[Vesalius and the nervous system]

Before we comment the subject of this lecture, we attract the reader's attention towards two remarks. We first want to point out that, although Vesalius is rightly considered as "the father of anatomy", in physiological matters--such as e.g. the physiology of the nervous system--he remained a faithful follower of Galen. A second preliminary remark explains why the books Vesalius devoted to the nervous system, namely the fourth and seventh books, as well as a part of the third book, don't belong to the best parts of the Fabrica, when we compare them with his Osteology and his Myology. We should not forget that some technical discoveries such as keeping brain-tissue in alcohol in order to harden it and colouring methods of Weigert, Marchi and Nissl, that made a refined macro- and microscopic examination of the nervous system possible, were only invented in the 19th century. The fourth book considers the peripheral nervous system. According to Vesalius, there are seven pairs of brain-nerves. His first pair corresponds to our Nervous opticus; his second pair concerns our Nervi oculomotorius, trochlearis and abducens; this third pair embraces a great part of our Nervus trigeminus; his fourth pair corresponds to our Nervus maxillaris; his fifth pair includes our Nervi facialis and acusticus; his sixth pair includes our Nervi vagus and accessorius; his seventh pair our Nervi hypoglossus and pharyngeus. Vesalius counts thirty pairs of spinal nerves. His description of the Plexus brachialis and the Plexus ischiadicus is closely related to the modern views in these matters. However, his teleologic views about them are remarkable, e.g. about the course of the Nervi recurrentes. The seventh book covers the brain. He successively and truly describes the cerebral membranes, the Ventriculi, the Cerebrum; his description relies on a series of horizontal slices. He also describes the brain-stem and the Cerebellum. Vesalius, who had doubts about the existence of the Plexus reticularis in Man, gives a tendentious description of the Infundibulum based on a false physiological theory about the secretion of "pituita", which he considers as the sluggish refuse of the ventricular system. A chapter of the third book is devoted to the blood circulation in the nervous system, with the unavoidable errors derived from Vesalius' galenic theories about blood distribution. We should point out the fact that Vesalius emphasizes quite rightly the metameric blood circulation of the spine. Finally, we should also emphasize the beauty of the images concerning the nervous system in Vesalius' works.