Critical thinking skills were taught to students in a lower-track freshman English class through the use of cross-disciplinary subject matter. Given a set of three transmission electron micrographs, or photographs of magnified tissue used in histology and pathology, students were asked to support their conclusions on which two of micrographs A, B, and C were alike. In the next two class periods, students were given another set of micrographs, but this time they were asked to determine which one of three micrographs was similar to micrograph A. As before, the students determined very quickly which micrographs were similar, but had difficulty defending their conclusions. As an aid in differentiating the photographs, students were asked to jot down each micrograph's characteristics. While examining their material, students realized that some ideas were not arranged logically or consistently. They noted, too, that the ordering of items was not consistent and reordered them. From these reordered notes, students made an outline and wrote a paper. This approach helped students recognize analysis; demonstrated the relationship of perceptual, thinking, and writing skills; provided an assignment related to another discipline; connected the process of prewriting to writing; provided a realistic context for comparison/contrast and for classifying and ordering ideas; and demonstrated the necessity of close observation and precision of expression. (Materials used in the study are appended.) (HOD)