THE EAR.
The apparatus of hearing is composed of three parts the outer, middle, and inner ear; the two first being accessory for the collection and transmission of sounds, and the latter the essential organ which receives the impressions thus conveyed.
The inner part, or drum, of the ear, is situated in the hardest bone of the body, called the petrosal. The nerve which passes into the drum of the ear and gives the sense of hearing, is called the auditory nerve. From the drum a small opening passes out into the outer part of the ear; this is the portion which is seen on top of the head. It is made up of a membrane known as the cartilage, which gives the ear its stiffness. This cartilage is covered by a fine, delicate skin, covered on the outside by fine, short hair. Situated on the inner side of the outer ear are numerous long hairs projecting outward, the use of which is to keep foreign bodies from dropping into the ear. The ear is moved backward and forward by small muscles which are attached around it.