Discovery reports (1956) Discovery reports discoveryreports27inst Year: 1956 296 DISCOVERY REPORTS LOCATION OF THE WAX PLUG It has long been supposed that the external meatus of the larger Cetacea is closed for a short distance immediately below the blubber, and that more proximally its lumen opens out again and widens gradually until it terminates in the glove-finger-like structure, which protrudes from the tympanic bulla. That this statement is inaccurate, and that the structure identified by Lillie and others as the epidermis of the meatus is only the corium of the latter, will be seen du
Discovery reports (1956) Discovery reports discoveryreports27inst Year: 1956 296 DISCOVERY REPORTS LOCATION OF THE WAX PLUG It has long been supposed that the external meatus of the larger Cetacea is closed for a short distance immediately below the blubber, and that more proximally its lumen opens out again and widens gradually until it terminates in the glove-finger-like structure, which protrudes from the tympanic bulla. That this statement is inaccurate, and that the structure identified by Lillie and others as the epidermis of the meatus is only the corium of the latter, will be seen during the course of the descrip- tion of the wax plug (see Text-fig. 1). It is not surprising that this part of the meatus has escaped the attention of most Cetacean anatomists since Lillie, for it lies in a deep groove between the squamosal and paroccipital process, and is invested in nearly a foot thickness of tough, fibrous tissue. More distally, near the ' blind' section, the meatus protrudes beyond the lateral limit of the bones, and its lumen is flattened dorso-ventrally so that the dorsal and ventral walls are nearly in apposition. The corium of the superior wall of the proximal part of the meatus conforms with the shape of its adjacent Text-fig. 1. Diagram showing the inter-relationships of the tympanic cavity, external meatus and epidermis in a typical Mysticete. The space occupied by the wax plug is cross-hatched. TC, tympanic cavity; TB, tympanic bulla; TM, tympanic membrane; TA, tympanic annulus; GF, glove-finger; C(ZC), core of the wax plug or the zona cornea of the epidermis of the glove-finger; O(SC), outer covering of the wax plug or the stratum corneum of the epidermis of the external auditory meatus; L, lumen of the external auditory meatus; C, corium of the dermis; ZG, zona germinativa of the epidermis; ZC, zona cornea of the epidermis; EM, external auditory meatus; BS, 'blind' section; B, blubber. bones, and is sharply convex on its dorsal aspect. Ventrall
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