The histological structure of the eustachian tube of the opossum, mole, bat, man, cat, horse, sheep, rat, and rabbit was compared at the (1) pharyngeal opening, (2) midportion of the tube, and (3) entrance of the tube into the tympanic cavity. The tubes were compared to man and characterized in terms of (1) the type of epithelium, (2) type and distribution of glands, (3) distribution of the lymphoid area, (4) type of connective tissue or cartilage or both, and (5) the absence or presence of a diverticulum. Special emphasis was placed upon the histological details of the human tubal cartilage.
Sucheston ME, Cannon MS. Eustachian Tube of Several Mammalian Species. Arch Otolaryngol. 1971;93(1):58–64. doi:10.1001/archotol.1971.00770060090011