PRESIDENT CARTER has appointed two men to be head of the Food and Drug Administration -- first Donald Kennedy, who has now returned to Stanford, and recenlty, as a successor, Jere Goyan, dean of the School of Pharmacy at the University of California. Both are scientists, and both were good choices, putting a specialist in a post that needs, but has often lacked, scientific talent.

Mr. Kennedy's main contribution was this: he understood the urgency of explaining to laymen the scientific reason for basing regulatory decisions on animal tests in which small numbers of animals are fed large doses of a chemical that large numbers of humans ingest in small amounts. Such tests form virtually the entire basis for regulating drugs, food additives and other potentially toxic substances. Continuing public confusion over the tests' validity -- generated in large part by the saccharin controversy -- could cripple the FDA'S ability to do its job, and undermine the work of other health and environmental agencies as well. Mr. Kennedy's campaign to explain all this was not completely successful -- note Congress' moratorium on the saccharin ban. But he brought exceptionally articulate and well-reasoned argument to an often emotional debate. Carrying on this public education (including the education of Congress) should be one of his successor's chief priorities.

Unlike Mr. Kennedy, Mr. Goyan's background is in clinical pharmacy -- how drugs act and how they are metabolized by the human body. We can therefore expect a greater emphasis on the work of FDA'S Bureau of Drugs, and this is all to the good. Attention needs to be paid to the control of drugs that may be both safe and effective in controlled laboratory tests but which can be seriously abused in general use -- overprescribed tranquilizers and antibiotics are prime examples. Also, the regulatory morass surrounding over-the-counter drugs needs attention. At the present rate, it will take a decade to remove from the market the many ingredients now being dispensed that may be neither safe nor effective.

But Mr. Goyan's single biggest challenge will be to build on his predecessor's good start in raising the level of scientific excellence at FDA and forging closer ties with those doing basic research outside government. For good regulation of food and drugs demands more than an efficient bureauracy and an ability to distinguish the important from the picayune. It requires the filling in of basic scientific gaps: more knowledge of the infinitely complex chemistry of the human body and a much improved ability to predict -- not just react to -- the effect any given chemical will have.