one. 3. Olfactory
ganglion and nerves. 4. Nasal branch
of the fifth pair. 5. Spheno-palatine ganglion.
6. Soft palate. 7. Hard palate, _a_.
Cerebrum, _b_. Anterior lobes, _c_. Corpus
callosum. _d_. Septum lucidum. _f_. Fornix.
_g_. Thalami optici. _h_. Corpora striata.]

Next in order of delicacy, and more closely allied with the physical
functions, is the sense of smell. Delicate perfumes, or the fragrance of
a flower, impart an exhilarating sensation of delight, while numerous
odors excite a feeling of disgust. The organ of smell is far less
complicated in its structure than the eye or the ear. It consists of two
cavities having cartilaginous walls, and lined with a thick mucous coat,
termed the _pituitary membrane_, over which are reflected the olfactory
nerves. Particles of matter, too minute to be visible even through the
microscope, are detached from the odorous body and come in contact with
the nerves of smell, which transmit the impressions or impulses thus
received to the brain. Fig. 65 shows the distribution of the olfactory
nerves in the nasal passages. The nose is supplied with two kinds of
filaments which are termed respectively nerves of _special_ and nerves
of _general sensation_. Compared with the lower animals, especially with
those belonging to the carnivorous species, the sense of smell in man is
feeble. The sensation of smell is especially connected with the
pleasures and necessities of animal life.

TASTE.

The sense of taste is directly connected with the preservation and
nutrition of the body. A delicious flavor produces a desire to eat a
savory substance. Some writers on hygiene have given this sense an
instinctive character, by assuming that all articles having an agreeable
taste are suitable for diet. The nerves of taste are distributed over
the surface of the tongue and palate, and their minute extremities
terminate in well developed _papillae_. These _papillae_ are divided
into three classes, termed, from their microscopic appearance,
_filiform_, _fungiform_ and _circumvallate_. The organ of taste is the
mucous membrane which covers the back part of the tongue and the palate.
The papillae of the tongue are large and distinct, and covered with
separate coats of epithelium. The filiform papillae are generally long
and pointed and are found over the entire surface of the tongue. The
fungiform are longer, small at the base and broad at the end. The
circumvallate are shaped like an invert