1)8 . PHYSICAL EXPRESSION. 



again, the beam of light, or its effects, must be 

 transmitted from the retina to the deep centres 

 affected. 



A lateral light falling upon the field of vision 

 stimulates the opposite hemisphere, and this causes 

 contraction of the head-rotatory muscles on the side 

 from which the light comes, causing it to be turned 

 towards the light or object seen. 





Fig. s. Hydrophobia, after Sir C. Bell. Head repelled by sight of water. 



Light acts as a stimulant of movement; con- 

 versely, darkness favours quietness. Strong light 

 dispels sleep. 



I think it can be shown that the stimulating 

 effects of a beam of light reflected from an object 

 may spread widely among the nerve-centres, 

 producing co-ordinated and organized sequences 



