Physician's engaging memoir also surprises

Lewis Thomas is a medical doctor as well as a critically acclaimed essayist and National Book Award winner. And to judge from his newest book, he must also be the kind of person one values as a friend - a lively conversationalist, amusing but never overbearing or tedious; a thinker with insatiable curiosity about how the world works; a man seldom at a loss to find good reasons for hope; and one who values integrity and compassion.

As for charm, well, here he is describing his humiliations at the hands of a computer - without quite admitting inferiority:

''I have been inputting, as they say, one bit of hard data after another into my brain all my life . . . a great deal held and stored somewhere, or so I am assured, but I possess no reliable device anywhere in my circuitry for retrieving it when needed. . . . Artifical Intelligence is one thing, and I never spend a day without admiring it, but human intelligence is something else again. If I succeed in . . . learning Homeric Greek, it will not be because the impulse to do so came in linear fashion from some prior stimulus. I will have blundered into it, thinking that something else led to it, when in fact that something else was heading in another direction, intent on other business. . . . My own mind, fallible, error-prone, forgetful, unpredictable, and ungovernable, is way over my head.''

Thomas began publishing books about 10 years ago at the urging of friends, long after establishing a solid reputation in his profession. He has been sought after as a researcher (Johns Hopkins, Tulane, University of Minnesota), a medical school dean (New York University, Yale), and an administrator (Bellevue, New York Board of Health, and currently Sloan-Kettering).

Small wonder, then, that the Alfred P. Sloan Foundation commissioned him to produce this new memoir, The Youngest Science: Notes of a Medicine-Watcher (Viking, 260 pp., $14.75), as the fourth in its series of books offering candid insights into professional life within the natural sciences.

This Thomas does, with a pleasingly personal yet profession-wide perspective, and with plenty of surprises. The biggest of them for many readers no doubt will be the reason he calls the field of medicine ''the youngest science.''

For his explanation, we have to back up to about 1918, when young Lewis's physician-father often took the boy along on his rounds. Practically all a doctor of that period had to offer, Thomas writes, was ''faith healing.'' The medicines in those small black bags, he says, did little or nothing to influence the outcome of an illness. Yet patients in their distress and ignorance were eager to invest medical practitioners with power and ability beyond their skills.

The elder Thomas's conversations with his son were ''intended to make clear to me, early on, the aspect of medicine that troubled him most all through his professional life; there were so many people needing help, and so little he could do for any of them. It was necessary for him to be available, and to make . . . calls at their homes, but I was not to have the idea that he could do anything much to change the course of their illnesses. It was important to my father that I understand this; it was a central feature of the profession, and a doctor should not only be prepared for it but be even more prepared to be honest with himself about it.''

In spite of his own skepticism, the elder Dr. Thomas wrote prescriptions. His patients expected them; a doctor who didn't provide them would soon have no practice at all. ''They did no harm, so far as he could see; if nothing else, they gave the patient something to do while the illness, whatever, was working its way through its appointed course.''

The contents of the prescriptions were ''a deep mystery, and intended to be a mystery,'' the purpose being ''essentially reassurance.'' The most popular remedies, Thomas notes, were ''tonics'' for ''bucking up the spirits.'' Opium was their prime ingredient during the 19th century, but after the peril of addiction was noticed (belatedly), alcohol took over. One of the most popular medicines ''for patients with chronic, obscure complaints'' combined tiny amounts of iron, quinine, and strychnine dissolved in ''the equivalent of bourbon.''

Even by the late '30s, when the younger Thomas was enrolled in Harvard Medical School and interning at Boston City Hospital, the purpose of the medical curriculum was to teach students to diagnose and explain, but little else.

''The treatment of disease was the most minor part . . . almost left out altogether. . . . During the third and fourth years of school we also began to learn something that worried us all . . . that we didn't know much that was really useful, that we could do nothing to change the course of the great majority of diseases . . . that medicine, for all its facade as a learned profession, was in real life a profoundly ignorant occupation.''

The major portion of Thomas's book deals with the period since 1937, the year when sulfa drugs made their appearance and started medicine down the road of what he and his colleagues now regard as a bona fide science.

While tracing his impressions as a medical researcher in the Pacific during World War II and at top hospitals and medical schools in the intervening decades , Thomas also recounts the enormous federal funding of medical research in the postwar period and the related explosion in the number of medical schools and their hospitals.

He notes that universities have unwittingly assumed responsibility for a major portion of American health care, and that tightening budgets could soon threaten the very existence of those learning institutions, unless they find ways to divest themselves of their hospitals.

Thomas also surveys the array of developing technology - for studying microorganisms, cell structure, genes, and the farthest recesses of the body. He predicts that medicine will someday explain the mechanisms of disease completely , and thus conquer illness.

Yet many of his comments cast doubt on whether material observation and increased understanding of bodily processes will really be able to answer the ultimate questions about immunity and susceptibility, sickness and wholeness. Thomas writes, for instance:

* The ''rare but spectacular phenomenon of spontaneous remission'' in cancer patients is ''inexplicable but real.''

* ''Hope is itself a kind of medicine. I believe this, although I cannot prove it.''

Commenting on the views of the body's interior made possible by electronics and fiber optics, he observes: ''I have seen a lot of my inner self, more than most people, and you'd think I would have gained some new insight, even some sense of illumination, but I am as much in the dark as ever. . . . I have the feeling now that if I were to keep at it, looking everywhere with lenses and bright lights . . . into the ventricles of my brain . . . or inside the arteries of the heart . . . , I would be brought no closer to myself. I exist, I'm sure of that, but not in the midst of all that soft machinery. . . . I now doubt that there is any center, any passenger compartment, any private green room where I am to be found in residence. . . . I'm glad I'm here outside, wherever that is.''

Thomas seems to be hinting that the essence of man - his intelligence, values , and capacity for good - somehow transcend particles, cells, and bodily mechanisms. One wonders if the search he describes will ultimately lead to a recognition that, as religious thinkers put it, man is spiritual.

In this book Thomas stops short of such speculation. But one also wonders if an observer a century hence - one with the intelligence and honesty of Lewis Thomas - might not come away, knowing as much as the body can possibly tell him, with Thomas's feeling that essentially man is to be found somewhere outside.