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under a necessity of talking in this matter, because I might in time become acquainted 

 with what others know. ... It is very certain that it is the principal organ of the soul, and 

 the instrument by which it works very wonderful effects. 



" If this substance is everywhere fibrous, as it appears in many places to be, you 

 must own that these fibres are disposed in the most artful manner; since all the diversity 

 of our sensations and motions depends upon them. We admire the contrivance of the 

 fibres of every muscle, and ought still more to admire their disposition in the brain, where 

 an infinite number of them, contained in a very small space, do each execute their 

 particular offices without confusion or disorder. . . . As for my own part, it is my opinion 

 that the true method of dissection would be to trace the nervous filaments through the 

 substance of the brain, to see which way they pass, and where they end ; but this method 

 is accompanied with so many difficulties, that I know not whether we may hope ever to see 

 it executed without a special manner of preparing. The substance of the brain is so soft, 

 and the fibres so tender, that they can hardly be touched without breaking. 



"The ancients were so far prepossessed about the ventricles as to take the anterior for 

 the seat of common sense, the posterior for the seat of memory, that the judgment, which 

 they said was lodged in the middle, might more easily reflect on the ideas which came 

 from either ventricles. I would only ask those who are still of the same opinion, to give 

 us the reason why we should believe them, for there is nothing satisfactory in all that has 

 been hitherto said in favour of it ; and as that fine arched cavity of the third ventricle 

 where they placed the Throne of Judgment does not so much as exist, we may easily see 

 what judgment is to be pronounce:! on the rest of this system. 



" Willis is the author of a very singular hypothesis. He lodges common sense in 

 the corpora, striala, the imagination in the corpus caUosum, and the memory in the 

 cortical substance ; but without being at pains to enter into details of his whole hypothesis, 

 we need only make the following remarks upon it. ... 



" M. Descartes knew too well how imperfect an history we have of the human 

 body, to attempt an exposition of its true structure ; and accordingly, in his Tractatus df 

 Homitw, his design is only to explain a machine capable of performing all the functions 

 done by man. Some of his friends have indeed expressed themselves on this subject 

 differently from him ; but it is evident from the beginning of that work, that he intended 

 no more than what I have said ; and in this sense, it may justly be said that M. Descartes 

 has gone beyond all the other philosophers. He is the only person who has explained 

 mechanically all the human actions, and especially those of the brain. The other 

 philosophers describe to us the human body itself. M. Descartes speaks only of a machine, 

 but in such a manner, as to convince us of the insufficiency of all that had been said 

 before him, and to teach us a method of inquiring into the uses of the parts with ' the 

 same evidence with which he demonstrates the parts of his machine called a man, which 

 none had done before him. 



" We must not therefore condemn M. Descartes, though his system of the brain 

 should not be found altogether agreeable to experience ; his excellent genius, which shines 

 nowhere more than in his Tractatus de Homine, casts a veil over the mistakes of his 

 hypotheses, especially since even Vesalius himself, and other anatomists of the first rank, 

 are not altogether free from such mistakes. And since we can forgive these great men 

 their errors, who passed the greatest part of their lives in dissecting, why should not 

 Descartes meet with the same indulgence, who has happily employed his time in other 

 speculations 1 . . . I find myself obliged to point out some parts of his system, without 

 relating the whole, in which they must see, if they have a mind to be instructed, the vast 

 difference there is between Descartes's imaginary machine, and the real machine of the 

 human body. The supposed connexion of the pineal gland with the brain by means of 

 arteries is likewise groundless ; for the whole basis of the gland adheres to the brain, or 

 rather the substance of the gland is continuous with that of the brain, though the 

 contrary be affirmed by Descartes." 



