388 PHILOSOPHICAL TRANSACTIONS. [aNNO 1 66g. 



will be found to be all of the same nature, that is, they make part of the white 

 substance of the corpus callosum, which passes towards the marrow of the back, 

 separated in divers layers by the intervening of the greyish substance. Which 

 being so, with what certainty can we be made to believe, that those three ope- 

 rations are performed in those three bodies? And who can tell us, whether the 

 nervous fibres have their beginning in the streaked body, or whether they ra- 

 ther pass through the callous body into the grey substance? 



In the system of M. Descartes, he finds, that that philosopher has rather de- 

 vised, in his Treatise of Man, an engine that performs all the actions men are 

 capable of, than described man as he really is; which he undertakes to prove 

 by divers instances, taken from the Cartesian fabric of the parts of the brain : in 

 the doing of which our author shows great dexterity, skill, and accuracy. And 

 from hence he proceeds. 



To observe the want of exactness in the cut or figures liitherto given of the 

 brain ; and although he acknowledges, that the best figures, hitherto made of 

 that part, are those of Dr. Willis, yet he finds several faults committed here 

 and there, and conceives there are many things to be added for making them 

 perfect; which certainly this able anatomist will consider further, and, as he shall 

 see cause, rectify. 



Having thus discussed the way hitherto practised of dissecting the brain, and 

 the little light to be thence derived, together with the defectiveness of the fi- 

 gures belonging thereto, he leaves it to the consideration of judicious men, 

 what faith is to be given to the explanations made upon such unsolid foundations; 

 and that done, he declares which are the only two ways of attaining a true 

 knowledge of an engine; viz. one, by having the contrivance of it discovered by 

 the author himself; the other, by taking it in pieces to the very least parts, and 

 examining them all both severally and jointly. 



He concludes his discourse by recommending the method which seems best 

 and most convincing to him, for making true discoveries in anatomy ; where he 

 advises, that for obtaining the true history of the parts, we should examine and 

 accordingly draw them in that state in which they are found naturally, without 

 at all forcing jthem ; thereby to find, whether the parts are indeed joined toge- 

 ther or separated, and what situation is assigned them by nature itself. And 

 he desires, that the anatomist would not only be intent upon the part on which 

 he is for the present employed, but also reflect upon all the operations he has 

 made before he came to that part, which may have caused some change or other 

 in the same, as to its situation, connexion, &c. 



Besides this exact attention on all the operations, he further counsels the 

 change of the ways of dissecting, and deduces the ill consequences of binding 



