can goad her language excessively; her images sometimes choke on themselves. There are times where her notion of the blood-unity among women--women bleed, monthly; men draw blood--takes on a mysticism that eludes me. It reminds me of an effort, at age 12, to read Swedenborg; grand things were happening, but I didn’t know what they were.

But in its portrait of Esther, of a changing, changeless and tormented Africa, and of the illusions that grow and are shattered there, “Antonia Saw the Oryx First” is a work of astonishing energy and vision.