1. Symmetry.—The ears should be symmetrical:
a. In respect to their position.
b. In respect to the more or less pronounced divergence of the ears from the cranium.
c. In respect to their form.
a. Position.—We must look for this form of asymmetry by observing the cranium according to the occipital norm. The asymmetry may be caused by one of the ears being placed too high up or too far back in respect to the other, or both asymmetries may occur together.
b. The asymmetry due to divergence is observed from two norms, the facial and the occipital.
c. Asymmetry of form is perceived by observing successively the two external ears according to the lateral norms; their morphological aspect should correspond on the two sides.
2. Anatomy and Malformations of the External Ear.—A preliminary anatomical note is necessary. The external ear consists of various parts, which were first studied and named by Fabricius of Acquapendente:
- The Helix.—This is the outermost fold of the ear; it takes its origin above the auricular foramen in a root starting from the inside of the concha and rises upward, to descend again describing a regular helix; and it terminates in the lobule. At the point where the helix bends downward to form the descending branch, a small cartilaginous formation can be discerned by the sense of touch; this is the Darwinian tubercle.
- The Antihelix.—This originates in two roots under the ascending branch of the helix and terminates in the antitragus; it is a cartilaginous formation.
- The Auricular Fossa.—This divides the helix from the antihelix.
- The Tragus.—This is a little triangular cartilaginous formation situated in front of the auricular foramen. Between the tragus and the antitragus is the intertragical fossa.
- The Concha.—This is the concavity, the internal fossa of the auricle, which leads to the channel of the internal ear.
Instances may be found of malformation of each and all of these various parts of the ear, which may be excessively developed, or almost wanting, or altered in form.