508 



Chapter VII. 



PERCEPTION. 



The object of nature in establishing the organ- 

 izations we have been reviewing is to produce 

 certain modified impressions on the extremities 

 of particular nervous filaments provided to 

 receive them ; but these impressions constitute 

 only the commencement of the series of cor- 

 poreal changes which terminate in sensation ; 

 for they have to be conveyed along the course 

 of the nerves to the brain, Oi: central organ of 

 the nervous system,* where, again, some phy- 

 sical change must take place, before the re- 

 sulting affection of the mind can be produced. 

 The particular part of the brain where this last 

 physical change, immediately preceding the 

 mental change, takes place, is termed the Sen- 

 sorium. Abundant proofs exist that all the 

 physical changes here referred to really occur. 



* It is usual to designate the end of the nerve which is next 

 to the sensorium, as the origin of that nerve; whereas it should 

 more properly be regarded as its termination ; for the series of 

 changes which end in sensation commence at the organ of sense, 

 and are thence propagated along the nerve to the sensorium. 



