By PATRICIA COHEN

Years ago Ruth Butler was walking through the Musée Rodin in Paris when she glimpsed a small oil painting of a woman with short brown hair, intense eyes and pursed lips. It was labeled a portrait of Rodin’s mother.

“I said, ‘That’s ridiculous,’ ” recalled Ms. Butler, who was on the museum’s board and is now professor emerita at the University of Massachusetts in Boston and the author of a Rodin biography. She recognized the portrait as that of Rose Beuret, Rodin’s model and later his wife.

“I thought that if even the Musée Rodin doesn’t care about Rose, then I should write about this,” Ms. Butler said as she sat sipping a cappuccino in the Petrie Court at the Metropolitan Museum of Art, gazing out at Central Park.

The book is “Hidden in the Shadow of the Master: The Model-Wives of Cézanne, Monet and Rodin,” recently published by Yale University Press. In it Ms. Butler tries to rescue from obscurity the women who she argues were so much a part of the triumphs of these visionaries.

“These artists would find people whose body and face make a statement that they could not otherwise make,” Ms. Butler said, arguing that the models have never been given their due. The women “made a contribution,” she added. “They deserve to be seen, not just visually but biographically.”

As artists in the second half of the 19th century shifted from painting historical, mythological and religious subjects to everyday life, they looked for a new kind of model. For the first time, Ms. Butler said, artists used the same model — often a wife or lover — over and over and over again in different paintings and in different scenes.

The switch was related in part to the end of official patronage, which centuries of artists had depended upon for support. The collapse of this system of sponsorship and the beginnings of an art market set off a series of changes for artists, not the least of which was often poverty.

The three artists that Ms. Butler focuses on — Auguste Rodin, Claude Monet and Paul Cézanne — all spotted their models on the streets of Paris, drawn to something unique in a face or manner. All later married and had sons. But the women were often treated badly.

Ms. Butler “provides good reason to look at these artists’ work again,” a reviewer in the British magazine The Spectator wrote, because “each look brings a lost soul back to life.”

Very little is known about Hortense Fiquet, Cézanne’s model and wife, who sat for 27 oil portraits and numerous drawings. Ms. Butler said she tried to get information from their descendants, but they either snubbed or misled her. The feeling in the family, she said, was that Hortense “was a lowlife, that she spent his money.”

“They didn’t like her,” she added.

Leaving the Petrie Court, Ms. Butler walks to the second-floor gallery where two large portraits of Hortense Fiquet are hung. On the right is “Madame Cézanne (Hortense Fiquet, 1850-1922) in the Conservatory,” from 1891. “She’s extremely beautiful,” Ms. Butler says. “Her body is full, round and powerful.” Hortense is in a blue dress, seated in the center of a sunny room splashed in yellows and ochres. Two symmetrical lines form her eyebrows, which sit above a sharply sculptured nose; her pile of brown hair is shaped into a smooth cap atop her head.

A few feet away is “Madame Cézanne in a Red Dress.” It is dated 1888-90, but Ms. Butler says it is almost certainly later than that, pointing to the radical change in style. Hortense is in the same Paris apartment, but the background is colored in cool blues, while the figure tilts to the right, as if she might slide out of the frame. Her right eye is in the shape of a small triangle with an arched eyebrow while the left is narrow and flat. “Her body is flattened out and off-kilter,” Ms. Butler notes. “It’s more abstract, angular.”

This is the last portrait Cézanne did of Hortense. They were living apart, Ms. Butler says, she in Paris, he in Aix. “My conclusion is that she said, ‘Well, I’m going to retire now.’ ”

In another room is a painting that was once titled “Camille Monet on a Garden Bench” but is now labeled “The Bench” (1873), an example of how these women have been erased from history, Ms. Butler says.

The picture was done when the Monets were living in Argenteuil, outside Paris, and were enjoying a flash of financial security. Camille, in an elegant gray-and-black dress, wide eyes and down-turned lips, is seated on a bench blankly gazing out, with a somewhat sinister-looking man hunched over her shoulder.

“Monet and Camille were a wonderful working couple,” Ms. Butler says. “She just loved to pose.”

Ms. Butler mentions an 1876 painting, “La Japonaise,” in which Camille is wearing a blond wig and dressed in a flowing red kimono. Biographers who have claimed that Monet was making fun of his wife in this work were “so remote from what was happening,” Ms. Butler declares. “They were having fun. She was a part of it.”

Nearby is a portrait of the Monets — Claude, Camille and their son, Jean — in their backyard during the summer of 1874 painted by their friend Édouard Manet, whose wife, Suzanne Leenhoff, also frequently posed for him before they were married. Another view of the same backyard scene by Renoir, hangs in the National Gallery of Art in Washington. (Manet is said to have whispered to Monet about Renoir: “He has no talent, that boy. Since you are his friend, tell him to give up painting.”)

Ms. Butler says: “My sense of Camille here is that she’s really adorable. She is seen as a beautiful woman at the center of a classical group.

“This is the high point of her life. She gets sick the following year and they ran out of money. She died four years later.”

The Met’s collection of Rodins, which the artist personally helped select when the museum opened a gallery devoted to his work in 1912, is the best in America, Ms. Butler notes. At the center of the long second-floor hallway is “The Bronze Age,” a large nude sculpture of a man, his right hand clutching his head. It was the first Rodin that the Met acquired, Ms. Butler says, and it had to be returned to the artist initially because the patina was flaking off.

Opposite the statue, behind a glass case, is a small mask of Rose Beuret from about 1880, the only one of her in the collection. She is 36; her eyes are cast down, one brow is slanted, the other curved like a tilde, on the tip of her nose is a smudge.

Although Hortense Fiquet was bewildered by Cézanne’s work, Rose Beuret and Camille Doncieux and Monet were very much partners, Ms. Butler says.

“Rodin and Rose worked together for 15 years,” she says. She ran the atelier before his commission for the “Gates of Hell” in 1880, after which he largely pushed her aside.

Ms. Butler said that in the end, all the women suffered greatly because of their relationships. Hortense Fiquet was nicknamed “la boule” (connoting a ball and chain), while Rodin didn’t marry Rose Beuret until the couple were in their 70s and she was near death.

Still, Ms. Butler wonders: “Would Rose have preferred to live with a railroad worker who came home for dinner every night? Would Camille have preferred to be married to a department store owner who would give her all the dresses she wanted?”

“Probably not,” she answers. “They knew they played a role and they were very proud of their work.”