342 MAMMALIAN ALVEOLINGUAL SALIVARY AREA 



intermediate element ; both disappear without giving rise to sprouts. 

 The lesser subUnguals appeared very late in the caudal portion of the 

 sulcus circumflexus. With reference to the site of inception, the sub- 

 maxillar}' is mesal, the subungualis major intermediate, the sub- 

 hnguales minores lateral. Secondarily, the duct of the sublingualis 

 major becomes interposed between that of the submaxillary and the 

 oral epithehum. The flange of the submaxillary is produced by an 

 apposition of the epithehum on the two sides of a lingual furrow, which 

 is at first a mere angle between the tongue and the alveolingual gutter ; 

 the appearance of a vertical flange seemed to indicate some degree of 

 shifting mesad of the epithehum of the gutter, and ventrad on the 

 part of the epithelium of the tongue. 



In the human embryo of 20 millimeters, submaxillary, sublingualis 

 major, and sublinguales minores were present. The submaxillary had 

 a much deeper flange than in cat embryos of equivalent development. 

 In its separation a postglandular flange and an intermediate element 

 were present; the latter in this, and in an embryo of 22 miUimeters, 

 showed some evidence of independent sprouting. The Barthohnian 

 element in the younger embryo was attached to the flange of the sub- 

 maxillary, but was prolonged forward along the lingual sulcus by a 

 keel of its own. On the two sides its disposition differed in reference 

 to the line of separation of the submaxillary duct, on one remaining 

 attached to the duct, on the other to the postglandular flange. In 

 the older embryo it was present on one side only, and was attached to 

 the duct of the submaxillary. Three lesser sublinguals arose from a 

 smaU crest attached to the circumflex sulcus. 



In view of the greater height of the submaxillary flange in the hu- 

 man embryo, as compared with that of the cat, it seemed reasonable 

 to infer here a greater mesal shift of the epithelium of the alveolingual 

 gutter, which, could it be proved to occur, would account for the juxta- 

 postion of the submaxillary and Barthohnian glands. Indirect evi- 

 dence to this effect seemed to be afforded by the narrowing of the 

 alveohngual region as a whole in the vicinity of the flange. 



The association of the early sprouts of the lesser sublingual glands 

 with a continuous, but evanescent, keel of epithelium presents an ad- 

 vance in organization, in comparison with a gland field of simple in- 

 dependent sprouts. Were the cranial members of such a series re- 



