If you want to know how someone feels about life, listen to what he has to say about birth. Augustine’s morbid sense of man’s fallenness is captured in his famous observation “inter faeces et urinam nascimur” – “we are born between feces and urine.” In “King Lear,” Shakespeare sees birth and death as equivalent torments: “Men must endure / Their going hence, even as their coming hither.” Beckett goes a step further, declaring that mothers “give birth astride of a grave.” According to Herodotus, one Thracian tribe put such pessimism into practice, wailing and lamenting around the cradle of the newborn.

The birth-haters, however, have always been in the minority. F. Gonzales-Crussi, whose experience as a doctor has allowed him to witness more of birth and death than most of us, voices the common opinion when he calls the process of birth “without exaggeration, miraculous.” As becomes a scientist, he does not mean this in any vague, “mystico-religious” sense; it is not the infusion of a soul that fills him with awe, but the physics and chemistry and biology that lead the zygote, “a viscid microscopic globule,” through its weird metamorphoses: “an amorphous mass, then a mulberry, a hollow ball, a trilayered disk, and then successively a worm, a tadpole, a fish, a mammal … finally becoming a real human being.” The true mystery and excitement of birth, to Mr. Gonzales-Crussi, is intellectual: “A gooey mass of molecules … becomes a being possessed of the ability to explain how a gooey mass of molecules can become a rational being.”

But “On Being Born and Other Difficulties” is no embryology textbook. It is, rather, a polymathic and digressive essay, a leisurely stroll through the science, history, and mythology of childbirth. Mr. Gonzales-Crussi is a literary descendant of Sir Thomas Browne, the 17th-century doctor-essayist. Like Browne’s “Pseudodoxia Epidemica,” “On Being Born” eagerly compiles errors, myths, and delusions, taking a certain pleasure in the absurdities it is dedicated to refuting. Brownean, too, is the not unappealing awkwardness of Mr. Gonzales-Crussi’s style, with its stiff diction and recondite vocabulary. (Some of this may be owed to his unfamiliarity with English idiom; as he informs us, he is a native Spanish-speaker.)

As Mr. Gonzales-Crussi outlines the state of our scientific knowledge about a series of biologi cal mysteries – the origins of life on Earth, the mechanisms of conception, the development of the embryo, the delicate combat of parturition – he also explores how our ancestors understood and misunderstood them.

Some of the most long-lived errors stemmed from a bewildering contempt for observation. For instance, Aristotle “affirmed that males have more teeth than females,” even though, as Mr. Gonzales-Crussi declares indignantly, “there is no justification for so glaring a blunder. For the question of normal dentition is not a subtle theme of metaphysics admitting of various differing conclusions. It is a question of fact, that could have been settled, as Bertrand Russell once put it, ‘by the simple device of asking Mrs. Aristotle to keep her mouth open while he counted.’ “

Similarly, from ancient Egypt all the way down to the 18th century, it was commonly believed that the uterus could move around inside a woman’s body, wreaking havoc on her mental and physical health in the process. (Thus “hysteria,” from the Greek word for womb.) Mr. Gonzales-Crussi examines several paintings by the 17th-century Dutch master Jan Steen, which depict young women with the classic symptoms of a vagrant uterus – melancholy,weariness,general languishing. Several of these paintings feature the mysterious image of a “length of ribbon close to, or trailing into, a charcoal burner.” Mr. Gonzales- Crussi decodes this detail by explaining that burning ribbon was used as a kind of smelling salt: “strong odors were thought to chase a displaced uterus away from abnormal locations.”

That both of these canards are connected with the alleged imperfection of female anatomy is, of course, no accident. Mr. Gonzales-Crussi is incensed by the ignorant misogyny that for so long distorted medicine’s approach to women’s health. (And maybe still does: Even today, male surgeons are twice as likely as females to order a hysterectomy.)

Often, however, myths about childbirth were well-meaning attempts to deal with facts that everyone could observe, but no one could explain. Thus the 17th-century philosopher Malebranche, confronted with a weirdly deformed stillborn baby, imagined that it resembled Saint Pius, at whose portrait the pregnant mother had often prayed.

In fact, the baby’s upturned eyes, shrunken forehead, and hunched shoulders were likely the result of iniencephaly, a birth defect of the skull. But in Malebranche’s eyes, it seemed highly reasonable that a strong impression made on the mother would directly affect her fetus. Indeed, Mr. Gonzales-Crussi writes, modern medicine confirms that the experience of a pregnant woman – what she hears, eats, drinks – can affect her baby, though not as directly as Malebranche supposed.

These are just a few of the hundreds of fascinating stories and theories that Mr. Gonzales-Crussi assembles. He takes equal care to explain the facts about human childbirth, of course, and these are no less extraordinary than the legends. But the distinctive contribution of “On Being Born” is not this information, which could be found in any number of handbooks for expectant mothers. It is, rather, the humane curiosity of Mr. Gonzales-Crussi, which, no less than his quaint prose, recalls the bygone age when science was honored as “natural philosophy.”