Text: The typical physiology, as well as the typical anatomy of hearing, is very simple. These "ear-stones", by the vibrations conducted to them, are made to rattle in this bag containing fluid, and, by beating against its sides, cause more disturbance to the nerve filaments there distributed than would be caused by the same vibrations if they acted directly on the nerve. The human ear may be divided into three parts ‹ the external, middle and internal ear. The two former have the function of conveying vibrations to the latter which appreciates them. The external ear consists of two parts, the "pinna", or auricle (1) and the external auditory cananl or "meatus" (2). The pinna is that part which is quite external and which we unscientifically call "the ear", as when we say that a certain person has large or small ears. It is composed almost entirely of cartilage or gristle, and has complicated foldings, to all of which names have been given, but which it is not our business to give here in detail. The general shape is that of an irregular funnel, having its apex in the auditory canal. The only part of which we shall speak particularly is the "helix" or the margin which is folded in. At the upper and posterior part of this is to be found, in many individuals, a small point or process, generally folded in like the rest of the helix, but sometimes projecting outwards. The pinna is furnished with nine muscles, three of which are called extrinsic and move it as a whole, while the remaining six would, it they contracted, move its parts on one another, and are called intrinsic. The extrinsic muscles are situated in front, above and behind, and move the pinna therefore forwards, upwards and backwards respectively. These three muscles do not have any function on hearing per se other than to more or less capture and direct outside sounds to the auditory canal.

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