254 THE ORGANS OF DIGESTION 



The period of eruption of the temporary teeth are 

 (C. S. Tome) : 



Lower central incisors 6 to 9 months 



Upper incisors 8 to 10 months 



Lower lateral incisors and first molars . 15 to 21 months 



Canines 16 to 20 months 



Second molars 20 to 24 months 



The period of eruption of the permanent teeth are : 



First molars 6j years 



Two middle incisors 7th year 



Two lateral incisors 8th year 



First bicuspid 9th year 



Second bicuspid 10th year 



Canine llth to 12th year 



Second molars 12th to 13th year 



Third molars 17th to 21st year 



The Tongue (Lingua). The tongue is the organ of the 

 special sense of taste, 1 also assisting in insalivation, mas- 

 tication, deglution, and articulate speech. It is situated 

 in the floor of the mouth, in the interval between the 

 horizontal rami of the mandible. It is attached to the 

 hyoid bone at the base by the genioglossus and hyo- 

 glossus muscles and the hyoglossal membrane; with the 

 epiglottis by three folds, the glosso-epiglottic folds, of 

 mucous membrane; with the soft palate by means 

 of the anterior pillars of the fauces; and with the 

 pharynx by the superior constrictor muscles and the 

 mucous membrane. 



The muscles controlling the tongue are the extrinsic, 

 which are inserted into the tongue, their terminal 

 fibers contained within the substance, namely, the 

 styloglossus, the hyoglossus, the palatoglossus, the 

 genioglossus, and part of the superior constrictor of 

 the pharynx (pharyngoglossus). The intrinsic muscles 

 of the tongue are : the superior lingualis, the chondro- 

 glossus, the transverse lingualis, the vertical lingualis, 

 and the inferior lingualis. 



1 See chapter Sense of Taste, page 406. 



