160 SPECIAL SENSES. 



of the sphenoid, and from this constricted portion it gradu- 

 ally dilates to its opening into the pharynx, the entire canal 

 presenting the appearance of two cones. The osseous portion 

 extends from the tympanum to the spine of the sphenoid. 

 The cartilaginous portion is an irregularly-triangular carti- 

 lage, bent upon itself above, forming a furrow, with its con- 

 cavity presenting downward and outward. The fibrous por- 

 tion occupies about half of the tube beyond the osseous por- 

 tion, and completes the canal, forming its inferior and external 

 portion. In its structure, the cartilage of the Eustachian tube 

 is intermediate between the hyaline and the fibre-cartilage. 



The circumflexus, or tensor-palati muscle, which has al- 

 ready been described in connection with deglutition, 1 is at- 

 tached to the anterior margin, or hook of the cartilage. The 

 attachments of this muscle have lately been accurately de- 

 scribed by Riidinger, who calls it the dilator of the tube, 2 

 though its action had been indicated by Yalsalva, in the early 

 part of the last century, 8 and was very fully described by 

 Toynbee, in 1853. 4 The following excellent summary of the 

 action of the muscles upon the tube is taken from the report 

 on otology, by Dr. J. Orne Green, contained in the Transac- 

 tions of the American Otological Society : 6 * 



"The relations and attachments of the muscles of the 

 Eustachian tube have been recently demonstrated very satis- 

 factorily by Riidinger. The tensor-palati muscle is a dilator 

 of the tube ; it is inserted along the whole length of the hook 



1 See vol. ii., Digestion, p. 185. 



8 KUDINGER, in STRICKER, Manual of Human and Comparative Histology, 

 The New Sydenham Society, London, 1873, vol. iii., p. 71. 



3 VALSALVA, De Aure Humana Tractatus. Opera, Lugd. Batav., 1742, p. 

 34. As some authors state that Valsalva did not describe the action of the di- 

 lator muscle, we quote the following : " * * * nam si musculus iste leviter digitis 

 trahatur, tune nasi interna foramina, tubaque Eustachiana dilatantur." 



4 TOYNBEE, Diseases of the Ear, Philadelphia, 1860, p. 215, The original ob- 

 servations of Toynbee were presented to the Royal Society, in 1853. 



6 GREEN, Report on the Progress of Otology, for 1869-'70. Transactions of 

 the American Otological Society, Third Annual Meeting, New York, 1870, p. 9. 



