WHEN I WAS a medical student there was a saying, almost a clich,e even then, that went this way: an internist is a doctor who knows everything but does nothing, a surgeon is a doctor who knows nothing but does everything, and a pathologist is a doctor who knows everything and does everything, but too late.

Like most clich,es, this one has a lot of truth in it. Internists are, generally, doctors who like to sit around and ponder, reviewing laboratory reports and X-ray studies, talking things over with their medical confrMeres before finally prescribing whatever medicines they think will help their patients. Surgeons, on the other hand, like to act as promptly as possible. Pondering is not for them. As one of my former mentors used to say, when, as a resident surgeon, I was trying to decide whether a patient should be treated medically or surgically, "You're a surgeon, dammit Nolen-- Surge!" Surgeons are never happier than when they are operating.

Mark Kramer spent a year in the company of two surgeons, trying to understand the world as they saw it. One surgeon, Russell Stearne, lives in a medium-sized community (50,000 to 100,000 population, I'd guess) and practices but also provides surgical care for subscribers to an HMO (health maintenance organization) associated with a nearby university. Stearne has a relatively busy practice. The average general surgeon in the United States does about three "hernia equivalents" a week; Stearne probably does four or five hernia equivalents a week.

Danny Andersson, the other surgeon Kramer studied, is a specialist in vascular surgery, a specialty which, like heart surgery, didn't even exist 30 years ago. He operates on the blood vessels of the body, cleaning them out when they become plugged with arteriosclerotic plaques, replacing them with plastic grafts when they blow apart or are in danger of doing so, and often bypassing obstructed vessels with grafts which act as detours. He also puts cardiac pacemakers in about 100 new patients each year, an operation which almost never takes more than an hour (Andersson once inserted one in 12 minutes), and for which Blue Shield will pay him $1,000. Blue Shield will also pay $1,750 for cleaning out a carotid artery in the neck (an operation the value of which, in many cases, is dubious) and $2,100 for each aortic replacement. Andersson may charge a bit more than Blue Shield will pay; Kramer doesn't say. One thing I will bet my scalpel on; Andersson doesn't charge less than what Blue Shield or any other provider will pay. I have never yet met a surgeon who charges less than a third-party payer will pay. Andersson earns, he says, a salary "about the same as that of the chief executive operator of a large U.S. corporation." Kramer says, "The size of his paycheck does affront my basic sense of how much good works ought to bring in." I agree--but the problem of appropriate fees is a difficult one, as Kramer makes clear, one to which no one has as yet found a satisfactory solution.

Kramer spent a lot of time in the operating room with each of these surgeons, but he also visited their homes, talked with their patients and parents, listened to them while they dictated operative notes, and stood by while they saw patients in their offices. He finds it difficult to understand how a surgeon can deal with patients who have serious diseases. Here is an exchange between Stearne and Kramer, immediately after Stearne has told a teen-age boy that he has cancer of the lymph nodes; " 'I tell maybe fifty patients a year that they have cancer--usually breast or colon. I didn't give it to them. It doesn't have emotional impact on me. I probably cure more than I don't. The patients get more of a charge out of it that I do.'

" 'What if you were in the patient's shoes and another doctor were giving you the news that you have cancer?'

" 'I don't know how I'd feel. Probably about the same as I feel telling them they have it.'

"Can it be that to be professionalized is to lose touch with all fear and sense of the desperate sweetness of life? Can one become so mechanistic in comprehending one's own somaticism that one might actually have cancer dispassionately? . . . For a few years one of Stearne's senior partners has been assisting in operations on cancer patients, all the while holding his own prostate cancer in check with hormonal treatments. I find the partner's insularity, like Stearne's, awesome."

I don't. Kramer, like most lay people, seems to think it's odd that surgeons don't become deeply involved, on an emotional level, with their patients. It isn't odd at all; if a surgeon becomes emotionally involved with a patient his judgment is apt to become impaired. That's one reason why, traditionally, a surgeon never operates on members of his own family. He (about 95 percent of general surgeons are male) might hesitate to do the operation that should be done to cure the patient because he's reluctant to risk hurting the patient. If he were emotionally involved with every patient on which he operated he would be so devastated after a patient dies, as some patients inevitably do, that he wouldn't be able to function. Surgeons have to be as objective as possible about the patients they treat. This doesn't mean they don't like or care about their patients; they do. But it's essential, if the patient is to be well served, that the surgeon's involvement not be a deep, emotional one.

Kramer's book gives, I think, a realistic view of how surgeons in private practice live and work. His descriptions of operating-room scenes, including the interplay between the nurses, anesthetists and doctors, is vivid and dramatic, but the drama isn't grossly exaggerated as is so often the case when the medical world is portrayed. He tells of one Sunday afternoon when Stearne is interrupted as he reads The New York Times by a call that requires an immediate emergency operation to replace a hemorrhaging abdominal blood vessel. While they're operating, Stearne and his co-workers are totally involved in a critical, technically difficult job. When the operation has been completed, Stearne is quick to get back to his Times. That's exactly the way it is.

Invasive Procedures is not a paean to surgeons, nor is it a hatchet job. It gives a balanced view of a surgeon's world as seen through the eyes of a lay person. Kramer writes about excessive fees, medical politics, incompetent surgeons protected by their colleagues, the inappropriate influence of pacemaker manufacturers on surgeons--all the nasty problems, big and small, that affect the medical world. But he also writes about the dedication to duty, the technical expertise, the devotion to the well-being of patients which he sees. The conclusion he seems to reach, one which I certainly believe to be true, is that surgeons love their work and that if they earned one half or one quarter as much as they do, they'd still want to be surgeons. As Kramer writes, "It must be very gratifying indeed to be on the team that can rescue persons in need." I can assure him that it is.