BIRDS-EYE VIEWS. ? 



deep semiliiiijir groove in the roof of the bony orbit. But it 

 does not belong to the eye at all, and seems to be stowed 

 there for want of room elsewhere. Its long duct runs along 

 the top of the orbit into the nose, pouring out a secretion 

 that lubricates the mucous membrane (^pituitary membrane) 

 of the nasal passages. 



The lachrymal glands keep the eye's face clean, and relate 

 chiefl}^ if not wholly, to the movements of the eyelid. The 

 eyeball itself rolls about by the indirect aid of a different 

 tissue — the areolar, or cellular, as it is indifferently called, — ^ 

 the interstices of which are tilled with fat. Ordinarily, the 

 socket of an eye is much too large for the ball, and of a 

 conical, instead of globular shape, so that the ball can no 

 more fit or fill it, than can a marble dropped into a candle 

 extinguisher. A bird's eyeball is more nearly fitted to its 

 socket than that of most mammals ; still, it rests wholly or 

 in great part upon a bed of flit. This soft, yielding, elastic 

 substance gently presses the eye forwards, and holds it there 

 in place, accurately adapted to the lids, while at the same 

 time it allows the ball to rotate any way upon its own axis, 

 and also keeps it greased. We have a great deal of fat in 

 our own ej'c-sockets in health. The reason that people's eyes 

 are sunken or "hollow" after a long illness, is because part 

 of it is wasted away. While there is so much fat all around 

 the eyeball, there is not a particle in the eye itself; this 

 comparatively clumsy and stupid material would be like a 

 bull in a china-shop in such a nervous quick-witted struc- 

 ture. 



Ducks are said to roll their eyes up in a thunder-storm, 

 and very likely they do, since all birds move their eyes about 

 more or less when they are not asleep. But the amount and 

 degree of motion that a bird's eye is capable of is small in 

 comparison with that enjoyed by most mammals' eyes. This 

 results partly from the shape of the orbit, and partly from 

 the shape of the l)all itself, which last is very singular, as 

 we shall see in the sequel. Nevertheless, there are as manv 



