466 HISTORY OF PHYSIOLOGY. 



this subject 3 . Thus he is the first who describes 

 in a distinct manner what has been called the 

 nervous center*, the pyramidal eminences which, 

 according to more recent anatomists, are the com- 

 munication of the brain with the spinal marrow : 

 and of which the decussation, described by Santo- 

 rini, affords the explanation of the action of a part 

 of the brain upon the nerves of the opposite side. 

 Willis proved also that the rete mirabile, the re- 

 markable net-work of arteries at the base of the 

 brain, observed by the ancients in ruminating ani- 

 mals, does not exist in man. He described the 

 different pairs of nerves with more care than his 

 predecessors ; and his mode of numbering them is 

 employed up to the present time. He calls the 

 olfactory nerves the first pair; previously to him, 

 these were not reckoned a pair : and thus the optic 

 nerves were, as we have seen, called the first. He 

 added the sixth and the ninth pairs, which the ana- 

 tomists who preceded him did not reckon. Willis 

 also examined carefully the different ganglions, or 

 knots which occur upon the nerves. He traced 

 them wherever they were to be found, and he gave 

 a general figure of what Cuvier calls the nervous 

 skeleton, very superior to that of Vesalius, which 

 was coarse and inexact. Willis also made various 

 efforts to show the connexion of the parts of the 

 brain. In the earlier periods of anatomy, the brain 

 had been examined by slicing it, so as to obtain a 

 3 Cuv. Sc. Nat. p. 385. 4 Ibid. 



