The Nose, Mouth and Pharynx. 455 



the premaxillary bone, are formed from the fronto-nasal 

 process ; whereas, the lateral portion of the lip and the rest 

 of the alveolar process are developed from the maxillary 

 process, and, therefore, in hare-lip, the cleft is generally 

 to the side of the median line. 



The Tongue. The tongue is composed of two 

 halves which are joined together at the septum, and the 

 bulk of it, which is formed by intrinsic muscles, is con- 

 trolled by the following extrinsic muscles, viz., by the 

 genio-hyo-glossus, the hyo-glossus, the stylo-glossus, the 

 palato-glossus and a part of the superior constrictor of 

 the pharnyx. Near the posterior part of the middle line 

 of the dorsum of the tongue is a small pit termed the fora- 

 men caecum, and this depression is the upper extremity of 

 a foetal structure the thyro-glossal duct which original- 

 ly extended from the dorsum of the tongue to the middle 

 portion of the thyroid gland, but which gradually became 

 obliterated. Should, however, this duct not be occluded 

 throughout its whole length, then a dermoid tumor, due 

 to distention of the unobliterated portion might develop. 

 The mucous membrane covering the tongue is continuous 

 with that over the areolar processes and dips in between 

 the tongue and these processes, while* in the middle line, 

 a ridge or duplicature of this membrane is not infrequent- 

 ly present in infants, constituting one form of tongue- 

 tie. On raising the anterior part of the tongue, the 

 ranine vein is seen running towards the tip, and this vein 

 overlies the ranine artery, beneath which is a second or 

 companion vein. These vessels, which are covered by 

 mucous membrane, lie on the lower aspect of the tongue 

 between the genio-hyo-glossus and the inferior lingualis 

 muscles, and are tortuous, so that, when the tongue is pro- 

 'truded, they are not overstretched. The nerves of the 

 tongue are as follows : The lingual branch of the inferior 



