d be avoided? 859. Show
how the quality of the blood influences sensation. 860. Give the 1st
condition of the cuticle that influences the impressions made on the
cutaneous nerves.

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861. 2d. When the cuticle is very thin and delicate, as on the hand of
the lady who is unaccustomed to manual labor. Let her pursue some
manual employment for several hours, and the extreme tenuity, or
thinness of the cuticle, will not protect the nerves and parts below
from becoming irritated and inflamed.

862. 3d. When the cuticle is removed by blistering or abrasion, the
pain indicates that the naked nerves are too powerfully stimulated by
the contact of external bodies. 4th. When the cuticle is coated with
impurities, blended with the secretion from the oil-glands, the
sensibility of the skin is lessened.

863. _The sensibility of the cutaneous nerves is modified by being
habituated to impressions._ If, for example, an individual should
immerse his feet in moderately warm water, at first it might induce a
smarting sensation; in a short time, the nerves would not only become
habituated to the warm water, but its warmth night be considerably
increased. The same results follow, if an individual is exposed to a
cold element. The impressions at first are highly disagreeable; but as
soon as the nerves become accustomed to the surrounding atmosphere, it
may impart the most agreeable sensations.

_Illustration._ 1st. Let a person from the tropical regions go to a
colder climate, and the cool mornings of the latter will at first
affect him unpleasantly; but, after a few days' exposure to the cooler
air, the sensation will be far from disagreeable.

2d. Let a person enter a room moderately heated; gradually increase
the temperature, until it attains extreme summer heat; not only the
cutaneous nerves, but the whole system, become habituated to the high
temperature. From these facts we learn that the sensations, are not
always a correct index of the real temperature. A well-adjusted
thermometer will indicate it with unerring certainty.

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861. The 2d condition. 862. The 3d and 4th condition. 863. Show how
habit influences the sensibility of the cutaneous nerves. Give
illustration 1st. Illustration 2d.

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864. _Touch is modified, in a high degree, by education._ Thus the
blind, whose "windows of the soul" are closed to the beauties of the
external world, cul