By Christina Ianzito

Henry Marsh’s best-selling memoir, “Do No Harm,” delivered a terrifying peek behind the surgical curtain. A neurosurgeon based in London, Marsh shared some of the more harrowing cases from his decades of experience — the time, for instance, when he removed a tumor on a young woman’s spinal cord and she woke up with half her body paralyzed (“nothing I could do would undo the damage that I had done”). In another operation his target was a thin-walled aneurysm deep within a woman’s brain that if ruptured would either kill her or she’d “at least suffer a catastrophic stroke.” (This one was a success.)

Now in his late 60s and retired from Britain’s National Health Service, Marsh is pondering the end of his own life. After spending a career that brought him face-to-face with so much suffering, he writes, he now hopes “simply to achieve a good death” — “quick and easy” — when his time comes. At home he’s stashed away a suicide kit just in case — a fact he reveals on the first page of his new book, “Admissions.”

But Marsh isn’t hanging it up yet. Much of his book focuses on his post-retirement experiences training surgeons in Ukraine and Nepal. His descriptions of his work there demonstrate again his gift with both scalpel and pen.

In vivid prose, he captures the terrifying risks he faces with each cut, each decision. Here, for example he writes of removing a tumor from the brain of a 6-year-old Nepalese child: “The white corpus callosum came into view at the floor of the chasm, like a white beach between two cliffs. Running along like two rivers, were the anterior cerebral arteries, on either side, bright red, pulsing gently with the heartbeat, which you must not damage under any circumstances.”

And yet, “the child was almost certainly doomed whatever we did.” He explains that the tumor would kill her if it wasn’t removed, yet was too big to completely excise without damaging her hypothalamus, the part of the brain related to hormone production — and “children with hypothalamic damage typically become morbidly obese dwarves.” He finishes knowing her future will be short and probably painful. “There is no pleasure or glory in this kind of operating,” he writes.

Marsh is widely respected in Britain but is sometimes described in news stories as a curmudgeon. He does have a bit of a temper. But it generally takes the form of righteous anger over what he perceives as incompetence and inefficiencies in the health-care system. He admits to feeling deep shame for one extreme incident, two weeks before his retirement, when he was so angry with a nurse for not removing a patient’s needless and painful gastric tube, he shouted, “I hate your guts!”

And yet, it’s hard not to like Marsh, who is so disarmingly self-effacing and honest about his regrets and failures (he didn’t have to include the fact that he once operated on the wrong side of a man’s head, for instance ) and how much he hasn’t learned along the way.

He writes that a long time ago, “I thought brain surgeons — because they handle the brain, the miraculous basis of everything we think and feel — must be tremendously wise and understand the meaning of life.” With age Marsh has come to realize “we have no idea whatsoever as to how physical matter gives rise to consciousness, thought and feeling.” Rather, he concedes. “I have learnt that handling the brain tells you nothing about life — other than to be dismayed by its fragility.”