14 



ON THE ORIGIN AND DEVELOPMENT OF THE 



been extracted. Breadth of the superior arch, 3i lines ; 

 length, 3 lines. 



9. 15th week Upper Jaw. The outer edges of the 

 palate, which in the last embryo lay unattached on the outer 

 lip of the dental groove, in the present subject adhered firmly 

 to it, except along a small portion posteriorly (a, Fig. 17). 

 This adhesion was firm anteriorly on 

 both sides of the median line, then 

 became weaker, and posteriorly at 

 the non-adherent portion (a\ be- 

 tween the lobules (r and t\ the lips 

 of the groove retained their original 

 smooth edges. When the lips of this 

 non-adherent portion were separated 

 by the needles, its floor and walls exhibited nothing but the 

 greyish-yellow mucous membrane of the original groove. The 

 outer lip of the dental groove was visible all around the ex- 

 ternal margin of the palate, and was divided on both sides 

 into three parts, an anterior (u\ a lateral (o), and a posterior 

 (). On the inner side of the latter was seen the longitudinal 

 lobule, which has hitherto been marked (r). The median 

 lobule (m) was rounded anteriorly, and had a process (?/, Figs. 

 8 and 10), which stretched forwards between the lobules (u u). 

 This was the additional lobule formerly mentioned. The sides 

 of the median lobule were straight and converged to its pos- 

 terior extremity, which was circular, and was received into 

 a curve in the middle of a transverse band, constituting the 

 anterior boundary of the palate, which appeared to have re- 

 ceded still more than in the last subject, and to have exposed 

 still more completely the lateral lobules (n n). The four rugse 

 seen in the last subject had become ridges beautifully crenated, 

 and converging, as represented in the sketch, towards a curve, 

 reversed and opposite to the one formerly mentioned in the 



