OF T1 



TJNIVEB 



THE SPECIAL SENSES. 



easily observe. For, in going from the dark into a 

 very light room you can not see well until the change 

 in the size of the pupil-window of your eye has been 

 made. So, also, when going from a bright room into 

 a dark place, at first it seems to be " pitch dark ;" 

 but, by and by, when your eye is adjusted to the 

 change, you may be surprised to find that it is not 

 so dark after all. 



The third or inner coat of the eye is 

 the retina. This lies only over the back 

 part of the inner eyeball. It is really 

 the end of the optic nerve, or nerve of sight, spread 

 out to receive the impression of the light in the eye. 

 By turning to the last section of this eye-manikin, 

 we find this clearly represented. Here is a small 

 part of the white coat of the back part of the eye- 

 ball. It shows the opening (23) where the optic 

 nerve enters through this coat. Turning down the 

 section which lies just before this, we see the open- 

 ing (21) for the nerve through (22) the choroid coat. 

 Turning forward another section we come to the retina 

 (15) into which the nerve is expanded and over 

 which the blood-vessels (19, 20) which enter the 

 eyeball with the nerve, are distributed. The retina 

 is an exceedingly delicate nervous screen on which 

 the action of the different parts of the eye makes a 

 picture of the object we look at. How this picture 

 is carried by the nerve to the brain and there grasped 

 or perceived by the mind we do not understand. 



