bichat's main contribution to medicine and physiology was his perception that the diverse body of organs contain particular tissues or "membranes", and he described 21 such membranes, including connective, muscle, and nerve tissue. bichat did not use a microscope because he distrusted it; therefore his analyses did not include any acknowledgement of cellular structure. nonetheless, he formed an important bridge between the "organ pathology" of giovanni battista morgagni and the "cell pathology" of rudolf ludwig carl virchow.