and is composed in front of cartilage (gristle) and behind of bone.  In its normal state this partition (septum) should be perfectly straight, thin and in the middle line, The cartilaginous (gristle) portion is seldom found in this condition as, owing to its prominent location and frequent exposure to injury, blows and falling on the nose, the partition (septum) is often bent or turned to one side or the other so far in some cases as to close the nostril.  The posterior part is composed of bone, and being well protected, is seldom found out of position or displaced, even when the cartilaginous portion is often badly deformed, The floor of the nose is formed by the upper jaw bone (maxillary) and the palate bone.  The outer wall of the nose or nose cavity is the most complicated, for it presents three prominences, the turbinated bones, which extend from before backwards and partially divide the nose cavity into incomplete spaces 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.