28 ON THE ORIGIN AND DEVELOPMENT OF THE 



the superior milk canine tooth, is rounded and granular, and is 

 bounded externally by a triangular lamina, which spreads out 

 into, and is continuous with, the inner edge of the ridge, having 

 its apex notched so as to fit the external aspect of the papilla. 



During the ninth week the ridge advances in an indistinct 

 manner to the median line, and there appears on each side of 

 that line an oblong papilla with a notched lamina in front of 

 it, and immediately afterwards another smaller papilla and 

 lamina external to the former. These last papillae are the 

 germs of the incisive teeth, and are placed in connection with 

 the lateral elements of the intermaxillary system. 



The primitive dental groove, which before the appearance 

 of the incisive germs terminated anteriorly at the outer ex- 

 tremity of the lateral intermaxillary lobules, now extends 

 forwards to the median line. The longitudinal lobule, and 

 the lobule opposite to it also, have lengthened out posteriorly, 

 and the intervening portion of the primitive groove has 

 become wider and not so curved. The sides of the groove 

 before and behind the anterior molar papilla have been 

 gradually approaching one another. 



During the tenth week the incisive papillae make very 

 little advance, their anterior laminae only increasing some- 

 what in size. Processes from the sides of the primitive dental 

 groove, particularly the external one, approach and finally 

 meet before and behind the papilla of the anterior molar, so 

 as to inclose it in a follicle, through the mouth of which it 

 may be seen. A similar follicle is gradually formed round 

 the canine by the advancement inwards of its external notched 

 lamina, which at first appeared as a production of the ridge or 

 external lip of the groove. The germ of the posterior milk- 

 molar also appears as a small papilla towards the end of this 

 week behind the anterior molar, at the side and apparently as 

 a production from the rounded lobule, which terminates pos- 

 teriorly the outer ridge. 



