FUNCTIONS OF THE BRAIN. 



25 



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Fig. 3. 



time, and, by virtue of a reflex tendency common in babies 

 of a certain age, extends liis 

 hand to grasp it, so that his 

 fingers get burned. So far we 

 have two reflex currents in 

 play : first, from the eye to the 

 extension movement, along the 

 line 1 — 1 — 1 — 1 of Fig. 3 ; and 

 second, from the finger to the 

 movement of drawing back the 

 hand, along the line 2 — 2 — 2 — 2. 

 If this were the baby's whole 

 nervous system, and if the re- 

 flexes were once for all organic, 

 we should have no alteration in his behavior, no matter 

 how often the experience recurred. The retinal image of 

 the flame would always make the arm shoot forward, the 

 burning of the finger Avould always send it back. But we 

 know that * the burnt child dreads the fire,' and that one 

 experience usually protects the fingers forever. The point 

 is to see how the hemispheres may bring this result to pass. 

 We must complicate our diagram (see Fig. 4). Let 

 the current 1 — 1, from the eye, discharge upward as well as 

 downward when it reaches the lower centre for vision, and 

 arouse the perceptional process s' in the hemispheres ; let 



the feeling of the arm's exten- 

 sion also send up a current 

 which leaves a trace of itself, 

 »7i' ; let tlio burnt finger leave 

 an analogous trace, s' ; and 

 let the movement of retrac- 

 tion leave m^ . These four 

 processes will now, by virtue 

 of assumption 2), be associ- 

 ated together by the path 

 s' — m'— s'^ — rrf , running from 



Fig. 4 -The dotted lines stand for affer- ^]g gj.gl- ^^ ^Jjg last, SO that if 

 ent paths, the broken lines for pMtlis xxi ju i. i. ^ , 



Kflei'Jnt'''at'hs'^*''''"'^'^"^'''''"'*^'' anything touches off s\ ideas 



of the extension, of the burnt 

 finger, and of the retraction will pass in rapid succession 



