178 SENSATION, IDEATION, 



said in regard to the functional activity of the Nervous 



System. 



It is only in comparatively low organisms, or in some of 

 the nerve actions of higher organisms, that ingoing im- 

 pressions would impinge upon a more or less isolated 

 group of nerve-cells, and be thence transmitted to other 

 cells and along outgoing fibres to groups of muscles. This 

 is what occurs in the simplest kinds of ' reflex action.' 

 But jus.t as complications seem almost inevitably to spring 

 up on the outgoing side, in the .form of new nervous 

 connections between groups of motor cells (serving to ren- 

 der possible those, complex simultaneous and successive 

 movements seen in'.the more elaborate ' reflex actions ' of 

 the Frog and other ajainials), so in the manner briefly 

 indicated in the last chapter, will analogous structural 

 complications spring up in the highest nerve centres on 

 the side of ingoing currents. Here connections become 

 established between the organic mechanisms concerned 

 with the passage of simultaneous or successive impressions, 

 excited by objects in the outside world. 



Thus, in relation with the most familiar ' external ob- 

 jects,' a connected internal symbolic register of their attri- 

 butes and relations is gradually established in the Brain. 

 There is an opening up, in some habitual but imperfectly 

 understood manner, of a series of interconnecting channels 

 or fibres between particular cells in each of the impressed 

 Sensory Centres and all the others. This would always 

 cecur in accordance with a fixed plan (p. 166). 



When, therefore, an external object is ' perceived ' by 

 any animal having developed sense-organs, an impression 

 upon one or more of its sense-centres suffices to rouse 

 into simultaneous conjoint activity not only these but also 

 other centres in parts of the brain which have previously 



