CH. II.] EXTERNAL IMPRESSIONS. 29 



is rendered evident from the continual operations of each concep- 

 tion on the body, and which must necessarily have their origin 

 in the brain, where the mind has its seat, and is in intimate 

 relation with the nervous system. 



30. The doctrines of the animal-sentient forces which follow 

 from these principles, divide naturally into two principal divi- 

 sions; namely: 1st. How are the material ideas produced in the 

 brain? (31-112.) 2d. What functions do they perform in the 

 animal economy? (113-344.) These two take place mainly 

 through the connection of the brain with the nerves, whereby 

 the animal forces of the nerves keep up a physical relation with 

 the animal-sentient forces of the brain. 



SECTION III. THE ANIMAL FORCES OF THE NERVES, CONSIDERED 



SOLELY IN THEIR RELATION WITH THE ANIMAL-SENTIENT 

 FORCES OF THE BRAIN.^ 



Of the External Impressions [Aussern sinnlichen Eindriicke] — 

 [Nerve feelings) . 



31. Every nerve has its beginning or origin in the brain (12) ; 

 and if an impression be made there, and propagated along the 

 nerve, it must necessarily take a direction from the brain outwards 

 towards the branches and their terminations, as the vital spirits 

 would also propagate it (17). If, on the contrary, a similar im- 

 pression be made on the terminations and propagated along the 

 trunk of the nerve, its direction must be toward the brain in the 

 same course as the vital spirits (18). If a nerve be divided, an im- 

 pression made on that point separated from the terminating fibrils, 

 but still in connection with the brain, takes the same direction if 

 it be propagated, just as if it had been made on the terminating 

 fibrils themselves, namely, upwards to the brain. On the con- 

 trary, if an impression be made on that end of the cut nerve which 

 is separated from its connection with the brain, but in connection 

 with the terminating fibrils, if propagated, it will go towards the 

 terminating fibrils. If an impression be made on the cerebral 

 origin, or on the terminating fibrils of the nerve, and it is 

 propagated, it will in both cases traverse the nerve only as far 

 as the point of section ; consequently, when an impression takes 



' The thierische kr'dfte of the nerves, here translated animal forces of the nerves, 

 are termed elsewhere nervenkrdfte, or nerve-forces ; both phrases are used in exactly 

 the same sense as the Latin term vis nervosa^ which has therefore been preferred, 

 wherever possible, to the literal rendering. — Vide note to § 353. 



