114 The Teeth 



Its sac may then become distended into a so-called dcntigerous cyst. 

 In rare instances, as age advances and the jaw is less crowded, one of 

 these belated teeth may make its appearance, which phenomenon may 

 raise the vain anticipation of a third natural set of teeth. 



When the teeth are irregularly crowded along the alveolus, a 

 judicious weeding out of some of them may effect a great improve- 

 ment. That there is considerable plasticity about the alveolar process 

 in a child is evidenced by the fact that a constant and vigorous thumb- 

 sucking causes repression of the lower incisors and an unsightly pro- 

 trusion of the upper. Cases are not rare in which the alveolar process 

 is drawn entirely out of the mouth by the contraction of an extensive 

 cicatrix left after a burn of the front of the neck. 



When it happens that the jaws cannot be separated, the surgeon 

 must not propose the extraction of a tooth in order that the patient 

 may be fed : as the patient lies in bed fluid food poured between the 

 cheek and the back teeth readily finds its way into the mouth. 



THE TONGUE 



The tongue is a mass of intrinsic and extrinsic muscles covered 

 with a mucous membrane. It is connected with the floor of the mouth, 

 lower jaw, soft palate, epiglottis, and hyoid bone. 



The mucous membrane consists of a basement membrane which 

 is elevated into papillae, depressed into glands, and covered with 

 squamous epithelium. Down the middle of the dorsum is the raphe, 

 which ends posteriorly in the foramen caecum. 



Fixing the tongue to the middle of the lower jaw is a fold of 

 mucous membrane, the/z#w. Sometimes, as a congenital defect, it 

 is so short that the tip of the tongue is closely bound down behind the 

 gum, and sucking is performed with difficulty ; the infant is then said 

 to be tongue-tied. It is best treated by raising the tongue by inserting 

 the left index and middle finger, one on each side of the frasnum, and 

 then snipping the band below the fingers with blunt scissors. This 

 being done, the band is torn through and the front of the tongue freed. 

 As the ranine vessels run beneath the tongue, on either side of the 

 frsenum, there would be danger of cutting them should the scissors be 



directed upwards. The old-fashioned 

 steel director is still made with a flat, 

 expanded, and cleft handle for raising 

 the tongue and shielding the ranine 

 vessels during division of the fraenum, but it is rarely used for that 

 purpose. That the ranine vessels are in danger of being wounded by 

 a clumsy operator is evident : the vein is readily seen through the thin 

 membrane at the side of the fraenum. Some children have a dangerous 

 trick of swallowing the tongue, and it may be necessary in such cases 

 to shorten the fraenum by a plastic operation. 



