called meatus passages. The turbinated bones are three in number, the
inferior, middle and superior. They vary in size and shape, and owing to
the relations they hear to the surrounding parts, and to the influence
they exert on the general condition of the nose and throat, are of great
importance. The inferior or lower turbinate bone is the largest and in a
way is the only independent bone. The middle and superior are small. They
are all concave in shape and extend from before backwards, and beneath the
concave surface of each one of the corresponding passages or openings
(meatus) is formed. The inferior or lower (meatus) opening or passage is
that part of the nasal (nose) passage which lies beneath the inferior
turbinate bone and extends from the nostrils in front to the passage
behind the nose (post-nasal) (posterior nares) toward the pharynx. The
middle opening (meatus) lies above the inferior turbinate bone and below
the middle turbinate bone. The superior opening (meatus) is situated above
the middle turbinate bone.

[RESPIRATORY DISEASES 7]

[Illustration: Bronchial Tubes and Lungs.]

The mucous membrane lining the nasal passages is similar to other mucous
membranes. It is here called the Schneiderian membrane after the name of a
German anatomist named Schneider. It is continuous through the ducts with
the mucous membrane of all the various accessory cavities of the nose. It
is quite thin, in the upper part over the superior turbinate bone and
partition (septum) while it is quite thick over the lower turbinate bone,
the floor of the nose cavity and the lower part of the partition. It is
well supplied with blood vessels, veins, and glands for producing the
necessary secretion.