MAMMALIAN ALVEOLINGUAL SALIVARY AREA 347 



submaxillary flange there has been a shifting or inroUing of epithelium 

 and that with this the subhnguahs major has been carried mesad. 

 The alveolar sulcus remains unchanged, save that its cranial extremity 

 now crosses Meckel's cartilage dorsally. 



In an embryo of lymilhmeters (Princeton Collection, No. 167) the 

 anlages have increased considerably in size. That of the submaxillary 

 is a sohd triangle of epitheUum, thickened at its free margin, with a 

 nearly vertical caudal border, and a tapering point craniad. Its ad- 

 vance along the Ungual sulcus has begun, and it now reaches to the 

 cranial border of the lingual nerve as it passes beneath the alveoUngual 

 gutter. The anlage has a length of 165 /^ ; its free angle is at the level 

 of the submaxillary ganglion (Fig. 5, ij). There is as yet no free 

 sprout. Caudal to the vertical border of the anlage a low postglandu- 

 lar flange extends for a few sections along the hngiial sulcus, repre- 

 senting the rudiment of the caudal portion of the early anlage. The 

 lingual sulcus caudal to the nerve is now reduced to a shallow furrow, 

 little more than an angle at the meeting of the tongue and the alveolin- 

 gual region. Here the anlage of the subhngualis major is attached 

 lateral to the submaxillary with which it is in contact. It is a solid 

 ridge 135 m in length. Craniad it extends to the Ungual nerve; cau- 

 dad it reaches beyond the vertical border of the submaxillary and is 

 attached lateral to the postglandular flange, to which it bears, the 

 same relation as farther craniad to the submaxillary anlage. As the 

 lingual nerve is approached the Ungual sulcus resumes its lumen, or, 

 more correctly, it has not here been reduced to a flange. In section it 

 is V-shaped, of moderate depth. The proliferation keels of the an- 

 lages have independent attachments, the submaxiflary just mesal, 

 the subhngualis major just lateral, to the fundus. The condition re- 

 sembles that of the prelingual portions of these keels in the human 

 embryo of 20 millimeters. 



The nature of the changes in the lingual sulcus is apparent from a 

 comparison of Figs. 4 and 5. The deep furrow of the younger embryo 

 has been obliterated by the apposition of its walls to the level of the 

 sublingualis major, and in consequence the flange of the submaxillary 

 has increased in depth. Dorsal to the sublingualis major the sulcus 

 seems to have opened wider than before, and its walls meet at a right 

 angle. The alveolar sulcus is shallower, a temporary condition, as 



