bird's-FvYE views. 13 



interlacing blood- vessels, and painted pitch-black all over. 

 The deposit of pigmentary or black coloring matter is very 

 heavy, and serves to absorb those rays of light not needed 

 in vision. The choroid membrane lines all the inside of the 

 eye as far forward as the edges of the bony plates, where it 

 splits into two laj'ers. The inner of these tnrns aAvay from 

 the wall of the ball, towards the axis or middle line of the 

 eye, and in so doing becomes gathered in plica>, or folds, 

 much as the top of a bag is Avrinkled by pulling the string. 

 These radiating folds come from all around, to collect to- 

 gether upon the rim of the crystalline lens (o) , or rather of 

 the delicate capsule {n) that encloses the lens, and adhere 

 there. Their terminations form what are called the ciliary 

 processes (^^ ^). The outer layer also curls away from the 

 sclerotic, and starts to go transversely across the eyeball, 

 but ends at once in the iris. 



The iris (1,1) is the most exquisitely beautiful structure 

 in a bird's eye. It is the many-colored curtain that hangs 

 vertically between the two apartments of the eye. It is the 

 ■highly ornamented framework of the window of the eye, 

 uniting the offices of sash and blind. The crystalline lens is 

 suspended in the round hole punched in the centre of the 

 iris. Viewed in front, from the outside, the iris appears as 

 a colored circular band around the pupil. It seems to lie 

 directly on the surface. But this is not so, for the cornea and 

 its humors are between us and it. It is like the dial-plate 

 of a watch, that we look straight at without noticing the 

 crystal that is interposed. The central aperture through 

 which come the shafts that the hands are fastened to, may be 

 likened to the pupil. Everybody knows what the "pupil" 

 is, in a vague way. It is the round black spot inside the 

 colored rim of the iris ; but few understand what the spot is. 

 The difficulty is, that the pupil is regarded as a material 

 thing — a tissue, structure, or organ — when it is not. It is 

 the absence of matter. The round black spot called the 

 pupil is not a "thing ;" it is a hole in a thing, — the hole in 



