ble
sensation.

720. The oil is most abundant near the roots of the hair A free use
of the brush spreads it along the hairs, and gives them a smooth,
glossy appearance. Soap should rarely be used in washing the head, as
it will remove the oil which is essential to the health and appearance
of the hair.

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718. Upon what does the color of the hair depend? What are the causes
of the hair becoming gray? What is the cause of the hair dropping out?
What is related of Marie Antoinette? 719. How is "dandruff" on the
scalp produced? What is the only necessary application to remove it?
Give observation. 720. Where is the oil of the hair most abundant?

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721. The uses of the hair vary in different regions of the body. Upon
the head, it aids in shielding the brain from injury by blows, and it
likewise serves to protect this part of the system from heat and cold,
thus maintaining equal temperature of the cerebral organ. About the
flections of the joints, as in the axilla, (armpit,) they prevent
irritation of the skin from friction; in the passages to the ears and
nostrils, they present an obstacle to the ingress of insects and
foreign bodies; while in the eyebrows and eyelids, they serve to
protect the organ of vision.

[Illustration: Fig. 119. A section of the end of the finger and nail. 4,
Section of the last bone of the finger. 5, Fat, forming the cushion at
the end of the finger. 2, The nail. 1, 1, The cuticle continued under and
around the root of the nail, at 3, 3, 3.]

722. The NAILS are hard, elastic, flexible, semi-transparent scales,
and present the appearance of a layer of horn. The nail is divided
into the _root_, the _body_, and the _free portion_. The root is that
part which is covered on both surfaces; the body is that portion which
has one surface free; the free portion projects beyond the end of the
finger.

723. The nail is formed of several laminae, or plates, that are fitted
the one to the other; the deepest is that which is last formed. The
nails, as well as the hoofs of animals and the cuticle, are products
of secretion. They receive no blood-vessels or nerves. If the cuticle
be removed in severe scalds they will separate with it, as the hoofs
of animals are removed by the agency of hot water. The nails increase
in length and thickness, by the deposition of albumen upon their under
surface, and at their roots, in a manner similar to the growth of