Frog Models, Artisans, and Academic Controversy

Knowledge of frog anatomy could be distributed in several ways, many of which required the assistance of artisans like Adolf Ziegler or his son, Friedrich. Academic agendas and commercial interests shaped the relationships between such craftsmen and scholars.

During Ziegler's time, comparative developmental anatomy was a thriving field of research into the animal world, and a home for heated debates about Darwin's new evolutionary theories. From the 1870s, the discipline was riven by controversies over ideas proposed by Ernst Haeckel, a zoologist at the University of Jena. He held that the embryonic development of organisms recapitulates the evolutionary transformations of their ancestors. Common evolutionary origins could therefore be observed in the structural similarities of early embryos. Opponents sought to discredit Haeckel's lofty theorisations by questioning the accuracy of his published images. This placed the quality of formal representations - image and models - at the center of scientific conflicts. As a producer of scientific images in wax, Ziegler found himself in the middle of this melee. But he maintained a cautionary intellectual posture that ensured him the commercial patronage of each side.

Though Adolf Ziegler developed his own reputation for scientific sophistication, most models were produced in tandem with the university professors that conducted these debates. Ziegler had based his original frog embryo series on a set of prints published in 1851 by Alexander Ecker, a professor of physiology and comparative anatomy from the University of Freiburg. Ecker also wrote a textbook on the anatomy of frogs due to their widespread use. He aimed to better inform those researchers that sustained the frog's position as "a commonplace on the altar of science" by using it in their experimental or anatomical work (1). For the primordial skulls, the elder Ziegler worked with a Professor Philipp Stöhr, specialist in histology, evolution, and embryology at the University of Würzburg.

These partnerships assured clients of the models' accuracy, for many believed that a mere artisan (as Ziegler and his colleagues were often perceived) could not be trusted to see and represent the embryo with adequate skill or discernment. Some academic researchers, however, such as Wilhelm His, questioned this division between the work of the hand and the work of the mind: "Just as I regard complicated spatial relations as only really understood when they are available as plastic representations, so too I consider the model, even more than the written word, the decisive record of the understanding of form of the researcher concerned," he wrote (2). Models, like Ziegler's of frog embryos and primordial skulls, were not only for teaching, but also for producing, communicating, standardizing, and laying claim to the frontiers of biological knowledge.