148 THE HOUSE 1 LIVE IN. 



hook, as you find at c. The lower one, /, is 

 also fastened in a very ingenious manner. 



The tendon that passes round a piece of the 

 bone of the forehead, is fastened to the very 

 top of the eye ball. Now it is easy to see that 

 if the upper muscle at d should contract or 

 shrink, it would operate just as if it were a 

 rope, and somebody pulled it ; that is to say, 

 it would pull the top of the eye ball forward, 

 and make the fore part, at a, turn downward, 

 so that a person would look towards his feet. 



COATS OF THE EYE. The eye is a large 

 hollow sack, containing a clear but thick liquid, 

 most of which is not unlike the white of an 

 egg. The covering of the eye consists of 

 several layers or coats. 



The outside, or sclerotic coat, as it is called, 

 can be seen in the engraving. It is very thin, 

 and a small portion of it at the fore part is 

 wanting. In this vacancy or opening is set the 

 cornea, a piece of membrane which is transpa- 

 rent, that is, can be seen through like glass. 

 This transparent part you will find near a. It 

 is placed in the sclerotica, as a crystal is set in 

 a watch ; or, if we compare the eye to a win- 



