l6o ANATOMY AND PHYSIOLOGY FOR NURSES 



being erupted first. For convenience a table is ap- 

 pended : 



The first four central incisors 5 to 7 months. 



" " " lateral incisors 6 " 10 " 



" " " molars II " 16 " 



" " " canines 14 " 21 " 



" " " second molars 20 " 36 " 



Those lettered a (Fig. 77) are the central incisors; 6, 

 the lateral incisors ; c, the cuspids ; and d and e, the tempo- 

 rary molars. All but the last (d and e) are replaced by 

 permanent teeth bearing the same names. In the per- 

 manent set the first and second bicuspids supplant the 

 temporary molars. By referring to the illustration (Fig. 

 78), it will be seen that while the ten temporary teeth are 

 visible in the mouth, the permanent teeth are being 

 formed within the alveolar margin of the jaws. 



The permanent teeth appear in the following order: 



The four first molars 5 to 6 years. 



" two central incisors, lower 6 " 7 " 



" " " " upper 7 " 8 " 



" four lateral incisors 7 " 9 " 



" " first bicuspids 9 " IO " 



" " second " 10 " n " 



" " canines II " 12 " 



" second molars 12 " 15 " 



" " third " (wisdom teeth) . 17 " 23 



Deglutition. Deglutition, or swallowing, is the act 

 by which food is forced from the mouth into the stomach. 

 The process may be divided into three stages: 



In the first stage, which is entirely voluntary, the 

 mouth is closed and respiration momentarily suspended. 

 The tongue, placed against the roof of the mouth, arches 

 upward and backward, and forces the bolus of food into 

 the fauces. 



