PLATE XXI, 



Fig. 7. 



Section of developing tooth of dog. x 1000. a, Stratum inter- 

 medium. B, Outer ameloblastic membrane, c, Ameloblasts showing 

 small masses of calcoglobulin. D, Inner ameloblastic membrane. 

 E, Enamel. 



Fig. 8. 



Human enamel. x 1,000. a, b, Bands of Retzius. 

 rod passing through bands without break of continuity. 



c, Enamel 



