. Outlines of zoology. ! -Under surface of rabbitsskull. Inc. I., First incisors; Inc. II., second in-cisors ; PMX; premaxilla; ,fs\ process of premaxilla; MX., maxilla;PAL., palatine; Z., zygomatic arch; BS.,basisphenoid; /., posterior part of jugal;BO., basioccipital; , paroccipitalprocess of exoccipital; SOC, supraoccipital;C, one of the condyles; ^Af.,external audi-tory meatus ; X3., tympanic bulla; GF.,glenoid fossa ; PT., pterygoid. teriorly ossified and expanded into the sieve - like cribriform platesthrough the apertures of which the branches of the olf
. Outlines of zoology. ! -Under surface of rabbitsskull. Inc. I., First incisors; Inc. II., second in-cisors ; PMX; premaxilla; ,fs\ process of premaxilla; MX., maxilla;PAL., palatine; Z., zygomatic arch; BS.,basisphenoid; /., posterior part of jugal;BO., basioccipital; , paroccipitalprocess of exoccipital; SOC, supraoccipital;C, one of the condyles; ^Af.,external audi-tory meatus ; X3., tympanic bulla; GF.,glenoid fossa ; PT., pterygoid. teriorly ossified and expanded into the sieve - like cribriform platesthrough the apertures of which the branches of the olfactory nervespass to the nose; the paired vomers along the ventral edge of themesethmoid ; and lastly, the anterior bony palate (formed from inwardextensions of maxilla and premaxilla), which in the rabbit is veryincomplete. Wedged in between the occipitals, the squamosals, and the bones ofthe basisphenoid region, there is on each side a periotic bone surround- 704 ?= a*f< p r S s § ~ .OP. ? ^:s a. -o. a, -^ •-Ss i3 o ?o P O. 2 « c to SKELETON. 705 ing the internal ear. It ossifies from three centres in the cartilaginousauditory capsule, and consists of a dense petrous portion enclosing theessential part of the ear and a more external porous mastoid portionwhich; is produced downwards into a mastoid process in front of theparoccipital process. From each periotic a tympanic bone extendsoutwards, swollen basally into a tympanic bulla in which the tympanumor drum of the ear is stretched, and continued around the externalauditory meatus. From an aperture between the tympanic and theperiotic the Eustachian tube passes to the pharynx. Stretching fromthe tympanum to the fenestra ovalis of the inner ear is the chain ofminute ear ossicles, the three links of which—malleus, incus, and stapes—possibly correspond respectively to the articular, the quadrate, andhyo-mandibular or columella of most other Vertebrates. The orbits are boun
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Keywords: ., bookcentury1900, bookdecade1910, bookidcu3192, booksubjectzoology
