THE DEVELOPMENT OF THE SALIVARY GLANDS IN MAN 47 



wide sulcus, where the epithelium shows a slight increase of thickness 

 (29), the anlage of the inferior dental ridge; its mesal limit is sharply 

 defined by a deep open furrow {14), wliich at the same time forms the 

 lateral border of the alveolingual region {12). The convexity corre- 

 sponds to the ental portion of the alveolar process, for which reason the 

 furrow is conveniently termed sulcus alveolaris. It corresponds to 

 the sulcus sublingualis of His, and to the lateral furrow of the sulcus 

 alveololingualis of Chievitz. The mesal limit of the alveolingual gutter 

 is given by the sulcus lingualis (8), to which are attached the anlages 

 of the submaxillary and greater subhngual glands, and a mesal de- 

 rivative which appears to be the apical gland of the tongue (Fig. 12). 

 The mesal wall of this furrow is formed by the tongue, which in the 

 sections presents a well-defined angle (Fig. i, jp) at its side, separating 

 from its general surface a narrow ventral strip sloping ventromesad. 

 This region (18) Chievitz has identified with the subhngua, the angle 

 or ridge (/p) above it with the pHca fimbriata. Between the Ungual 

 and alveolar sulci, a less extensive and more ephemeral furrow (16) 

 grooves the floor of the gutter, in places showing a slight thickening 

 of the epithelium along its fundus. It is distinguishable in His's cut 

 of Zw. {Anat. mensch. Emb. Ill, Fig. 65, left side) and in Chievitz's 

 figure of his 8 weeks embryo ('85, Fig. 7). In the 20 milKmeter embryo 

 of the Columbia Collection it is well marked (Figs. 4, 7, 12-19, 16), 

 while in the 22 millimeter embryo it has almost disappeared (Fig. 

 23, 16). ■ From its position it may be termed the intermediate fur- 

 row; in man it apparently supplies no derivatives. 



Ventral to the alveolingual region is an area of mesenchyme well 

 defined topographically. It is limited entad by the hyoglossus muscle 

 and hypoglossal nerve, ectad by Meckel's cartilage, and ventrad by 

 the mylohyoid muscle. While presenting no especial structural char- 

 acters of its own, it becomes continuous at the posterior border of the 

 muscle with the conspicuous circumscribed mass of condensed mesen- 

 chyme, described by KoUiker, Chievitz, and others, which forms a sort 

 of scrotum into which the sprout of the submaxillary descends (Fig. 



17.39)- 



The hngual nerve (30) passes craniad in the suboral mesenchyme, 

 crossing the alveolingual region obliquely in its course to the tongue. 

 Here it presents a bulky ganglionic enlargement (Fig. 17, j/) which 



