PULPS AND SACS OF THE HUMAN TEKTH. O 



The median portion ol" the dental areh was formed by 

 tlie two lateral lobules (n n)y which separated the lips from 

 the median lobule (m), and extended also a little on each side 

 of it. 



The lateral portions of the arch presented externally the 

 ridge (o), formerly mentioned, smooth and convex on its exter- 

 ual surface, internally moulded into three curves, the anterior 

 long and shallow, the second deeper, the third or posterior 

 almost semicircular. I>ehiud the last curve, the internal edge 

 of tlie ridge formed a deep notch, which swept outward and 

 forward, so as to mould the former into an almost isolated 

 lobule (q). The ridge now disappeared, but its edge continued 

 backwards and inwards, winding around the posterior extremity 

 of the horse-shoe lobe (r), so as to form a groove {k I:, Figs. 2 

 and 4), on the surface of the soft mucous membrane. The in- 

 ternal division of the lateral parts of the dental arch was 

 formed by three bulgings, apparently productions from the 

 horse-shoe lobe (c), and which were separated from the cui-ves 

 of the ridge (p), by a groove which was deeper at their sides 

 than in their intervals. The anterior one was lengthened and 

 indistinct, the middle one was more developed, the posterior 

 circular, convex, and altogether isolated. The isolation of this 

 bulging was produced by a longitudinal lobule (r), apparently 

 cut off from the external edge of the hoi-se-shoe lobe (c), and 

 forming a partial inner ridge corresponding with the outer 

 one. This new lobule (;•) reached back 

 as far as the posterior extremity of the 

 horse-shoe lobe (c), and terminated an- 

 teriorly near the middle of the centre 

 bulging. 



Lower Jau:. — In the situation of the 

 dental arch, there existed a groove (//, 

 Fig. o), very distinct posteriorly, but having no outer lip an- 

 teriorly. The inner lip (//<), presented po^ttiiorly a larL'c lobe 



