152 THE HOUSE I LIVE IN. 



eye, and push this hard, dry, dead body down- 

 wards, or to one side. This is often successful, 

 and the process is attended with less pain than 

 the extraction of a tooth. 



OPTIC NERVE. The optic nerve, which I 

 mentioned as entering at the back part of the 

 eye, expands or spreads itself as it enters, and 

 this is called the retina. The rays of light, 

 passing through the fore part of the eye, 1st, 

 through the cornea, 2, the aqueous humor, 

 (part of which lies before, and part behind the 

 pupil,) 3, the crystalline lens, and 4, the 

 vitreous humor strike on the retina, and an 

 image or picture of every object which is be- 

 fore the eye, is formed on the retina, inverted ; 

 that is, bottom upwards. Thus, if I am look- 

 ing at a tree, there is a kind of image or shad- 

 ow of that tree on the retina of my eye, with 

 the bottom upward. Why everything which we 

 look at does not appear to us inverted, rather 

 than with the right end upwards, is not known. 



THE TEARS. Washing windows is often a 

 slow and troublesome process, but there is a 

 small gland, not unlike the gland which fur- 



