CHAPTER IX 

 THE EAR, THE EYE, THE SKIN, AND THE FOOT 



THE EAR 



The ear has to do with the sense of hearing. It consists of 

 three parts: 



The external ear comprises three cartilages, the largest of 

 which is the trumpet-shaped conchal cartilage which determines 

 the shape of the ear and is covered by thin skin. A fine, flexible 

 ear is an evidence of breeding. 



The middle ear is called the drum on account of the thin mem- 

 brane which separates it from a tympanic air-containing cavity. 

 Across it a chain of three bones is stretched. These bones trans- 

 mit the sound-waves from the outer to inner ear. They are named 

 the malleus, from its resemblance to a hammer; the incus, which is 

 shaped Uke an anvil ; and the stapes, which is stirrup shaped. A 

 connection is made between the middle ear and the pharynx by 

 means of the eustachian tube to equalize the pressure of air upon 

 the ear-drum. 



The internal ear is composed of a series of chambers in the sub- 

 stance of the temporal bone, soft structures, and fluids. In it are 

 found the ramifications of the auditory or eighth cranial nerve, 

 which has to do with the reception of sound-waves. The actual 

 organ of hearing is the cochlea, a bony structure similar in shape to 

 a snail's shell. 



The function of the ear is to record the sensations of sound. 

 When sound-waves reach the ear-drum they set it in motion. In 

 turn, the latter causes the chain of ossicles to vibrate and the 

 auditory nerve transmits the impulses to the auditory center of the 

 brain. 



THE EYE 



The eye is the organ of vision. It comprises the eyeball, the 

 optic nerve, and the accessory structures — the eyelids, the con- 

 junctiva, and the lacrimal apparatus. 



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