l
tastes are in reality a complex of taste, smell, touch, and temperature.
Smell contributes so largely to the sense of taste that many articles of
food become "tasteless" when we have a catarrh, and many nauseating
doses of medicine can be taken without discomfort if the nose is held.
Probably none of us, if we are careful to exclude all odors by plugging
the nostrils with cotton, can by taste distinguish between scraped
apple, potato, turnip, or beet, or can tell hot milk from tea or coffee
of the same temperature.

SMELL.--In the upper part of the nasal cavity lies a small brownish
patch of mucous membrane. It is here that the olfactory nerve endings
are located. The substance smelled must be volatile, that is, must exist
in gaseous form, and come in direct contact with the nerve endings.
Chemical action results in a nerve current.

The sensations of smell have not been classified so well as those of
taste, and we have no distinct names for them. Neither do we know how
many olfactory qualities the sense of smell is capable of revealing. The
only definite classification of smell qualities is that based on their
pleasantness or the opposite. We also borrow a few terms and speak of
_sweet_ or _fragrant_ odors and _fresh_ or _close_ smells. There is some
evidence when we observe animals, or even primitive men, that the human
race has been evolving greater sensibility to certain odors, while at
the same time there has been a loss of keenness of what we call scent.

VARIOUS SENSATIONS FROM THE SKIN.--The skin, besides being a protective
and excretory organ, affords a lodging-place for the end-organs giving
us our sense of pressure, pain, cold, warmth, tickle, and itch.
_Pressure_ seems to have for its end-organ the _hair-bulbs_ of the skin;
on hairless regions small bulbs called the _corpuscles of Meissner_
serve this purpose. _Pain_ is thought to be mediated by free nerve
endings. _Cold_ depends on end-organs called the _bulbs of Krause_; and
_warmth_ on the _Ruffinian corpuscles_.

Cutaneous or skin sensation may arise from either _mechanical_
stimulation, such as pressure, a blow, or tickling, from _thermal_
stimulation from hot or cold objects, from _electrical_ stimulation, or
from the action of certain _chemicals_, such as acids and the like.
Stimulated mechanically, the skin gives us but two sensation qualities,
_pressure_ and _pain_. Many of the qualities which we commonly ascribe
to the skin sensations are rea