DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 281 



of 10 to 12 millimeters there is a sKght diffuse tliickening in the region 

 of the submaxillary ganghon and a minimal keel along the as yet 

 angular Ungual sulcus; in embryos of 12 to 13 milUmeters the keel 

 becomes indistinguishable in the course of the intermediate segment 

 of the sulcus. 



Meanwhile, caudal to the Ungual nerve and opposite its bulky gang- 

 lion, a flange is formed. This has, at first, a wavehke form with its 

 maximum height opposite the submaxillary ganghon, thence dinrin- 

 ishing equally craniad and caudad. Its cranial extremity, at first, 

 is in the vicinity of the Ungual crossing. The ventral border is first 

 thickened at the point where the flange is highest. 



The advance beyond the lingual crossing is begun in one of the 13.5 

 milUmeter embryos, and new conditions are estabUshed at the cranial 

 end of the anlage. The flange stops and gives place to a keel. This 

 differs from the flange in involving the basal ceUs alone, instead of the 

 whole thickness of the epitheUum, and, further, it is parietal and not 

 fundal in attachment. The advancing submaxillary has reached a 

 point in the intermediate segment of the lingual sulcus, which ceases 

 to be reduced to a flange, but instead deepens to an open sulcus with 

 nearly parallel walls and a distinct lumen. The keel of the submaxil- 

 lary is attached to the lateral wall near, but not at, the fundus, from 

 which it diverges as it proceeds craniad. This condition is present 

 in embryos of 15 milUmeters. It thus appears that the angular 

 boundary between the tongue and the alveolingual gutter is deepened, 

 as the tongue enlarges, to an open sulcus in the cranial portion of its 

 course, while caudad a flange is formed in the vicinity of the bulky 

 submaxillary ganglion, opposite which the process is at a maximum. 

 The ganglion may, therefore, be looked upon as the cause of the forma- 

 tion of the flange. Craniad the flange is smaller, the fissure at its 

 base deeper, until a point is reached where the compressing influence 

 of the gangUon is no longer felt, and an open furrow results. The 

 flange is composed of two layers of epithelium, lateral and mesal, in 

 apposition by their periderm strata, the bulging nuclei interlocking 

 and obscuring the line of contact of the layers, while the faintly staining 

 cell bodies produce the pale axial streak of the sections. The flange 

 is fundal in position. Could it be opened along its periderm axis, the 

 Ungual sulcus would be restored, and it is reasonable to expect that 



