ACTION OF LIGHT ON AN INFANT. 97 



The infant as born has, then, such an apparatus as 

 allows of these two reflex actions to light. Now, in 

 these reflex actions the light excites or stimulates 

 these reflex movements. A plain beam of white 

 light effects this. I do not know the effects of 

 different rays of the spectrum. 



I am not aware of other effects of light in the 

 infant in its youngest stage, but, at five months 

 old, holding a brightly coloured object well within 

 the field of vision of the infant attracts its atten- 

 tion, as it is said. We see the child's eyes and head 

 move, so as to bring their axes in a straight line 

 towards the object. This is a mechanical effort; 

 there is work done. What force can excite this 

 movement and direct it with such precision ? We 

 know of no force passing from the object to the 

 child, except the light reflected; a screen hiding 

 the object from the child's eyes, i.e. cutting off the 

 rays of light reflected from the object, prevents 

 the object from exerting its effect upon the child. 

 The beam of light reflected from the object excites 

 the movement that follows action of the light ; the 

 effect of the light must penetrate the retina, and 

 travel to the centres for the muscles seen excited 

 to action. 



A few words must now be said as to the effects 

 of "the sight of objects." When we see an object, 

 all our subjective impressions of that object are the 

 effects of the beam of light reflected from the object; 

 and all the objective, observable effects of the sight 

 of that object are the effects of the excitation, or 

 stimulation, produced by that beam of light. Here, 



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