THE NERVOUS SYSTEM. 463 



of the brain upon the nerves of the opposite side. Willis piw ed also 

 that the Rete Mirabile, the remarkable net-work of arteries at the 

 base of the brain, observed by the ancients in ruminating animals, 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 anatomists who pre- 

 ceded him did not reckon. Willis also examined carefully the different 

 Ganglions, or knots which occiir 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 section. Varolius endeavored to unravel it, and was followed by 

 Willis. Vicq d'Azyr, in modern times, has carried the method of sec- 

 tion to greater perfection than had before been given it ; B as Vieussens 

 and Gall have done with respect to the method of Varolius and Willis. 

 Recently Professor Chaussier* makes three kinds of Nerves : the 

 Encephalic, which proceed from the head, and are twelve on each side ; 

 the Rachidian, which proceed from the spinal marrow, and are 

 thirty on each side; and Compound Nerves, among which is the 

 Great Sympathetic Nerve. 



One of the most important steps ever made in our knowledge of 

 the nerves is, the distinction which Bichat is supposed to have esta- 

 blished, of a ganglionic system, and a cerebral system. And we may 

 add, to the discoveries in nervous anatomy, the remarkable one, made 

 in our own time, that the two offices of conducting the motive im- 

 pressions from the central seat of the will to the muscles, and of pro- 

 pagating sensations from the surface of the body and the external 

 organs of sense to the sentient mind reside in two distinct portions 

 of the nervous substance : a discovery which has been declared ' to 

 be " doubtless the most important accession to physiological (anatomi- 

 cal) knowledge since the time of Harvey." This doctrine was first 

 published and taught by Sir Charles Bell : after an interval of some 



Guv. p. 40. * Diet. Sc. Nat. xxxv. 467. 



1 Dr. Charles Henry's Report of Brit. Assoc. iii. p. 62. 



