236 DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 



large ; its nature can better be appreciated after a brief consideration 

 of the changes in the vestibule with which it is associated. 



The marginal portion of the oral cavity in its early stages is a narrow 

 space extending almost horizontally to the buccal sulcus. With the ap- 

 pearance of the dental anlages the limits of the future vestibule are de- 

 lined. In theembryoof 13.5 millimeters the superior aniage {64) appears 

 as a shallow furrow lined with thickened epithelium, which is continu- 

 ous laterad with that lining the buccal sulcus (Figs. 49-57). Caudad 

 the furrow becomes very faint, but can be followed into the orbito- 

 parotid interval, where it is finally lost a short distance craniad of, 

 and in line with, the orbital angle. The epithelial thickening also 

 diminishes in width caudad, and at the orbital angle becomes confined 

 to the forming fundus of the secondary buccal sulcus. These struc- 

 tures are too minute to appear in a model of the scale on wliich the 

 oral epithehum of this embryo was reproduced (Fig. 35), where, indeed, 

 the larger ectopalatine sulcus {62) can barely be indicated. In the 

 sections (Figs. 49-53) the furrow of the dental aniage is parallel to the 

 larger sulcus and lateral to it, extending from the orbitoparotid interval 

 craniad a short distance beyond the plane of the angulus oris. The 

 mesal limit of the thickened epithehum is a sagittal hne about midway 

 between these furrows, which caudad reaches the secondary buccal 

 sulcus near the buccomasseteric crossing. WTiile the epithelial 

 thickening of the roof thus retains its primitive continuity, that of 

 the floor has separated into three areas: a minimal residuum of its 

 mesal border can be recognized along the fundus of the lingual sulcus ; 

 its lateral portion extends from the buccal sulcus to the minute furrow 

 before referred to in connection with the parotid fold, wliich is the 

 inception of a new fundus of the buccal sulcus ; finally, an intermediate 

 thickened region comprises the inferior dental aniage and the inferior 

 alveobuccal sulcus (Figs. 36, 49-54). The former is of the same 

 structure as the superior dental aniage, but larger and ental in posi- 

 tion. Both furrow and thickening disappear caudad before the orbital 

 angle is reached. Craniad the formation extends beyond the plane 

 of the angulus oris, there converging towards its fellow of the opposite 

 side. The earUer emergence of the ventral anlageS would seem to 

 stand in relation to the more rapid expansion of the epithelium of the 

 floor, depending in turn upon the greater enlargement of the mandibu- 



