. The anatomy of the human body. Human anatomy; Anatomy. THE OSSICULA OF THE EAR. 673 posterior border of the sphenoid, forms the external wall of the canal, which is habitu- ally collapsed. The base of the triangular cartilage, which forms the guttural orifice of the tube, is notched in the middle, and terminates in two thickened elongated angles ; of these, the posterior one, which is more distinct, is movable, and may be pushed upward and backward. The anterior angle is firmly fixed to the posterior margin of the pteiy- goid process. As catheterism and injection of the Eustachian tube have
. The anatomy of the human body. Human anatomy; Anatomy. THE OSSICULA OF THE EAR. 673 posterior border of the sphenoid, forms the external wall of the canal, which is habitu- ally collapsed. The base of the triangular cartilage, which forms the guttural orifice of the tube, is notched in the middle, and terminates in two thickened elongated angles ; of these, the posterior one, which is more distinct, is movable, and may be pushed upward and backward. The anterior angle is firmly fixed to the posterior margin of the pteiy- goid process. As catheterism and injection of the Eustachian tube have become com- mon operations in treating diseases of the ear, it is of importance to define the exact position of its guttural orifice; it is situated (m, fig. 234) upon the side of the pharynx, immediately behind, and a little above the inferior turbinated bone. The mucous membrane which lines the Eustachian tube is thin, but at the mouth of the tube it assumes the characters of the mucous membrane of the pharynx and of the pitui- tary membrane, with both of which it is continuous ; it is also continuous with the mu- cous membrane of the tympanum ; hence the close sympathy which exists between the lining membrane of these several parts.* The use of the Eustachian tube is to renew the air contained within the tympanum; but it also gives exit to the mucous secretion of that cavity, t Besides the orifice of the Eustachian tube, and that of the canal for the internal mus- cle of the malleus, the anterior funnel-shaped part of the circumference of the tympanum presents two orifices placed one above the other : the uppermost of these is the internal orifice of the canal for the chorda tympani nerve ; the lower one is an oblique fissure, which transmits a fibrous cord called the anterior muscle of the malleus. M. Huguier has shown me a number of which the chorda tympani nerve does, not escape through the fissure of Glasserius, but runs in a very narrow special canal, ab
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