i62 HISTORY OF PHYSIOLOGY. 



higher principle, of a more peculiarly physiological kind. But it may 

 still be instructive to notice a case in which the principle, which is 

 thus brought into view, is far more completely elevated above the 

 domain of matter and mechanism than in those we have yet con- 

 sidered ; a case where we have not only Irritation, but Sensation ; 

 not only Life, but Consciousness and Will. A part of science in 

 which suggestions present themselves, brings us, in a very striking 

 manner, to the passage from the physical to the hyperphysical sciences. 

 We have seen already (chap, i.) that Galen and his predecessors had 

 satisfied themselves that the nerves are the channels of perception ; a 

 doctrine which had been distinctly taught by Herophilus 1 in the Alex- 

 andrian school. Herophilus, however, still combined, under the com- 

 mon name of Nerves, the Tendons ; though he distinguished such 

 Nerves from those which arise from the brain and the spinal marrow, 

 and which are subservient to the will. In Galen's time this subject 

 had been prosecuted more into detail. That anatomist has left a Trea- 

 tise expressly upon The Anatomy of the Nerves ; in which he describes 

 the successive Pairs of Nerves : thus, the First Pair are the visual 

 nerves : and we see, in the language which Galen uses, the evidence 

 of the care and interest with which he had himself examined them. 

 " These nerves," he says, " are not resolved into many fibres, like all 

 the other nerves, when they reach the organs to which they belong ; 

 but spread out in a different and very remarkable manner, which it is 

 not easy to describe or to believe, without actually seeing it." He 

 then gives a description of the retina. In like manner he describes 

 the Second Pair, which is distributed to the muscles of the eyes ; the 

 Third and Fourth Pairs, which go to the tongue and palate; and so 

 on to the Seventh Pair. This division into Seven Pairs was esta- 

 blished by Marinus, 2 but Vesalius found it to be incomplete. The ex- 

 amination which is the basis of the anatomical enumeration of the 

 Nerves at present recognized was that of Willis. His book, entitled 

 Cerebri Anatome, cui accessit Nervorum descriptio ct usus, appeared at 

 London in 1664. He made important additions to the knowledge of 

 this subject. 3 Thus he is the first who describes in a distinct manner 

 what has been called the Nervous Centre* the pyramidal eminences 

 which, according to more recent anatomists, are the communication of 

 the brain with the spinal marrow : and of which the Decvssation 

 described by Santorini, affords the explanation of the action of a part 



1 Spr. i. 534. Die. Sc. Ned. xxxv. 467. 3 Cuv. Sc. Na.t. p. 385. " Ibid. 



