I56 HUMAN BIOLOGY 



is unwise to probe into the ear with a hard object or even 

 with the corner of a towel. It is not necessary to insert 

 the finger in the meatus to cleanse it ; it is one inch long, 

 but only about one fourth inch across. (How large is the 

 little finger ?) The cartilaginous ears on the sides of the 

 head should be carefully washed because of their many 

 crevices. If ear wax is deposited too fast, it will cause 

 temporary deafness and earache. It may be syringed out 

 with warm water. Earache is usually caused by a small 

 boil which requires time to relieve itself by bursting. 

 Warm water poured into the upturned ear, or hot flannels 

 or compresses applied to the side of the head will lessen 

 the suffering. Each ear has three muscles for moving it. 

 Once they were doubtless useful to all, but like the scalp 

 muscle they have become so weakened by disuse as to be 

 useless to most people. They are vestigial organs. 



The middle ear, or drum chamber, contains air (Fig. 

 128). It is separated from the outer ear by the drum 

 membrane. It contains three bones which stretch across 

 it and conduct the sound waves from the drum membrane 

 to the inner ear. State the order in which they are 

 placed (see Fig. 128). The middle ear is connected with 

 the pharynx by a tube (the Eustachian tube ; pronounced 

 yoo-stake'e-an, see Fig. 128). This tube is opened every 

 time we swallow. It allows the air from the throat to 

 enter the middle ear and keep the air pressure equal on 

 each side of the drum skin. This tube and the middle 

 ear are lined with mucous membrane. 



A cold in the head or a sore throat may extend through 

 this tube to the middle ear and affect the hearing. This 

 occurs because the tube is closed by congestion of its lin- 

 ing ; the air of the middle ear may be partly absorbed, 

 and the pressure of the outside air may cause the drum 



