to Orthodox Jewish practice, modern-day kohanim are obligated to guard against ritual defilement as prescribed by the Talmud. In order to protect them from coming into contact with or proximity to the dead, Orthodox cemeteries traditionally designate a burial ground for kohanim which is at a distance from the general burial ground, so that the sons of deceased kohanim can visit their fathers' graves without entering the cemetery. They are also careful not to be in a hospital, airplane, or any enclosed space where dead bodies are also present. Exceptions to Tumah defilement The Talmud prescribes that if a kohen, even the Kohen Gadol, chances upon a corpse by the wayside, and there is no one else in the area who can be called upon to bury it, then the Kohen himself must forgo the requirement to abstain from Tumah and perform the burial (Meis Mitzvah). The Talmud also permits the Kohen to defile himself in the case of the death of a Nasi (Rabbinic leader of a religious academy). The Talmud relates that when Judah haNasi died, the Priestly laws forbidding defilement through contact with the dead were suspended for his burial ceremony. Marital defilement A male Kohen may not marry a divorcee, a prostitute, or a dishonored woman () () A Kohen who enters into such a marriage loses the entitlements of his priestly status while in that marriage. The Kohen is not permitted to forgo his status and marry a woman prohibited to him (). However, in the event that a Kohen transgresses a marital restriction, upon termination of the marriage the Kohen is allowed to re-assume his function and duties as a full Kohen. Modern-day kohanim are also prohibited from marrying a divorcee (even their own divorced wife); a woman who has committed adultery, had been involved in incest, or had relations with a non-Jew; a convert; or the child of two converts. A born-Jewish woman who has had premarital relations may marry a kohen only if all of her partners were Jewish. The daughter of a Jewish mother and non-Jewish father, while halakhically Jewish, is prohibited from marrying a kohen according to the Shulchan Aruch, reiterated by Rav Moshe Feinstein. Due to a small doubt about this in the Talmud (Yevamos 45A-B), if such a marriage is performed the couple would not have to get divorced, see Shulchan Aruch 4:19. The sons of such a