42 



HUMAN EMBRYOLOGY AND MOKPHOLOGY. 



in a series of laminae, recalling and corresponding to the papillae 

 foliatae of low primates and of rodents. Between the papillae 

 foliatae occur taste buds. On the under surface of the tongue at 

 birth, on each side of the sublingual papillae and over the position 

 of the ranine artery, are two fimbriated folds of mucous membrane, 

 the plicae fimbriatae, vestiges of the tongue-like processes of 

 Lemurs and possibly the entire tongue of lowly Vertebrates. 

 Their function and meaning are unknown, but they may be 

 connected with the sense of taste. A remnant of the plicae 

 fimbriatae can commonly be seen in the adult. 



The Lymphatics of the Tongue, the highways for the spread of 

 lingual cancer, run for the greater part with the lingual vein and 

 terminate in the uppermost of the deep cervical glands, over the 

 jugular vein at the angle of the jaw. Many also terminate in the 

 submaxillary lymphatic glands which lie in and around the 

 salivary glands of the same name. The tongue rarely shows any 

 malformation. 



The Epiglottis. — The origin of the larynx, trachea, bronchi 

 and lungs as a depression and bud from the floor of the pharynx, 

 will be dealt with later (page 256); but the origin at the 3rd 

 week of the furcula (Fig. 34), a process from which the epiglottis 

 is derived, may be noted here. It arises from the 4th visceral 

 arch. The upper part of the thyroid cartilage also arises from 

 the 4th. The superior laryngeal is the nerve of the 4th arch, 

 hence it supplies the epiglottis and upper part of the larynx. 



upper dental ridge 



Aub. impar. 



prim, pharynx 



Parotid 



lower dental ridge 



lingual nerve 



sublingual gl. 

 submaxillary gl. 



Pia. 32 - 



-Showing the origin of the Submaxillary and Sublingual Glands from furrows 

 between the gum and tongue during the flth week. (After His.) 



Origin of the Salivary Glands.— Between the tongue and gum 

 of the foetus there are two furrows (Fig. 32). From the hypoblast 



