CHAPTER 3 THE HUMAN EYE

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CHAPTER 3

THE HUMAN EYE

Section I. GENERAL

light, and response of the whole patchwork makes a

3-1. Introduction.

All creatures endowed with sight

rough image but is coarse and inefficient in making

have eyes of some sort; some are simple and others

visible any details of the outline in pattern resolution.

complex, some adapted to long range vision and others

to short distances. Animals and birds of the mountains

3-2. Comparison of Eye and Camera. The human

and plains, where vision is unobstructed for great

distances, have visual ability which enables them to pick

eye, which is rather a sturdy organ of wonderful design,

out objects too small for human perception. This ability

may be called a living automatic camera. A high-grade

appears to be associated with small nerve, endings in

camera closely resembles the eye in basic essentials.

the retina, faster retinal response to observed motion,

Each has a compound lens to refract light rays and to

and better interpretation by the brain. The other extreme

project them to definite points by focusing. Each has a

is represented by the short range compound eye as

diaphragm to regulate the entering light, a sensitized

found in insects and crabs. This arrangement consists

surface to receive and record optical images, and a

of a patchwork of individual "eyes," each of which

lightproof chamber to shut out extrenous light and to

records a spot of shade or

protect the receiving and recording mediums (fig 3-1).

Figure 3-1. Comparison of eye and camera .

3-1