Talk:Petrus Camper
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To understand the laws of morphology, Petrus Camper demonstrated the principle of correlation in all organisms by the mechanical exercise he called a metamorphosis. In his 1778 lecture, "On the Points of Similarity between the Human Species, Quadrupeds, Birds, and Fish; with Rules for Drawing, founded on this Similarity," Petrus Camper metamorphized a horse into a human being using comparative anatomical physiology. The concept that animals or groups of animals were all variations on one and the same basic plan has been called the "Unity of Plan," a phrase not used by Petrus Camper. The word "metamorphosis," which he favored, came from the Greek, meta or "over" and morphe or "form," refers to a change of form. The underlying similarity between all vertebrates had imporessed many observers for centuries. Plato had his theory of universal Ideas or Forms and Aristotle recognized that the parts were the same in all the animals belonging to the same class, only they differed in "excess or defect" (later known as the "Principle of Correlation"). After the Renaissance, the Unity of Type was recognized by Pierre Belon de Mans, Marco Aurelio Severino, Claude Perrault, Jan Swammerdam, and Gottfried Wilhelm Leibniz. Petrus Camper was preceded by several colleagues in his century. Maupertuis in 1751, Buffon in 1753, Diderot in 1754, Kant in 1763, Robinet in 1766, and Vicq-d'Azyr in 1774 discussed in various fashions the concept of basic anatomical similarity among the vertebrates. Petrus Camper's contribution to the concept of vertebrate uniformity were his graphic metamorphoses, which greatly impressed Denis Diderot and Johann Wolfgang Goethe. In 1923 and 1939 some Dutch authors suggested that Camper foreshadowed Goethe's famous idea of "type" — a common structural pattern in some manner. This is confirmed by Peter Hanns Reill who argues convincingly that the practitioners in the life sciences switched from pure mechanism to "vitalism" in the second half of the eighteenth century. Whereas mechanical natural philosophy focused on two types of force, imparted force and conserved force, Georges de Buffon and his followers added an active or self-activating force, which had a teleological character. The teleological principle reintroduced both development and contingency as explanatory concepts. Progressive development was not continuous, but proceeded through a series of drastic changes, "revolutions," in which the outward form was changed drastically, followed by a gradual development in the newly formed shape. The image often used for these revolutions was "metamorphosis." The goal of mediation between regular development and free creation was to find the similar tendencies between dissimilar things; this hidden organizer was the ground on which all reality rested. In eighteenth-century language, this hidden, informing agent was called by terms such as "internal mold" (Buffon), "prototype" (Robinet), "Mittelkraft" (Schiller), "Urtype" (Goethe), "schemata" (Kant), or "Haupttypus" (Herder). As a comparative anatomist and incredibly skilled draftsman, Petrus Camper could demonstrate the hidden prototype inherent in it's physiology "with a few strokes of the pencil" by progressively tracing one animal into another.
by Miriam Claude Meijer, Ph.D.
