78 Wie Hin Eh. ADDISON AND Sits Ace PIG ON arin. 
Fig. 20 Osteodentine of apex of tooth of 7-day albino rat imbedded in the 
surface epithelium, showing cells in the lacunae in the matrix. » 175. 
ERUPTION OF TEETH 
Eight to ten days 
During the process of eruption (fig. 21), the tooth and its 
formative organs gradually move forward as a whole, and the 
apex of the dentine forming the anterior end of the tooth pierces 
the surface epithelium. This procedure is accompanied by 
new changes in the tooth-forming organs. For while the same 
process of cell-division continues at the basal end of the dental 
papilla and enamel-organ, these structures are subjected to 
Fig. 21 Longitudinal section of the upper tooth of an 8-day albino rat, show- 
ing the apex of the tooth piercing the surface epithelium. X 10. 
Fig. 22 Longitudinal section of the upper tooth of a 12-day albino rat, show- 
ing the increased size and curvature of the tooth, the basal end directed more 
towards the palatal surface and the progression of the apex of the tooth through 
the epithelium. X 10. 
Fig. 23 Longitudinal section of the upper incisor of a 26-day albino rat, 
showing the well-established occlusal surface, the approximation of the basal 
end towards the palatal surface, abundant blood-vessels in the pulp, and the 
position of the granular osteodentine filling in apex of the pulp chamber. X 10. 
