DED UCTION. ANTIC IP A TION. 1 47 



tive problem: the effects given, to find the 

 cause, without any hint as to its nature. Sev- 

 eral years would seem long enough for a mind 

 like Darwin's. 



He had seen Duchenne's photograph of a 

 young man contracting the grief-muscles while 

 looking up at a strongly illuminated surface, 

 but had entirely forgotten the picture. The 

 problem remained unsolved. One day while 

 on horseback, with the sun behind him, he met 

 a young girl whose eyebrows as she looked 

 up at him became extremely oblique, with the 

 proper furrows on her forehead. He had been 

 unable to reach the cause by contemplation 

 of the effects. Now he had observed a cause 

 producing effects identical with those which 

 puzzled him. There was now a basis for ex- 

 periment He went home and caused three of 

 his children, without their knowing why, to 

 look up at the top of a tall pine against a 

 bright sky. "With all three," he said, "the 

 orbicular, corrugator, and pyramidal muscles 

 were energetically contracted, through reflex 

 action " to protect the eyes against the light. 

 But they wanted to see, and a " curious struggle 

 arose between these muscles, that tended to 

 lower the brows and close the lids and all or 

 only the central fasciae of the frontal muscle, 



