46 MIND IN EVOLUTION CHAP. 



not by the immediate, perceptible surroundings as such, 

 but by whatever consideration affects the attainment of the 

 end. Hence, far from being tied to a uniform response to 

 \ a given stimulus, purposive action deals with the whole 

 I present situation at any moment by correlating it with any 

 ^relevant facts, however remote, finally shaping its action in 

 [the way which, all things taken into account, will be most 

 ijikely to lead to its desired end. Hence the piLC^osiye 

 act is determined by its end, and it is thus to be contrasted 

 generically with the predetermined response of structure to 

 stimulus, the adjective " predetermined" meaning that the 

 structure must respond to the stimuli acting upon it as 

 such, and cannot bring them into relation with remote but 

 relevant facts so as to modify its behaviour appropriately. 

 To illustrate. The blinking reflex is carried out by the 

 muscles of the eyelids quite independently of real danger 

 to the eye, and most people are unable to hinder it even if 

 they try. Darwin l has told us how he tried to prevent 

 himself from starting back when a snake struck at the 

 plate glass which was a perfectly safe screen. Darwin's 

 intelligence grasped the truth of the situation, but his 

 lower motor-centres were rigidly bound to act in accord- 

 ance with ancestral custom. In a mammal the whole 

 machinery of breathing may be destroyed, but the suitable 

 movements of the nostrils and glottis still continue if their 

 connection with the medulla remains intact. 2 The nostrils 

 dilate and contract not to let in air, but because their 

 muscles are governed by a rhythmic alternation of stimuli 

 emanating from the respiratory centre in the medulla. As 

 long as the centre and the connections remain intact, they 

 go on with their work whether it assists in breathing or 

 not. 3 In the same way might the screw of a sinking steamer 

 rotate wildly in the air as the bows plunge down. The 

 screw rotates not to propel the ship, but because its motion 

 is governed by connections with the engine, and as long as 



1 Expression of the Emotions, p. 40 (2nd ed.). 



2 Foster, II. p. 616. 



3 A friendly critic points out that respiratory movements are automatic 

 rather than reflex (though constantly subject to reflex influences), but I 

 let the illustration stand as exemplifying a highly mechanical process in 

 the life of the organism. 



