THE EUSTACHIAN TUBE 617 



richly supplied with mucus secreting, tubulo-acinar glands, and 

 toward its pharyngeal end the mucosa is much infiltrated with lym- 

 phoid tissue, thus forming the tulal tonsil of Gerlach. 



The cartilage of the Eustachian tube is firmly adherent to the 

 bony wall. At the point of attachment it has a hyaline structure, 



FIG. 449. TRANSECTION OF THE EUSTACHIAN TUBE; DIAGRAMMATIC. 



1, cartilaginous plate ; 2, median or hooked end of the cartilage ; 3, " dilator tubae " ; 

 4, levator palati ; 5, fibrocartilage at the base of the skull ; 6 and 7, mucous glands ; 8, 

 adipose tissue ; 9, 11, lumen of the tube ; 10, 12, connective tissue. Low magnification. 

 (After Kildinger.) 



the fibres of the perichondrium penetrating only the surface of the 

 cartilaginous plate. Lower down the cartilage becomes infiltrated 

 with fibres and conforms to the typical elastic or reticular variety. 

 Like the cartilage of the auricle it is rich in cellular elements. Its 

 transection presents a peculiar hook-like form, by means of which 

 the posterior surface, the superior margin, and the upper portion 

 of the anterior surface are invested by cartilage, while the remain- 

 ing portions of the anterior surface and the whole of the inferior 

 margin are entirely membranous. 



VASCULAR SUPPLY, The mucosa of the middle ear is richly 

 supplied with blood vessels, the larger of which lie in the deeper 



