476 THE OUTGO OF ENEEGY 



a little behind the subject, so that he shall see 

 about half of the corneal image of the black 

 pupil of the subject's eye projecting beyond the 

 corneal border of the sclera. Note, from within 

 outwards, the optical section or profile of the 

 margin of the sclera, the anterior half of the 

 pupil, a clear portion of the cornea, and finally 

 a dark stripe which is the most anterior portion 

 of the cornea. 1 



Watch carefully the clear interval between this 

 dark stripe and the profile of the pupil while the 

 subject, keeping the eye steadily in one position, 

 accommodates first for the distant and then for 

 the near object. 



The interval between the corneal stripe and 

 the border of the pupil diminishes on accommo- 

 dation for near objects. Hence the border of the 

 pupil moves forward. If this were not the case, 

 the interval would become larger, for the pupil 

 narrows in accommodation. Accidental turning 

 of the subject's eye towards the observer would 

 also cause the interval to appear larger. As the 

 margin of the iris lies upon the lens, this obser- 

 vation is evidence that the anterior surface of the 



1 The sclera projects over the iris. The inner surface of the 

 projecting portion is in shadow. The profile view of the image 

 formed of this projecting portion by the refraction of the cornea 

 is the dark line observed in the above experiment. It is dark 

 by contrast with the image of the well-lighted iris. 



