42 ELEMENTARY PHYSIOLOGY. 



THE EYE. 

 (Third Section of Head Manikin.) 



This (46) is one of the nerves of special sensa- 

 tion the optic nerve, or nerve of sight. It connects 

 with and terminates in the eye. This nerve is 

 impressible only by light. Without the eye, the light 

 would not impress it. The eye is an instrument to 

 gather the light which is reflected to it from objects 

 and to bring it to bear on the optic nerve in such a 

 way that an impression is made and carried to the 

 brain, where the mind receives the impression as a 

 picture of the objects from which the light came. 

 How all this is done is very mysterious. But the 

 organs which are concerned in the process can be 

 easily examined and studied. 



Let us notice, first, that the eye is 

 the Eyl! 0n f l d ged in a deep socket of the bones 



of the head. Besides this feature of 

 protection, there is placed behind and around the 

 eye, quite a layer of fat, so that, even if the eye is 

 struck, the force of the stroke is very much lessened 

 by this fatty cushion. In front, it is guarded by the 

 eyelids, eyebrows and eyelashes. The eyelids serve 

 as a curtain. The eyebrows prevent the perspiration 

 from running down from the forehead upon the lids. 

 The eyelashes prevent dust from entering between 

 the eyelids. 



(Manikin of the Eye.) 



Turning aside this outer section which 



ratus. APP *~ represents the natural open eye, we see 



a gland lying in the outer corner above 



