OSSEOUS PORTION OF THE EUSTACHIAN TUBE. (J7 



1. OSSEOUS AND CARTILAGINOUS PORTIONS OF THE 

 EUSTACHIAN TUBE. 



The osseous portion of the Eustachian tube of Man forms an 

 elongated triangular fissure, the greatest diameter of which is 

 almost vertical. The base of the triangle is above, and is 

 bounded by the thin bony lamella which sometimes completely 

 separates the Eustachian tube from the rounded semi-canal of 

 the tensor tympani. If the bony lamella happens to be broad, 

 it curves somewhat upwards anteriorly, in consequence of 

 which the upper end of the tube is of smaller diameter, and 

 comes to occupy a position anterior to the bony semi-canal. 

 As the bony end of the median tubal opening appears dentated 

 and obliquely cut at its point of junction with the cartilage, 

 it is more largely bounded by osseous substance mesially and 

 posteriorly than anteriorly and laterally, an arrangement which, 

 as Henle has already remarked, is deserving of notice, to 

 enable us to understand the mode of attachment of the cartilage 

 to the bone. 



If a temporal bone, in which the connection with the Eus- 

 tachian tube is preserved uninjured, be carefully deprived of 

 its salts, and then be divided through the middle of the 

 tympanic cavity, so that successive sections may be made 

 towards the Eustachian tube, dividing this at right angles, the 

 gradual transition of the tympanic cavity into the bony portion 

 of the tuba, and the relations of this to the cartilaginous por- 

 tion, may be clearly seen, each section aiding the observer to 

 understand the succeeding one. 



By this means it may be shown that the cartilage of the 

 Eustachian tube interdigitates with the dentated margin oi 

 the bony portion, and is a direct continuation of the walls 

 of the osseous tuba Eustachii, yet in such a mode, that the 

 hyaline cartilage substance does not immediately succeed to 

 the bone, but that a connection is established between the 

 two by means of nbro-cartilaginous tissue. This is prolonged 

 for some distance into the substance of the cartilage, so that 

 C. F. Th. Krause arrived at the conclusion that the upper end 

 of the Eustachian tube was composed of nbro-cartilage ; and it 



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