236 THE REASON WHY. 



If the whole body were an eye, where were hearing ? if the whole were hearing 

 where were smelling ?" CORINTHIANS zir. 



978. Why do we feel inconvenienced by sudden light? 



Because an excess of light enters the eye before the iris has had 

 time to adjust the pupil to the amount of light to be received. 



979. Why if we look upon a very bright light, and then 

 turn away, are we unable to see ? 



Because the iris has so reduced the pupil while we were looking 

 at the bright light, that immediately upon turning to a darker object, 

 the pupil is too small to admit sufficient rays to enable us to see. 



Fig. 64. CAPILLARY BLOOD-TESSELS OP THE BT. 



A A. Capillary veins distributed over the sclerotic coat. 



B. One of the trunks of the optic nerve. 



0. A nerve communicating with the ciliary processes. 



D. A vein running parallel with the nerve to the ciliary processet. 



E. Side view of the iris. 



980. Why do we see better after a short time ? 



Because the iris has relaxed and enlarged the pupil, therefore we 

 receive more rays of light from the comparatively dark object, and 

 are enabled to see it more clearly. 



981. Why do cats, bats, owls, Sfc., see in the dark ? 

 Because their eyes are made highly sensitive to small quantities 



of light. It is also believed that there are certain properties of 

 light which affect their eyes, but do not affect ours. In other words, 



