=The Tonsils.=--The tonsils vary in size and in _tonsillitis_ swell and may even meet in the median line. They are frequently removed. When they are enlarged one often gets a _third tonsil_ or _adenoids_, a lymphoid growth at the back of the pharynx which causes mouth-breathing by day and snoring by night. A child with adenoids is starved for air and what air is breathed in is not warmed. The growth should be removed. A short frenum produces _tongue-tie_, which may be remedied by snipping. Cancer of the tongue is fairly common and necessitates a radical operation. In mumps the parotid glands are inflamed and enlarged. =The Ear.=--The special organ of hearing is the ear, to which there are three parts, the external, the middle, and the internal ear. The _external ear_ consists of the _pinna_ or expanded cartilaginous portion, for the concentration and direction of sound waves, and the _external auditory canal_, partly cartilage, partly bone, which is directed forward, inward, and downward and conveys sound to the middle ear. [Illustration: FIG. 21.--The small bones of the ear; external view (enlarged). (After Gray.)] The _middle ear_ or _tympanum_ is an irregular cavity in the petrous portion of the temporal bone. Its outer wall is formed by the _membrana tympani_ or _drum_, an oval translucent membrane placed obliquely at the bottom of the external auditory canal. The middle ear communicates with the inner ear through the _fenestra ovalis_ or oval window and contains the _ossicles_, the _malleus_ or hammer, the _incus_ or anvil, and the _stapes_ or stirrup, which are arranged in a movable chain from the drum to the oval window. The _malleus_, which is connected with the membrana tympani, articulates by its head with the body of the incus, while the stapes articulates with the _incus_ by its head and is connected by its base with the margin of the oval window. Connection is made between the middle ear and the pharynx and the pressure of the air upon the drum made equal on either side by means of the _Eustachian tubes_. These tubes are about an inch and a half long, have cilia, and convey wax and other matter from the ear to the pharynx. Occasionally in a cold or for some other reason they become stopped up and trouble results in the middle ear. Some of the _mastoid cells_ also connect with the middle ear and may become infected, causing mastoid disease. [Illustration: FIG. 22.--Interior view of left bony labyrinth after removal of the superior and external walls: 1, 2, 3, the superior, posterior, and external or horizontal semicircular canals; 4, fovea hemi-elliptica; 5, fovea hemispherica; 6, common opening of the superior and posterior semicircular canals; 7, opening of the aqueduct of the vestibule; 8, opening of the aqueduct of the cochlea; 9, the scala vestibuli; 10, scala tympani; the lamina spiralis separating 9 and 10. (From Quain, after Sömmerring.)]