There are moments - certain passages, certain phrases - in this book, where, if you have the misfortune to belong to what might be termed the Radically Squeamish Tendency, you find yourself snapping it shut and urgently seeking some fresh air.

It is no reflection on the quality of Gavin Francis's prose. As he has shown in his two previous books, he is a fine, subtle and observant writer. It is just that the book concerns itself with the landscape of the body, and the chapter on, say, the eye, and cataract surgery, may cause readers of a certain disposition to turn pale. These same readers might not necessarily look forward with keen anticipation to the chapter on the large bowel and rectum, even if this particular body part is, to quote the heading, a magnificent work of art.

Those caveats aside, this is an illuminating and arresting book. Francis is an Edinburgh GP, and he has been around: he has worked as a paediatrician, a physician on a long-stay geriatric ward, a trainee surgeon in orthopaedics and neurosurgery, an expedition medic in the Arctic and Antarctic. His second book, Empire Antarctica, was the Scottish Book of the Year 2013. He is, in other words, an expert guide on this tour of the human body, starting with the brain and making its way to the feet via the head, chest, upper limb, abdomen, pelvis and lower limb.

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The chapters blend literary and historical references, and Francis's own medical training and career ("I lifted a brain from its bucket, blinking at the fumes that rose from the preserving fluids. It was a beautiful object") with the experiences of some of his own patients, their identities so disguised as to render them unrecognisable.

It is the latter that gives the book some of its most genuinely affecting moments. "People who suffer a complete valve failure, if they're conscious at all, have the conviction that they are about to die - and usually they're right," reads a line in the chapter on the heart. One woman collapsed at her 70th birthday party. In the hospital resuscitation room, as the nurses cut off her dress and pearls, she gripped Francis's forearms, exclaiming in horror, "Help me Doctor! I'm dying." Her pulse could not be found; she died within minutes.

Cases like these bring to mind the old question: how do doctors and nurses cope with so much pain and anguish? Doctors, for the most part, he writes, are not emotionally cold, "but become adept at shrugging off the burden of other people's misery".

There is much to fascinate in these pages. Did you know that the high-performance alloys in prosthetic hips, knees and shoulders are why these devices are collected by the crematorium after their owners' death, melted down and turned into precision parts for wind turbines, satellites and aeroplane engines?

Or that the nerve that co-ordinates orgasm, 'pudendal', derives its name from the Latin pudere - 'to be ashamed'? Or that Bell's palsy takes its name from Charles Bell, a surgeon and anatomist of the early 19th century, who came from a distinguished Edinburgh family?

Elsewhere, in order to explain how the body has been understood over the centuries, Francis touches on the Romans' taste for crucifixion, on Homer's Iliad, and Leonardo's superb The Last Supper (which reflected his peerless ability to depict a wide range of facial expressions).

When the bodies of old men are dissected so that medical students can study facial anatomy, some of their zygomaticus muscles, which we use to smile, revealed notable differences: some were thick and well-defined, suggesting that their owners had led laughter-filled lives. Others were shrivelled, implying years of misery.

Here and there, Francis comes up with some crisp, telling little phrases: the patient with a foreign body in his rectum who was, naturally, mortified and who, on being questioned, "flushed an ever deeper scarlet: a senator snapped at a strip club". Or the female patient's estranged mother who struck Francis as being like "a rococo cathedral: high, stately and with an expensively dressed facade".

In its wider sense, this eloquent book (which is dedicated to "life's enthusiasts"), informs the lay reader not simply about the ways in which medical insight has deepened and widened but also about the limitless wonders of our bodies. And, unavoidably, given the subject, some of the ills our flesh is heir to, as well.