"I'm curious, doctor," the congressman began matter of factly. Then he popped a question to Dr. Vincent T. DeVita, Jr. about other nation's efforts in the fight against cancer.

The question, warm and seemingly spontaneous, was asked at a hearing the other day by Rep. William H. Natcher (D-Ky.). chairman of the House Appropriations subcommittee for Labor-HEW.

Only the question wasn't Natcher's. It was written -- even with the "I'm curious, doctor" led-in -- by an obscure public employe who is as vital to the lawmaking process as the people elected to make the laws: the congressional staff assistant.

Which is not to say that William H. Natcher does not think for himself. It is only to say that the business of legislating is so complex, so tim-consuming and so voluminous that it could not go on without the staff assistant.

Take, for example, the $3.6 billion appropriation President Carter is asking Congress to provide for operation of the National Institutes of Health for fiscal 1981.

The Constitution requires that Natcher and the members of his subcommittee review the president's spending requests. But the NIH budget, which is huge, is only a fraction of what the subcommittee must master.

That is why, when DeVita appeared the other day to defend the $1 billion portion of the NIH budget for his National Cancer Institute, several subcommittee staff assistants were stationed strategically behind the members.

They were there to help pose questions of the type that Natcher was pursuing about cancer research abroad -- seemingly obscure, but in fact not. The chaiman's line of inquiry took DeVita into an explanation and defense of research going on overseas with $10 million of NIH money.

Similarly, Natcher asked other detailed questions about NCI budgeting for studies on the use on Interferon, a promising cancer drug from Europe that has excited many members of Congress.

That excitement last year translated into pressure, and Congress earmarked money forcing NCI to move more quickly on Interferon. Pressure continues, and the subcommittee will be hearing more about Interferon when public health lobbyists testify soon.

As Natcher interrogated witnesses, his subcommittee staff director, Henry A. Neil Jr., a solemn-faced man with a Kojak hairdo, sat vigilantly at his side, ready to provide help and suggest questions.

When Rep. Silvio O. Conte (Mass.), the ranking Republican on the Appropriations Committee strolled in his GOP staff assistant, Jim Fabiani, quickly brought him up to date and slipped him some prepared questions.

By the time Natcher's House subcommittee and its Senate counterpart, headed by Sen. Warren G. Magnuson (D-Wash.), have decided how to deal with the NIH budget they will have heard dozens of witnesses and compiled a record of several thousand pages.

Staff assistants, unknown people like Neil, Fabiani, Terry Lierman, Gar Kaganowich, Marcia McCord, Scott Lilly and others, will play an essential role in the development of the NIH appropriation.

If you picture Congress as a theater and its members as lead actors in the drama of legislation, then it becomes clear that there must be script writers, stage managers, prompters and gofers.

Those are the roles filled by congressional staff assistants, mostly bright, mostly energetic and mostly well-paid men and women. Their job is (a) to be anonymous, (b) to understand what's going on, (c) to be alter egos and devil's advocates and (d) to be anonymous all over again.

Sometimes they are too bright and energetic. Several years ago, Harley Dirks, then the head of the Senate Labor-HEW staff, resigned when it was learned he produced a Broadway-quality hearing record on the NIH budget.

The hearings had been canceled. Dirks took prepared questions that would have been asked matched them with answers NIH provided for the record, inserted "good mornings" and "thank-yous" at the appropriate points and had the whole thing printed as an official record.

Dirks went on to success as a lobbyist for the American Medical Association, but the memory of the bogus-hearing caper lingers on Capitol Hill and makes Labor-HEW subcommittee staff members ultra-sensitive about their roles and publicity.

After Dirks left in 1976, his job was taken by Terry L. Lierman, a management specialist who had worked in five of the 11 NIH biomedical research institutes before he joined the subcommittee in 1973.

"Good staff knows what the committee members want," Lierman said recently. "Sen. Magnuson says that health matters should be nonpartisan, and you can see by the way this subcommittee operates, that it is."

Republicans chair the subcommittee meetings as much as Democrats. Lierman and his GOP counterpart, kaganowicn, in effect work for members of both parties offering questions and guidance on the NIH issues.

On the House side, Neil and Fabiani perform similarly. Neil has been with the subcommittee since 1969, doing essentially the same kind of questioning and priority-setting he had done during the previous 10 years as a budget officer dealing with NIH inside the Department of Health Education and Welfare.

If Neil and Lierman typify the staffers with extensive backgrounds in health matters, Jim Fabiani and Scott Lilly represent another side -- the staffer who must learn quickly and certainly which end is up.

Lilly handled NIH and other health issues for Rep. David R. Obey (D-Wisc.), a subcommittee member. Before he went to work for Obey seven years ago, he was a Democratic campaign worker.

His job is to know more about NIH than Obey, who takes a keen interest in the agency, will ever dare ask. "A good staffer will know the member well enough to structure questions properly and raise the issues that are important," Lilly said.

"A problem is that any other member is outgunned by the agency. NIH will flood you with information, but they don't provide the data that helps on policy. Any director can convince you that the best use of an extra $100 million is in their institute. The subcommittees have to be able to dig under that surface sales job -- and we really haven't a good way to deal with that," he said.

Fabiani is the subcommittee's lone GOP professional staffer, hired last year by Conte. After nine years as dean at the Deerfield Academy in Massachussets, and with no health or budget background, Fabiani still is somewhat awed.

"Some days I find myself discouraged, when I'm going off on tangents. But then other days it works well -- I see someone like Mr. Obey walk in here and target things and it all gets done," Fabiani said.

"The job is to synthesize and digest, gather information. Henry Neil and I have gone out to NIH and visited institutes, gathering data that the members don't have time to do. We cooperate closely with the majority side. I lean on them and they lean on me for help."

Time is always the problem, Sen. Thomas F. Eagleton (D-Mo.) made the point adroitly but unwittingy at a recent hearing of the Senate subcommittee, where he was putting the NIH director, Dr. Donald Frederickson, through a wringer over fiscal 1981 research spending increases.

Frederickson told Eagleton that a major new HEW study had just been completed on health research needs, and thereupon handed the thick document across the table to the senator.

Eagleton perused it for a moment, then passed it over his shoulder to Marcia McCord, his staff adviser on NIH and other health issues.

"Read that by noon," Eagleton said. Everyone laughed, including McCord, but everyone knew the document would soon become part of her bedside reading stack.