166 REFLEX ACTION AND 



represented. Some of the essential complications of the 

 process are, however, of an obvious nature. 



It is not only that impressions of touch become organi- 

 cally related to other impressions of the same kind, that 

 visual impressions become classed with visual impressions, 

 and so on. Unions also would seem to spring up in some 

 less explicable way between central nerve units of different 

 orders- — that is, between contiguous sensory ganglia. Thus 

 if in the experience of any organism, such as a Cuttle- 

 fish, visual impressions are usually quickly followed by 

 tactile impressions, it would seem for various reasons to 

 be almost certain that communicating fibres would become 

 developed between corresponding portions of the visual 

 and tactile ganglia, and any motor response that might 

 follow would thus be either directly or indirectly related 

 to foci of excitement in both these sense centres. In the 

 same manner the odour from some Cod-fish, or other 

 object of prey, may reach the voracious Shark either before 

 the object is seen or simultaneously, and these two im- 

 pressions will, in a very large number of cases, be followed 

 by certain tactile and by certain gustatory impressions. 

 The first impressions become related to and may find an 

 outcome in the production of movements of pursuit ; while 

 those engendered during the process of capture (viz., of 

 touch and taste combined) immediately call into play the 

 complicated simultaneous and successive movements of 

 jaws, throat, oesophagus, and stomach, which form part of, 

 or are accustomed to succeed, the act of swallowing. 



From what has been said in this chapter, it may be 

 safely concluded that as, by the frequent repetition of like 

 Btimuli, the structural connections of nerve currents (or 

 the precise paths of ingoing impressions through nerve 

 centres and along outgoing nerve fibres) are developed and 



