THE DEVELOPMENT OF THE SALIVARY GLANDS IN MAN 55 



continuous, appear as solid, deeply staining cell masses ; only in some of 

 the terminal buds are pale centers conspicuous. In embryo 14 of this 

 series the lumen of the submaxillary duct is hned with a well-marked 

 simple squamous epithelium, from which it might be inferred that a 

 potential lumen is retained in the flange by reason of the non-adhesion 

 of the periderm cells derived from the opposite sides of the sulcus, 

 although it seems more reasonable to suppose them derived from a 

 secondary differentiation in situ from the cells of the anlage. In 

 either event, we may certainly reject His's description of the constric- 

 tion and separation of an open fold, such as occurs in the case of the 

 orbital inclusion according to Hammar. 



The intermediate sulcus (Figs, i, 4, 7, 12-18, 16) is a distinct 

 though shallow furrow with a slight irregular thickening of the epi- 

 thelium along its fundus. It is directed caudad and laterad, crossing 

 the alveolingual region oblicjuely, without however becoming con- 

 tinuous with either the lingual or alveolar sulcus (Fig. 4). Its 

 cranial extremity is at the level of the sublingual anlage. Caudad it 

 terminates on the right side, a little beyond the lingual crossing ; on 

 the left, it extends considerably farther, lying close to, but not joining, 

 the alveolar sulcus (Figs. 4-18). Between it and the Ungual sulcus 

 the floor of the alveolingual gutter presents small irregular thicken- 

 ings near the interruption of the sublingual flange, where on each 

 side they form two short ridges (Fig. 7, 40). Between the intermediate 

 sulcus and the alveolar sulcus, at the level of the Ungual crossing, a 

 faint furrow is seen in some sections (Fig. 12). 



14. Columbia Collection, Embryo No. 3. Length 22 millimeters 

 (Figs. 21-24). The Ungual sulcus (5) extends from the frenulum to a 

 point opposite the caudal border of the lingual ganglion, where it ter- 

 minates abruptly without any conspicuous preUminary reduction in size. 

 It is throughout its course a simple furrow, angulate except in its most 

 cranial sections, where it is rounded at the fundus. Nowhere is there 

 attached to it an epitheUal keel or flange. From its cranial extremity, 

 opposite the orifice of the submaxillary duct, a sprout arises directed 

 mesad and caudad into the substance of the tongue (Fig. 22, 11). 

 This appears in three sections (of 30 m) . In the last only is the 

 anlage free ; in the other sections it is attached accurately to the 

 fundus of the sulcus. On the right side a Uke condition obtains. The 



