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EXPERIMENTAL PHYSIOLOGY. 



are not curved alike. In the most common form the vertical meridian is an arc of a 

 smaller circle than is the horizontal and, being more sharply curved, it refracts 

 more than does the latter. Rays which diverge in a vertical plane from a point 



T.T. 



FIG. 42. The focussing of parallel rays from a distant object by (A) a 

 normal, (-B)e. short-sighted and (C) a 'long-sighted eye. PF in each case shows the 

 position of the principal focus of the combined refracting surfaces of the eye, 

 represented by the single surface of the schematic eye. 



object are brought to a focus by such eyes in front of the focus for the horizontal 

 rays. The result is that the eye can never see a point image of a point object. 

 If the rays through one meridian are focussed on the retina then those which pass 

 through the meridian at right angles to the first must reach the retina as a pencil 



