CHAPTER IX THE HEAD AND NECK In the previous sections the trunk and extremities The student must now devote his attention to the most difficult, and yet in many ways the most interesting, part of anatomy, viz. the head and neck. It will be convenient to take the neck first. Close attention, assisted by repeated observation, is absolutely necessary, as it is by the narrowest scrutiny only that certain details can be understood. For example, one frequently hears some such expression as "a beautiful light in the eye." But the explanation of such an expression is beset with great difficulties. In the first place, the light is not in the eye at all, but is reflected from it. Secondly, the manner of the reflection of the light depends to a large extent upon the curvature of the reflecting surface of the eyeball itself and of the surrounding lids and prominences. Thirdly, not only the surface of the eyeball, made up of the transparent cornea and the opaque white sclerotic, but also its internal parts, and in particular the iris, reflect and modify the light which falls upon it. And again, the expression, dependent upon the movements of the facial muscles surrounding the organ, is a very important factor in modifying " the light of the eye." In expression one part of the face seldom acts alone almost always there is a correlated action
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