174 ADVANCED PHYSIOLOGY 



These keep the membranes always moist, even though the 

 air which is constantly going back and forth through the 

 nose would tend to dry them. In addition to the gland 

 cells of the nasal membranes, there are, mingled with them in 

 the deeper parts of the canals, many ciliated cells, whose 

 cilia are in constant motion, causing a current in the mucous 

 fluids. The turbinated bones might seem to be actual ob- 

 structions in the nasal passages, but they really serve a 

 double purpose. 



1. They so fill up the passages that very coarse materials 

 taken in with the air are strained out by them, but a far 

 more effectual cleansing is obtained because the canals run- 

 ning between these bones are so crooked. Particles inhaled 

 through them lodge and stick on their moist surfaces, so that 

 they may be driven away by the cilia, which beat about in 

 such a way that they gradually push along any dust which 

 touches them, until it is driven from the air passages into the 

 throat, where it is swallowed with the saliva or expelled from 

 the mouth. In this way the dust particles of the air are 

 prevented, to a considerable extent, from reaching the lungs. 



2. During cold weather, the position of the turbinated bones 

 in the nose passages and the warmth of the membranes which 

 cover them make them serve, almost precisely, the purpose of 

 a radiator. Just as air forced over steam pipes is warmed, 

 so air breathed through the meshes of the turbinated bones is 

 warmed and thus does not chill the delicate lung passages. 



These facts explain, in part, the injury that may result 

 from mouth breathing. When the mouth is open, air rushes 

 rapidly into the throat and lungs, carrying dust particles 

 along with it. Moreover, such air is not properly warmed 

 and is taken into the lungs too cold. These two things make 

 a person more liable to diseases of the throat and lungs, and 

 because of the close connection between the ears and the 

 throat, sometimes produce deafness. For the benefit of his 

 future health, every young person should notice carefully 



