The pinna may be congenitally absent, malformed, or abnormally small (microtia) or large (macrotia). Small fistulae may be found, due to failure in fusion of the various tubercles from which the embryonic ear is formed, and of greater consequence is imperfect closure of the first branchial cleft, from which the external auditory meatus, middle ear, and Eustachian tube are formed. Where the cleft is not closed it may present as a fissure, commencing either at the tragus or helix, and extending perhaps into the middle ear, the membrana tympani being defective or even absent. Sometimes a small tubercle is found near the upper extremity of the helix presenting a tuft of hair. It is known as Darwin's tubercle, and is supposed to represent the tip of the tapering ear of lower animals. Supernumerary auricles, small and ill-formed, are rarely found on the cheek or side of the neck. The subcutaneous tissue on the outer aspect of the pinna is dense and closely adherent to the perichondrium, and hence inflammatory processes in this position are generally small, but very painful. Tophi, or gouty deposits of urate of soda, are sometimes found along the margin of the helix.
Extravasations of blood (othematoma) occur not infrequently on the outer aspect of the pinna, sometimes from injury and at others spontaneously, the latter being found particularly in the insane, and due probably to disease of the vessels. The extravasated blood is generally absorbed, but its absorption is frequently accompanied by deformity of the pinna, and hence it is sometimes desirable to evacuate such collections soon after their formation. Notwithstanding its generous blood-supply from the temporal and posterior auricular arteries, the pinna is a frequent seat of frost-bite, owing to its exposed position and the absence of fatty tissue over its vessels.
The pinna and cartilaginous meatus are very firmly adherent to the skull, sufficiently in some cases to bear the weight of the body. Even where, however, the pinna has been almost detached, it will, as a rule, rapidly heal if stitched in position. The skin under the lobule of the ear is a frequent site of sebaceous cysts. The glands in this region are not infrequently enlarged from irritation of the scalp due to phtheiriasis, and eczematous conditions of the external ear.
The external auditory meatus, rather over an inch in length, has a wall lined with skin, which is composed of cartilage over rather more than the outer half, and of bone over the remainder. It is directed forwards and inwards, and is curved, with the convexity pointing upwards and backwards, so that both osseous and cartilaginous portions are directed downwards. When introducing a speculum, therefore, the pinna should be held upwards and backwards, so as to bring the cartilaginous canal into line with the osseous. The narrowest point is at the junction of cartilaginous and osseous parts. In the infant the meatus is shorter, straighter, and almost entirely cartilaginous. The wall of the meatus presents certain gaps on its anterior and lower aspect, filled with fibrous tissue (fissures of Santorini). Through these a parotid abscess may burst into the external ear. The osseous wall, owing to its close relationship anteriorly to the condyle of the jaw, is sometimes fractured by falls or blows on the chin. The skin of the meatus is very adherent to the underlying structures, particularly over the osseous portion, and is furnished over the cartilaginous part with hairs and ceru-minous glands. Accumulations of wax secreted by these glands is a frequent cause of deafness. The osseous portion of the canal, in common with the back of the pinna, is supplied by the auricular branch of the vagus, and hence irritation of this part from wax- or foreign bodies frequently causes coughing, and may cause vomiting, yawning, sneezing, or even epileptiform attacks. Abscesses in this region are generally very localized and extremely painful, being affected by every movement of the jaw in chewing or even in speaking. Polypi not infrequently are found in the external auditory meatus, and may be removed by snaring. Care should, however, be taken not to mistake masses of granulation tissue springing from the cerebral dura, and protruding through the thin layer of bone separating dura and meatus, for polypi. If such be avulsed, the way is laid open for durai or even cerebral pyogenic implication, and death has sometimes resulted from such mistakes. Exostoses occasionally occur in the osseous portion. They are generally of the ivory type and of slow growth.
The tympanic membrane in the infant lies almost horizontally, and is attached peripherally to a separate ring of bone, which is complete save in its upper segment. In the adult the membrane is nearly vertical, but is inclined from above and behind downwards, forwards and inwards, so that its anterior and inferior edges form acute angles with the meatal wall.