IV 



REFLEX ACTION 53 



Each action that achieves its end leaves behind it a tend- 

 ency to repeat that action, while the unsuccessful actions 

 are inhibited. Thus in the individual life, below the level 

 of intelligence, success the attainment of the equilibrium 

 to which the organism is tending plays the part which in 

 the life of the species falls to Natural Selection. It con- 

 firms the tendency which makes for organic equilibrium, 

 and checks the opposing tendencies. 



This selective force acts equally upon reflexes with a 

 hereditary basis. In the co-ordinating movements of the 

 eyes or the legs many irregular and unsuitable movements 

 occur at first, but are gradually discarded in favour of the 

 movements required by the organic : equilibrium. 1 Children 

 make random movements aboutthe breast and often suck 

 at the wrong place.' 2 Even the localisation of a part of 

 the body by the hand is arrived at after this fashion, as is 

 shown by the following very instructive instance given 

 by Prof. Preyer. 3 



..." In the case of two children, who in the first half-year 

 suffered from local itching eruptions of the skin (milk-crust), the 

 reflexive movements of the limbs were quite irregular, and at the 

 beginning absolutely unsuited, afterwards not in all cases suited, 

 to relieve the pain or the feeling of tickling ; at all events, apart 

 from the turnings of the head, which was the most tormented, 

 and which was moved hither and thither like a pendulum when 

 the arms were confined (fourth month). Many times when the 

 arms had escaped from the tethers in the night, the face was 

 scratched to bleeding in several places that were evidently not 

 troublesome (fourth to sixth month). At every unguarded 

 moment the hands went to the head, and the skin, even the 

 sound part of it, was rubbed and scratched. These scratching 

 movements cannot be inborn, they must be acquired. The 

 result of an accidental contact of the head and hand appearing in 

 the diminution of the tickling sensation must have induced a 

 preference of the movement of the hand to the head among all 

 sorts of movements." . . . 



1 Preyer, I. p. 39. 



2 Ib. p. 134. Puppies also miss the teat, and will try moreover to suck 

 one another or the master's finger. (Wesley Mills, pp. 118, 119.) 



3 Ib. p. 223. Mr. Lloyd Morgan suggests, by way of contrast, the 

 apparent accuracy with which young birds, only a day or so old, scratch a 

 spot artificially irritated. 





