KAFKA TO THE BONE : What it might feel like to wake up in Kafka’s skin : FRANZ KAFKA: The Jewish Patient,<i> By Sander L. Gilman (Routledge: $18.95, paper; $65 cloth; 327 pp.)</i>

Why are we so obsessed with Franz Kafka? Some critics argue that his intellectual concerns make him the most representative writer of the 20th century. Yet his enduring appeal surely lies also in the visceral quality of his writing.

Kafka’s textual conundrums are always rooted in the most private anguish, in the need, as he himself once put it, to convey something incommunicable, “which I have in my bones and can only be experienced in these bones.”

One of the strengths of Sander Gilman’s psychohistorical study, “Franz Kafka: The Jewish Patient,” is that it focuses on some of Kafka’s most intimate obsessions. Gilman explores the links between Kafka’s reflections about his body, his masculinity, his tuberculosis and his Jewishness and the centuries-old discourse about the supposed differences between Jews and Christians.

Gilman, a prolific scholar who teaches at the University of Chicago, brings to this task vast erudition in German literature, the history of medicine and the representation of Jews and other outsiders in Western culture.

Gilman’s account of the depiction of Jews in popular and high culture of middle Europe makes for fascinating, horrific reading. Jews were believed to have bodies different from those of Christians or--even more ominously--Aryans.

The litany of traits attributed to Jews and their rituals was self-contradictory. Ritual circumcision was believed to spread tuberculosis and weaken Jewish masculinity. Yet Jews were also said to be less likely to contract TB than their Christian compatriots. They were prone to neurasthenia, skin disease and hypochondria. Such prejudices were not confined to Central Europe. Gilman cites the English scientist Sir Francis Galton, who believed that there was such a thing as a “Jewish gaze” common to Jews everywhere.

Here is Gilman’s explanation of the bewildering range of traits attributed to Jews: “At the turn of the century, Jews are both the archbankers and the archrevolutionaries, both the false nobility of Paris and the Wandering Eastern Jews of Warsaw, all things to all groups who need to define outsiders.”

Ultimately, he argues, the obsession with Jewish physical difference led to the barbaric experiments on the bodies of Jewish children at Auschwitz, where Kafka’s favorite sister, Ottla, was murdered. His two other sisters also died in the death camps.

That historical context helps to explain some of Kafka’s seemingly bizarre personal habits: Embracing the theories of a 19th century American food faddist, Horace Fletcher, Kafka insisted on chewing his food over and over again, thereby forcing his father, Hermann Kafka--not the quietest of eaters himself--to retreat behind the newspaper. In winter he used to exercise naked with the window open.

Such oddities seem less strange when seen in the context of Jewish fears about those notions of Jews’ proneness to disease and, in the case of males, effeminacy. The latter fears were further exacerbated by the rise of the athletic German youth movement. In response, Jewish activists called for “muscle Jews” who would excel physically.

Seemingly bizarre remarks of Kafka’s, such as his telling lover Milena Jesenka that Christians saw “the same Negro face” in all Jews, suddenly begin to make sense. That particular observation, Gilman informs us, comes from a common stereotype in anti-Semitic lore: the black Jew.

Gilman also draws intriguing parallels between the memoirs of the French officer Alfred Dreyfus--accused of being a traitor in the notorious anti-Semitic trial--and Kafka’s grim story “The Penal Colony.” Included in the illustrations are Dreyfus’ drawing of the bed into which he was strapped, which Gilman associates with the torture machine in the story and with Kafka’s drawing of himself as a torture victim in the margins of a letter to Milena.

These are suggestive connections. Yet Gilman goes too far when he claims that Kafka was “haunted” throughout his life by the Dreyfus trial. To my knowledge, there is only a single reference to Dreyfus in Kafka’s entire correspondence.

Unfortunately, Gilman takes one of his main cues from the work of two French philosophers, Gilles Deleuze and Felix Guattari, whose elaborate theory about “minor literature” is based on an elementary misreading of a straightforward Kafka text. Although he admits that the inventive duo misinterpreted what Kafka meant by minor literature, he nonetheless adopts their notion that writers like Kafka are afraid of becoming their “imaginary father’s body.”

Hermann Kafka, a self-made businessman, was a solid block of a man, every inch the butcher’s son that he was. Franz Kafka, on the other hand, did not have an ounce of superfluous flesh. On physical grounds alone, one can see why Kafka did not regard himself as a Kafka.

In the famous “Letter to Father,” he specifically identified himself as a Lowy with certain Kafka traits--Lowy being the maiden name of his mother, whose ancestors included rabbis as opposed to butchers. Though Gilman cites this passage, he is so intent on showing that the “Letter” is about Kafka’s “own body’s predestination to become his father’s” that he ignores Kafka’s main point. Close readers of Kafka are unlikely to be persuaded by his far-fetched interpretation of this key autobiographical text.

Gilman flattens the complexity of Kafka’s ambivalent Jewishness when he argues that he was afraid of “becoming the Eastern Jew, whom he imagines as poor, ill, unable to command the language of high culture.” Many Central European Jews did fear and despise the Eastern Jews, but Kafka was not among them. In the diaries, he does make a few caustic comments about wonderworking rabbis and their followers.

Yet he also envied the unproblematic Jewish identity of the Eastern Jews who, unlike himself, still lived in an intact Jewish community. In his daydreams he imagined the very different life that he might have led had he been born in an Eastern shtetl. Far from being afraid of becoming an Eastern Jew, he took the unusual step of publicly exhorting the assimilated German-speaking Jews of Prague to overcome their fear of Yiddish.

Gilman brings fresh air into the often claustrophobic world of Kafka studies. He shows that the perspective of the social historian--whether of medicine, psychiatry or anti-Semitism--can illuminate some dark corners in our understanding of Kafka.

However, in his eagerness to ground Kafka’s metaphors in the general discourse about Jews, he downplays the irreducible otherness of Franz K. Certain things about Kafka are bound to elude us forever. He was mystified by his own ability to transform the unhappiness in his bones into art.

He suspected that his writing came from a “merciful surplus of strength” that permitted him to “ring simple, or contrapuntal . . . changes” on his basic theme of unhappiness. “But then what kind of a surplus is it?” he asked. He had no idea, nor do we.