670 



BERTHA E. MARTIN 



cusp. The center of this dentine mass contains blood corpuscles 

 and odontoblasts which are actively forming dentine, so that at 

 a slightly later stage one would probably find an entirely solid 

 mass of dentine (text fig. 14). 



Fig. 11 Section through fourth front tooth at l^irth showing absence of den- 

 tinal tubules and enclosure of odontoblasts within dentine. E, enamel; D, den- 

 tine. X 560 (reduced J). 



Fig. 12 Section through third front tooth at birth showing cellular dentine. 

 E, enamel; D, dentine; BV, blood-vessel. X 560 (reduced 5). 



Discussion 



From the preceding account it is clear that the anterior part 

 of the jaw contains either five or six tooth germs. It is also clear 

 that toward the anterior end of the jaw dentine becomes less 

 normal in structure until dentinal tubules are no longer formed, 

 the cells of the pulp cavity secreting dentine upon all sides of 

 themselves and becoming inclosed within this secretion. This 

 process continues until a mass of dentine is formed, the cells 



