PULPS AND SACS OF THE HUM^VN TEETH. 



23 



but a longitudinal section showed that the lijya only had 

 adhered, the ivalls liad not. The follicle s .^ i 

 (6, rig. 22) had become a sac, in conse- 

 quence of which a cavity (b) remained be- 

 tween it and the surface of the gum. Gela- 

 tinous substance had been deposited in the '^' "' 

 sac (6), and in the neighbourhood of the cavity below it 

 (6), as in the other sacs. 



The lower jaw exhibited changes analogous to those in the 

 upper. 



Fig. 23. 



12. Child at Birth. — A longitudinal section was made 

 i \ /^ ^ through the posterior part of the 

 under jaw, when the sacs and pulps 

 of the posterior milk-molar, and of 

 the first permanent molar, and the 

 arrangements represented in Fig. 23, 

 were obseiTed. (5) The sac and 

 pulp of the posterior milk-molar ; 

 (G) the sac and pulp of the first permanent molar ; (6) the 

 cavity marked (J, Fig. 22). 



The sac of the permanent tooth (6) was now almost wholly 



imbedded in the base of the coronoid process of the jaw. Tlie 



cavity (6) which was attached to the upper part of the sac of 



the permanent tooth by its posterior extremity, adhered by its 



anterior extremity to that point of the gmu which was attached 



to the anterior edge of the base of the coronoid process, so 



as to di"ag its surface at that point into a dimi)le. The cavity 



(6) was consequently longer than it was at its hrst formation. 



The granidar substance had wholly disappeared. The 



interior of the sacs had a villous highly-vascular appearance, 



like a portion of injected intestinal mucous membrane. Tlie 



original opening of the sac (6) into the cavity (6) was indicated 



on its iniK-r suvfac(^ by an indistinct circular lip. The sac.< 



