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TEXT-BOOK OF PHYSIOLOGY. 



The cavity of the mouth communicates posteriorly with the 

 pharynx by a narrow orifice, the isthmus of the fauces. This orifice 

 is bounded above by the soft palate, laterally by the anterior and 

 posterior half arches, and below by the tongue. 



^*The pharynx is an oval-shaped cavity extending from the base of 

 the skull to the lower border of the cricoid cartilage, a distance of 



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FIG. 68. VERTICAL SECTION OF THE NASAL FOSSA AND MOUTH, i. Left nares. 

 2. Lateral cartilage of the nose. 3. Portion of the internal alar cartilage form- 

 ing the skeleton of the lower part. 4. Superior meatus. 5. Middle meatus. 

 6. Inferior meatus. 7. Sphenoidal sinuses. 8. External boundary of the pos- 

 terior nares. 9. Internal elliptical opening of the Eustachian tube. 10. Soft 

 palate, u. Vestibule of the mouth. 12. Vault of palate. 13. Genioglossus 

 muscle. 14. Geniohyoid muscle. 15. Cut margin of the mylohyoid muscle. 

 1 6. Anterior pillar of the palate (anterior half -arch), presenting a triangular figure 

 with the base inferiorly, covering partly the tonsil. 17. Posterior pillar (poste- 

 rior half-arch) of the palate. 18. Tonsil. 19. Follicular (mucous) glands at the 

 base of the tongue. 20. Cavity of the larynx. 21. Ventricle of the larynx. 

 22. Epiglottis. 23. Cut os hyoides. 24. Cut thyroid cartilage. 25. Thyro- 

 hyoid membrane. 26. Section of posterior portion of the cricoid cartilage. 

 27. Section of the anterior portion of the same cartilage. 28. Crico-thyroid 

 membrane. 



about 12 centimeter^\ (See Fig. 68.) Its walls are formed mainly by 

 three pairs of muscles the superior, middle, and inferior constrictors 

 each consisting of red, striated muscle-fibers, and hence capable 

 of rapid and energetic contractions. Superiorly the pharynx is 

 attached to and supported by the basilar process of the occipital 



