60 THE DEVELOPMENT OF THE SALIVARY GLANDS IN MAN 



palatinus and are continuous with the isthmian glands. Craniad, 

 isolated lobules were found in front of the caruncle. The submaxil- 

 lary duct is ventral to the lesser sublinguals caudad, then mesal, and 

 finally at its orifice dorsal to them. In the supramylohyoid portion of 

 its course it is often accompanied by portions of the gland, which may 

 be in contact with the lesser sublinguals ; in other cases the two glands 

 are widely separated.' 



An attempt may now be made to reconstruct the history of the de- 

 rivatives of the alveolingual region. Of these the development of the 

 submaxillary has been followed in most detail. The anlage arises 

 from the lingual sulcus at, and just caudal to, the hngual crossing 

 (His, Chievitz) ; its development consists in the formation of a postlin- 

 gual sprout which invades the mesenchj-me distad, and of a prelingual 

 duct prolonged proximad along the lingual sulcus. The time of its 

 appearance cannot be stated definitely. In Hammar's embryo of 

 13.2 millimeters the anlage has attained a certain degree of develop- 

 ment ; if my interpretation of Sudler"s figure is correct, it is present in 

 an embr^'o of 1 1 millimeters, where it forms a nearly semicircular pro- 

 jection from the sulcus. In Hammar's youngest embrjo it has a 

 triangular outline and the structure of an epithelial flange. Hammar 

 interprets this as the result of a process of folding affecting the walls 

 of the lingual sulcus. This view is supported by the findings in the 

 20 millimeter embryo, where the sulcus gradually diminishes as the 

 flange increases in depth, until where the latter has attained a maxi- 

 mum, the sulcus becomes a shallow furrow indenting its base. The 

 first indication of the sprout is a thickening of the free angle of the 

 flange which is present in the 13.2 millimeter embryo (Hammar). 

 At about the same period, or even antedating the appearance of the 

 sprout, the duct begins to separate from the lingual sulcus. This 

 may be accomplished by a destruction of the intermediate portion ot 

 the flange, progressing craniad from its caudal border, for in the em- 

 bryos of 14 millimeters (Chievitz, Sudler) the anlage is a plug inclined 

 at an acute angle to the sulcus, in the position of the hypothenuse of 

 the primitive flange. In neither of these embryos is a thickened free 

 extremity noted. The flange is placed vertically above the lingual 

 nerve as it crosses the sulcus of the same name. In subsequent stages 

 the bud gives origin to the body of the gland and the duct system dis- 



