DEVELOPMENT OF THE TEETH IN MAMMALIA 25 



infant, but the calcification, being slightly further advanced, 

 gives a better image on the photographic plate, and has 

 therefore been chosen as an illustration. 



FIG. 8. Right side of jaws of male infant one month old. First molar 

 more calcified than second molar. Independent deposits on the second 

 molar are well shown ; they become gradually united by extension of the 

 calcification. A single calcified tip of one cusp of the first permanent 

 molar only is seen. There is no important difference between this stage 

 and the condition af birth. From Symington and Rankin's Atlas of 

 Skiagrams. 



The first indication of tooth formation is the differentia- Summary, 

 tion of a band of epithelial tissue just beneath the surface 

 of the forming jaw : this is the primitive dental lamina. 



The primitive dental lamina separates at an early stage 

 into two laminas at right angles, or nearly so, to one another 



