DEVELOPMENT OF THE SENSE ORGANS 



369 



papillae of the tongue, on the under surface of the tongue, on both surfaces of the 

 epiglottis, on the palatine tonsils and arches and on the soft palate. After birth 

 many of the taste buds degenerate, persisting on the lateral walls of the vallate 

 and foliate papillae, on a few fungiform papillae and on the laryngeal surface of the 

 epiglottis. 



The anlages of the taste buds appear as thickenings of the lingual epithelium 

 in 1 1 cm. fetuses (Keibel) . The cells of the taste bud anlage lengthen and later 

 extend to the surface of the epithelium. They are differentiated into the sensory 

 taste cells with modified cuticular tips and into supporting cells. The taste buds 

 are suppled by nerve fibers of the seventh, ninth and tenth cerebral nerves; 

 the fibers branch and end in contact with the walls of the taste cells. 



B 



Fore-or 



Organ of 

 Jacobson 



Olfactory plate 

 D 



Latnasa-l process 



___ Med. nasal process 



Median nasal ( /^ ^--f" : A 



process \ >^-r \ V .t Maxillary 



Nasal fossa Fpilhelial plate 



FIG. 350. Sections through the olfactory anlages of human embryos. A, 4.9 mm.; 5,6.5mm.; C, 8.8 

 mm.; D and E, 10 mm. embryo. (A, B and C from Keibel and Elze.) 



in. THE OLFACTORY ORGAN 



The olfactory epithelium arises as paired thickenings or placodes of the 

 cranial ectoderm (Fig. 350 A). The placodes are bent inward to form the nasal 

 fossa about which the nose develops. 



In embryos of 4 to 5 mm. the placodes are sharply marked off from the sur- 

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