348 MAMMALIAN AL\T:0LINGUAL SALIVARY AREA 



though its epithelium were drawn upon in the changes affecting the 

 lingual sulcus. A new furrow {12) has appeared on the side of the 

 tongue dorsal to the lingual sulcus, which evidently corresponds to a 

 shallow concavity of the younger embryo. 



In an embryo of 19 millimeters (Princeton Collection, No. 168) the 

 subhngualis major is more intimately related to the submaxillary; a 

 narrow plate of epithelium now serves to attach both anlages to the 

 lingual sulcus (Fig. 6, g). This contains no visible periderm, and yet 

 its interpretation as a flange produced by folding together of the walls 

 of the lingual sulcus seems justified on comparison with the conditions 

 in the embryo of 1 7 millimeters (Fig. 5 ) . It can be seen that the Lingual 

 sulcus has become deeper and more hke a fissure, while the distance 

 between its fundus and the suprahngual furrow {12) dorsad, and the 

 alveolar sulcus laterad, has diminished. At the same time the attach- 

 ment of the subhngualis major has been carried from the sulcus- itself 

 into the resulting flange. It thus appears that the connection of the 

 two anlages in the pig is purely secondary, and is occasioned by the 

 closure of the lingual sulcus, which in producing the flange of the sub- 

 maxillary draws into itself material from the surface of the tongue and 

 the floor of the alveohngual gutter. The portion of the sulcus thus 

 affected is caudal to the lingual nerve (Figs. 6-8) ; opposite the nerve 

 the sulcus retains its lumen, and the prolongations of the anlages are 

 attached as in the 17 millimeter embryo. The flange ventral to the 

 attachment of the sublingualis major has increased in height (com- 

 pare Figs. 5 and 6) ; this is evidently the result of growth in the flange 

 itself, the increment supplied by continued infolding being relatively 

 smafl, as appears from the size of the plate dorsal to the subhngualis 

 major. 



In front of the lingual nerve the epithelium at the fundus of the lin- 

 gual sulcus is slightly thickened. At the cranial border of the nerve 

 the epithelial plate of the submaxillary appears, and rather abruptly ac- 

 quires a considerable depth, projecting ventrad from the sulcus. The 

 sagittal length of its attached border is 1 20 fi- The depth of the flange 

 increases rapidly caudad and at its maximum (Fig. 6) extends slightly 

 ventrad of the submaxillary ganglion. The caudal border is nearly 

 vertical. The angle at which it joins the ventral margin presents a 

 pyriform enlargement, the sprout, which is on the point of beginning 



