8. The nail serves as a protection to the end of the finger, and also enables us to grasp more firmly, and to pick up small objects. The hair, too, is a protection to the parts it covers. On the head, it shields the brain from extremes of heat and cold, and moderates the force of blows upon the scalp. On the body, it is useful in affording a more extensive surface for carrying off the perspiration. [Sidenote: 9. On what does the complexion depend? Light and dark races? Freckles?] 9. COMPLEXION.--In the deeper cells of the cuticle lies a pigment, or coloring matter, consisting of minute colored grains. On this pigment _complexion_ depends; and, according as it is present in less or greater amount, occasions the difference of hue, that exists between the light and dark races of men, and between the blonde and brunette of the white races. Freckles are due to an irregular increase of coloring matter. [Sidenote: 10. Influence of the sun? How illustrated? Jews?] 10. The sun has a powerful influence over the development of this pigment, as is shown by the swarthy hue of those of the white race who have colonized in tropical climates. It is also well illustrated by the fact, that among the Jews who have settled in northern Europe, there are many who are fair complexioned, while those residing in India, are as dark as the Hindoos around them. [Sidenote: 11. What is an Albino? Where are Albinos found?] 11. An Albino is a person who may be said to have no complexion; that is, there is an entire absence of coloring matter from the skin, hair, and _iris_ of the eye. This condition more frequently occurs among the dark races, and in hot climates, although it has been observed in almost every race and clime. [Sidenote: 12. What are sebaceous glands? How do they act? Sebaceous glands of the face? How do they act?] 12. SEBACEOUS GLANDS.--There are in the skin certain {45} small glands, which produce an oily substance, called _sebaceous_ matter. These glands are little rounded sacs, usually connected with the hair-bulbs; and upon these bulbs, they empty their product of oil, which acts as a natural and adequate dressing for the hair (4, Fig. 14). A portion of the sebaceous matter passes out upon the surface, and prevents the cuticle from becoming dry and hard. The glands situated upon the face and forehead, open directly upon the skin. In these, the sebaceous matter is liable to collect, and become too hard to flow off naturally. [Sidenote: 13. Black points, called worms? Animalcules? Service performed by sebaceous matter?]