. Chordate anatomy. Chordata; Anatomy, Comparative. 402 CHORDATE ANATOMY A lacrimal duct from each eye opens into the nasal passage, and serves to moisten the olfactory epithelium. Some reptiles, lizards for example, have added to the nasal passage a more expanded and glandular vestibule, which is apparently a mechanism for eliminating dust from the air taken into the lungs. Novel also in this group are the paired turbinal bones or conchae, which project into the nasal passages, and serve to increase and support the olfactory membrane. A nasopharyngeal cavity distinct from the mouth cavity als
. Chordate anatomy. Chordata; Anatomy, Comparative. 402 CHORDATE ANATOMY A lacrimal duct from each eye opens into the nasal passage, and serves to moisten the olfactory epithelium. Some reptiles, lizards for example, have added to the nasal passage a more expanded and glandular vestibule, which is apparently a mechanism for eliminating dust from the air taken into the lungs. Novel also in this group are the paired turbinal bones or conchae, which project into the nasal passages, and serve to increase and support the olfactory membrane. A nasopharyngeal cavity distinct from the mouth cavity also first appears in this group, as the result of the ingrowth and extension of the palatine bones. Thus a bony palate is formed, and the nariai passages open by secondary choanae into the pharynx. The vomer bone, therefore, no ECTOTURBINALS: ENDOTURBINALS. Fig. 354.—Diagrams of cross sections of the nasal passage in A, ruminant and B, man, showing the contrast in the number of turbinal bones. Since olfactory epithelium covers these bones, the keenness of the sense of smell is proportional to the number and size of turbinals. Compared with many mammals the sense of smell in man is degenerate. longer lies in the roof of the mouth, but in the nasopharyngeal passage. By the formation of the palate, the nasopharyngeal cavity is both enlarged and elongated. In birds there are three pairs of conchae, and Jacobson's organ disappears. In mammals there is an enormous enlargement of the nasal passages, and a corresponding multiplication of conchae, the single pair of reptilian conchae persisting as the maxillo-turbinals, while ethmo-turbinals, upper and lower, are added. Jacobson's organ nearly disappears in the higher mammals. The contrast between the upper olfactory and the lower respiratory region persists. That the olfactory organ of man is degenerate, is evidenced by the reduction of. the conchae in size and number, and in the ontogenetic loss of three pairs of turbinal bon
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Keywords: ., bookcentury1900, bookpublisherphi, booksubjectanatomycomparative
