78 THE EUSTACHIAN TUBE, BY PROFESSOR RUDINGER. 



They occur with more or less modification in the greater 

 number of animals examined, attaining their highest develop- 

 ment in the Eustachian tube of the Marmot and Otter, in 

 which only a single sinuous fissure, without any safety tube, 

 is present. 



Fig. 292. 



Fig. 292. Transverse section of the cartilaginous portion of the 

 Eustachian tube of the Ox. 1, Median lamella of cartilage ; 2, 

 mesially directed long process ; 3, uncinate process of cartilage ; 

 4, lateral extremity of the cartilage ; 5, musculus dilatator tubse ; 

 6, safety tube, with the fold of the mucous membrane ; 7, dilated 

 portion of the Eustachian tube at the commencement of the accessory 

 fissure ; 8, accessory fissure. Magnified 184 diameters. 



The Eustachian tube of the Bat and of the Horse presents a 

 peculiar structure, the mucous membrane forming a lateral 

 dilatation like an air sac, which is surrounded by muscles and 

 glands. (See fig. 294.) 



In the Bat this sac is of an elongated quadrangular form, 

 owing to the disposition of the glands and muscles in relation 

 with it externally. 



