DISEASES OF THE EAR. 395 



When prolapse of the vagina or eversion of the uterus 

 is threatened, the perineum may be supported during the 

 pains by the hand. Should these complications occur, the 

 treatment is as previously directed (pages 271, 283). 



DISEASES OF THE EAR. 



The ear is usually divided into external ear, middle ear 

 (tympanum), and internal ear. The latter is the essential 

 part of hearing, as it contains the auditory cells and the 

 terminations of the auditory nerve. It is the most com- 

 plicated sensory structure in the body, and is inclosed in a 

 bony case. 



The external ear may be regarded as protective to 

 other parts of the organ, and serves to collect the atmos- 

 pheric undulations that move the apparatus of the middle 

 ear, which is made up of a membrane or drum-head at- 

 tached to several small bones, the whole conveying the 

 aerial undulations to the fluid within the inner ear, which 

 fluid, when thus moved, stimulates the nerve-endings and 

 gives rise in the nerve of hearing to those molecular move- 

 ments which, being conveyed to the cells of that part of 

 the brain concerned with hearing, give rise to that special 

 consciousness and those judgments which we call " hear- 

 ing." Yibrations from the atmosphere or from solids 

 usually act through the drum-head, but the auditory nerve 

 may be affected through the bones of the head directly. 



The middle ear is protected not only by the outer ear 

 (flap of the ear), itself covered with hair, but by the hairs 

 within, and especially by ear-wax a secretion from glands 

 that are modifications of the sebaceous glands (cerrw- 

 minous glands) and which must be disagreeable to insects, 



