Human Idiot, compared with that of the perfect Brain of Man. 327 



tlve feelings, and therefore it cannot create them. If a person attempt to command 

 any instinctive impulse to be felt, he will find it as impossible to do, as to rise 

 from his chair, merely by willing it, without the aid of the muscles. 



I have ascertained and demonstrated, by repeated dissections, that all the 

 plexuses of the brain are continuous with each other ; that no part of the nervous 

 system is isolated ; and, consequently, the different parts must exercise a mutual 

 influence on each other. I have proved that the spinal nerves, as well as those 

 of the brain, are not inserted in the same way as the roots of plants penetrate 

 the earth, which has been heretofore believed, but that they are united with the 

 parts from which they are supposed to arise, and that the spinal nerves form a 

 chain of communication with each other, after they enter the spinal marrow. It 

 is in consequence of the integrity of the whole nervous system, that the various 

 sympathies, both natural and morbid, exist between the different organs of the 

 body. If the continuity of the sentient or nervous filaments were to be inter- 

 cepted at any one place, their functions would be arrested at that point, in the 

 same manner as the division of a nerve, destroys sensation and voluntary motion 

 in the parts to which the nerve is sent. 



Some anatomists, it is true, have supposed that the various reticulations of the 

 nerves, and the intermixture of the filaments of the brain, were merely to bring 

 them into contact, and that there was no incorporation of the sentient substances. 

 This opinion is consequent upon another, as ill supported by facts ; namely, that 

 there is a subtile or nervous fluid, which carries impressions made on the nerves 

 to the brain, and thus causes sensation ; and that the same fluid, proceeding from 

 the brain to the muscles, produces voluntary motions. It has never been, however, 

 attempted to explain how this imaginary fluid could become the instrument of 

 sensation or volition, more than the sentient substance itself. For ray part, I am 

 satisfied with the knowledge of the undoubted fact, that the peculiar matter which 

 exists in the nerves, and the white filaments of the brain, is endowed with the 

 power oi feeling — a power perfectly distinct from every other in nature ; and I 

 think it is equally obvious that the various modifications of sensorial function we 

 observe are the result, and require for their 'production, the multitude of sub- 

 divisions and re-unions that take place in the sentient filaments of the brain and 

 nerves. Voluntary motion appears to me to be the natural consequence of the 

 connexion between the central part of the nervous system, and the muscles which 

 move in obedience to the will or desire of the individual. 



