RETENTION AND INTEEFEEENCE OF IMPEESSIONS. 2G9 



the force, but by lateral diffusion to preserve or delay a part, and the 

 multipolar at once permitting of conservation and of a discharge into, 

 perhaps, a multitude of new channels. 



Upon the same principle that multicaudate vesicles permit of the es- 

 cape of nervous influence from the single channel in which it interference of 

 has been coming into many new ways, so likewise they impressions, 

 must be the seats of the interference of influences delivered into them 

 from many centripetal fibres at the same time. Thus we may imagine 

 a tricaudate vesicle into the granular material of which an influence is 

 delivered simultaneously by two centripetal fibrils, and these, reacting on 

 one another in the interior of the vesicle, give rise to a resultant which 

 may differ from them both, and this is passed on through the third, the 

 centrifugal fibril. 



Regarded in this way, the function of a nerve vesicle may therefore be 

 stated to be, 1st. To permit the escape of an entering influence out of the 

 solitary channel in which it has been isolated into any number of diverg- 

 ing tracts ; 2d. -To combine influences which are entering it from various 

 directions into a common or new result ; 3d. By permitting of lateral dif- 

 fusion to take off and keep in store for a certain duration a part of the 

 passing influence. 



Our attention can not fail to be arrested by this last effect ; for if there 

 be a property which is characteristic of the nervous mechan- ^ 



. n, . Retention of 



ism in its utmost degree ot development, it is this of retain- the vestiges of 

 ing the relics or traces of impressions which have formerly im P ressions - 

 been made upon it. As it goes on increasing in perplexity as we rise 

 through the animal series, the provision for the retention of such impres- 

 sions becomes more and more strikingly marked. Ganglionic masses, 

 which, from their position and structure, are marked out for this duty, 

 appear in that ascending scale in increasing magnitude. To these we 

 may aptly apply the designation of registering ganglia, since Registering 

 they truly store up the traces of ancient impressions and keep ganglia. 

 them in reserve. These ganglia must, moreover, be the scenes of the in- 

 teraction and interference of the impressions they thus contain. 



The registering ganglia thus introduce the element of time into the ac- 

 tion of the nervous mechanism. The impression which T 



<"*" i -i -i i Introduction 



without them would have forthwith ended in action is de- of the element 

 layed for a season, nay, perhaps even as long, though it may me< 

 be in a declining way, as the structure itself endures ; and with the in- 

 troduction of this condition of duration come all those important effects 

 which ensue from the various action of many received impressions, old 

 and new, upon one another. 



This internal origination of new results through the interaction of im- 

 pressions retained in the registering ganglia is too important a phenom- 



