THE TEETH. 143 



nucleated cells, blood-vessels and nerves. The cells are caudate and 



anastomose with each other, those situated superficially being termed 



Odontoblasts. 



What Arteries and Nerves supply the Teeth ? The Arteries r.re 

 derived from the inferior dental, and from the alveolar and infraorbiial 

 branches of the internal maxillary. The Nerves are derived from the inferior 

 dental branch of the inferior maxillary division of the 5th, and also from the 

 anterior and posterior dental branches of the superior maxillary division of 

 the same nerve. 



When do the Temporary Teeth appear ? Their eruption begins 

 about the 7th month after birth, with the central incisors, and ends with the 

 appearance of the second molars, about the age of two years. The lo^er 

 teeth slightly antedate the upper. Their formula is as follows : 



Mo. Mo. Ca. In. In. In. In. Ca. Mo. Mo. 



JUpper... i i i i 



i i i i i = io~! 



i I I i i = ioj 



HO.WlS. 



I .-* 



f32. 



i i = 16] 



(.Lower... i i i i 



24 12 18 9 7 7 9 18 12 24 months. 



When do the Permanent Teeth appear ? The first molars appear 

 about the end of the 6th year, followed by the incisors about the 7th or 

 8th year, the bicuspids from the 9th to the loth year, the canines about the 

 nth or 1 2th year, the second molars 'from the I2th to the I3th year, and the 

 third molars from the 1 7th to the 25th year. Those of the lower jaw are 

 slightly in advance of the corresponding upper ones. Their formula is as 

 follows : 



Wis.Mo.Mo. Bi. Bi. Ca. In. In. In In. Ca. Bi. Bi. Mo. Mo.Wis. 

 ("Upper. i i i i i i i 



(Lower. i i i i i i i 



18 12 6 10 9 ii 8 7 7 8 ii 9 10 6 12 18 years. 



What is the greatest Number of Teeth at one time in the jaws, and 

 when ? Forty-eight, namely, all the temporary and permanent teeth except 

 the third molars, occurring between the 5th and 7th years of age. 



Describe the Development of the Teeth. They arise from the mucous 

 membrane covering the maxillary arches, in which, about the 6th foetal week, 

 appears a depression, the Primitive Dental Groove, from the floor of which 

 arise papillae of mucous membrane to form the pulp of the milk-teeth. 



In the Follicular Stage, membranous septa form across the groove, and its 

 margins become thick and prominent. 



The Saccular Stage extends from the 1 3th week to the i6th, and is marked 

 first by the projection of the papillae from the follicles, next by the growth of 

 the follicular margins, the formation of processes or Opercula thereon, which 

 meet and close in the papillae ; and finally by the closing in of the dental 



