. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. ma. m Figure 23. Outline drawings of the lower jaw, Meckel's cartilage, and associated structures in a rabbit embryo (greatest length: 45 mm), based on a model prepared by E. Gaupp. A) medial view. B) lateral view. Abbreviations: , chorda tympani (VII); D, dentary; Ety, ectotympanic; "Go," "gonial" ossification; Inc, incus; Ma, malleus; , manubrium mallei; , Meckel's cartilage; , ossified zone; St, stapes. Compare with Figure 22. ducting chain consisting of angular, artic- ular, quadr
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. ma. m Figure 23. Outline drawings of the lower jaw, Meckel's cartilage, and associated structures in a rabbit embryo (greatest length: 45 mm), based on a model prepared by E. Gaupp. A) medial view. B) lateral view. Abbreviations: , chorda tympani (VII); D, dentary; Ety, ectotympanic; "Go," "gonial" ossification; Inc, incus; Ma, malleus; , manubrium mallei; , Meckel's cartilage; , ossified zone; St, stapes. Compare with Figure 22. ducting chain consisting of angular, artic- ular, quadrate and stapes. Tympanic vibrations would produce a force acting on the distal extremity of the retroarticu- lar process, initiating small rotational movements about its long axis that were transmitted to the quadrate. The quadrate would rotate slightly about its long axis and thereby activate the stapes. Angular and articular complex presumably vibrat- ed as a unit, much as in monotremes (Ait- kin and Johnstone, 1972: 247). Because of its stiffness and and mass this system of auditory ossicles would still be rather in- efficient and probably worked effectively only at frequencies below one kilohertz. Indirect sound conduction from the sub- strate via the snout and hyoid apparatus may have been significant in addition, particularly if the hyoid arch supported the tympanic membrane posteriorly (Presley, 1984: fig. 1). The external audi- tory meatus, lodged in the squamosal sul- cus, presumably carried on forward and below from the ventral termination of the bony sulcus (Presley, 1977; Fig. 22).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Harvard University. Museum of Comparative Zoology. Cambridge, Mass. : The Museum
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