EXPLANATION OF THE PLATES. 



DEVELOPMENT OF THE TEETH. PLATE I. page 1. 



a. Fig. 1. A tooth-germ a bulging on a mucous membrane. 



b. Diagrams illustrating the three stages of dentition. 

 Fig. 1. Follicular. 2. Saccular. 3. Eruptive stage. 



c. Diagrams illustrative of the formation of a temporary and its 



corresponding permanent tooth from a mucous membrane. 

 Fig. 1. Mucous membrane. Fig. 2. Mucous membrane, with a gra- 

 nular mass deposited in it. Fig. 3. A furrow or groove on 

 the granular mass. (Primitive dental groove.) 



Fig. 4. A papilla (a tooth germ) on the floor of the groove. 



Fig. 5. The papilla enclosed in a follicle in the bottom of the groove 

 (the latter in the condition of a secondary dental groove). 



Fig. 6. The papilla acquiring the configuration of a pulp, and its sac 

 acquiring opercula. The depression for the cavity of re- 

 serve behind the inner operculum. 



Fig. 7. The papilla become a pulp, and the follicle a sac, in conse- 

 quence of the adhesion of the opercular lips. The second- 

 ary dental groove in the act of closing. 



Fig. 8. The secondary groove adherent, except behind the inner 

 operculum, where it has left a shut cavity of reserve for the 

 formation of the pulp and sac of the permanent tooth. 



Fig. 9. The last change rendered more complete by the deposition of 

 the granular body (the enamel organ of Hunter, Purkinje, and 

 Raschkow). Deposition of tooth substance commencing. 



Fig. 10. The cavity of reserve receding from the surface of the gum, 

 and dilating it at its distal extremity, in which a pulp is 

 forming. Kudimentary opercula developing near its proximal 

 extremity and dividing it into a follicular and an extra-folli- 

 cular compartment. Temporary tooth pulp nearly covered 

 with tooth substance, and granular body almost absorbed. 



Fig. 11. The cavity of reserve become a sac with a pulp, and further 

 removed from the surface of the gum. Temporary tooth pulp 

 covered with tooth substance, and granular body absorbed. 

 (See Hunter, Nat. Hist, of Human Teeth, p. 95.) 



Fig. 12. The temporary tooth acquiring its fang by the triple 



b 



