"The Mater," referred to several times in the novel, is the Mater Misericordiae, a large hospital run by the Catholic Sisters of Mercy. It lies on the west end of Eccles Street, not far away from Bloom's house near the east end of the street. Since the hospital contained a hospice ward in 1904, characters in the novel associate it with death and dying.
When Mulligan, a medical student, says in Telemachus that he sees people "pop off every day in the Mater and Richmond and cut up into tripes in the dissectingroom," he is referring to two different hospitals: the Richmond Lunatic Asylum (now known as St. Brendan's Hospital) which he has already snidely characterized as “Dottyville," and the Mater Misericordiae, a large and distinguished teaching hospital.
In Hades Bloom passes by the hospital when the funeral procession travels up Berkeley Street (the western end of Eccles terminates at Berkeley). He thinks of the day several weeks earlier (May 23) when a bee stung him in his garden and a young doctor named Dixon treated his wound: "The Mater Misericordiae. Eccles street. My house down there. Big place. Ward for incurables there. Very encouraging. Our Lady's Hospice for the dying. Deadhouse handy underneath. Where old Mrs Riordan died. . . . Nice young student that was dressed that bite the bee gave me. He's gone over to the lying-in hospital they told me. From one extreme to the other." He thinks the same thoughts in Lestrygonians: "Still I got to know that young Dixon who dressed that sting for me in the Mater and now he's in Holles street where Mrs Purefoy." When Bloom arrives at the maternity hospital in Oxen of the Sun, he does indeed encounter "a young learningknight yclept Dixon" there, drinking with the other medical students.
In Oxen Lynch says that "The bedside manner it is that they use in the Mater hospice"—presumably because bedside manner is about all that can be done for the incurables. When Bloom thinks, in Ithaca, of friends who have passed on, he remembers one who died there: "Michael Hart (phthisis, Mater Misericordiae hospital)."