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Part II. Secretion and the Mechanical Organization of the Body: Glands as the Centerpiece of Malpighi’s Investigations
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p a r t t w o secretion and the mechanical organization of the body Glands as the Centerpiece of Malpighi’s Investigations At the beginning of the seventeenth century glands occupied a minor area in anatomy. Thomas Wharton’s 1656 treatise specifically devoted to them, Adenographia, marked a turning point after which glands gained a central position on the anatomical stage and retained it for many decades. Although Wharton’s work provided a description and taxonomy of the glands of the entire body and functioned as a catalyst for further investigations, later anatomists provided a different classification and understanding of their operations. Franciscus Sylvius introduced the distinction between conglomerate , or composite, and conglobate, or simple, glands—associated with the lymphatic system. Many anatomists identified a wealth of glands unknown to Wharton, such as the lachrymal glands, the parotids, and other glands in the digestive tract and reproductive organs. Crucially, the revival of glands and the identification of many organs as glandular were major aspects of the new anatomy, enabling a mechanistic explanation of many operations. Whereas Wharton believed that glands selectively attracted a fluid from the nerves, Steno and most later anatomists believed that glands mechanically filtered arterial blood. Malpighi’s microscopic investigations led to a reclassification of body parts such as the liver, cerebral cortex, kidneys, and spleen as glandular, thus operating mechanically. Glands were the main—although not the only—body part attracting the attention of anatomists with regard to the body’s organization, however. On the one hand, fat proved a challenge to the mechanistic thinking of Descartes and Malpighi, not so much for its origin, which Malpighi located in the conglobate glands, as for its purpose. On the other hand, blood became a focus of attention both because it was the fluid filtered by glands and because of the recent spate of investigations on blood transfusions involving animals and humans, a procedure with significant anatomical as well as medical implications. 104 Secretion and the Mechanical Organization of the Body Here we shall witness the growth of a range of techniques of investigation aimed at grasping the structure and mode of operation of glands: besides the refinement and creative deployment of techniques that we have seen in part I, such as microscopy, injections, vivisection, and the microscope of nature, they involved maceration in water and other liquids, staining, chymical analysis, and the reliance on pathology, whereby diseased states hardening and enlarging the affected body parts made them witnesses to the anatomical structure and especially the glandular composition of many organs. I have called these techniques “mining for stones” and “the microscope of disease.” In the 1664 De musculis et glandulis, Steno traced the very beginning of the revival of glands to a single sheet, published in 1642 by the Padua prosector Johann Georg Wirsung, announcing the discovery of the pancreatic duct. The sheet, which was circulated among distinguished anatomists of the time, shows a sausage-shaped pancreas between the spleen ll on the right and the intestine g on the left, where h is the bile duct. The pancreatic duct cc with its ramifications dd runs across the length of the pancreas, below the artery ff and the vein ee. Although several inadequacies in this rather primitive plate were soon pointed out, following Steno, we can take it as marking a first stage of the revival of glands in the seventeenth century. Figure PII. Johann Georg Wirsung: pancreas with its duct ...