- Galen on the Brain: Anatomical Knowledge and Physiological Speculation in the Second Century AD
As someone with both scientific and classical training, with degrees in medicine and philosophy, Julius Rocca is ideally suited to the project he has undertaken in this book: that of examining, in detail, Galen's anatomical and physiological understandings of the brain within their specific cultural context. He offers a full account of Galen's descriptions of the structure and function of the brain, and of how and why they were produced, in practical, epistemological, conceptual, and personal terms. Although Galen's extensive program of animal dissections and vivisections (including various experiments) plays an important part in this story, so does the intellectual background to these investigations—the preexisting ideas and disputes about the brain—as well as Galen's ambition.
The first section of the book fills in this intellectual background. The opening chapter sets out both the development of anatomical understandings of the brain before Galen, and the key classical debate about the location of the hegemonikon: the ruling or controlling principle of the soul. This dispute between those who identified the brain as the governing center and those who preferred the heart was crucial, as were the fundamental conceptualizations of the workings of the human being behind it: They shaped Galen's research into and writing about the brain. His key commitment was to proving, to demonstrating, the brain's hegemonic status.
The second chapter follows with an outline of the methods and materials Galen used in pursuit of this goal. Demonstration was a crucial issue for Galen in his highly competitive environment, and anatomy alone was not sufficient to meet his criteria for certainty. Properly obtained anatomical knowledge also had to fit the formal demands of Aristotelian logic and be part of a wider pattern of physiological (and, indeed, teleological) explanation and understanding. In particular, his construals of the brain's workings supported, and were in turn supported by, preexisting ideas about the role of pneuma, a form of warm air integral to somatic functioning. [End Page 513]
Galen set himself, therefore, an epistemologically impossible task. As a result, his overall project faltered, despite his extensive and judicious use of both ape and ox brains for dissection and his technical proficiency and rigor. Still, as Rocca clearly sets out in the next pair of chapters (supported by the author's own dissections, performed according to Galen's instructions), Galen provides a very impressive account of the anatomy of the brain: one that seems to have been fuller and more descriptively accurate than that which preceded it and also had a new focus on the ventricular system, the part of the cerebral architecture that Galen associated with the hegemonikon. The next part of the book then examines Galen's further investigations into, and theorizations of, ventricular function in this context.
This is where Galen's pneumatic physiology takes center stage. It was the ability of the cerebral ventricles to alter the vital pneuma into its final psychic form—the form in which it supported the soul's governing capacities, such as sensation and voluntary movement—that was crucial in establishing their hegemonic status. This ability was mapped onto the retiform and choroid plexuses, although these ventricular structures did not provide a perfect fit, since the former, for example, is present in oxen but absent in apes and humans. Galen had experimental difficulties in this area too, though his observations of the effects of pressure on, and then incision into, the different ventricles of an exposed brain were successful in confirming their centrality in the animal's controlling consciousness, supporting the identification with the hegemonikon. He stuck to his pneumatic model, though one wonders what the alternatives were, given his other commitments.
The story of Galen and the brain is complex, and Rocca fully embraces this complexity. He provides not only a meticulous analysis of Galen's anatomical and physiological writings, but a steady attention to their wider cultural context...