. 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
. 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. Ventrally the corium of this part of the meatus is not covered by bone and is thus, in the living animal, subjected to pressure transmitted through the fibrous tissues. The ventral aspect of the corium is consequently slightly concave and its upper surface bulges towards the lumen of the meatus. The' glove-finger' has frequently been referred to as the tympanic membrane, but, for reasons which they state, Fraser and Purves (1954) disagree with this interpretation. The homologue of the tym- panic membrane is the triangular ligament which is inserted into the manubrium of the malleus. This ligament has a deep but very narrow concavity on its lateral aspect which is continuous with the external meatus, and is thus not fundamentally different from the tympanic membrane of the Odonto- ceti and other mammals. Between the glove-finger and the tympanic annulus there is another circular concavity which is also continuous with the meatus. The concavity in the tympanic ligament, that which encircles the glove-finger and the whole length of the auditory meatus from the tympanic annulus to the constricted lateral extremity, is filled by the wax plug. A section (PI. XV, fig. 2) taken near the centre of the so-called blind section in Balaenoptera acutoros
Size: 3620px × 1381px
Photo credit: © The Bookworm Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, booksubjectocean, booksubjectscientificexpediti