295 



nerves towards the brain, so as to produce the phenomena of sensation, 

 for, when the nerves are tied, the parts below the ligature lose the power 

 of sensation, while, as will be seen in the proper place, this action is pro- 

 pagated <rom the brain towards the nervous extremities, and from the cen- 

 tre to the circumference, in producing motions of every kind. This dou- 

 ble current, in contrary directions, may take place in the same nerves, 

 and it is not necessary to arrange the nerves into two classes of sensation 

 and of motion. 



All the impressions received by the organs of sense, and by the senti- 

 ent extremities of nerves, are transmitted to the cerebral mass. The 

 brain is, therefore, the centre of animal life ; all sensations are carried to 

 it ; it is the spring of all voluntary motion ; this centre is to the functions 

 of relation, as the heart to the functions of nutrition. One may say of 

 the brain, as of the heart, omnibus dat et ab omnibus accijiit. It receives 

 from all, and gives to all*. 



The existence of a centre, to which all the sensations are carried, and 

 from which all motions spring, is necessary to the unity of a thinking 

 being, and to the harmony of the intellectual functions. But is this seat 

 of the principle of motion and of sensation, circumscribed within the nar- 

 row limits oi' a mathematical point, or rather should it not be considered 

 as diffused over nearly the whole brain ? The latter appears to me the 

 more probable opinion; were it otherwise, what could be the use of those 

 divisions of the organ into several internal cavities; what could be the 

 use of those prominences all varying in their form; and of the arrange- 

 ment of the two substances which enter into their structure ? We may 

 conjecture, and with considerable probability, that each .perception, each 

 class of ideas, each faculty, is assigned to some peculiar part of the brain. 

 It is, indeed, impossible to determine the peculiar functions of each part 

 of the organ ; to say what purpose is served by the ventricles, what is the 

 use of the commissures, what takes place in the peduncles ; but it is im- 

 possible to study an arrangement of such combination, and to believe 

 that it is without design, and that this division of the cerebral mass, into 

 so many parts, so distinct, and of such various forms, is not relative to 

 the different function, which each has to fill in the process of thought. 

 That ingenious comparison, mentioned in the panegyric of Mery, by 

 Fontenelle, is very applicable to the brain. " We anatomists," he once 

 said to me, 4i are like the porters in Paris, who are acquainted with the 

 narrowest and most distant streets, but who know nothing of what takes 

 place in the houses." What then are we to think of the system of Gall, 

 and of his division of the outside of the skull into several compartments, 

 which, according to the depression or projection of the osseous case, in- 

 dicate the absence or the presence of certain faculties, moral or intellec- 

 tual? I cannot help thinking, that this physiological doctrine of the func- 

 tions of the brain, resting on too few well observed facts, is frivolous; while 

 his anatomical discoveries on the anatomy of this organ, and on the ner- 

 vous system, are of the highest importance, and well founded. 



CLIII. Analysis of the Understanding. In vain were the organs of 

 sense laid open to all impressions of surrounding objects ; in vain were 

 their nerves fitted for their transmission : these impressions were to us as 

 if they had never been, were there not provided a seat of consciousness 

 in the brain. For it is there, that every sensation is felt ; light and sound, 



* See APPENDIX, Note E E, 



