Further essays by the prolific physician-writer (Et Cetera, Et Cetera, 1990, etc.). Most of these 14 essays (some based on lectures, others revised from Foreign Affairs, Missouri Review, etc.) bear the Thomas watermarks of elegant prose and humanistic values--although sometimes (as in "Fifty Years Out," about all the subjects Thomas still wishes to explore), the impression is water-thin. More substantial are the pieces on AIDS, in which Thomas happily reports that "the work, in short, is going beautifully" but adds that "it is still in its early stages." A few ideas keep cropping up (repetitiveness is a problem here)--for instance, that we all share an "ur-ancestor," a bacteria that lived three or four billion years ago; and that two key discoveries formed modern medicine, one being that traditional methods such as bleeding don't work, the other that antibiotics can kill the disease without killing the patient. Like an oyster working a grain of sand, Thomas accretes around these few facts some glistening pearls of prose--among them, a call for massive public-health programs in the Third World; a look at the Gaia hypothesis; a sermon against war; and a worried appraisal of our failure to provide good preschool education. Invariably, he wants to see crises resolved through scientific research, often high-tech; holistic and alternative medicines take several knocks, which won't endear him to younger readers. A literary stethoscope: polished, professional, predictable.