66 THE DEVELOPMENT OF THE SALIVARY GLANDS IN MAN 



advancing side by side may eventually fuse, and then separating from 

 the sulcus, give rise to the united ducts, or failing to fuse, permit the 

 greater sublingual to attain an independent orifice. An alternative 

 supposition is possible. It may be that the fold continues to advance 

 after the stage of 20 millimeters, forming a flange in the region to 

 which the crests are attached, as previously in the region of the sub- 

 maxillary ganglion, and that the inrolling incident to the formation of 

 this portion of the flange is the means of uniting the two ducts. In 

 this case it must further be supposed that the proximal portion of the 

 sublingual crest is suppressed in those cases in which the two glands 

 have a common orifice, to which suppression the interruption of the 

 sublingual crest in the 20 millimeter embryo may be preliminary. 

 While there is no evidence to decide, the latter supposition is interest- 

 ing in that it calls in question the primitiveness of the attachment of 

 the sublingual bud in Chievitz's 10 weeks embryo. Here also the 

 anlage may have been estabhshed prior to the completion of the flange, 

 and subsequently annexed as the flange drew mto itself more of the 

 adjacent epithelium. 



It is evident that the anlages of the subma.xillary and greater sub- 

 lingual glands afford abundant material for variation, in irregular sepa- 

 ration of their flanges, in the possible active development of such 

 rudiments as the postglandular flange and the dorsal accessory sub- 

 maxillary, and in the mutual relations of the keels of the ducts. In Figs. 

 26 and 27 these factors are schematically indicated ; the first based 

 largely upon conditions in the 20 millimeter embryo presents conditions 

 actually observed ; in the second a schema of possibilities is drawn, 

 which might be reahzed by the full development of these rudiments. 

 In both the ventral accessory element has been omitted. It is at- 

 tached to the concavity of the submaxillary duct craniad to its division 

 into three major branches (Bujard). While the human adult fails to 

 utiHze this abundant material at all full)', it is interesting to note that 

 its possibilities are realized in other primates (Huntington), and that 

 individual and specific types of this complex jjresent themselves as 

 more or less complete realizations of the human embryonic plan. 



Of the mesal derivatives of the lingual sulcus our knowledge is 

 meager. In the 20 millimeter embryo a flange of the same form as 

 the sublingual is directed mesad into the substance of the tongue. In 



