Abstract
This essay explores the collections of Observationes, whether medicae or chirurgicae, published in Amsterdam from about 1640 to about 1690, or from Nicolaas Tulp to Frederik Ruysch. Since many Observationes were illustrated, I pay special attention to the role of images, with special emphasis on those representing diseased states. The works by Gerardus Blasius appear especially informative about contemporary practices including clinical teaching, physical examinations, postmortems, collecting, and visual representation.