THE EYE. 33 



e^^e looks upwards, and so forth. There are two 

 other muscles ohliquely placed for rolling the eye, 

 but these w^e will not consider. The four muscles 

 named are called the four straight muscles, and 

 when they all contract at once, the eyeball is pressed 

 back into the socket and the 'haw' (Fig. 5, D) 

 which is a thin sheet of grissle also imbedded in the 

 fat and whose edge can always be seen on the inner 

 angle of the eye, is pressed or squeezed out of the 

 fat and made to project over the eye. 



27. — We must now turn our attention to the 

 front half of the eye as we see it in the living 

 animal, because it is this we have to examine with 

 the candle in the darkened stable. Still referring 

 to the diagram, let us study the parts in their 

 order, beginning at the transparent 'cornea,' (our 

 watch-glass). 



The light has first of all to pass through the 

 cornea before it can pass through the hole we call 

 the 'pupil,' and if the cornea receives any injury, as 

 it often does from the whip, spots may be left which 

 will split the light or otherwise daze the animal 

 and make him shy. If, however, these spots are 

 on the outer margin and not opposite the pupil, it 

 is plain that the light will not be interfered with, 

 or in other words, the spots are of less consequence. 



Covering the outer tunic or white of the eye, there 

 is a very delicate membrane we have not mentioned, 

 but which holds many blood vessels. This is called 

 the 'conjunctiva,' and is that we see so red when 



D 



