MUCOUS MEMBRANE OF THE EUSTACHIAN TUBE. 75 



heits-rohre) to the semi-cylindrical space beneath the cartila- 

 ginous hook, and the fissure connected therewith I have called 

 the " accessory" or " auxiliary fissure " (Hilfs-spalte). These two 

 names sufficiently express their physiological significance. 

 The two divisions are caused by the peculiar configuration 



Fig. 290. 



Fig. 290. Transverse section of the Eustachian tube of Man, 

 through its upper third. 1, 2, Cartilage ; 3, musculus dilatator tuba? ; 

 4, lateral submucous layer ; 5, median projection of the mucous 

 membrane, with its vessels ; 6, lateral projection of the mucous 

 membrane, with its vessels ; 7, large vessel on the roof of the tuba ; 

 8, safety tube, with the mucous membrane ; 9, accessory tube. Mag- 

 nified 184 diameters. 



of the cartilage, and are separated from each other by pro- 

 jections of the mucous membrane. Whilst the mucous mem- 

 brane at the concavity of the hook behaves itself, in all 

 essential respects, like that of pneumatic canals generally, that 

 is to say, it is closely adherent to the surrounding parts, and is 



