42 



HANDBOOK OF I'H\SIOLOGY 



NEUROPHYSIOLOGY I 



FIG. 27. Thomas Willis and the illustration of the base of 

 the brain taken from his book De cerebri anatome. The circle of 

 Willis, named for him, had been depicted by several anato- 

 mists before him. Willis was fortunate in having Christopher 

 Wren as his illustrator. 



was not .solely concerned with vision but that it car- 

 ried the stimulus that led to the contractile response 

 of the iris to light. In the post-mortem examination 

 on a child with fixed pupils he found a lesion blocking 

 the inflow from the optic nerves to the thalamus and 

 inferred that this impairment of sen.sory inflow was 

 responsible for the motor deficit that had been the 

 clinical sign. This was indeed the recognition of a 

 reflex arc, and the pupillary reflex was for many years 

 known by his name. 



As noted above, Willis had di.ssected the spinal 

 accessory nerve to its junction with the cord but he 

 believed it to convey voluntary control. Lacking a 

 .scientific acumen equal to his skill as a dissector, and 

 influenced by Galen, he thought this nerve anasto- 

 mosed with the vagus (the "wandering' nerve). 

 Schneider, on the other hand, had no doubts as to 

 the action of the olfactory nerves for it was his work 

 on the nasal mucosa and olfactory processes that led 

 to his identification of them. Willis also was aware of 

 their function for he called them the 'smelling' nerves. 

 He noted that within the skull they had 'mammillary 

 processes' and said, "As to the Fibres and Filaments 

 or little strings stretching out from the more soft 

 nerves through the holes of the Sieve-like Bone into 

 the caverns of the Nose, these are found in all Crea- 

 tures who have the mammillary Processes: so it is 

 not to be doubted, but that these Processes, with this 

 appendix and its medullary origine is the Organ of 

 Smell."-' Willis called in his knowledge of compara- 



" The quotations arc from Pordagos translation (1683) of 

 Willis, T. Cerebri anatome: cui acces\it nervorum descnpho el usus. 

 London: Flesher, 1664. 



five anatomy and noted that "the filaments or little 

 strings" of the organ of smell were "more remarkable 

 in hunting Hounds than in any other Animal whatso- 

 ever. 



The ner\es that had ijoth sensory and motor 

 branches proved the most difficult. Magendie (238) 

 at first thought the fifth nerve was sensory and nutrient 

 to the face, and the seventh nerve entirely motor, 

 since cutting it caused facial paralysis without reliev- 

 ing neuralgia. In 1820 Charles Bell (147), dissecting 

 the nerves of the face, noticed that the fibers of the 

 seventh nerve went to muscle whereas those of the 

 fifth entered the skin. He suspected they .served diff'er- 

 ent functions, and being himself an anatomist rather 

 than an experimentalist, asked his brother-in-law, 

 John Shaw, to make a study of the effect of sections 

 of these nerves. Using an unusual experimental 

 animal, the donkey, Shaw was able to demonstrate 

 paralysis in the one case, loss of reaction to touch in 

 the other; neither he nor Bell whose fine drawings 

 illustrate his findings recognized the mixed nature of 

 these nerves. After this beginning several workers 

 added their contributions to the further clarification 

 of the cranial nerves, prominent among these being 

 Mayo (239) (who taught the course in anatomy and 

 physiology at King's College, London). 



It was only in the eighteenth century that doubt 

 was first thrown on the assumption that the sympa- 

 thetic trunk (or 'intercostal' nerve, as it was then 

 called) was an appendage of the brain. This grew 

 from the transection experiments of Pourfour du 

 Petit (240) and his oijsers'ations on contraction of the 

 pupil. For centuries anatomists had shown this nerve 

 as stemming from the brain. V'esalius (7), in his 

 drawings of the human nervous system, put it in one 

 trunk with the vagus. (In the dog, though not in man, 

 the two nerves lie in the same sheath in the neck 

 region.) Eustachius (241) separated the two, but like 

 many after him, including Willis, he depicted an 

 intracranial origin. These drawings of the anatomists 

 must have been designed to be consistent with Galen- 



■238. Magendie, F. J. physiol. exper. et path. 4: 176, 302, 1824. 



239. Mayo, H. Anatomical and Physiological Commentaries. 

 London: Underwood, vol. I, 1822; vol. II, 1823. 



240. Pourfour du Petit, Franqois (1664-1741). Memoire 

 dans lequel il est demonstre que les nerfs intercostaux 

 fournissent des rameaux que portent des esprits dans les 

 ncrfs. Hnt. Acad. ray. Sc. Paris i, 1727. 



241. Eustachius, Bartolommeo (1520-1574). Tabulae anato- 

 micae (posthumous). Rome : Gonzaga, 1 7 1 4. 



