An Irish-born amateur historian appears to have solved one of the great mysteries of Western art, namely how much of his left ear did Vincent van Gogh slice off late on the evening of Dec. 23, 1888.

The answer is, pretty much the entire ear. Until now, the scholarly consensus has been that van Gogh, 35 at the time, severed only his left earlobe, which he then washed, wrapped in newspaper and took as a gift to a prostitute in the southeastern French city of Arles, his home since February, 1888.

However, a search of the archives of writer Irving Stone (1903-1989), whose best-selling 1934 biographical novel Lust for Life did so much to both stoke and fix the public’s image of van Gogh as the suicidal genius/madman recognized only in death, has uncovered a detailed, annotated illustration by the internist who tended the legendary painter’s wound on Christmas Eve day, 1888.

The search was undertaken in 2010 at the Stone archives at the University of California, Berkeley, at the behest of historian Bernadette Murphy. She includes the first-ever reproduction of the diagram in her book Van Gogh’s Ear, published Tuesday, under what has been until now great secrecy, in the United States, Canada, England, Germany and the Netherlands.

Murphy also presented her findings on Tuesday morning at a media conference at the Van Gogh Museum in Amsterdam, which is about to host a nine-week exhibition titled On the Verge of Insanity: Van Gogh and His Illness.

In the course of her decade-long research into van Gogh’s life and death, Murphy discovered that Stone, while working up what became Lust for Life, had actually visited Arles in August, 1930, and met with van Gogh’s physician, Félix Rey. At some point in their conversation, Stone asked the 65-year-old Rey if he would kindly draw an illustration of van Gogh’s injury. The doctor tore off a page from his prescription pad and proceeded to draw, in black ink, a picture of the artist’s ear before he attacked it with a cut-throat razor and a picture of it afterward. The top picture has a dotted line clearly showing the trajectory of the slice while the bottom reveals a tiny remnant of the lobe.

An illustration done by Dr. Félix Rey, who tended to van Gogh’s ear wound on Dec. 24, 1888 in Arles.

At the bottom of the page, Rey says he’s “happy to give [Stone] the information you have requested concerning my unfortunate friend. I sincerely hope that you won’t fail to glorify the genius of this remarkable painter, as he deserves.” (After van Gogh recovered from his injury, he “went to great lengths to hide the wound,” Murphy writes, “purchasing a hat immediately after leaving the hospital.”)

Murphy, who has never published a book until now, argues that van Gogh’s action, while certainly the work of a mentally and emotionally disturbed individual, was not “a completely random act of self-harm” but something at once “deliberate and conscious.”

Indeed, in her book, she claims to have discovered the identity of the woman to whom van Gogh gave his ear as “a personal, intimate gift,” which, she goes on to say, was “meant to alleviate what he perceived as her suffering.”

The traditional story of the gift has van Gogh, distraught over the imminent departure of painter Paul Gauguin from Arles after a failed attempt at creating a sort of artistic brotherhood there, taking the ear to a brothel, where he gives it to a prostitute named Rachel. “Keep this object carefully,” he tells her before fleeing into the night.

Murphy claims that Rachel was not a prostitute but rather a chambermaid in Arles’s red-light district, that her real name was Gabrielle and that as a child she had been seriously bitten by a dog. Van Gogh, Murphy says, saw the 19-year-old Gabrielle as “a wounded angel.” (Prostitution, Murphy notes, was legal in France until after the Second World War, but prostitutes had to be at least 20 years old.) Further, she says she has contacted Gabrielle’s living relatives, but, at their request, is keeping Gabrielle’s surname a secret “until I am given permission by the family.”

Another apparent coup for Murphy is her debunking of the long-circulating story that had dozens, even a hundred or so, of Arles residents signing a petition in late February, 1889, urging the mayor to return the recovering van Gogh to his family or, failing that, put him in an asylum. Murphy reproduces the petition, revealing that it has only 30 names in a city that had a population of 15,000 at the time. She also notes that at least four of the signatures are likely forgeries as the signatories were illiterate. Moreover, virtually all the signatories had close ties to Bernard Soulè, a real-estate agent who wanted to break van Gogh’s lease, and François Crévoulin, whose grocery store was adjacent to van Gogh’s home.

As of this writing, Murphy remains something of the mystery woman to van Gogh’s mystery man. Repeated requests to her publisher for additional biographical information were not answered. In Van Gogh’s Ear, only the skimpiest of details are provided. At one point, she writes: “I, too, am the outsider, and I have had to confront confusion, prejudice and presumption.” As for her van Gogh fascination, its wellsprings are explained very vaguely: “I had health problems. … I had plenty of time on my hands. … I have enjoyed unravelling puzzles.”

Doubtless this obscurity will become less obscure as both she and Van Gogh’s Ear make their rounds and the findings are debated and tested by the van Gogh establishment.